Descriptor: "Ice core" / Publisher: hal ccsd - Searchworks@Jio Institute Digital Library Search Results

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400 results on '"Ice core"'

1. Air-Interface: δ18O Records of Past Meteoric Water Using Benthic Ostracods from Deep Lakes

Author: Ulrich von Grafenstein, Inga Labuhn, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Géochrononologie Traceurs Archéométrie (GEOTRAC), Ramstein G., Landais A., Bouttes N., Sepulchre P., Govin A. (eds), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, δ18O, Climate change, 15. Life on land, Ice core, 13. Climate action, Benthic zone, Paleoclimatology, Meteoric water, Hydrometeorology, Precipitation, Physical geography, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Geology, ComputingMilieux_MISCELLANEOUS
Abstract: Oxygen-isotope records offer an alternative way to quantitatively reconstruct paleoclimate, which, at first view, is independent of an ecosystem’s reaction to climate change. The ice core records from high latitude inland ice, where the former precipitation and its isotopic composition (δ18OP) are preserved in an almost original state, are widely accepted as valuable sources of paleoclimate information. Worldwide systematic observation of δ18OP (Rozanski et al. 1992), starting in the late sixties, together with the incorporation of the water isotopes in several generations of general circulation models (Hoffmann et al. 1998; Jouzel et al. 1987) and models of intermediate complexity have, not only increased the confidence in δ18OP as a powerful paleotemperature indicator in a number of key regions, but have also demonstrated its importance as a primary hydrometeorological parameter in regions where temperature dependence is less evident or absent.
Published: 2021

2. Water Isotopic Signature of Surface Snow Metamorphism in Antarctica

Author: Amaelle Landais, Frédéric Prié, Laurent Arnaud, Mathieu Casado, Ghislain Picard, Giuliano Dreossi, Barbara Stenni, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Institute of Environmental Physics [Heidelberg] (IUP), Universität Heidelberg [Heidelberg], Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut des Géosciences de l’Environnement (IGE), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institute of Polar Sciences [Venezia-Mestre] (CNR-ISP), Consiglio Nazionale delle Ricerche [Roma] (CNR), Dipartimento di Scienze Ambientali, Informatica e Statistica [Venezia] (DAIS), University of Ca’ Foscari [Venice, Italy], Landais, Amaelle, 1 Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA‐CNRS‐UVSQ, Université Paris‐Saclay Gif sur Yvette France, Picard, Ghislain, 4 Institut des Geosciences de l'Environnement (IGE) Université Grenoble Alpes / CNRS, UMR 5001 Grenoble France, Arnaud, Laurent, Dreossi, Giuliano, 5 Institute of Polar Sciences Consiglio Nazionale delle Ricerche Mestre‐Venezia Italy, Stenni, Barbara, 6 Dipartimento di Scienze Ambientali, Informatica e Statistica DAIS Ca'Foscari University of Venice Mestre‐Venezia Italy, Prié, Frederic, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Universität Heidelberg [Heidelberg] = Heidelberg University, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), and ANR-16-CE01-0011,EAIIST,Projet International d'exploration de la calotte polaire de l'Antarctique de l'Est(2016)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Paleoclimate, 010504 meteorology & atmospheric sciences, excess, water isotopes, Snow metamorphism, Geochemistry, 15. Life on land, 010502 geochemistry & geophysics, ddc:551.31, 01 natural sciences, metamorhism, Isotopic signature, Geophysics, Ice core, Settore GEO/08 - Geochimica e Vulcanologia, 13. Climate action, Ice cores, Paleoclimatology, ddc:551.9, General Earth and Planetary Sciences, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Geology, 0105 earth and related environmental sciences
Abstract: Water isotope ratios of ice cores are a key source of information on past temperatures. Through fractionation within the hydrological cycle, temperature is imprinted in the water isotopic composition of snowfalls. However, this signal of climatic interest is modified after deposition when snow remains at the surface exposed to the atmosphere. Comparing time series of surface snow isotopic composition at Dome C with satellite observations of surface snow metamorphism, we found that long summer periods without precipitation favor surface snow metamorphism altering the surface snow isotopic composition. Using excess parameters (combining D,17O, and 18O fractions) allow the identification of this alteration caused by sublimation and condensation of surface hoar. The combined measurement of all three isotopic compositions could help identifying ice core sections influenced by snow metamorphism in sites with very low snow accumulation., Plain Language Summary: Water isotopes in ice core records are often used to reconstruct past climate temperature variations. Classically, the temperature signal is thought to be imprinted in water isotopes of precipitation, and then archived in the ice core as it falls, and in cold areas of Antarctica, piles up for very long period. Here, we show that the surface snow isotopic composition varies in between precipitation events, suggesting that there might be more than one contribution to the isotopic signal in ice core records. This is particularly important for low accumulation sites, where the snow at the surface remains exposed for very long time periods. The combined use of several isotopic ratios in surface snow helps us disentangle the processes that create this signal., Key Points: During summer without precipitation, intense snow metamorphism shows a strong water isotopic signature. During summer without precipitation, intense snow metamorphism shows a strong water isotopic signature. The d‐excess and 17O‐excess of the snow is a proxy of snow metamorphism for low accumulation regions., FP7 Ideas: European Research Council (FP7 Ideas) http://dx.doi.org/10.13039/100011199, Foundation Prince Albert of Monaco, Alexander von Humboldt‐Stiftung (Humboldt‐Stiftung) http://dx.doi.org/10.13039/100005156, DFG project CLIMAIC, https://doi.pangaea.de/10.1594/PANGAEA.934273
Published: 2021

3. Cosmic-ray variability on the multi-millennial time scale: A new multi-proxy reconstruction

Author: Edouard Bard, Natalie A. Krivova, Meanié Baroni, Sami K. Solanki, Gennady A. Kovaltsov, Chi Ju Wu, Ilya Usoskin, University of Oulu, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), and Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
Subjects: 2HAL, Cosmic ray, BARD Édouard, Proxy (climate), law.invention, Texte intégral (accès ouvert), Maxima and minima, web-evolution-climat-ocean, Ice core, law, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Climatology, Physics::Space Physics, Radiocarbon dating, Maxima, Heliosphere, Holocene, Geology, Document sous DOI (Digital Object Identifier)
Abstract: https://pos.sissa.it/358/1164/pdf; International audience; On the time scale of up to millennia the flux of cosmic rays outside the Heliosphere can be assumed roughly constant, and the cosmic-ray variability observed near Earth is driven by solar magnetic activity. Thus, using data on cosmogenic isotopes measured in natural terrestrial archives, past solar activity can be reconstructed. The most important cosmogenic isotopes are radiocarbon 14C and beryllium 10Be. However, because of the diversity of the proxy archives, it is difficult to build a homogeneous reconstruction, and previous studies showed inconsistencies with each other. Here we report a new consistent multi-proxy reconstruction of the cosmic-ray variability over the Holocene (last 9000 years), using all available long-span datasets of 10Be and 14C in terrestrial archives (six 10Be series of different ice cores from Greenland and Antarctica, as well as the global 14C production series). We have applied a new method, based on a Bayesian approach, which yields the most probable values of the solar modulation as well as straightforward estimates of the related uncertainties. The final reconstruction indicates the presence of a slow 6 – 7 millennia 'wave' in the long-term evolution of solar activity, with lows at ca. 5500 BC and 1000 AD. Two distinct components of solar activity were confirmed: the main component, corresponding to the "normal" moderate level, and a component corresponding to grand minima. A possible existence of a component representing grand maxima cannot be separated from the main component in a statistically significant manner.
Published: 2021

4. Antarctic surface temperature and elevation during the Last Glacial Maximum

Author: Takashi Obase, J. S. Edwards, Vladimir Ya. Lipenkov, William H. G. Roberts, Edward J. Brook, Michael Sigl, Ayako Abe-Ouchi, Jérôme Chappellaz, Mirko Severi, R. Beaudette, Jakob Schwander, Ikumi Oyabu, Sam Sherriff-Tadano, John M. Fegyveresi, Takakiyo Nakazawa, Catherine Ritz, Todd A Sowers, Tyler R. Jones, Zhengyu Liu, Jenna Epifanio, Eric J. Steig, Jeffrey P. Severinghaus, Anders Svensson, Jinho Ahn, Carlos Martín, Eric Lefebvre, Jiang Zhu, Christo Buizert, Emma C. Kahle, Nelia Dunbar, Masa Kageyama, Hideaki Motoyama, Kaden Martin, Tyler J. Fudge, Shuji Aoki, Kenji Kawamura, Bette L. Otto-Bliesner, Richard B. Alley, Chengfei He, Hugh F. J. Corr, College of Earth Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA., Université Grenoble Alpes (UGA), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation du climat (CLIM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, ice, F800, surface temperature, 010502 geochemistry & geophysics, 01 natural sciences, Proxy (climate), Ice core, stable isotope, Glacial period, climate modeling, SIPLE DOME, ComputingMilieux_MISCELLANEOUS, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Multidisciplinary, Last Glacial Maximum, temperature elevation, EPICA DOME-C, Firn, POLAR ICE, VOSTOK ICE CORE, ABRUPT CLIMATE-CHANGE, VOLCANIC SYNCHRONIZATION, Climatology, [SDE]Environmental Sciences, environmental temperature, CORE WD2014 CHRONOLOGY, Geology, cooling, surface property, thermometry, General Science & Technology, water, Borehole, F700, Climate change, borehole, Article, topography, paleoclimate, Paleoclimatology, ISOTOPIC COMPOSITION, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ATMOSPHERIC NITROUS-OXIDE, 0105 earth and related environmental sciences, East Antarctica, 15. Life on land, calibration, Climate Action, AIR-CONTENT, 13. Climate action, [SDU]Sciences of the Universe [physics], Antarctica, global climate
Abstract: Antarctic paleotemperatures It has been widely thought that East Antarctica was ∼9°C cooler during the Last Glacial Maximum, close to the ∼10°C difference between then and now determined independently for West Antarctica. Buizert et al. used borehole thermometry, firn density reconstructions, and climate modeling to show that the temperature in East Antarctica was actually only ∼4° to 7°C cooler during the Last Glacial Maximum. This result has important consequences for our understanding of Antarctic climate, polar amplification, and global climate change. Science , abd2897, this issue p. 1097
Published: 2021

5. Causes of Enhanced Bromine Levels in Alpine Ice Cores During the 20th Century: Implications for Bromine in the Free European Troposphere

Author: Susanne Preunkert, Nathan Chellman, Monica M. Arienzo, Michel Legrand, Joseph R. McConnell, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: Atmospheric Science, Bromine, 010504 meteorology & atmospheric sciences, chemistry.chemical_element, 010501 environmental sciences, Atmospheric sciences, 01 natural sciences, Troposphere, Geophysics, Ice core, chemistry, 13. Climate action, Space and Planetary Science, [SDE]Environmental Sciences, Earth and Planetary Sciences (miscellaneous), Environmental science, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: International audience
Published: 2021

6. Two thousand years of temperature variability on the lower East Antarctic Plateau inferred from the analysis of stable isotopes of water and inert gases in the Aurora Basin North ice core

Author: Servettaz, Aymeric, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Paris-Saclay, Amaëlle Landais, Anaïs Orsi, and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: Isotopes stables, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Climate, Climat, Temperature, Ice core, Antarctica, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Carotte de glace, Antarctique, Température, Stable isotopes
Abstract: Antarctica is a major component in Earth’s climate system, as the equator to pole temperature gradient controls the characteristics of the general circulation of the atmosphere. Antarctica is also very useful to understand climate variability, as past climate information preserved in the ice may help extend the short observational records. However, the ice core drilling locations are unevenly spread across the glaciated continent, and the temperature reconstructions from the high elevation East Antarctic plateau suffer from poor temporal resolution, because low snow accumulation hampers our interpretation of water isotopes. Here, we present new temperature reconstructions from the Aurora Basin North (ABN, 77°S, 111°E, 2700 masl) ice core. First, we use the regional atmospheric model MAR to characterize the recent climate at ABN, and show that precipitation events are intermittent, and occur under temperature 2°C warmer than average. The large precipitation events are marked in the snow isotopes with δ18O values on par with summer levels, even during the winter, as attested by snow measurements and the isotope-enabled atmospheric model ECHAM5-wiso. Precipitations are consistently associated with a blocking on the Wilkes Land coast, North-East of ABN, and the blockings are more likely to occur during negative phases of the Southern Annular Mode (SAM), the main mode of variability in the southern hemisphere climate. Consequently, SAM positive phases are marked by cold temperatures at ABN, but not necessarily low δ18O, as precipitations may be weakened. The temperature reconstructed from the δ18O in the 300-m-deep, 2000-year ice core drilled at ABN supports stable conditions, with a temperature remaining within a ± 1°C range. We present a second temperature reconstruction from the same core, based on the inversion of borehole temperature and past firn temperature gradients, estimated with the stable isotope composition of Ar and N2 gases trapped in bubbles. This second temperature reconstruction, representative of changes in the snow, suggests that temperature at ABN was about 3°C colder during two periods of the last 2000 years: from 300 to 550 CE, and from 1000 to 1400 CE. This medieval cold anomaly is concurrent with a positive SAM phase, and could not be identified from the δ18O alone. This work highlights the importance of using multiple proxies to determine past temperature variability in Antarctica, as δ18O may be biased towards warm precipitation events.; L’Antarctique joue un rôle majeur dans le climat de la Terre, car le gradient de température entre l’équateur et les pôles contrôlent la circulation atmosphérique. L’Antarctique est également utile pour comprendre la variabilité du climat, puisque les informations préservées dans la glace peuvent complémenter les observations récentes. Cependant, l’emplacement des forages de carotte de glace sont irrégulièrement répartis sur le continent, et les reconstructions de température sur le plateau Est-Antarctique sont entravées par la faible résolution temporelle résultant d’une trop faible accumulation de neige à haute altitude. Nous présentons ici de nouvelles reconstructions de température à partir de la carotte de glace d’Aurora Basion North (ABN, 77°S, 111°E, 2700 m d’altitude). D’abord, nous utilisons le Modèle Atmosphérique Régional (MAR) pour caractériser le climat récent à ABN, et montrons que les événements de précipitation sont intermittents, et sont marqués par une température 2°C supérieure à la moyenne. Les événements de fortes précipitations sont enregistrés dans les isotopes de l’eau, avec des valeurs de δ18O avoisinant les valeurs estivales, même en hiver, comme l’attestent des mesures dans la neige et le modèle atmosphérique ECHAM5-wiso, qui est équipé avec les isotopes de l’eau. Les précipitations sont systématiquement associées avec un blocage atmosphérique sur la côte de Wilkes Land, au nord-est d’ABN, et ces blocages sont favorisés par les phases négatives du Southern Annular Mode (SAM), le principal mode de variabilité dans le climat de l’hémisphère Sud. Par conséquent, les phases positives du SAM sont marquées par des température froides à ABN, mais pas nécessairement par un δ18O faible, car les précipitations peuvent être réduites. La température reconstruite à partir de la carotte forée à ABN, qui fait 300 m et couvre 2000 ans, reste relativement stable, à ± 1°C de la température moyenne. Nous détaillons une deuxième reconstruction de température faite sur la même carotte, basée sur l’inversion de la température de trou de forage et des anciens gradients de température dans le névé, estimés avec les isotopes stables des gaz Ar et N2 piégés dans les bulles. Cette seconde reconstruction de température révèle deux périodes environ 3°C plus froides à ABN au cours des 2000 dernières années : de 300 à 550 EC, et de 1000 à 1400 EC. Cette anomalie froide médiévale est synchrone avec une phase positive du SAM, et n’a pas pu être identifiée à partir du δ18O seul. Cette étude souligne l’importance d’utiliser plusieurs indicateurs pour déterminer les variations passées de température, car le δ18O pourrait surreprésenter les événements chauds à forte précipitation.
Published: 2021

7. Temperature signals of ice core and speleothem isotopic records from Asian monsoon region as indicated by precipitation δ18O

Author: Wusheng Yu, Zhaowei Jing, Baiqing Xu, Jingyi Zhang, Xiaoxin Yang, Jean Jouzel, Ninglian Wang, Dongmei Qu, Tandong Yao, Lonnie G. Thompson, Huabiao Zhao, Jing Gao, Guangjian Wu, Yaoming Ma, Chinese Academy of Sciences [Beijing] (CAS), CAS Center for Excellence in Tibetan Plateau Earth Sciences, The Ohio State University Press, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Northwest University (Xi'an), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, δ18O, Speleothem, 010502 geochemistry & geophysics, Monsoon, Atmospheric sciences, 01 natural sciences, Proxy (climate), Geophysics, Ice core, 13. Climate action, Space and Planetary Science, Geochemistry and Petrology, Paleoclimatology, Earth and Planetary Sciences (miscellaneous), East Asian Monsoon, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: Ice cores and speleothem δ 18 O records from Asia have been widely used as a proxy to reconstruct paleoclimate changes. However, whether those δ 18 O records are a proxy of temperature or monsoon intensity has remained a great controversy. Generally, ice core δ 18 O records from non-monsoon and transition regions indicate temperature, but ice core and speleothem δ 18 O records from monsoon regions have been regarded as proxies for monsoon intensity or precipitation. Here, we address the controversy by showing three 20-yr long daily precipitation δ 18 O ( δ 18 Op) series and 120 monthly δ 18 Op series based on 17461 precipitation samples throughout Asia. We find that the δ 18 Op signals preserved in precipitation are consistent with those in ice cores, both in the non-monsoon and monsoon regions. The results confirm previous research that ice core δ 18 O records in the non-monsoon region provide reliable histories of surface temperature. However, ice core δ 18 O records can still directly indicate surface temperature in the monsoon domain if winter/spring precipitation is heavy. When winter/spring precipitation is sparse, inverted ice core records show good agreement with surface temperature records. This may be due to the effect of cloud-top temperatures (which differ from surface temperatures) on summer δ 18 Op values. Similarly, inverted speleothem δ 18 O records in the monsoon regions are similar to Greenland/Antarctic ice core δ 18 O/δD time series and other paleotemperature records. Our findings provide a reinterpretation of Asian ice core and speleothem δ 18 O records, and demonstrate that temperature signals have been preserved in those archives from the Asian monsoon region.
Published: 2021

8. Reconstructing atmospheric circulation and sea-ice extent in the WestAntarctic over the past 200 years using data assimilation

Author: Elizabeth R. Thomas, Hugues Goosse, Quentin Dalaiden, Jeanne Rezsöhazy, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and UCL - SST/ELI/ELIC - Earth & Climate
Subjects: Atmospheric Science, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Atmospheric circulation, Climate reconstruction, AntarcticIce cores, Climate models, Data assimilation, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Context (language use), 010502 geochemistry & geophysics, Snow, 01 natural sciences, Ice shelf, Ice core, 13. Climate action, Climatology, Sea ice, Climate model, Southern Hemisphere, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: The West Antarctic climate has witnessed large changes during the second half of the twentieth century including a strong and widespread continental warming, important regional changes in sea-ice extent and snow accumulation, as well as a major mass loss from the melting of some ice shelves. However, the potential links between those observed changes are still unclear and instrumental data do not allow determination of whether they are part of a long-term evolution or specific to the recent decades. In this study, we analyze the climate variability of the past two centuries in the West Antarctic sector by reconstructing the key atmospheric variables (atmospheric circulation, near-surface air temperature and snow accumulation) as well as the sea-ice extent at the annual timescale using a data assimilation approach. To this end, information from Antarctic ice core records (snow accumulation and $$\delta ^{{18}}\hbox{O}$$ ) and tree-ring width records situated in the mid-latitudes of the Southern Hemisphere are combined with the physics of climate models using a data assimilation method. This ultimately provides a complete spatial reconstruction over the West Antarctic region. Our reconstruction reproduces well the main characteristics of the observed changes over the instrumental period. We show that the observed sea-ice reduction in the Bellingshausen-Amundsen Sea sector over the satellite era is part of a long-term trend, starting at around 1850 CE, while the sea-ice expansion in the Ross Sea sector has only started around 1950 CE. Furthermore, according to our reconstruction, the Amundsen Sea Low pressure (ASL) displays no significant linear trend in its strength or position over 1850–1950 CE but becomes stronger and shifts eastward afterwards. The year-to-year sea-ice variations in the Ross Sea sector are strongly related to the ASL variability over the past two centuries, including the recent trends. By contrast, the link between ASL and sea-ice in the Bellingshausen-Amundsen Sea sector changes with time, being stronger in recent decades than before. Our reconstruction also suggests that the continental response to the variability of the ASL may not be stationary over time, being significantly affected by modification of the mean atmospheric circulation. Finally, we show that the widespread warming since 1958 CE in West Antarctica is unusual in the context of past 200 years and is explained by both the deeper ASL and the positive phase of the Southern Annular Mode.
Published: 2021

9. Deep ice as a geochemical reactor: Insights from iron speciation and mineralogy of dust in the Talos Dome ice core (East Antarctica)

Author: G. Baccolo, B. Delmonte, E. Di Stefano, G. Cibin, I. Crotti, M. Frezzotti, D. Hampai, Y. Iizuka, A. Marcelli, V. Maggi, Department of Earth and Environmental Sciences [Milano], Università degli Studi di Milano-Bicocca = University of Milano-Bicocca (UNIMIB), DIAMOND Light source, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences [Roma], Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), Laboratori Nazionali di Frascati (LNF), Istituto Nazionale di Fisica Nucleare (INFN), Institute of Low Temperature Science [Sapporo], Hokkaido University [Sapporo, Japan], RICMASS Rome Int Ctr Mat Sci Superstripes, I-00185 Rome, Italy, This research has been supported by the Ministero dell'Istruzione, dell'Università e della Ricerca (grant no. PNRA18-00098), Horizon 2020 (grant no. Beyond EPICA (815384)), and Diamond Light Source (grant nos. sp7314, sp8372 and sp9050)., Primary logistical support was provided by PNRA at Talos Dome. This is TALDICE publication no. 62. This publication was generated in the frame of Beyond EPICA. The project has received funding from the European Union’s Horizon 2020 Research And Innovation Programme under grant agreement no. 815384 (Oldest Ice Core). It is supported by national partners and funding agencies in Belgium, Denmark, France, Germany, Italy, Norway, Sweden, Switzerland, the Netherlands and the United Kingdom. Logistic support is mainly provided by PNRA and IPEV through the Concordia Station system. The opinions expressed and arguments employed herein do not necessarily reflect the official views of the European Union funding agency or other national funding bodies. This is Beyond EPICA publication number 22. We thank Paolo Gentile for providing mineral standards and also Paul Niles and Tanya Peretyazhko for the fruitful discussions., European Project: 331615,EC:FP7:PEOPLE,FP7-PEOPLE-2012-IIF,TALDICE HOLOCENE(2013), European Project: 815384,Beyond EPICA, Università degli Studi di Milano-Bicocca [Milano] (UNIMIB), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Diamond Light Source: sp7314, sp8372, sp9050, Ministero dell’Istruzione, dell’Università e della Ricerca, MIUR: PNRA18-00098, Baccolo, G., Delmonte, B., Di Stefano, E., Cibin, G., Crotti, I., Frezzotti, M., Hampai, D., Iizuka, Y., Marcelli, A., Maggi, V., Baccolo, G, Delmonte, B, Di Stefano, E, Cibin, G, Crotti, I, Frezzotti, M, Hampai, D, Iizuka, Y, Marcelli, A, and Maggi, V
Subjects: 010504 meteorology & atmospheric sciences, media_common.quotation_subject, GEO/04 - GEOGRAFIA FISICA E GEOMORFOLOGIA, Geochemistry, Weathering, Mineral dust, 010502 geochemistry & geophysics, 01 natural sciences, Dome (geology), Ice core, GE1-350, Dissolution, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, media_common, QE1-996.5, biology, Geology, biology.organism_classification, Grain size, Environmental sciences, Speciation, Settore GEO/08 - Geochimica e Vulcanologia, [SDU]Sciences of the Universe [physics], Talos, Ice cores, mineral dust, paleoclimate, jarosite, Antarctica
Abstract: Thanks to its insolubility, mineral dust is considered a stable proxy in polar ice cores. With this study we show that below an ice-depth of 1000 m, the Talos Dome ice core (Ross Sea sector of East Antarctica) presents evident and progressive signs of post-depositional processes affecting the mineral dust records. We applied a suite of established and cutting edge techniques to investigate the properties of dust present in the Talos Dome ice core, ranging from concentration and grain-size to elemental-composition and Fe-mineralogy. Results show that through acidic/oxidative weathering, the conditions of deep ice at Talos Dome promote the dissolution of specific minerals and the englacial formation of others, deeply affecting dust primitive features. The expulsion of acidic atmospheric species from ice-grains and their concentration in localized environments is likely the main process responsible for englacial reactions and is related with ice re-crystallization. Deep ice can be seen as a "geochemical reactor" capable of fostering complex reactions which involve both soluble and insoluble impurities. Fe-bearing minerals can efficiently be used to explore such transformations.
Published: 2021

10. Scaling Properties and Persistence of Long-Term Solar Activity

Author: Fabio Lepreti, Vincenzo Carbone, Antonio Vecchio, Università della Calabria [Arcavacata di Rende] (Unical), INAF - Osservatorio Astronomico di Roma (OAR), Istituto Nazionale di Astrofisica (INAF), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), and Radboud university [Nijmegen]
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Astronomy, MathematicsofComputing_GENERAL, Environmental Science (miscellaneous), Atmospheric sciences, Solar irradiance, 01 natural sciences, Ice core, Meteorology. Climatology, 0103 physical sciences, scaling laws, Range (statistics), 010303 astronomy & astrophysics, Scaling, 0105 earth and related environmental sciences, Series (stratigraphy), long-range correlations, Isotope, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Term (time), TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, Detrended fluctuation analysis, Environmental science, QC851-999, solar activity
Abstract: The long-range correlations associated with the presence of persistence are investigated by applying the detrended fluctuation analysis (DFA) on three different proxies of long-term solar activity. The considered datasets are a sunspot number reconstruction (SNR04) obtained from the atmospheric activity of the cosmogenic isotope 14C derived from tree rings, a total solar irradiance reconstruction (TSIR12) obtained from several 10Be ice core records from Greenland and Antarctica in combination with the global record of 14C in tree rings and a new multi-proxy sunspot number reconstruction (SNR18), also derived from 10Be datasets and the global 14C production series. The DFA scaling exponents found for the three time series are similar (lying in the range between 0.70 and 0.77) and the scaling ranges are comparable. These results indicate the presence of long-range correlations with persistence, in substantial agreement with the findings of previous studies carried out on other solar activity indices and proxies.
Published: 2021

11. A debris-covered glacier at Kerguelen (49°S, 69°E) over the past 15 000 years

Author: Georges Aumaître, Vincent Favier, Vincent Jomelli, Didier Bourlès, Joanna Charton, Adrien Gilbert, Irene Schimmelpfennig, Karim Keddadouche, Fanny Brun, Deborah Verfaillie, Fatima Mokadem, Université Paris 1 Panthéon-Sorbonne (UP1), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Université Catholique de Louvain = Catholic University of Louvain (UCL), Université Grenoble Alpes (UGA), French INSU LEFE Glacepreker project, IPEV Kesaaco 1048 project, and ANR-11-LABX-0046,Dynamite,Dynamiques Territoriales et spatiales(2011)
Subjects: 010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, glacier fluctuations, Antarctic Cold Reversal, in situ cosmogenic chlorine-36 dating, Ice core, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Paleoclimatology, paleoclimate, Cryosphere, Glacial period, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Ecology, Evolution, Behavior and Systematics, Holocene, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, sub-Antarctic, Geology, Glacier, 13. Climate action, Moraine, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Physical geography
Abstract: ASTER Team: Georges Aumaître, Didier L. Bourlès and Karim Keddadouche; International audience; Debris-covered glaciers constitute a large part of the world's cryosphere. However, little is known about their long-term response to multi-millennial climate variability, in particular in the Southern Hemisphere. Here, we provide first insights into the response of a debris-covered glacier to multi-millennial climate variability in the sub-Antarctic Kerguelen Archipelago, which can be compared to that of recently investigated debris-free glaciers. We focus on the Gentil Glacier and present thirteen new 36 Cl cosmic-ray exposure ages from moraine boulders. The Gentil Glacier experienced at least two glacial advancesthe first one during the Late Glacial (19.0-11.6 ka) at ~14.3 ka and the second one during the Late Holocene at ~2.6 ka. Both debris-covered and debris-free glaciers advanced broadly synchronously during the Late Glacial, most probably during the Antarctic Cold Reversal event (14.5-12.9 ka). This suggests that both glacier types at Kerguelen were sensitive to abrupt temperature changes recorded in Antarctic ice cores, associated with increased moisture. However, during the late Holocene, the advance at about ~2.6 ka was not observed in other glaciers and seems to be an original feature of the debris-covered Gentil Glacier, either related to distinct dynamics or distinct sensitivity to precipitation changes.
Published: 2021

12. El Niño-Southern Oscillation signal in a new East Antarctic ice core, Mount Brown South

Author: Alexander D. Fraser, Christoph Kittel, Mark A. J. Curran, Andrew Klekociuk, A. S. Criscitiello, Nerilie J. Abram, CT Plummer, Helle Astrid Kjær, Ailie J. E. Gallant, Tessa Vance, Andrew D. Moy, Vincent Favier, Camilla K. Crockart, Lingwei Zhang, Paul Vallelonga, Jonathan Wille, Lenneke M. Jong, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: food.ingredient, 010504 meteorology & atmospheric sciences, SURFACE MASS-BALANCE, Stratigraphy, Dome, 010502 geochemistry & geophysics, Environmental protection, 01 natural sciences, Environmental pollution, food, LAW DOME, Ice core, CLIMATE VARIABILITY, TD169-171.8, Spring (hydrology), Paleoclimatology, GE1-350, 14. Life underwater, 0105 earth and related environmental sciences, ANNULAR MODE SAM, Global and Planetary Change, geography, geography.geographical_feature_category, Sea salt, Paleontology, Snow, SNOW ACCUMULATION RATES, Mount, Environmental sciences, Oceanography, DECADAL VARIABILITY, TD172-193.5, 13. Climate action, [SDU]Sciences of the Universe [physics], [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, INDIAN-OCEAN, Period (geology), WILHELM-II LAND, SEA-ICE, ENSO, Geology
Abstract: Paleoclimate archives, such as high-resolution ice core records, provide a means to investigate past climate variability. Until recently, the Law Dome (Dome Summit South site) ice core record remained one of few millennial-length high-resolution coastal records in East Antarctica. A new ice core drilled in 2017/2018 at Mount Brown South, approximately 1000 km west of Law Dome, provides an additional high-resolution record that will likely span the last millennium in the Indian Ocean sector of East Antarctica. Here, we compare snow accumulation rates and sea salt concentrations in the upper portion (∼ 20 m) of three Mount Brown South ice cores and an updated Law Dome record over the period 1975–2016. Annual sea salt concentrations from the Mount Brown South site record preserve a stronger signal for the El Niño–Southern Oscillation (ENSO; austral winter and spring, r = 0.533, p < 0.001, Multivariate El Niño Index) compared to a previously defined Law Dome record of summer sea salt concentrations (November–February, r = 0.398, p = 0.010, Southern Oscillation Index). The Mount Brown South site record and Law Dome record preserve inverse signals for the ENSO, possibly due to longitudinal variability in meridional transport in the southern Indian Ocean, although further analysis is needed to confirm this. We suggest that ENSO-related sea surface temperature anomalies in the equatorial Pacific drive atmospheric teleconnections in the southern mid-latitudes. These anomalies are associated with a weakening (strengthening) of regional westerly winds to the north of Mount Brown South that correspond to years of low (high) sea salt deposition at Mount Brown South during La Niña (El Niño) events. The extended Mount Brown South annual sea salt record (when complete) may offer a new proxy record for reconstructions of the ENSO over the recent millennium, along with improved understanding of regional atmospheric variability in the southern Indian Ocean, in addition to that derived from Law Dome.
Published: 2021

13. Interglacial Antarctic–Southern Ocean climate decoupling due to moisture source area shifts

Author: Amaelle Landais, Valérie Masson-Delmotte, Alexandre Cauquoin, Jean Jouzel, Bénédicte Minster, A. Grisart, Elise Fourré, Françoise Vimeux, I. Crotti, Thomas Extier, Ryu Uemura, Barbara Stenni, E. Selmo, Martin Werner, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), ANR-19-CE27-0011,NEANDROOTS,450-350 ka : un seuil dans l'évolution humaine ? Comprendre les racines du monde néandertalien(2019), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Department of Environmental Sciences, Informatics and Statistics [Venezia], University of Ca’ Foscari [Venice, Italy], Institute of Industrial Science (IIS), The University of Tokyo (UTokyo), Department of Chemistry, Life Sciences and Environmental Sustainability [Parma], Università degli studi di Parma = University of Parma (UNIPR), Environnements et Paléoenvironnements OCéaniques (EPOC), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Alfred Wegener Institute for Polar and Marine Research (AWI), Hydrosciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Graduate School of Environmental Studies [Nagoya], Nagoya University, This work is a contribution to EPICA, a joint European Science Foundation/European Commission (EU) scientific programme, funded by the European Union and by national contributions from Belgium, Denmark, France, Germany, Italy, the Netherlands, Norway, Sweden, Switzerland and the United Kingdom. The main logistic support was provided by Institut Polaire Français Paul-Emile Victor and Programma Nazionale Ricerche in Antartide (at Dome C) and Alfred Wegener Institute (at Dronning Maud Land). We thank the Dome C logistics teams and the drilling team that made the science possible., and European Project: 0817493(2008)
Subjects: Cryospheric science, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Oceanic climate, 010502 geochemistry & geophysics, Atmospheric sciences, Palaeoclimate, 01 natural sciences, Sea surface temperature, Ice core, 13. Climate action, Settore GEO/08 - Geochimica e Vulcanologia, [SDU]Sciences of the Universe [physics], Interglacial, Sea ice, General Earth and Planetary Sciences, 14. Life underwater, Glacial period, Quaternary, Global cooling, Geology, 0105 earth and related environmental sciences
Abstract: Succession of cold glacials and warm interglacials during the Quaternary results from large global climate responses to variable orbital configurations, accompanied by fluctuating greenhouse gas concentrations. Despite the influences of sea ice and atmospheric and ocean circulations in the Southern Ocean on atmospheric CO2 concentrations and climate, past changes in this region remain poorly documented. Here, we present the 800 ka deuterium excess record from the East Antarctica EPICA Dome C ice core, tracking sea surface temperature in evaporative regions of the Indian sector of the Southern Ocean from which moisture precipitated in East Antarctica is derived. We find that low obliquity leads to surface warming in evaporative moisture source regions during each glacial inception, although this relative temperature increase is counterbalanced by global cooling during glacial maxima. Links between the two regions during interglacials depends on the existence of a temperature maximum at the interglacial onset. In its absence, temperature maxima in the evaporative moisture source regions and in East Antarctica were synchronous. For the other interglacials, temperature maxima in the source areas lag early local temperature maxima by several thousand years, probably because of a change in the position of the evaporative source areas. Interglacial temperature coupling between East Antarctica and the Southern Ocean was set by the position of moisture source regions, according to an 800,000-year-long deuterium-excess ice-core record from East Antarctica.
Published: 2021

14. A 120,000-year long climate record from a NW-Greenland deep ice core at ultra-high resolution

Author: Maria Hörhold, Trevor Popp, Anders Svensson, Anne-Katrine Faber, A. E. Sveinbjörnsdottir, Dorthe Dahl-Jensen, Bruce H. Vaughn, Bo Møllesøe Vinther, Tyler R. Jones, Vasileios Gkinis, Valérie Masson-Delmotte, Sune Olander Rasmussen, James W. C. White, Hans Oerter, Nikol Vaxevani, Anna-Sofie Pedersen, J. P. Steffensen, Niels-Ole Ørum, Hans Christian Steen-Larsen, Christian Holme, Camilla-Marie Jensen, Thea Quistgaard, Jean Jouzel, Yongbiao Weng, Anine-Maria Lütt, Vasileios Mandrakis, Mika Lanzky, Amaelle Landais, Emilie Capron, Niels Bohr Institute [Copenhagen] (NBI), Faculty of Science [Copenhagen], University of Copenhagen = Københavns Universitet (KU)-University of Copenhagen = Københavns Universitet (KU), Institut des Géosciences de l’Environnement (IGE), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), University of Manitoba [Winnipeg], Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), University of Colorado [Boulder], Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), University of Iceland [Reykjavik], University of Copenhagen = Københavns Universitet (UCPH)-University of Copenhagen = Københavns Universitet (UCPH), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), ANR-07-VULN-0009,NEEM,NEEM-FRANCE(2007), ANR-19-MPGA-0001,HOTCLIM,Characterisation & Dynamics of Past Warm Climates(2019), European Project: 243908,EC:FP7:ENV,FP7-ENV-2009-1,PAST4FUTURE(2010), European Project: 246815,EC:FP7:ERC,ERC-2009-AdG,WATERUNDERTHEICE(2010), and European Project: 610055,EC:FP7:ERC,ERC-2013-SyG,ICE2ICE(2014)
Subjects: Statistics and Probability, Cryospheric science, Data Descriptor, 010504 meteorology & atmospheric sciences, δ18O, Science, DEUTERIUM, Library and Information Sciences, 010502 geochemistry & geophysics, Palaeoclimate, 01 natural sciences, Education, H-2/H-1, Ice core, Glacial period, Stadial, 0105 earth and related environmental sciences, Eemian, Stable isotope ratio, CHRONOLOGY AICC2012, HYDROGEN, ANTARCTIC ICE, DIFFUSION, RATIOS, Computer Science Applications, VARIABILITY, Geochemistry, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Period (geology), CONTINUOUS-FLOW ANALYSIS, Physical geography, STABLE WATER ISOTOPES, Statistics, Probability and Uncertainty, Geology, Chronology, Information Systems
Abstract: We report high resolution measurements of the stable isotope ratios of ancient ice (δ18O, δD) from the North Greenland Eemian deep ice core (NEEM, 77.45° N, 51.06° E). The record covers the period 8–130 ky b2k (y before 2000) with a temporal resolution of ≈0.5 and 7 y at the top and the bottom of the core respectively and contains important climate events such as the 8.2 ky event, the last glacial termination and a series of glacial stadials and interstadials. At its bottom part the record contains ice from the Eemian interglacial. Isotope ratios are calibrated on the SMOW/SLAP scale and reported on the GICC05 (Greenland Ice Core Chronology 2005) and AICC2012 (Antarctic Ice Core Chronology 2012) time scales interpolated accordingly. We also provide estimates for measurement precision and accuracy for both δ18O and δD., Measurement(s) isotope analysis • water ice core Technology Type(s) cavity ring-down spectroscopy Factor Type(s) δ18O • δD Sample Characteristic - Location Greenland Ice Sheet Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14216441
Published: 2021

15. Brief communication: New radar constraints support presence of ice older than 1.5 Myr at Little Dome C

Author: Jie-Bang Yan, David A. Lilien, Drew Taylor, Catherine Ritz, Olaf Eisen, Prasad Gogineni, Robert Mulvaney, Heinrich Miller, Daniel Steinhage, Carlos Martín, Charles O'Neill, Massimo Frezzotti, Dorthe Dahl-Jensen, Frédéric Parrenin, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Lilien, D. A., Steinhage, D., Taylor, D., Parrenin, F., Ritz, C., Mulvaney, R., Martin, C., Yan, J. -B., O'Neill, C., Frezzotti, M., Miller, H., Gogineni, P., Dahl-Jensen, D., and Eisen, O.
Subjects: 010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, law.invention, Paleontology, Dome (geology), Drill site, Ice core, law, CHRONOLOGY, GE1-350, Glacial period, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, Radar, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, QE1-996.5, Geology, East antarctica, Ice thickness, Environmental sciences, Stratigraphy, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology
Abstract: The area near Dome C, East Antarctica, is thought to be one of the most promising targets for recovering a continuous ice-core record spanning more than a million years. The European Beyond EPICA consortium has selected Little Dome C (LDC), an area ∼ 35 km southeast of Concordia Station, to attempt to recover such a record. Here, we present the results of the final ice-penetrating radar survey used to refine the exact drill site. These data were acquired during the 2019–2020 austral summer using a new, multi-channel high-resolution very high frequency (VHF) radar operating in the frequency range of 170–230 MHz. This new instrument is able to detect reflectors in the near-basal region, where previous surveys were largely unable to detect horizons. The radar stratigraphy is used to transfer the timescale of the EPICA Dome C ice core (EDC) to the area of Little Dome C, using radar isochrones dating back past 600 ka. We use these data to derive the expected depth–age relationship through the ice column at the now-chosen drill site, termed BELDC (Beyond EPICA LDC). These new data indicate that the ice at BELDC is considerably older than that at EDC at the same depth and that there is about 375 m of ice older than 600 kyr at BELDC. Stratigraphy is well preserved to 2565 m, ∼ 93 % of the ice thickness, below which there is a basal unit with unknown properties. An ice-flow model tuned to the isochrones suggests ages likely reach 1.5 Myr near 2500 m, ∼ 65 m above the basal unit and ∼ 265 m above the bed, with sufficient resolution (19 ± 2 kyr m−1) to resolve 41 kyr glacial cycles.
Published: 2021

16. Chronostratigraphy of a 270-ka sediment record from Lake Selina, Tasmania: Combining radiometric, geomagnetic and climatic dating

Author: Quentin Simon, Michael-Shawn Fletcher, Yusuke Yokoyama, Aster Team, Andy I.R. Herries, Agathe Lisé-Pronovost, Zenobia Jacobs, David Heslop, Patricia Gadd, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Australian GovernmentDepartment of Industry, Innovation and ScienceAustralian Research CouncilIN140100050IN170100062DP190100874La Trobe University DVCR FellowshipUniversity of Melbourne McKenzie FellowshipCentre National de la Recherche Scientifique (CNRS)French National Research Agency (ANR)IRD
Subjects: Marine isotope stage, 010506 paleontology, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Stratigraphy, authigenic 10Be/9Be ratio, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, 010502 geochemistry & geophysics, 01 natural sciences, law.invention, Ice core, law, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Earth and Planetary Sciences (miscellaneous), Quaternary Geochronology paleomagnetism, Glacial period, Radiocarbon dating, Chronostratigraphy, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Australia, Geology, Pleistocene, lake sediment, 13. Climate action, [SDU]Sciences of the Universe [physics], [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, Geomagnetic excursion, radiocarbon, Radiometric dating, Physical geography, optically stimulated luminescence, Relative dating
Abstract: Lake sediment archives covering several glacial cycles are scarce in the Southern Hemisphere and they are challenging to date. Here we present the chronostratigraphy of the oldest continuous lake sediment archive in Tasmania, Australia; a 5.5 m and 270 ka (Marine Isotope Stage 8) sediment core from Lake Selina. We employ radiometric dating (radiocarbon and optically stimulated luminescence) and relative dating (geomagnetic and climate comparisons). Bayesian modeling of the radiometric ages reaches back to 80 ka (1.7 m) and relative dating using a dynamic programing algorithm allows dating of the full sequence. Elemental data, magnetic properties and beryllium isotopes from Lake Selina reveal a close fit to Antarctic ice core climate proxies. Weaker correlation during the Last Glacial Period (MIS 2–4) is attributed to additional local factors impacting Lake Selina proxies at a time of climate changes and human arrival into Tasmania. Over that period, full vector paleomagnetic records and authigenic 10Be/9Be ratios are combined to identify the Laschamp geomagnetic excursion for the first time in Australia and constrain the chronology. The multi-method approach provides two preferred age models, indiscernible within their uncertainties, which allows the use of a geomagnetic dipole-independent (full archive) or a climate-independent (111 ka to present) age model.
Published: 2021

17. Characteristics of ice rises and ice rumples in Dronning Maud Land and Enderby Land, Antarctica

Author: Ian Lee, Kenichi Matsuoka, Jørgen Dall, René Forsberg, Vikram Goel, Cesar Deschamps Berger, Norwegian Polar Institute, Department of Geosciences [Oslo], Faculty of Mathematics and Natural Sciences [Oslo], University of Oslo (UiO)-University of Oslo (UiO), National Centre for Polar and Ocean Research, Ministry of Earth Sciences [India], Department of Earth Sciences, University of Washington [Seattle], Technical University of Denmark [Lyngby] (DTU), and National Centre for Polar and Ocean Research (NCPOR) from the Ministry of Earth Sciences (MoES), Government of India MoES/16/22/12-RDEASUS National Geospatial-Intelligence Agency European Space Agency DTU Research Council of Norway230945Research Council of Norway24780Norwegian Antarctic Research Expeditions Center for Ice, Climate and Ecosystems (ICE) of the Norwegian Polar Institute India's Ministry of Earth Sciences Research Council of Norway
Subjects: 010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, Ice shelf, Antarctic glaciology, Ice dynamics, Glacier mass balance, Ice core, Paleoclimatology, Satellite imagery, 14. Life underwater, ice shelves, [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology, 0105 earth and related environmental sciences, Earth-Surface Processes, ice rise, geography, geography.geographical_feature_category, Ice rise, Drilling, Ice shelves, 15. Life on land, Coring, 13. Climate action, Physical geography, Geology
Abstract: Ice rises and rumples, locally grounded features adjacent to ice shelves, are relatively small yet play significant roles in Antarctic ice dynamics. Their roles generally depend upon their location within the ice shelf and the stage of the ice-sheet retreat or advance. Large, long-stable ice rises can be excellent sites for deep ice coring and paleoclimate study of the Antarctic coast and the Southern Ocean, while small ice rises tend to respond more promptly and can be used to reveal recent changes in regional mass balance. The coasts of Dronning Maud Land (DML) and Enderby Land in East Antarctica are abundant with these features. Here we review existing knowledge, presenting an up-to-date status of research in these regions with focus on ice rises and rumples. We use regional datasets (satellite imagery, surface mass balance and ice thickness) to analyze the extent and surface morphology of ice shelves and characteristic timescales of ice rises. We find that large parts of DML have been changing over the past several millennia. Based on our findings, we highlight ice rises suitable for drilling ice cores for paleoclimate studies as well as ice rises suitable for deciphering ice dynamics and evolution in the region.
Published: 2020

18. Millennial-scale atmospheric CO2 variations during the Marine Isotope Stage 6 period (190–135 ka)

Author: Jérôme Chappellaz, Thomas F. Stocker, Bernhard Bereiter, Jai Chowdhry Beeman, Loïc Schmidely, Jinhwa Shin, Hubertus Fischer, Christoph Nehrbass-Ahles, Jochen Schmitt, Roberto Grilli, Lucas Silva, Amaelle Landais, Grégory Teste, Frédéric Parrenin, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: Marine isotope stage, 0303 health sciences, Global and Planetary Change, 010504 meteorology & atmospheric sciences, Stratigraphy, Northern Hemisphere, Paleontology, Atmospheric sciences, 01 natural sciences, 03 medical and health sciences, chemistry.chemical_compound, Ice core, chemistry, 13. Climate action, [SDU]Sciences of the Universe [physics], Carbon dioxide, [SDE]Environmental Sciences, Period (geology), Environmental science, Glacial period, Stadial, 030304 developmental biology, 0105 earth and related environmental sciences, Temperature record
Abstract: Using new and previously published CO2 data from the EPICA Dome C ice core (EDC), we reconstruct a new high-resolution record of atmospheric CO2 during Marine Isotope Stage (MIS) 6 (190 to 135 ka) the penultimate glacial period. Similar to the last glacial cycle, where high-resolution data already exists, our record shows that during longer North Atlantic (NA) stadials, millennial CO2 variations during MIS 6 are clearly coincident with the bipolar seesaw signal in the Antarctic temperature record. However, during one short stadial in the NA, atmospheric CO2 variation is small ( ∼5 ppm) and the relationship between temperature variations in EDC and atmospheric CO2 is unclear. The magnitude of CO2 increase during Carbon Dioxide Maxima (CDM) is closely related to the NA stadial duration in both MIS 6 and MIS 3 (60–27 ka). This observation implies that during the last two glacials the overall bipolar seesaw coupling of climate and atmospheric CO2 operated similarly. In addition, similar to the last glacial period, CDM during the earliest MIS 6 show different lags with respect to the corresponding abrupt CH4 rises, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6i at around 181.5± 0.3 ka, CDM 6i lags the abrupt warming in the NH by only 240± 320 years. However, during CDM 6iv ( 171.1± 0.2 ka) and CDM 6iii ( 175.4± 0.4 ka) the lag is much longer: 1290± 540 years on average. We speculate that the size of this lag may be related to a larger expansion of carbon-rich, southern-sourced waters into the Northern Hemisphere in MIS 6, providing a larger carbon reservoir that requires more time to be depleted.
Published: 2020

19. Temperature Trends in the Northwestern Tibetan Plateau Constrained by Ice Core Water Isotopes Over the Past 7,000 Years

Author: Hongxi Pang, Shuang-Ye Wu, Theo M. Jenk, Margit Schwikowski, Shugui Hou, Wangbin Zhang, Jean Jouzel, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Atmospheric Science, geography, Plateau, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Isotope, Climate change, Glacier, 010502 geochemistry & geophysics, 01 natural sciences, Geophysics, Ice core, 13. Climate action, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Physical geography, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: International audience
Published: 2020

20. Stratospheric ozone changes from explosive tropical volcanoes: Modelling and ice core constraints

Author: Joel Savarino, Xin Yang, Anna E. Jones, Alison Ming, Nicolas Caillon, Robert Mulvaney, James Keeble, Mohit Dalvi, Paul T. Griffiths, V. Holly L. Winton, Nathan Luke Abraham, Markus M. Frey, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), ANR-16-CE01-0011,EAIIST,Projet International d'exploration de la calotte polaire de l'Antarctique de l'Est(2016), Ming, A [0000-0001-5786-6188], Winton, VHL [0000-0001-7112-6768], Keeble, J [0000-0003-2714-1084], Abraham, NL [0000-0003-3750-3544], Dalvi, MC [0000-0003-1669-0811], Griffiths, P [0000-0002-1089-340X], Caillon, N [0000-0002-6318-6194], Jones, AE [0000-0002-2040-4841], Mulvaney, R [0000-0002-5372-8148], Savarino, J [0000-0002-6708-9623], Frey, MM [0000-0003-0535-0416], Yang, X [0000-0002-3838-9758], and Apollo - University of Cambridge Repository
Subjects: Atmospheric Science, Ozone, 010504 meteorology & atmospheric sciences, Explosive material, Atmospheric sciences, 01 natural sciences, volcanic eruption, chemistry-climate modeling, chemistry.chemical_compound, Ice core, isotopes in ice cores, Ozone layer, Earth and Planetary Sciences (miscellaneous), Samalas, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, Vulcanian eruption, Chemistry, ozone, Geophysics, chemistry, Volcano, 13. Climate action, Space and Planetary Science, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Environmental science, Antarctica
Abstract: Major tropical volcanic eruptions have emitted large quantities of stratospheric sulphate and are potential sources of stratospheric chlorine although this is less well constrained by observations. This study combines model and ice core analysis to investigate past changes in total column ozone. Historic eruptions are good analogues for future eruptions as stratospheric chlorine levels have been decreasing since the year 2000. We perturb the pre‐industrial atmosphere of a chemistry‐climate model with high and low emissions of sulphate and chlorine. The sign of the resulting Antarctic ozone change is highly sensitive to the background stratospheric chlorine loading. In the first year, the response is dynamical, with ozone increases over Antarctica. In the high HCL (2Tg emission) experiment, the injected chlorine is slowly transported to the polar regions with subsequent chemical ozone depletion. These model results are then compared to measurements of the stable nitrogen isotopic ratio, δ 15N(NO3‐), from a low snow accumulation Antarctic ice core from Dronning Maud Land (recovered in 2016‐17). We expect ozone depletion to lead to increased surface ultraviolet (UV) radiation, enhanced air‐snow nitrate photo‐chemistry and enrichment in δ 15N(NO3‐) in the ice core. We focus on the possible ozone depletion event that followed the largest volcanic eruption in the past 1000 years, Samalas in 1257. The characteristic sulphate signal from this volcano is present in the ice‐core but the variability in δ 15N(NO3‐) dominates any signal arising from changes in UV from ozone depletion. Prolonged complete ozone removal following this eruption is unlikely to have occurred over Antarctica.
Published: 2020

21. Triple isotopic composition of oxygen in water and dioxygen during deglaciations recorded in the EPICA Dome C ice core to link climate, biosphere productivity and water cycle

Author: Antoine Grisart, Clément Piel, Nicolas Pasquier, Frédéric Prié, Bénédicte Minster, Thomas Extier, Thomas Blunier, Amaelle Landais, Ji-Woong Yang, Joana Sauze, Barbara Stenni, Alexandru Milcu, Margaux Brandon, Écotron Européen de Montpellier, Centre National de la Recherche Scientifique (CNRS), Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Université Paul-Valéry - Montpellier 3 (UPVM)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)
Subjects: Biosphere, chemistry.chemical_element, 15. Life on land, Atmospheric sciences, Oxygen, Isotopic composition, Dome (geology), Ice core, Productivity (ecology), chemistry, 13. Climate action, Environmental science, Water cycle, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: High precision measurements of triple isotopic composition of oxygen in water is a useful tool to infer the dynamic of past hydrological cycle when measured in ice core together with δ18O and δD. In particular, the triple isotopic composition of oxygen in water provides information on the climatic conditions of the evaporative sources. In parallel, it has been shown that the triple isotopic composition of oxygen in the atmospheric dioxygen can be a useful tracer of the global biosphere productivity and hence reconstruct the dynamic of the global biosphere productivity in the past from measurements performed in the air bubbles. Measuring triple isotopic composition of oxygen both in the water and in the atmospheric dioxygen trapped in bubbles in ice cores is thus a strong added value to study the past variability of water cycle and biosphere productivity in parallel to climate change.Here, we first present new laboratory experiments performed in closed biological chambers to show how the triple isotopic composition of oxygen in atmospheric dioxygen can be used for quantification of the biosphere productivity with determination of fractionation coefficients. Then, we present new records of triple isotopic composition of oxygen in water and O2 trapped in bubbles from the EPICA Dome C ice core over the deglaciations of the last 800 ka.
Published: 2020

22. A Micro-Mechanical Model for the Transformation of Dry Polar Firn Into Ice Using the Level-Set Method

Author: Xavier Faïn, Fabien Gillet-Chaulet, Patricia Martinerie, Kévin Fourteau, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: 010504 meteorology & atmospheric sciences, 010502 geochemistry & geophysics, 01 natural sciences, Physics::Geophysics, Ice core, porous material, lcsh:Science, Porosity, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 0105 earth and related environmental sciences, Dislocation creep, pore closure, Firn, modeling, Mechanics, Level-Set, Snow, Creep, 13. Climate action, finite element, [SDE]Environmental Sciences, Compressibility, General Earth and Planetary Sciences, firn densification, lcsh:Q, Displacement (fluid), Geology
Abstract: International audience; Interpretation of greenhouse gas records in polar ice cores requires a good understanding of the mechanisms controlling gas trapping in polar ice, and therefore of the processes of densification and pore closure in firn (compacted snow). Current firn densification models are based on a macroscopic description of the firn and rely on empirical laws and/or idealized geometries to obtain the equations governing the densification and pore closure. Here, we propose a physically-based methodology explicitly representing the porous structure and its evolution over time. In order to handle the complex geometry and topological changes that occur during firn densification, we rely on a Level-Set representation of the interface between the ice and the pores. Two mechanisms are considered for the displacement of the interface: (i) mass surface diffusion driven by local pore curvature and (ii) ice dislocation creep. For the latter, ice is modeled as a viscous material and the flow velocities are solutions of the Stokes equations. First applications show that the model is able to densify firn and split pores. Using the model in cold and arid conditions of the Antarctic plateau, we show that gas trapping models do not have to consider the reduced compressibility of closed pores compared to open pores in the deepest part of firns. Our results also suggest that the mechanism of curvature-driven surface diffusion does not result in pore splitting, and that ice creep has to be taken into account for pores to close. Future applications of this type of model could help quantify the evolution and closure of firn porous networks for various accumulation and temperature conditions.
Published: 2020

23. Estimation of gas record alteration in very low-accumulation ice cores

Author: Kévin Fourteau, Vladimir Ya. Lipenkov, Xavier Faïn, Jérôme Chappellaz, Patricia Martinerie, Alexey A. Ekaykin, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Arctic and Antarctic Research Institute (AARI), and Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet)
Subjects: 010506 paleontology, 010504 meteorology & atmospheric sciences, Antarctic Plateau, lcsh:Environmental protection, Stratigraphy, Mineralogy, age structure, 01 natural sciences, Methane, chemistry.chemical_compound, lcsh:Environmental pollution, Ice core, lcsh:TD169-171.8, Glacial period, lcsh:Environmental sciences, 0105 earth and related environmental sciences, estimation method, lcsh:GE1-350, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, geography, geography.geographical_feature_category, Bedrock, methane, Firn, Paleontology, carbon dioxide, Glacier, East Antarctica, chemistry, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, lcsh:TD172-193.5, Carbon dioxide, Antarctica, Layering, ice core, Geology
Abstract: We measured the methane mixing ratios of enclosed air in five ice core sections drilled on the East Antarctic Plateau. Our work aims to study two effects that alter the recorded gas concentrations in ice cores: layered gas trapping artifacts and firn smoothing. Layered gas trapping artifacts are due to the heterogeneous nature of polar firn, where some strata might close early and trap abnormally old gases that appear as spurious values during measurements. The smoothing is due to the combined effects of diffusive mixing in the firn and the progressive closure of bubbles at the bottom of the firn. Consequently, the gases trapped in a given ice layer span a distribution of ages. This means that the gas concentration in an ice layer is the average value over a certain period of time, which removes the fast variability from the record. Here, we focus on the study of East Antarctic Plateau ice cores, as these low-accumulation ice cores are particularly affected by both layering and smoothing. We use high-resolution methane data to test a simple trapping model reproducing the layered gas trapping artifacts for different accumulation conditions typical of the East Antarctic Plateau. We also use the high-resolution methane measurements to estimate the gas age distributions of the enclosed air in the five newly measured ice core sections. It appears that for accumulations below 2 cm ice equivalent yr−1 the gas records experience nearly the same degree of smoothing. We therefore propose to use a single gas age distribution to represent the firn smoothing observed in the glacial ice cores of the East Antarctic Plateau. Finally, we used the layered gas trapping model and the estimation of glacial firn smoothing to quantify their potential impacts on a hypothetical 1.5-million-year-old ice core from the East Antarctic Plateau. Our results indicate that layering artifacts are no longer individually resolved in the case of very thinned ice near the bedrock. They nonetheless contribute to slight biases of the measured signal (less than 10 ppbv and 0.5 ppmv in the case of methane using our currently established continuous CH4 analysis and carbon dioxide, respectively). However, these biases are small compared to the dampening experienced by the record due to firn smoothing.
Published: 2020

24. Impacts of extremely asymmetrical polar ice sheets on the East Asian summer monsoon during the MIS-13 interglacial

Author: Feng Shi, André Berger, Qiuzhen Yin, Zhengtang Guo, Gilles Ramstein, Irina Nikolova, CAS Center for Excellence in Life and Paleoenvironment, Université Catholique de Louvain = Catholic University of Louvain (UCL), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modélisation du climat (CLIM), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), University of Chinese Academy of Sciences [Beijing] (UCAS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and UCL - SST/ELI/ELIC - Earth & Climate
Subjects: Ice sheet, Marine isotope stage, 010506 paleontology, Archeology, 010504 meteorology & atmospheric sciences, Greenland, Antarctic ice sheet, Greenland ice sheet, 01 natural sciences, Ice core, Sea ice, East Asian Monsoon, Astronomical forcing, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, geography, geography.geographical_feature_category, Geology, MIS-13 interglacial, 13. Climate action, Climatology, Asian monsoon, Interglacial, Antarctica
Abstract: Marine Isotope Stage (MIS) 13 (∼500 ka ago) was a relatively weak interglacial according to the benthic δ18O and Antarctic ice core records. However, proxy records from the Northern Hemisphere indicate that MIS-13 was at least as warm as or even warmer than more recent interglacials, with an extremely strong summer monsoon and possible melting of the Greenland ice sheet. In this study, assuming an asymmetric hemispheric climate, we investigate the response of the East Asian summer monsoon to various Greenland and Antarctic ice sheet sizes using a set of sensitivity experiments with the HadCM3 model through factor separation analysis. Results show that with no Greenland ice sheet and a large Antarctic ice sheet there is an enhancement of summer monsoon precipitation in the East Asian monsoon region of up to ∼7%, in agreement with the direction of change from proxy reconstructions for China. This enhancement is associated with a stronger land–sea thermal contrast, more water vapor transport to East Asia and a northward shift of the Intertropical Convergence Zone. The response to the Greenland ice sheet removal is related to thermodynamic and topographical effects that influence the East Asian monsoon through an orographically induced wave train. The response to the larger Antarctic ice sheet involves stronger upwelling of circumpolar deep water in the Southern Ocean melts the sea ice, leading to a warmer SST. This warming propagates to the North, affecting the East Asian summer monsoon.
Published: 2020

25. La datation des archives glaciaires

Author: Christo Buizert, Edwin D. Waddington, V. Gabriela Ciobanu, Tyler J. Fudge, Nancy A. N. Bertler, Jeffrey P. Severinghaus, Mai Winstrup, Edward J. Brook, Howard Conway, James E. Lee, Paul Vallelonga, E. D. Keller, Dorthe Dahl-Jensen, Troy Baisden, Frédéric Parrenin, Thomas Blunier, Richard C. A. Hindmarsh, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
Subjects: 010504 meteorology & atmospheric sciences, lcsh:Environmental protection, Stratigraphy, WEST ANTARCTICA, Antarctic ice sheet, 010502 geochemistry & geophysics, 01 natural sciences, Physical Geography and Environmental Geoscience, lcsh:Environmental pollution, Ice core, Deglaciation, Ice age, lcsh:TD169-171.8, SIPLE-DOME, Glacial period, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, ISOTOPIC COMPOSITION, lcsh:Environmental sciences, Holocene, 0105 earth and related environmental sciences, lcsh:GE1-350, Global and Planetary Change, SHEET ELEVATIONS, GAS RECORDS, Firn, Paleontology, HIGH-RESOLUTION RECORD, ABRUPT CLIMATE-CHANGE, Climate Action, AIR-CONTENT, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, WD2014 CHRONOLOGY, lcsh:TD172-193.5, CONTINUOUS-FLOW ANALYSIS, Physical geography, Geology, Chronology
Abstract: In 2013, an ice core was recovered from Roosevelt Island in the Ross Sea, Antarctica, as part of the Roosevelt Island Climate Evolution (RICE) project. Roosevelt Island is located between two submarine troughs carved by paleo-ice-streams. The RICE ice core provides new important information about the past configuration of the West Antarctic Ice Sheet and its retreat during the most recent deglaciation. In this work, we present the RICE17 chronology and discuss preliminary observations from the new records of methane, the isotopic composition of atmospheric molecular oxygen (δ18O-Oatm), the isotopic composition of atmospheric molecular nitrogen (δ15N-N2) and total air content (TAC). RICE17 is a composite chronology combining annual layer interpretations, gas synchronization, and firn modeling strategies in different sections of the core. An automated matching algorithm is developed for synchronizing the high-resolution section of the RICE gas records (60–720 m, 1971 CE to 30 ka) to corresponding records from the WAIS Divide ice core, while deeper sections are manually matched. Ice age for the top 343 m (2635 yr BP, before 1950 C.E.) is derived from annual layer interpretations and described in the accompanying paper by Winstrup et al. (2017). For deeper sections, the RICE17 ice age scale is based on the gas age constraints and the ice age-gas age offset estimated by a firn densification model. Novel aspects of this work include: 1) stratigraphic matching of centennial-scale variations in methane for pre-anthropogenic time periods, a strategy which will be applicable for developing precise chronologies for future ice cores, 2) the observation of centennial-scale variability in methane throughout the Holocene which suggests that similar variations during the late preindustrial period need not be anthropogenic, and 3) the observation of continuous climate records dating back to ∼ 65 ka which provide evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.
Published: 2020

26. Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period

Author: Joseph R. McConnell, Amaelle Landais, Emilie Capron, Christo Buizert, Robert Mulvaney, Mirko Severi, Thomas Blunier, Michael Sigl, Raimund Muscheler, Frank Wilhelms, Jørgen Peder Steffensen, Florian Adolphi, Tobias Erhardt, Sepp Kipfstuhl, Anders Svensson, Dorthe Dahl-Jensen, Helle Astrid Kjær, Vasileios Gkinis, Bo Møllesøe Vinther, Frédéric Parrenin, Matthias Bigler, Hubertus Fischer, Thomas F. Stocker, Sune Olander Rasmussen, Paul Vallelonga, Eliza Cook, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )
Subjects: 010504 meteorology & atmospheric sciences, 530 Physics, δ18O, lcsh:Environmental protection, Stratigraphy, Lag, 010501 environmental sciences, 01 natural sciences, 03 medical and health sciences, lcsh:Environmental pollution, Ice core, lcsh:TD169-171.8, Glacial period, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, Tephra, lcsh:Environmental sciences, 030304 developmental biology, 0105 earth and related environmental sciences, lcsh:GE1-350, 0303 health sciences, Global and Planetary Change, geography, geography.geographical_feature_category, Palaeontology, Paleontology, Volcano, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Climatology, lcsh:TD172-193.5, Abrupt climate change, Geology, Teleconnection
Abstract: The last glacial period is characterized by a number of millennial climate events that have been identified in both Greenland and Antarctic ice cores and that are abrupt in Greenland climate records. The mechanisms governing this climate variability remain a puzzle that requires a precise synchronization of ice cores from the two hemispheres to be resolved. Previously, Greenland and Antarctic ice cores have been synchronized primarily via their common records of gas concentrations or isotopes from the trapped air and via cosmogenic isotopes measured on the ice. In this work, we apply ice core volcanic proxies and annual layer counting to identify large volcanic eruptions that have left a signature in both Greenland and Antarctica. Generally, no tephra is associated with those eruptions in the ice cores, so the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. Using this approach, we pinpoint 82 large bipolar volcanic eruptions throughout the second half of the last glacial period (12–60 ka). This improved ice core synchronization is applied to determine the bipolar phasing of abrupt climate change events at decadal-scale precision. In response to Greenland abrupt climatic transitions, we find a response in the Antarctic water isotope signals (δ18O and deuterium excess) that is both more immediate and more abrupt than that found with previous gas-based interpolar synchronizations, providing additional support for our volcanic framework. On average, the Antarctic bipolar seesaw climate response lags the midpoint of Greenland abrupt δ18O transitions by 122±24 years. The time difference between Antarctic signals in deuterium excess and δ18O, which likewise informs the time needed to propagate the signal as described by the theory of the bipolar seesaw but is less sensitive to synchronization errors, suggests an Antarctic δ18O lag behind Greenland of 152±37 years. These estimates are shorter than the 200 years suggested by earlier gas-based synchronizations. As before, we find variations in the timing and duration between the response at different sites and for different events suggesting an interaction of oceanic and atmospheric teleconnection patterns as well as internal climate variability.
Published: 2020

27. Atmospheric Nitrous Oxide Variations on Centennial Time Scales During the Past Two Millennia

Author: Thomas Blunier, Soon-Do Hur, Jinho Ahn, Axel Timmermann, Edward J. Brook, Yeongjun Ryu, Ji-Woong Yang, Seong-Joong Kim, Seoul National University [Seoul] (SNU), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Oregon State University (OSU), Institute for Basic Science (IBS), Pusan National University, IT University of Copenhagen (ITU), Korea Polar Research Institute (KOPRI), Korea Basic Science Institute, KBSI: IBS-R028-D1 National Research Foundation of Korea, NRF: NRF-2018R1A2B3003256, We thank Soonil An and Seok-Woo Son for valuable comments. Financial support was provided by the Basic Science Research Program through the National Research Foundation of Korea (NRF) (NRF-2018R1A2B3003256). A.?T. was supported by the Institute for Basic Science (Project Code IBS-R028-D1)., Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and IT University of Copenhagen
Subjects: 0106 biological sciences, Atmospheric Science, 010504 meteorology & atmospheric sciences, N2O EMISSIONS, Subtropics, 01 natural sciences, Proxy (climate), STYX GLACIER, Ice core, Paleoclimatology, Ozone layer, paleoclimate, HOLOCENE, Environmental Chemistry, 0105 earth and related environmental sciences, General Environmental Science, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, Eemian, geography, geography.geographical_feature_category, nitrous oxide, 010604 marine biology & hydrobiology, Global warming, Glacier, ASIAN SOUTHWEST MONSOON, NORTHERN-HEMISPHERE, SUMMER MONSOON, CLIMATE, VARIABILITY, 13. Climate action, Climatology, GREENLAND ICE CORE, VICTORIA LAND, Environmental science, ice core
Abstract: The continuous growth of atmospheric nitrous oxide (N2O) is of concern for its potential role in global warming and future stratospheric ozone destruction. Climate feedbacks that enhance N2O emissions in response to global warming are not well understood, and past records of N2O from ice cores are not sufficiently well resolved to examine the underlying climate-N2O feedbacks on societally relevant time scales. Here, we present a new high-resolution and high-precision N2O reconstruction obtained from the Greenland NEEM (North Greenland Eemian Ice Drilling) and the Antarctic Styx Glacier ice cores. Covering the N2O history of the past two millennia, our reconstruction shows a centennial-scale variability of similar to 10 ppb. A pronounced minimum at similar to 600 CE coincides with the reorganizations of tropical hydroclimate and ocean productivity changes. Comparisons with proxy records suggest association of centennial- to millennial-scale variations in N2O with changes in tropical and subtropical land hydrology and marine productivity.Plain Language Summary Nitrous oxide (N2O) is a greenhouse and ozone-depleting gas. The growing level of N2O in the atmosphere is of global concern, and records of past N2O variations can provide an important context for understanding the links between N2O and climate change. In this study, we report new, high-quality N2O records covering the last two millennia using ice cores obtained from Greenland and Antarctica. Our N2O records show rapid centennial-scale changes in atmospheric N2O and confirm a pronounced minimum near 600 CE. Comparison with climate records suggests that hydroclimate change on land and changes in marine productivity contribute to centennial- to millennial-scale N2O variations.
Published: 2020

28. Antarctic Sea Ice Proxies from Marine and Ice Core Archives Suitable for Reconstructing Sea Ice over the past 2000 Years

Author: Amy C. F. King, Victoria L Peck, Elizabeth R. Thomas, Juliane Mueller, Claire S. Allen, Johan Etourneau, Mirko Severi, Xavier Crosta, V. Holly L. Winton, British Antarctic Survey (BAS), Natural Environment Research Council (NERC), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Chimica 'Ugo Schiff', University of Florence, Alfred Wegener Institute [Potsdam], Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), and EPOC - CNRS, UMR 5805
Subjects: 010504 meteorology & atmospheric sciences, ice cores, Antarctic sea ice, 010502 geochemistry & geophysics, 01 natural sciences, Ice core, Paleoclimatology, paleoclimate, Sea ice, 14. Life underwater, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, sea ice, Current (stream), Indian ocean, Oceanography, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, General Earth and Planetary Sciences, Antarctica, Climate model, Sedimentary rock, marine sediments, Geology
Abstract: International audience; Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate archives, from marine sedimentary records and coastal Antarctic ice cores, provide a means of understanding sea ice variability and its drivers over decadal to centennial timescales. In this study, we collate published records of Antarctic sea ice over the past 2000 years (2 ka). We evaluate the current proxies and explore the potential of combining marine and ice core records to produce multi-archive reconstructions. Despite identifying 92 sea ice reconstructions, the spatial and temporal resolution is only sufficient to reconstruct circum-Antarctic sea ice during the 20th century, not the full 2 ka. Our synthesis reveals a 90 year trend of increasing sea ice in the Ross Sea and declining sea ice in the Bellingshausen, comparable with observed trends since 1979. Reconstructions in the Weddell Sea, the Western Pacific and the Indian Ocean reveal small negative trends in sea ice during the 20th century (1900-1990), in contrast to the observed sea ice expansion in these regions since 1979.
Published: 2019

29. Glacial-interglacial dust and export production records from the Southern Indian Ocean

Author: H. Eri Amsler, Alexandra Auderset, Simone Moretti, Samuel L Jaccard, James Gilgannon, Xavier Crosta, Lena M Thöle, Elisabeth Michel, Alfredo Martínez-García, Alain Mazaud, Joerg Lippold, Hendrik Vogel, Oeschger Centre for Climate Change Research (OCCR), University of Bern, Helmholtz Zentrum für Umweltforschung = Helmholtz Centre for Environmental Research (UFZ), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Climat et Magnétisme (CLIMAG), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Paléocéanographie (PALEOCEAN), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Marine isotope stage, Polar front, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 010504 meteorology & atmospheric sciences, Iron fertilization, 010502 geochemistry & geophysics, 01 natural sciences, Geophysics, Oceanography, Ice core, 13. Climate action, Space and Planetary Science, Geochemistry and Petrology, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Interglacial, Earth and Planetary Sciences (miscellaneous), Ice age, Upwelling, 14. Life underwater, Glacial period, Geology, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences
Abstract: We present 230Th-normalized dust and export production fluxes for two contrasted marine sediment cores spanning the Antarctic Polar Front, close to the Kerguelen Plateau in the Southern Indian Ocean, covering the last glacial cycle. We report glacial lithogenic fluxes comparable to the South Atlantic and higher than in the South Pacific sectors of the Southern Ocean. Structural and temporal discrepancies with dust reconstructions from Antarctic ice cores and the Atlantic and Pacific sectors of the Subantarctic Zone (SAZ) point towards Southern Africa and/or the Kerguelen Plateau as an additional source of lithogenic material to the Southern Indian Ocean during the last ice age. In the SAZ, export production proxies respond to iron (Fe) fertilization with total organic carbon (TOC) fluxes as high as those previously reported from the Atlantic sector of the Southern Ocean. However, the correlation between export production and dust proxies is weaker than in the other sectors, and shows a muted response of export production during peak glacials. We hypothesize that this muted response may be related to macronutrient (co-)limitation imposed on phytoplankton growth possibly induced by a northward displacement of wind-driven upwelling and/or the polar frontal system during peak glacials. The Antarctic Zone (AZ) record depicts the typical pattern of enhanced export production during interglacials and comparatively low productivity during glacials suggesting a decrease in the supply of macronutrients to the AZ surface during ice ages compared to warm periods, as previously proposed. However, a muted response of opal fluxes during marine isotope stage (MIS) 5e argues for a southward migration of the frontal system during warmer MIS 5e, possibly causing silicic acid (co-)limitation at this site. These results illustrate the important role of Fe fertilization and changes in wind-driven upwelling intensities in modulating the strength and efficiency of the biological carbon pump in the Southern Ocean, but also highlight the potential role of frontal movements in explaining export production variability at sites located close to the Antarctic Circumpolar Current (ACC) fronts. Overall, our new datasets provide new insights on the regional differences in dust and export production patterns that need to be considered in order to evaluate the efficiency of carbon sequestration in the different sectors of the Southern Ocean during ice ages.
Published: 2019

30. Variations climatiques et variations du cycle hydrologique aux basses latitudes au cours du Quaternaire : une approche combinant modèle et données

Author: Extier, Thomas, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Paris Saclay (COmUE), Amaëlle Landais, Didier Roche, and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Isotopic composition of atmospheric oxygen, Cycle hydrologique des basses latitudes, Chronologie, Climate modeling, Low latitude hydrological cycle, Composition isotopique de l'oxygène de l'air, Ice core, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Carotte de glace, Modélisation du climat, Chronology
Abstract: Quaternary glacial-interglacial cycles are recorded in various climatic archives from high to low latitudes. The EPICA Dome C ice core provides a high-resolution record over the last 800 ka of δ18Oatm (i.e. δ18O of atmospheric O2) which combines past variations of the low latitude water cycle and of the biosphere productivity. In absence of annual layer counting, this proxy can be used for orbital dating in association with the June 21st insolation at 65°N to build an ice core chronology. However a lag of 6 ka between the δ18Oatm and the insolation, classically observed during glacial-interglacial terminations, is applied to the entire record during the chronology construction. This lag and the complexity of the δ18Oatm signal are the main reasons why the ice core chronology presents a high 6 ka uncertainty which limits their interpretation, jointly with other paleoclimate archives, in terms of past climate and environmental variations. To solve this issue I have developed a new ice core chronology based on the relation between the δ18Oatm and the δ18Ocalcite of east-asian speleothems, using new isotope measurements allowing for the first time a complete record over the last 800 ka at Dome C. This new chronology reduces the uncertainties compared to the actual ice core chronology strongly based on δ18Oatm and shows a better sequence of events between the high and low latitudes records. Then, I have developed a model to reproduce the isotopic composition of atmospheric O2 to address the lack of quantitative interpretations of this proxy and to check our assumption of synchronicity with the δ18Ocalcite over several climatic cycles. To reproduce the variations of the δ18Oatm, it was necessary to couple the intermediate complexity climate model iLOVECLIM and the vegetation model CARAIB. Finally, the δ18Oatm variations simulated with the new coupled model over several thousand years are in phase with the insolation of the Northern hemisphere (except during Heinrich events) and with low latitudes δ18Ocalcite variations. This can be explained by changes in the low latitude water cycle related to changes in the isotopic composition of meteoric water used by the terrestrial biosphere during photosynthesis.; Le climat du Quaternaire est défini par une succession de périodes glaciaires et interglaciaires enregistrées dans les archives climatiques à différentes latitudes. La carotte de glace d’EPICA Dome C fournit un enregistrement haute résolution sur les derniers 800 ka du δ18Oatm (i.e. δ18O de la molécule d’oxygène de l’air) qui combine les variations passées du cycle hydrologique des basses latitudes et de la productivité de la biosphère. En l’absence du comptage des couches annuelles, ce proxy peut être utilisé comme méthode de datation orbitale des carottes de glace, en lien avec l’insolation au 21 juin à 65°N. Cependant, un décalage de 6 ka entre le δ18Oatm et l’insolation, généralement observé lors des terminaisons glaciaires-interglaciaires, est appliqué sur l’ensemble de l’enregistrement lors de la construction de l’échelle d’âge. Ce décalage et la complexité du signal du δ18Oatm expliquent l’incertitude élevée de 6 ka des carottes de glace, ce qui limite leur interprétation en termes de variations climatiques et environnementales conjointement à d’autres archives. J’ai donc développé une nouvelle chronologie pour les carottes de glace, basée sur le lien entre le δ18Oatm et le δ18Ocalcite des spéléothèmes est-asiatiques, à partir de nouvelles mesures isotopiques permettant d’avoir pour la première fois un enregistrement complet sur les derniers 800 ka à Dome C. Cette nouvelle chronologie permet de réduire les incertitudes par rapport à la chronologie actuelle et d’avoir une meilleure séquence des évènements entre les hautes et basses latitudes. J’ai ensuite développé un modèle simulant la composition isotopique de l’oxygène atmosphérique afin de répondre au manque d’interprétations quantitatives de ce proxy ainsi que pour vérifier son lien avec le δ18Ocalcite sur plusieurs cycles climatiques. Pour modéliser le δ18Oatm nous avons dû coupler le modèle climatique de complexité intermédiaire iLOVECLIM avec le modèle de végétation CARAIB. Le δ18Oatm simulé par le modèle couplé sur plusieurs dizaines de milliers d’années confirme que ses variations sont en phase avec celles de l’insolation de l’hémisphère Nord (hormis lors d’évènements de Heinrich) et avec celles du δ18Ocalcite via des modifications du cycle hydrologique des basses latitudes, impactant la composition isotopique de l’eau de pluie utilisée par la biosphère terrestre lors de la photosynthèse.
Published: 2019

31. Climate and low latitude water cycle variations during the Quaternary : a model-data approach

Author: Extier, Thomas, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Paris Saclay (COmUE), Amaëlle Landais, and Didier Roche
Subjects: Isotopic composition of atmospheric oxygen, Cycle hydrologique des basses latitudes, Chronologie, Climate modeling, Low latitude hydrological cycle, Composition isotopique de l'oxygène de l'air, Ice core, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Carotte de glace, Modélisation du climat, Chronology
Abstract: Quaternary glacial-interglacial cycles are recorded in various climatic archives from high to low latitudes. The EPICA Dome C ice core provides a high-resolution record over the last 800 ka of δ18Oatm (i.e. δ18O of atmospheric O2) which combines past variations of the low latitude water cycle and of the biosphere productivity. In absence of annual layer counting, this proxy can be used for orbital dating in association with the June 21st insolation at 65°N to build an ice core chronology. However a lag of 6 ka between the δ18Oatm and the insolation, classically observed during glacial-interglacial terminations, is applied to the entire record during the chronology construction. This lag and the complexity of the δ18Oatm signal are the main reasons why the ice core chronology presents a high 6 ka uncertainty which limits their interpretation, jointly with other paleoclimate archives, in terms of past climate and environmental variations. To solve this issue I have developed a new ice core chronology based on the relation between the δ18Oatm and the δ18Ocalcite of east-asian speleothems, using new isotope measurements allowing for the first time a complete record over the last 800 ka at Dome C. This new chronology reduces the uncertainties compared to the actual ice core chronology strongly based on δ18Oatm and shows a better sequence of events between the high and low latitudes records. Then, I have developed a model to reproduce the isotopic composition of atmospheric O2 to address the lack of quantitative interpretations of this proxy and to check our assumption of synchronicity with the δ18Ocalcite over several climatic cycles. To reproduce the variations of the δ18Oatm, it was necessary to couple the intermediate complexity climate model iLOVECLIM and the vegetation model CARAIB. Finally, the δ18Oatm variations simulated with the new coupled model over several thousand years are in phase with the insolation of the Northern hemisphere (except during Heinrich events) and with low latitudes δ18Ocalcite variations. This can be explained by changes in the low latitude water cycle related to changes in the isotopic composition of meteoric water used by the terrestrial biosphere during photosynthesis.; Le climat du Quaternaire est défini par une succession de périodes glaciaires et interglaciaires enregistrées dans les archives climatiques à différentes latitudes. La carotte de glace d’EPICA Dome C fournit un enregistrement haute résolution sur les derniers 800 ka du δ18Oatm (i.e. δ18O de la molécule d’oxygène de l’air) qui combine les variations passées du cycle hydrologique des basses latitudes et de la productivité de la biosphère. En l’absence du comptage des couches annuelles, ce proxy peut être utilisé comme méthode de datation orbitale des carottes de glace, en lien avec l’insolation au 21 juin à 65°N. Cependant, un décalage de 6 ka entre le δ18Oatm et l’insolation, généralement observé lors des terminaisons glaciaires-interglaciaires, est appliqué sur l’ensemble de l’enregistrement lors de la construction de l’échelle d’âge. Ce décalage et la complexité du signal du δ18Oatm expliquent l’incertitude élevée de 6 ka des carottes de glace, ce qui limite leur interprétation en termes de variations climatiques et environnementales conjointement à d’autres archives. J’ai donc développé une nouvelle chronologie pour les carottes de glace, basée sur le lien entre le δ18Oatm et le δ18Ocalcite des spéléothèmes est-asiatiques, à partir de nouvelles mesures isotopiques permettant d’avoir pour la première fois un enregistrement complet sur les derniers 800 ka à Dome C. Cette nouvelle chronologie permet de réduire les incertitudes par rapport à la chronologie actuelle et d’avoir une meilleure séquence des évènements entre les hautes et basses latitudes. J’ai ensuite développé un modèle simulant la composition isotopique de l’oxygène atmosphérique afin de répondre au manque d’interprétations quantitatives de ce proxy ainsi que pour vérifier son lien avec le δ18Ocalcite sur plusieurs cycles climatiques. Pour modéliser le δ18Oatm nous avons dû coupler le modèle climatique de complexité intermédiaire iLOVECLIM avec le modèle de végétation CARAIB. Le δ18Oatm simulé par le modèle couplé sur plusieurs dizaines de milliers d’années confirme que ses variations sont en phase avec celles de l’insolation de l’hémisphère Nord (hormis lors d’évènements de Heinrich) et avec celles du δ18Ocalcite via des modifications du cycle hydrologique des basses latitudes, impactant la composition isotopique de l’eau de pluie utilisée par la biosphère terrestre lors de la photosynthèse.
Published: 2019

32. An application of hierarchical Bayesian modeling to better constrain the chronologies of Upper Paleolithic archaeological cultures in France between ca. 32,000–21,000 calibrated years before present

Author: Laurent Klaric, Caroline Renard, Pascal Bertran, Miriam Mesa, Philippe Lanos, William E. Banks, Sylvain Ducasse, De la Préhistoire à l'Actuel : Culture, Environnement et Anthropologie (PACEA), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), Institut national de recherches archéologiques préventives (Inrap), Université de Bordeaux (UB), Préhistoire et Technologie (PréTech), Université Paris Nanterre (UPN)-Centre National de la Recherche Scientifique (CNRS), IRAMAT-Centre de recherche en physique appliquée à l’archéologie (IRAMAT-CRP2A), Institut de Recherches sur les Archéomatériaux (IRAMAT), Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Montaigne-Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université Bordeaux Montaigne-Université de Technologie de Belfort-Montbeliard (UTBM), Géosciences Rennes (GR), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Travaux et recherches archéologiques sur les cultures, les espaces et les sociétés (TRACES), École des hautes études en sciences sociales (EHESS)-Université Toulouse - Jean Jaurès (UT2J)-Ministère de la Culture et de la Communication (MCC)-Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux, ANR-10-LABX-52, LabEx Cluster of Excellence 'LaScArBx', Centre National de la Recherche Scientifique (CNRS)-Université Paris Nanterre (UPN), Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne-Centre National de la Recherche Scientifique (CNRS)-Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Ministère de la Culture et de la Communication (MCC)-École des hautes études en sciences sociales (EHESS)-Université Toulouse - Jean Jaurès (UT2J)-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0052,LaScArBx,Using the world in ancient societies : processes and forms of appropriation of space in Long Time(2010), Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne (UBM)-Centre National de la Recherche Scientifique (CNRS)-Université de Technologie de Belfort-Montbeliard (UTBM)-Université d'Orléans (UO)-Université Bordeaux Montaigne (UBM)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), École des hautes études en sciences sociales (EHESS)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Ministère de la Culture et de la Communication (MCC)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université de Rennes 2 (UR2), and Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010506 paleontology, Archeology, Hierarchical Bayesian Age-modeling, 010504 meteorology & atmospheric sciences, Pleistocene, [SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, Archaeological record, Data analysis, 01 natural sciences, law.invention, Ice core, law, Hierarchical Bayesian Age- Modeling, Radiocarbon dating, Archaeological culture, Paleoclimatology, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Chronology, Global and Planetary Change, Geology, Archaeology, Europe, Upper Paleolithic, Radiometric dating
Abstract: International audience; Investigations of chronology play a key role in the majority of archaeological research endeavors and are particularly pertinent to examinations of culture-environment relationships, especially during periods characterized by rapid and marked climatic variability and environmental reorganization. Rigorous evaluations of available data and robust methods are required if one wishes to reconstruct reliable chronologies, and this is especially the case when examining periods that are associated with a relatively few radiometric measurements. Such is the case for the Upper Paleolithic archaeological record documented in present-day France from 32,000 to 21,000 calibrated years BP. We take into account critically examined radiocarbon measurements from contextually secure archaeological contexts and employ a recently-developed method of Hierarchical Bayesian Modeling to reconstruct the chronology of archaeological cultures from the Middle Gravettian to the Badegoulian. The calculated chronological intervals for each typo-technologically defined culture phase are compared to the Greenland ice core climatic record and a terrestrial paleoenvironmental record from Bergsee Lake (Southern Germany)—itself expressed in calendar years calculated with the same calibration curve employed in our age model—thereby permitting each archaeological culture to be correlated accurately with documented paleoclimatic variability.
Published: 2019

33. Holocene dust in East Antarctica: Provenance and variability in time and space

Author: Delmonte B.[1], Winton H.[2, Baroni M.[4], Baccolo G.[1], Hansson M.[5], Andersson P.[6], Baroni C.[7, Salvatore M.C.[7, Lanci L.[9], Maggi V.[1], Dipartimento di Scienze dell'Ambiente e del Territorio (DISAT), Università degli studi di Milano [Milano], Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Department of Physical Geography and Quaternary Geology, Stockholm University, Swedish Museum of Natural History (NRM), Università degli Studi di Milano [Milano] (UNIMI), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), SYNTHESYS project [SE-TAF-5636], 'Friends of the Museum' Grant, Franco-Italian project SOLARICE [IPEV1145, PNRA16_00008], Università degli Studi di Milano = University of Milan (UNIMI), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Delmonte, B, Winton, H, Baroni, M, Baccolo, G, Hansson, M, Andersson, P, Baroni, C, Salvatore, M, Lanci, L, and Maggi, V
Subjects: Archeology, Provenance, 010504 meteorology & atmospheric sciences, ice cores, provenance, Flux, 010502 geochemistry & geophysics, 01 natural sciences, dust stratigraphy, Ice core, Holocene, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, dust, East Antarctica, Ecology, Spacetime, Paleontology, East antarctica, Physical geography, ice core, Geology
Abstract: International audience; In this paper, we provide a comprehensive overview of the state-of-knowledge of dust flux and variability in time and space in different sectors of East Antarctica during the Holocene. By integrating the literature data with new evidences, we discuss the dust flux and grain-size variability during the current interglacial and its provenance in the innermost part of the East Antarctic plateau as well as in peripheral regions located close to the Transantarctic Mountains. The local importance of aeolian mineral dust aerosol deflated from low-elevation areas of peripheral East Antarctica is also discussed in the light of new data from several coastal, low-elevation sites.
Published: 2019

34. A comparison of 36 Cl nuclear bomb inputs deposited in snow from Vostok and Talos Dome, Antarctica, using the 36 Cl/Cl ‐ ratio

Author: Mélanie Baroni, Edouard Bard, Xavier Giraud, S. Pivot, Chaire Evolution du climat et de l'océan, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Collège de France - Chaire Evolution du climat et de l'océan, and Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Atmospheric Science, 010504 meteorology & atmospheric sciences, biology, Geochemistry, 010501 environmental sciences, Nuclear weapon, biology.organism_classification, Snow, 01 natural sciences, Dome (geology), Geophysics, Ice core, Space and Planetary Science, Talos, Earth and Planetary Sciences (miscellaneous), Environmental science, Cosmogenic nuclide, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: International audience
Published: 2019

35. Construction of a tephra-based multi-archive coherent chronological framework for the last deglaciation in the Mediterranean region

Author: Amaelle Landais, Giuseppe Siani, Elisabeth Michel, Sébastien Nomade, Aline Govin, Dominique Genty, Lucie Bazin, Bénédicte Lemieux-Dudon, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Centro Euro-Mediterranea sui Cambiamenti Climatici, Bologna BO, Italy, Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Climat et Magnétisme (CLIMAG), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), and Paléocéanographie (PALEOCEAN)
Subjects: Mediterranean climate, 010506 paleontology, Archeology, Global and Planetary Change, 010504 meteorology & atmospheric sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Geology, 01 natural sciences, Proxy (climate), Ice core, 13. Climate action, [SDU]Sciences of the Universe [physics], Paleoclimatology, Deglaciation, Climate model, Physical geography, Tephra, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Chronology
Abstract: International audience; Proxy records from different climate archives such as ice cores, speleothems or sediment cores are essential to define the sequence of events over to the last deglaciation. However, multi-archive comparison and compilation of data, necessary to assess the robustness of climate models, are rapidly limited by inconsistencies between archives' chronology. Here we present the development and validation of the Datice chronological integration tool for the construction of multi-archive coherent chronologies. This chronology building tool, first developed to date ice cores only, can now integrate deposition-like archives such as sediment cores and speleothems, independently or coherently. The robustness of this dating method resides in its capacity to build coherent chronologies for multiple archives with a proper calculation of chronological uncertainties. Using this tool, we were able to construct a coherent chronology for the last deglaciation in the Mediterranean region based on volcanic tephra layers correlation in terrestrial and marine sediment cores. We confirm the synchronicity, within chronological errors, of the sequence of events characterizing the last deglaciation between Greenland and the Mediterranean region, independently of any climatic alignment assumptions. Using this chronological framework, we however highlight some regional expression of this transition period in term of vegetation cover over the Mediterranean region.
Published: 2019

36. Unveiling the anatomy of Termination 3 using water and air isotopes in the Dome C ice core, East Antarctica

Author: Barbara Stenni, Markus Leuenberger, Anais Orsi, Frédéric Prié, Thomas Extier, Jean Jouzel, Amaelle Landais, Camille Bréant, Patricia Martinerie, Valérie Masson-Delmotte, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Scienze Geologiche [Trieste], Università degli studi di Trieste, Climate and Environmental Physics [Bern] (CEP), Physikalisches Institut [Bern], Universität Bern [Bern]-Universität Bern [Bern], Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Università degli studi di Trieste = University of Trieste, and Universität Bern [Bern] (UNIBE)-Universität Bern [Bern] (UNIBE)
Subjects: 010506 paleontology, Archeology, 010504 meteorology & atmospheric sciences, δ18O, Ice core, Context (language use), 01 natural sciences, Latitude, Antarctic temperature, Deglaciation, Bipolar seesaw, Deglaciations, Water and air isotopes, Glacial period, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, Termination 3, Heinrich like events, Northern Hemisphere, Geology, Settore GEO/08 - Geochimica e Vulcanologia, 13. Climate action, [SDU]Sciences of the Universe [physics], Climatology, Interglacial, Firn densification model
Abstract: Each glacial – interglacial transition of the Quaternary occurs in a different orbital context leading to various timing for the deglaciation and sequence of high vs low latitudes events. Termination 3, 250 kyears before present (ka), is an unusual deglaciation in the context of the last 9 deglaciations recorded in the old EPICA Dome C (EDC) Antarctic ice core: it exhibits a three-phase sequence, two warming phases separated by a small cooling, the last phase suggesting a particularly rapid temperature increase. We present here new high resolution δ15N and deuterium excess (d-excess) data from the EDC ice core to provide a detailed temperature change estimate during this termination. Then, we combined the δD and δ18O to discuss the relationship between high and low latitude changes through the d-excess. We also provide the high vs low latitude sequence of events over this deglaciation without chronological uncertainty using low latitude ice core proxies. In agreement with previous studies based on speleothem analyses, we show that the first phase of Termination 3 (256–249 ka) is associated with small Heinrich like events linked to changes in ITCZ position, monsoon activity and teleconnections with Antarctica. In a context of minimum Northern Hemisphere insolation, this leads to a rather strong Antarctic warming, as observed in the δ15N record in contrast to the relatively small δD increase. The second warming phase occurs during the rise of the Northern hemisphere insolation, with a large Heinrich like event leading to the characteristic Antarctic warming observed in the δ15N and δD increase as for the more recent terminations.
Published: 2019

37. 40Ar/39Ar dating of the Thorsmork ignimbrite and Icelandic sub-glacial rhyolites

Author: Brigitte Van Vliet-Lanoë, Vincent Scao, Sébastien Nomade, Hervé Guillou, Agust Guðmundsson, Céline Liorzou, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Paléocéanographie (PALEOCEAN), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), JFS Geological Services, Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 010506 paleontology, Archeology, Global and Planetary Change, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Geochemistry, Sediment, Geology, Volcanism, 01 natural sciences, Ice core, Volcano, 13. Climate action, Rhyolite, Geochronology, Glacial period, Tephra, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: Robust correlation of paleoclimatic archives (e.g. marine sediments, ice, speleothems) necessitates an increase of the number of independent and accurately dated stratigraphic markers using numerical methods. Icelandic rhyolitic volcanism has a strong chronological interest because these products are found as tephra in the North Atlantic marine archives as well as in Greenland ice cores. In this study, we have dated, using the 40Ar/39Ar method, subglacial rhyolites of the Tindfjallajokull, Kerlingarfjoll and Torfajokull volcanoes which are the main sources of rhyolitic tephra identified in marine and glaciological records. The Thorsmork ignimbrite (Tindfjallajokull) which correlates with the rhyolitic component (II-RHY-1) of the North Atlantic Ash Zone II (NAAZ II) layer is dated at 55.6 ± 2.4 ka, an age that agrees with the ones given by the ice core chronologies (GICC05: 55.4 ± 1.2 ka). The eruptions of Rauðfossafjoll and Fannborg are respectively dated at 77.0 ± 3.0 ka and 149.3 ± 3.4 ka. These new ages along with the published ones confirm, as already concluded by Flude et al. (2010) that there is no clear evidence, at least at the latitude of Iceland, that climate warming is the main mechanism that triggered rhyolitic eruptions. Combining major and trace element compositions with our new age determinations, it appears that the Rauðfossafjoll and the Snaefell rhyolitic eruptions have not yet been discovered in marine sediment cores. Nevertheless, given the accuracy and precision of our dating, these rhyolitic eruptions have the potential to become chronostratigraphic markers, once tephra shards corresponding to these eruptions are discovered in ice and or marine sediment records. The Fannborg eruption might be recorded in the marine core LINK 16 during MIS 6 prior to the transition to MIS5e.
Published: 2019

38. Multiple sources for tephra from AD 1259 volcanic signal in Antarctic ice cores

Author: Biancamaria Narcisi, Joel Savarino, Barbara Delmonte, V. G. Batanova, Jean-Robert Petit, Italian National agency for new technologies, Energy and sustainable economic development [Frascati] (ENEA), Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Dipartimento di Scienze dell'Ambiente e del Territorio (DISAT), Università degli Studi di Milano [Milano] (UNIMI), Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Narcisi, B, Petit, J, Delmonte, B, Batanova, V, Savarino, J, CLIPS, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Università degli studi di Milano [Milano], Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Université Grenoble Alpes (UGA), Narcisi, B., Petit, J. R., Delmonte, B., Batanova, V., Savarino, J., and Università degli Studi di Milano = University of Milan (UNIMI)
Subjects: Volcanic isochron, Archeology, 010504 meteorology & atmospheric sciences, Ice core, 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, Tephra, Samalas AD 1257 eruption, ComputingMilieux_MISCELLANEOUS, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Ice cores, tephra, cryptotephra, Antarctica, volcanic isochron, Samalas AD 1257 eruption, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, geography, geography.geographical_feature_category, Vulcanian eruption, Cryptotephra, Glass shard microanalysis, Geology, Volcanic glass, Spatial heterogeneity, Volcano, 13. Climate action, Ice cores, Antarctica, Polar, Glass shard microanalysi, Ice sheet, Antarctic rifting volcanism
Abstract: Strong volcanic signals simultaneously recorded in polar ice sheets are commonly assigned to major low-latitude eruptions that dispersed large quantities of aerosols in the global atmosphere with the potential of inducing climate perturbations. Parent eruptions responsible for specific events are typically deduced from matching to a known volcanic eruption having coincidental date. However, more robust source linkage can be achieved only through geochemical characterisation of the airborne volcanic glass products (tephra) sometimes preserved in the polar strata. We analysed fine-grained tephra particles extracted from layers of the AD 1259 major bipolar volcanic signal in four East Antarctic ice cores drilled in different widely-spaced locations on the Antarctic Plateau. The very large database of glass-shard geochemistry combined with grain size analyses consistently indicate that the material was sourced from multiple distinct eruptions. These are the AD 1257 mega-eruption of Samalas volcano in Indonesia, recently proposed to be the single event responsible for the polar signal, as well as a newly-identified Antarctic eruption, which occurred in northern Victoria Land in AD 1259. Finally, a further eruption that took place somewhere outside of Antarctica has also contributed to tephra deposition. Our high-resolution, multiple-site approach was critical for revealing spatial heterogeneity of tephra at the continental scale. Evidence from ice-core tephra indicates recurrent explosive activity at the Antarctic volcanoes and could have implications for improved reconstruction of post-volcanic effects on climate from proxy polar records.
Published: 2019

39. Multiradionuclide evidence for an extreme solar proton event around 2,610 B.P. (∼660 BC)

Author: Marcus Christl, Edouard Bard, Ala Aldahan, Paschal O’Hare, Hans-Arno Synal, John R. Southon, Jürg Beer, Grant M. Raisbeck, Raimund Muscheler, Florian Mekhaldi, Junghun Park, Emma Anderberg, Simon Fahrni, Florian Adolphi, Göran Possnert, Department of Geology [Lund], Lund University [Lund], Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Swiss Federal Insitute of Aquatic Science and Technology [Dübendorf] (EAWAG), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology in Zürich [Zürich] (ETH Zürich), Laboratory of Ion Beam Physics, Angström Laboratory, Uppsala University, Department of Earth System Science [Irvine] (ESS), University of California [Irvine] (UCI), University of California-University of California, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), University of California [Irvine] (UC Irvine), University of California (UC)-University of California (UC), Collège de France - Chaire Evolution du climat et de l'océan, Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Chaire Evolution du climat et de l'océan
Subjects: Solar proton, Radionuclide, Multidisciplinary, 010504 meteorology & atmospheric sciences, Conjunction (astronomy), Event (relativity), Lead (sea ice), solar storms, ice cores, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Atmospheric sciences, 01 natural sciences, solar proton events, Earth, Atmospheric, and Planetary Sciences, Ice core, 13. Climate action, Physical Sciences, 0103 physical sciences, Energy spectrum, Environmental science, 010303 astronomy & astrophysics, radionuclides, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Production rate
Abstract: Significance This study provides evidence of an enormous solar storm around 2,610 B.P. It is only the third such event reliably documented and is comparable with the strongest event detected at AD 774/775. The event of 2,610 years B.P. stands out because of its particular signature in the radionuclide data [i.e., carbon-14 (14C) data alone does not allow for an unequivocal detection of the event]. It illustrates that present efforts to find such events based solely on 14C data likely lead to an underestimated number of such potentially devastating events for our society. In addition to 14C data, high-resolution records of beryllium-10 and chlorine-36 are crucial for reliable estimates of the occurrence rate and the properties of past solar proton events., Recently, it has been confirmed that extreme solar proton events can lead to significantly increased atmospheric production rates of cosmogenic radionuclides. Evidence of such events is recorded in annually resolved natural archives, such as tree rings [carbon-14 (14C)] and ice cores [beryllium-10 (10Be), chlorine-36 (36Cl)]. Here, we show evidence for an extreme solar event around 2,610 years B.P. (∼660 BC) based on high-resolution 10Be data from two Greenland ice cores. Our conclusions are supported by modeled 14C production rates for the same period. Using existing 36Cl ice core data in conjunction with 10Be, we further show that this solar event was characterized by a very hard energy spectrum. These results indicate that the 2,610-years B.P. event was an order of magnitude stronger than any solar event recorded during the instrumental period and comparable with the solar proton event of AD 774/775, the largest solar event known to date. The results illustrate the importance of multiple ice core radionuclide measurements for the reliable identification of short-term production rate increases and the assessment of their origins.
Published: 2019

40. Multi-tracer study of gas trapping in an East Antarctic ice core

Author: Vladimir Ya. Lipenkov, Xavier Faïn, Johannes Freitag, Henning Löwe, Christoph Florian Schaller, Kévin Fourteau, Patricia Martinerie, Martin Schneebeli, Laurent Arnaud, Elizabeth R. Thomas, Rebecca Tuckwell, Olivier Magand, Robert Mulvaney, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Alfred Wegener Institute [Potsdam], Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Institut Fédéral de Recherches sur la Forêt, la Neige et le Paysage (WSL), Institut Fédéral de Recherches [Suisse], Arctic and Antarctic Research Institute (AARI), Russian Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), and Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: 010506 paleontology, 010504 meteorology & atmospheric sciences, Stratification (water), Mineralogy, 01 natural sciences, Methane, chemistry.chemical_compound, Ice core, TRACER, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, Porosity, lcsh:Environmental sciences, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, lcsh:GE1-350, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Firn, lcsh:QE1-996.5, lcsh:Geology, chemistry, 13. Climate action, Gas pycnometer, [SDU]Sciences of the Universe [physics], [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Layering
Abstract: We study a firn and ice core drilled at the new "Lock-In" site in East Antarctica, located 136 km away from Concordia station towards Durmont d'Urville. High resolution chemical and physical measurements were performed on the core, with a particular focus on the trapping zone of the firn where air bubbles are formed. We measured the air content in the ice, closed and open porous volumes in the firn, firn density, firn liquid conductivity and major ion concentrations, as well as methane concentrations in the ice. The closed and open porosity volumes of firn samples were obtained by the two independent methods of pycnometry and tomography, that yield similar results. The measured increase of the closed porosity with density is used to estimate the air content trapped in the ice with the aid of a simple gas trapping model. Results show a discrepancy, with the model trapping too much air. Experimental errors have been considered but do not explain the discrepancy between the model and the observations. The model and data can be reconciled with the introduction of a reduced compression of the closed porosity compared to the open porosity. Yet, it is not clear if this limited compression of closed pores is the actual mechanism responsible for the low amount of air in the ice. High resolution density measurements reveal the presence of a strong layering, manifesting itself as centimeter scale variations. Despite this heterogeneous stratification, all layers, including the ones that are especially dense or less dense compared to their surroundings, display similar pore morphology and closed porosity as function of density. This implies that all layers close in a similar way, even though some close in advance or later compared to the bulk firn. Investigation of the chemistry data suggests that in the trapping zone, the observed stratification is partly related to the presence of chemical impurities.
Published: 2019

41. Persistent Draining of the Stratospheric 10 Be Reservoir After the Samalas Volcanic Eruption (1257 CE)

Author: Edouard Bard, Jean-Robert Petit, Sophie Viseur, Mélanie Baroni, Chaire Evolution du climat et de l'océan, Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Université de Lorraine (UL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), European Project: 306045,EC:FP7:ERC,ERC-2012-StG_20111012,COMBINISO(2013), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Collège de France - Chaire Evolution du climat et de l'océan, Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, ice cores, Atmospheric sciences, 01 natural sciences, chemistry.chemical_compound, Altitude, Ice core, Earth and Planetary Sciences (miscellaneous), samalas eruption, Sulfate, Stratosphere, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, Vulcanian eruption, solar reconstructions, stratospheric volcanic eruptions, Snow, Geophysics, Deposition (aerosol physics), Volcano, chemistry, 13. Climate action, Space and Planetary Science, beryllium-10, Environmental science
Abstract: International audience; More than 2,000 analyses of beryllium-10 (Be-10) and sulfate concentrations were performed at a nominal subannual resolution on an ice core covering the last millennium as well as on records from three sites in Antarctica (Dome C, South Pole, and Vostok) to better understand the increase in Be-10 deposition during stratospheric volcanic eruptions. A significant increase in Be-10 concentration is observed in 14 of the 26 volcanic events studied. The slope and intercept of the linear regression between Be-10 and sulfate concentrations provide different and complementary information. Slope is an indicator of the efficiency of the draining of Be-10 atoms by volcanic aerosols depending on the amount of SO2 released and the altitude it reaches in the stratosphere. Intercept gives an image of the Be-10 production in the stratospheric reservoir, ultimately depending on solar modulation. The Samalas event (1257 CE) stands out from the others as the biggest eruption of the last millennium with the lowest positive slope of all the events. We hypothetize that the persistence of volcanic aerosols in the stratosphere after the Samalas eruption has drained the stratospheric Be-10 reservoir for a decade, meaning that solar reconstructions based on Be-10 should be considered with caution during this period. The slope of the linear regression between Be-10 and sulfate concentrations can also be used to correct the Be-10 snow/ice signal of the volcanic disturbance.
Published: 2019

42. Asynchrony between Antarctic temperature and CO$_2$ associated with obliquity over the past 720,000 years

Author: Makoto Igarashi, Jean Jouzel, Keisuke Suzuki, Koji Fujita, Takayuki Kuramoto, Ryu Uemura, Shinichiro Horikawa, Valérie Masson-Delmotte, Takayuki Miyake, Ayako Abe-Ouchi, Kenji Kawamura, Shuji Fujita, Motohiro Hirabayashi, Hideaki Motoyama, Toshitaka Suzuki, Yoshiyuki Fujii, Kumiko Goto-Azuma, Yoshinori Iizuka, Hiroshi Ohno, University of the Ryukyus [Okinawa], National Institute of Polar Research [Tokyo] (NiPR), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), The Graduate University for Advanced Studies, japan (SOKENDAI), Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan, Center for Climate System Research [Kashiwa] (CCSR), The University of Tokyo (UTokyo), Institute of Low Temperature Science [Sapporo], Hokkaido University [Sapporo, Japan], Shinshu University [Nagano], Graduate School of Science and Engineering [Yamagata], Yamagata University, ANR-07-BLAN-0125,DOME A,Dome A : Observation et Modélisation d'un Environnement extrême en Antarctique(2007), ANR-14-CE01-0001,ASUMA,Amélioration de la précision de l'estimation de bilan de masse de surface en Antarctique(2014), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: 010504 meteorology & atmospheric sciences, Lag, Science, [SDE.MCG]Environmental Sciences/Global Changes, General Physics and Astronomy, 010502 geochemistry & geophysics, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Proxy (climate), Carbon cycle, Ice core, 14. Life underwater, Glacial period, lcsh:Science, 0105 earth and related environmental sciences, Multidisciplinary, Ocean current, General Chemistry, Phase lag, Sea surface temperature, 13. Climate action, Climatology, [SDE]Environmental Sciences, lcsh:Q, Geology
Abstract: The δD temperature proxy in Antarctic ice cores varies in parallel with CO2 through glacial cycles. However, these variables display a puzzling asynchrony. Well-dated records of Southern Ocean temperature will provide crucial information because the Southern Ocean is likely key in regulating CO2 variations. Here, we perform multiple isotopic analyses on an Antarctic ice core and estimate temperature variations at this site and in the oceanic moisture source over the past 720,000 years, which extend the longest records by 300,000 years. Antarctic temperature is affected by large variations in local insolation that are induced by obliquity. At the obliquity periodicity, the Antarctic and ocean temperatures lag annual mean insolation. Further, the magnitude of the phase lag is minimal during low eccentricity periods, suggesting that secular changes in the global carbon cycle and the ocean circulation modulate the phase relationship among temperatures, CO2 and insolation in the obliquity frequency band.
Published: 2018

43. Alpine ice evidence of a three-fold increase in atmospheric iodine deposition since 1950 in Europe due to increasing oceanic emissions

Author: Nathan Chellman, Monica M. Arienzo, Kelly E. Gleason, Lucy J. Carpenter, Mat J. Evans, Michel Legrand, Tomás Sherwen, Susanne Preunkert, Joseph R. McConnell, Laboratoire d'Ingénierie des Matériaux (LIM), Centre National de la Recherche Scientifique (CNRS), Desert Research Institute (DRI), Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: Ozone, 010504 meteorology & atmospheric sciences, Chemical transport model, Climate, Iodide, GEOS-Chem, chemistry.chemical_element, Social Sciences, 010501 environmental sciences, Atmospheric sciences, Iodine, 01 natural sciences, chemistry.chemical_compound, Earth, Atmospheric, and Planetary Sciences, Alpine ice core, Ice core, Seawater, Tropospheric ozone, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, chemistry.chemical_classification, Pollutant, tropospheric ozone, Air Pollutants, Multidisciplinary, iodine, Atmosphere, Ice, 15. Life on land, Europe, trend, chemistry, 13. Climate action, Physical Sciences, [SDE]Environmental Sciences, Environmental science, Nitrogen oxide, Seasons, Environmental Sciences
Abstract: Significance Our measurements show a tripling of iodine in Alpine ice between 1950 and 1990. A 20th century increase in global iodine emissions has been previously found from model simulations, based on laboratory studies, but, up to now, long-term iodine records exist only in polar regions. These polar records are influenced by sea ice processes, which may obscure global iodine trends. Our results suggest that the increased iodine deposition over the Alps is consistent with increased oceanic iodine emissions coupled with a change in the iodine speciation, both driven by increasing anthropogenic NOx emissions. In turn, the recent increase of iodine emissions implies that iodine-related ozone loss in the troposphere is more active now than in the preindustrial period., Iodine is an important nutrient and a significant sink of tropospheric ozone, a climate-forcing gas and air pollutant. Ozone interacts with seawater iodide, leading to volatile inorganic iodine release that likely represents the largest source of atmospheric iodine. Increasing ozone concentrations since the preindustrial period imply that iodine chemistry and its associated ozone destruction is now substantially more active. However, the lack of historical observations of ozone and iodine means that such estimates rely primarily on model calculations. Here we use seasonally resolved records from an Alpine ice core to investigate 20th century changes in atmospheric iodine. After carefully considering possible postdepositional changes in the ice core record, we conclude that iodine deposition over the Alps increased by at least a factor of 3 from 1950 to the 1990s in the summer months, with smaller increases during the winter months. We reproduce these general trends using a chemical transport model and show that they are due to increased oceanic iodine emissions, coupled to a change in iodine speciation over Europe from enhanced nitrogen oxide emissions. The model underestimates the increase in iodine deposition by a factor of 2, however, which may be due to an underestimate in the 20th century ozone increase. Our results suggest that iodine’s impact on the Northern Hemisphere atmosphere accelerated over the 20th century and show a coupling between anthropogenic pollution and the availability of iodine as an essential nutrient to the terrestrial biosphere.
Published: 2018

44. SO 2 Oxidation Kinetics Leave a Consistent Isotopic Imprint on Volcanic Ice Core Sulfate

Author: James Farquhar, Joseph Erbland, Elsa Gautier, Joel Savarino, Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS), Université Grenoble Alpes (UGA), CHANG, CLIPS, Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Department of Geology and ESSIC, Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Department of Geology [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Atmospheric Science, geography, Vulcanian eruption, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Kinetics, Geochemistry, 010502 geochemistry & geophysics, 01 natural sciences, chemistry.chemical_compound, Geophysics, chemistry, Ice core, Volcano, 13. Climate action, Space and Planetary Science, Earth and Planetary Sciences (miscellaneous), Environmental science, Sulfate, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: International audience; This work presents measurements of time-resolved mass-independently fractionated sulfate of volcanic origin from Antarctic ice core records that cover the last 2,600 years. These measurements are used to evaluate the time dependence of the deposited isotopic signal and to extract the isotopic characteristics of the reactions yielding sulfate from stratospheric volcanic eruptions in the modern atmosphere. Time evolution of the signal in snow (years) with respect to the fast SO 2 oxidation in the stratosphere suggests that photochemically produced condensed phase is rapidly and continuously separated from the gas phase and preserved during transportation and deposition on the polar ice cap. On some eruptions, a nonzero isotopic mass balance highlights that a part of the signal can be lost during transport and/or deposition. The large number of volcanic events studied allows the Δ 33 S versus Δ 36 S and δ 34 S versus Δ 33 S slopes to be constrained at À1.56 (1σ = 0.25) and 0.09 (1σ = 0.02), respectively. The Δ 33 S versus Δ 36 S slope refines a prior determinations of Δ 36 S/Δ 33 S = À4 and overlaps the range observed for sulfur seen in early Earth samples (Archean). In recent volcanogenic sulfate, the Δ 33 S versus δ 34 S differs, however, from the Archean record. The similitude for Δ 36 S/Δ 33 S and the difference for Δ 33 S/δ 34 S suggest similar mass-independently fractionated sulfate processes to the Archean atmosphere. Using a simple model, we highlight that a combination of several mechanisms is needed to reproduce the observed isotopic trends and suggest a greater contribution from mass-dependent oxidation by OH in the modern atmosphere. Plain Language Summary Large volcanic eruptions inject sulfurous gases in the stratosphere, where they rapidly form sulfuric acid aerosols. These aerosols can reside in the stratosphere for years, cover the entire globe, and profoundly modify the climate by scattering and absorbing solar radiation. Sulfuric acid aerosols formed by this process acquire an isotopic anomaly that traces these processes and allows identification of these eruptions in ice core records, providing a means to distinguish between high and low climatic impact eruptions in ice core volcanic deposits. This study provides a characterization of this time-dependent isotopic signature that is used to constrain its origin and to understand the processes underlying its production and evolution.
Published: 2018

45. Regionalization of the Atmospheric Dust Cycle on the Periphery of the East Antarctic Ice Sheet Since the Last Glacial Maximum

Author: Baccolo G.[1, 2, Delmonte B.[2], Albani S.[4], Baroni C.[5, Cibin G.[7], Frezzotti M.[8], Hampai D.[9], Marcelli A.[9, 10] Revel M.[11], Salvatore M.C.[5, 6] Stenni B.[12], Maggi V.[2, Department of Earth and Environmental Sciences [Milano], Università degli Studi di Milano-Bicocca [Milano] (UNIMIB), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Earth Sciences Department, University of Pisa - Università di Pisa, DIAMOND Light source, Italian National agency for new technologies, Energy and sustainable economic development [Frascati] (ENEA), INFN Frascati, Istituto Nazionale di Fisica Nucleare (INFN), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Department of Environmental Sciences, Informatics and Statistics [Venezia], University of Ca’ Foscari [Venice, Italy], Università degli Studi di Milano-Bicocca = University of Milano-Bicocca (UNIMIB), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Baccolo, G., Delmonte, B., Albani, S., Baroni, Carlo, Cibin, G., Frezzotti, M., Hampai, D., Marcelli, A., Revel, M., Salvatore, M. C., Stenni, B., Maggi, V., Baccolo, G, Delmonte, B, Albani, S, Baroni, C, Cibin, G, Frezzotti, M, Hampai, D, Marcelli, A, Revel, M, Salvatore, M, Stenni, B, and Maggi, V
Subjects: 010504 meteorology & atmospheric sciences, ice cores, Antarctic ice sheet, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Mineral dust, 010502 geochemistry & geophysics, 01 natural sciences, Atmospheric mineral dust, Ice core, Geochemistry and Petrology, chemical index of alteration, Glacial period, Holocene, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Antarctica, Glacial geology, glaciers, Atmospheric mineral dust, chemical index of alteration, Holocene, ice cores, weathering, Last Glacial Maximum, 15. Life on land, Antarctica, weathering, Geophysics, Glacial geology, not available, Settore GEO/08 - Geochimica e Vulcanologia, 13. Climate action, Interglacial, glaciers, Physical geography, Ice sheet, ice core, Geology
Abstract: Ice cores from inner East Antarctica provided some of the longest and most detailed climatic reconstructions and allowed understanding the relationships between atmospheric mineral dust and climate. In this work we present synchrotron radiation X-ray Fluorescence geochemical data of dust from the TALDICE ice core drilled at Talos Dome, a peripheral ice dome of East Antarctica (Western Ross Sea). Results highlight a dominant southern South American origin for dust at TALDICE during the Last Glacial Maximum, similarly to other sites located further inland onto the polar plateau. On the contrary, a different scenario concerns Talos Dome during the Holocene if it is compared to more inner sites. The tight connection between high southern latitudes and Antarctica that characterizes cold climate stages becomes weaker since the onset of the last climatic transition and throughout the Holocene. The net effect of this process at Talos Dome is a modification of the atmospheric and environmental settings, owing to local Antarctic sources of Victoria Land to gain importance and become the dominant ones. At the same time in inner East Antarctica the provenance of dust remains remote also during Holocene, revealing an evolution of the homogeneous scenario observed in glacial periods. The enhanced sensitivity of peripheral ice sheet sites to local dust sources makes Talos Dome an ideal site to assess the climatic and atmospheric changes of the peripheral sectors of East Antarctica during the current interglacial period.Plain Language Summary During the Last Glacial Maximum, about 20,000 years ago, mineral dust from South America was massively transported toward Antarctica as a consequence of impressive environmental and climatic changes. Many ice cores drilled from the inner sectors of the Antarctic ice sheets support this scenario. Little is known when attention is shifted to peripheral areas and to interglacial periods. A new record of mineral particles at Talos Dome, a peripheral area of the East Antarctic ice sheet (Western Ross Sea sector), is here presented to partially close these gaps. Combining the data about concentration, composition, and grain size of the dust deposited at Talos Dome, it was possible to appreciate the influence played by local Antarctic dust sources to the depositional budget of the site. These local sources, corresponding to localized ice-free areas, are extremely important when attention is given to the peripheries of the ice sheets. This is particularly true for interglacial periods, when the transport and the deposition of mineral dust from South America to Antarctica is much reduced.
Published: 2018

46. Accumulation rate in a tropical Andean glacier as a proxy for northern Amazon precipitation

Author: Jean-Denis Taupin, Rafael da Rocha Ribeiro, Edson Ramirez, Elias Simão Assayag, Norberto Dani, Jefferson Cardia Simões, Universidade Federal do Rio Grande do Sul [Porto Alegre] (UFRGS), Universidad Mayor de San Andrés (UMSA), Hydrosciences Montpellier (HSM), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), and Universidade Federal de Manaus
Subjects: Atmospheric Science, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Amazon rainforest, Amazonian, Multivariate ENSO index, Glacier, 010502 geochemistry & geophysics, 01 natural sciences, La Niña, Ice core, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Climatology, Precipitation, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Geology, Pacific decadal oscillation, 0105 earth and related environmental sciences
Abstract: International audience; Andean tropical glaciers have shown a clear shrinkage throughout the last few decades. However, it is unclear how this general retreat is associated with variations in rainfall patterns in the Amazon basin. To investigate this question, we compared the annual net accumulation variations in the Bolivian Cordillera Real (Andes), which is derived from an ice core from the Nevado Illimani (16° 37′ S, 67° 46′ W), covering the period 1960–1999 using the Amazonian Rainfall Index, Northern Atlantic Index (TNA), Multivariate ENSO Index (MEI), and Pacific Decadal Oscillation (PDO). The accumulation rate at the Nevado Illimani ice core decreased by almost 25% after 1980, from 1.02 w.eq. a−1 (water equivalent per year) in the 1961–1981 period to 0.76 w.eq. a−1 in the 1981–1999 period. The Northern Amazonian Rainfall (NAR) index best reflects changes in accumulation rates in the Bolivian ice core. Our proposal is based on two observations: (1) This area shows reduced rainfall associated with a more frequent and intense El Niño (during the positive phase of the MEI). The opposite (more rain) is true during La Niña phases. (2) Comparisons of the ice core record and NAR, PDO, and MEI indexes showed similar trends for the early 1980s, represented by a decrease in the accumulation rates and its standard deviations, probably indicating the same causality. The general changes observed by early 1980s coincided with the beginning of a PDO warm phase. This was followed by an increase in the Amazonian and tropical Andean precipitation from 1999, coinciding with a new PDO phase. However, this increase did not result in an expansion of the Zongo Glacier area.
Published: 2018

47. Surface formation, preservation, and history of low-porosity crusts at the WAIS Divide site, West Antarctica

Author: M. K. Spencer, Richard B. Alley, Atsuhiro Muto, Anais Orsi, John M. Fegyveresi, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] ( LSCE ), Université de Versailles Saint-Quentin-en-Yvelines ( UVSQ ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay-Centre National de la Recherche Scientifique ( CNRS ), Pennsylvania State University (Penn State), Penn State System, Temple University [Philadelphia], Pennsylvania Commonwealth System of Higher Education (PCSHE), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: [ SDU.OCEAN ] Sciences of the Universe [physics]/Ocean, Atmosphere, Daytime, 010506 paleontology, 010504 meteorology & atmospheric sciences, Antarctic ice sheet, 010502 geochemistry & geophysics, Atmospheric sciences, 01 natural sciences, Discontinuity (geotechnical engineering), Ice core, [ SDU.ENVI ] Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, Porosity, lcsh:Environmental sciences, ComputingMilieux_MISCELLANEOUS, Earth-Surface Processes, Water Science and Technology, 0105 earth and related environmental sciences, lcsh:GE1-350, lcsh:QE1-996.5, Crust, Snow, Surface energy, lcsh:Geology, 13. Climate action, Climatology, Geology
Abstract: Observations at the West Antarctic Ice Sheet (WAIS) Divide site show that near-surface snow is strongly altered by weather-related processes such as strong winds and temperature fluctuations, producing features that are recognizable in the deep ice core. Prominent glazed surface crusts develop frequently at the site during summer seasons. Surface, snow pit, and ice core observations made in this study during summer field seasons from 2008–2009 to 2012–2013, supplemented by automated weather station (AWS) data with short- and longwave radiation sensors, revealed that such crusts formed during relatively low-wind, low-humidity, clear-sky periods with intense daytime sunshine. After formation, such glazed surfaces typically developed cracks in a polygonal pattern likely from thermal contraction at night. Cracking was commonest when several clear days occurred in succession and was generally followed by surface hoar growth; vapor escaping through the cracks during sunny days may have contributed to the high humidity that favored nighttime formation of surface hoar. Temperature and radiation observations show that daytime solar heating often warmed the near-surface snow above the air temperature, contributing to upward mass transfer, favoring crust formation from below, and then surface hoar formation. A simple surface energy calculation supports this observation. Subsequent examination of the WDC06A deep ice core revealed that crusts are preserved through the bubbly ice, and some occur in snow accumulated during winters, although not as commonly as in summertime deposits. Although no one has been on site to observe crust formation during winter, it may be favored by greater wintertime wind packing from stronger peak winds, high temperatures and steep temperature gradients from rapid midwinter warmings reaching as high as −15 °C, and perhaps longer intervals of surface stability. Time variations in crust occurrence in the core may provide paleoclimatic information, although additional studies are required. Discontinuity and cracking of crusts likely explain why crusts do not produce significant anomalies in other paleoclimatic records.
Published: 2018

48. Multi-channel and multi-polarization radar measurements around the NEEM site

Author: Prasad Gogineni, Jilu Li, Carl Leuschen, Ayyangar R. Harish, Fernando Rodriguez-Morales, Maurine Montagnat, Ilka Weikusat, Jose A. Vélez González, John Paden, Center for Remote Sensing of Ice Sheets (CReSIS), University of Kansas [Lawrence] (KU), Indian Institute of Technology Kanpur (IIT Kanpur), Department of Electrical and Computer Engineering University of South Alabama, 6001 USA South Dr., Mobile, AL 36688-0002, USA, Department of Electrical and Computer Engineering, University of South Alabama-University of South Alabama, Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Alfred Wegener Institute for Polar and Marine Research (AWI), and Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
Subjects: 010504 meteorology & atmospheric sciences, Ice stream, 010502 geochemistry & geophysics, 01 natural sciences, law.invention, Physics::Geophysics, Ice core, law, Ice divide, [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology, Radar, lcsh:Environmental sciences, Physics::Atmospheric and Oceanic Physics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, lcsh:GE1-350, geography, geography.geographical_feature_category, Ice crystals, lcsh:QE1-996.5, Vertical plane, Geodesy, lcsh:Geology, Azimuth, Astrophysics::Earth and Planetary Astrophysics, Ice sheet, Geology
Abstract: Ice properties inferred from multi-polarization measurements, such as birefringence and crystal orientation fabric (COF), can provide insight into ice strain, viscosity, and ice flow. In 2008, the Center for Remote Sensing of Ice Sheets (CReSIS) used a ground-based VHF (very high frequency) radar to take multi-channel and multi-polarization measurements around the NEEM (North Greenland Eemian Ice Drilling) site. The system operated with 30 MHz bandwidth at a center frequency of 150 MHz. This paper describes the radar system, antenna configurations, data collection, and processing and analysis of this data set. Within the framework derived from uniaxial ice crystal model, we found that ice birefringence dominates the power variation patterns of co-polarization and cross-polarization measurements in the area of 100 km2 around the ice core site. The phase shift between ordinary and extraordinary waves increases nonlinearly with depth. The ice optic axis lies in planes that are close to the vertical plane and perpendicular or parallel to the ice divide depending on depth. The ice optic axis has an average tilt angle of about 11.6° vertically, and its plane may rotate either clockwise or counterclockwise by about 10° across the 100 km2 area, and at a specific location the plane may rotate slightly counterclockwise as depth increases. Comparisons between the radar observations, simulations, and ice core fabric data are in very good agreement. We calculated the effective colatitude at different depths by using azimuth and colatitude measurements of the c axis of ice crystals. We obtained an average effective c axis tilt angle of 9.6° from the vertical axis, very comparable to the average optic axis tilt angle estimated from radar polarization measurements. The comparisons give us confidence in applying this polarimetric radio echo sounding technique to infer profiles of ice fabric in locations where there are no ice core measurements.
Published: 2018

49. Palynology of the Last Interglacial Complex at Lake Ohrid: palaeoenvironmental and palaeoclimatic inferences

Author: Gaia Sinopoli, Bernd Wagner, Eleonora Regattieri, Laura Sadori, Odile Peyron, Alessia Masi, Alexander Francke, Dipartimento di biologia ambientale, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Dipartimiento di Scinze della Terra, University of Pisa - Università di Pisa, Institute for Geology & Mineralogy Cologne, Université de Cologne, Institut des Sciences de l'Evolution de Montpellier (UMR ISEM), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-École pratique des hautes études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Montpellier (UM)-Institut de recherche pour le développement [IRD] : UR226-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010506 paleontology, Archeology, 010504 meteorology & atmospheric sciences, global and planetary change, 01 natural sciences, Albania/FYROM, lake Ohrid, Marine Isotope Stage 5, Ice core, Paleoclimatology, Glacial period, Stadial, vegetation changes, palynology, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, palaeoclimatology, Palynology, Eemian, last interglacial complex, Geology, 15. Life on land, 13. Climate action, last nterglacial complex, Interglacial, [SDE]Environmental Sciences, Physical geography, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: In this article, we present new, high-resolution, pollen results obtained from the DEEP site sequence recovered from Lake Ohrid (Albania/FYROM) for the Last Interglacial Complex (LIC), corresponding to Marine Isotope Stage 5 (MIS 5) of the marine isotope stratigraphy. LIC covers the period between 130 and 70 ka and includes the Eemian (Last Interglacial, LI) and the succession of stadial and interstadial phases of the Early Last Glacial. During the LIC, the pollen record shows an alternation of periods characterized by forest and open vegetation, clearly resembling the well-known vegetational succession of other European records. Our results reveal three key phases for the LI: a first period (128-125 ka) with a rapid increase in temperature and precipitation, a central phase (125–118.5 ka) characterized by a slight cooling, and a late phase (118.5–112 ka), with a decline both in temperatures and precipitation. Besides the LI, we identify four more forested periods dominated by mesophilous trees and intercalated by colder and drier steppe phases, during which, however, most arboreal taxa never disappear. During the Early Last Glacial we also identify several abrupt events that can be correlated to the succession of cold events recorded in the Greenland ice core records, associated to a weakening of the North Atlantic Meridional Overturning Circulation. The new high-resolution record indicates that Lake Ohrid is an important site to understand the response of vegetation to fluctuations in regional moisture availability and temperature changes, and thus provides new evidence for the connection between the Mediterranean Region and Northern Hemisphere climate oscillations.
Published: 2018

50. Ocean as the main driver of Antarctic ice sheet retreat during the Holocene

Author: Ruth Yam, Irena Brailovski, Didier Swingedouw, J.G. Crespin, Pascale Braconnot, Hugues Goosse, Olivier Marti, Johan Etourneau, Xavier Crosta, Valérie Masson-Delmotte, Aldo Shemesh, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Earth and Planetary Science [Rehovot], Weizmann Institute of Science [Rehovot, Israël], Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Instituto Andaluz de Ciencias de la Tierra (IACT), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de Granada = University of Granada (UGR), Institut d'Astronomie et de Géophysique Georges Lemaître (UCL-ASTR), Université Catholique de Louvain = Catholic University of Louvain (UCL), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Department of Environmental Sciences and Energy Research [Rehovot], Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), CERFACS, Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de Granada (UGR), and UCL - SST/ELI/ELIC - Earth & Climate
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Antarctic ice sheet, Glacier, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, Ice shelf, Sea surface temperature, Ice core, 13. Climate action, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Circumpolar deep water, 14. Life underwater, Glacial period, Geology, Holocene, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences
Abstract: International audience; Ocean-driven basal melting has been shown to be the main ablation process responsible for the recession of many Antarctic ice shelves and marine-terminating glaciers over the last decades. However, much less is known about the drivers of ice shelf melt prior to the short instrumental era. Based on diatom oxygen isotope (δ18Odiatom; a proxy for glacial ice discharge in solid or liquid form) records from western Antarctic Peninsula (West Antarctica) and Adélie Land (East Antarctica), higher ocean temperatures were suggested to have been the main driver of enhanced ice melt during the Early-to-Mid Holocene while atmosphere temperatures were proposed to have been the main driver during the Late Holocene. Here, we present a new Holocene δ18Odiatom record from Prydz Bay, East Antarctica, also suggesting an increase in glacial ice discharge since ~4500 years before present (~4.5 kyr BP) as previously observed in Antarctic Peninsula and Adélie Land. Similar results from three different regions around Antarctica thus suggest common driving mechanisms. Combining marine and ice core records along with new transient accelerated simulations from the IPSL-CM5A-LR climate model, we rule out changes in air temperatures during the last ~4.5 kyr as the main driver of enhanced glacial ice discharge. Conversely, our simulations evidence the potential for significant warmer subsurface waters in the Southern Ocean during the last 6 kyr in response to enhanced summer insolation south of 60°S and enhanced upwelling of Circumpolar Deep Water towards the Antarctic shelf. We conclude that ice front and basal melting may have played a dominant role in glacial discharge during the Late Holocene.
Published: 2018

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