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Your search keyword '"Department of Earth Sciences [Aarhus]"' showing total 8 results
Start Over Author "Department of Earth Sciences [Aarhus]" Topic 010504 meteorology & atmospheric sciences
8 results on '"Department of Earth Sciences [Aarhus]"'

1. Reply to: 'The mountains of North-East Greenland are not remnants of the Caledonian topography. A comment on Pedersen et al. (2012)'

Author

Søren B. Nielsen, Kerry Gallagher, Vivi Kathrine Pedersen, Department of Earth Science [Bergen] (UiB), University of Bergen (UiB), Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], Terre, Temps, Traçage, 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)-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), 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)-Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), and 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)

Subjects
Topography, Vitrinite reflectance, 010504 meteorology & atmospheric sciences, Paleozoic, Passive margins, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, North east, 15. Life on land, 010502 geochemistry & geophysics, 01 natural sciences, Paleontology, Geophysics, Fission track analysis, Erosion, Passive margin, Tectonophysics, Northeast Greenland, Geology, 0105 earth and related environmental sciences, Earth-Surface Processes
Abstract

International audience; In this reply, we comment on the issues raised by Japsen, Chalmers, and Green [Japsen et al. (2013). The mountains of North-East Greenland are not remnants of the Caledonian topography. A comment on Pedersen et al. (2012): Tectonophysics]. We find that new vitrinite reflectance measurements from one location in the region may suggest a more complicated post-Caledonian evolution than proposed by Pedersen et al. (2012) for the southernmost part of the studied area. Overall, however, we cannot reconcile our AFT data set with a complete obliteration of the topography in late Paleozoic times, followed by episodic post-Caledonian exhumation and re-burial, as suggested by Japsen et al. (2013).

Published
2013

2. Benchmarking numerical models of brittle thrust wedges

Author

Buiter, Susanne J H, Schreurs, Guido, Albertz, Markus, Gerya, Taras V., Kaus, Boris, Landry, Walter, le Pourhiet, Laetitia, Mishin, Yury, Egholm, David L., Cooke, Michele, Maillot, Bertrand, Thieulot, Cedric, Crook, Tony, May, Dave, Souloumiac, Pauline, Beaumont, Christopher, Mantle dynamics & theoretical geophysics, Mantle dynamics & theoretical geophysics, Geological Survey of Norway (NGU), Centre for Earth Evolution and Dynamics [Oslo] (CEED), Department of Geosciences [Oslo], Faculty of Mathematics and Natural Sciences [Oslo], University of Oslo (UiO)-University of Oslo (UiO)-Faculty of Mathematics and Natural Sciences [Oslo], University of Oslo (UiO)-University of Oslo (UiO), Institute of Geological Sciences [Bern], University of Bern, ExxonMobil Upstream Research Company, Department of Earth Sciences [Swiss Federal Institute of Technology - ETH Zürich] (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), Institute of Geosciences, Johannes Gutenberg - Universität Mainz (JGU), Computational Infrastructure for Geodynamics, Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], Department of Geosciences, University of Massachusetts [Lowell] (UMass Lowell), University of Massachusetts System (UMASS)-University of Massachusetts System (UMASS), Laboratoire Géosciences et Environnement Cergy (GEC), Fédération INSTITUT DES MATÉRIAUX DE CERGY-PONTOISE (I-MAT), Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine, Department of Earth Sciences [Utrecht], Utrecht University [Utrecht], Three Cliffs Geomechanical Analysis Ltd, École des Mines de Paris, Department of Oceanography [Halifax] (DO), Dalhousie University [Halifax], and Johannes Gutenberg - Universität Mainz = Johannes Gutenberg University (JGU)

Subjects
010504 meteorology & atmospheric sciences, Plasticity, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Thrust, Geometry, Geology, Classification of discontinuities, 010502 geochemistry & geophysics, 01 natural sciences, Horizontal translation, Wedge (geometry), Boundary friction, Shear zones, Critical taper, Benchmarking, Brittleness, Thrust wedges, Numerical modelling, 550 Earth sciences & geology, Geotechnical engineering, Boundary value problem, 0105 earth and related environmental sciences
Abstract

International audience; We report quantitative results from three brittle thrust wedge experiments, comparing numerical resultsdirectly with each other and with corresponding analogue results. We first test whether the participatingcodes reproduce predictions from analytical critical taper theory. Eleven codes pass the stable wedgetest, showing negligible internal deformation and maintaining the initial surface slope upon horizontaltranslation over a frictional interface. Eight codes participated in the unstable wedge test that examinesthe evolution of a wedge by thrust formation from a subcritical state to the critical taper geometry. Thecritical taper is recovered, but the models show two deformation modes characterised by either mainlyforward dipping thrusts or a series of thrust pop-ups. We speculate that the two modes are caused bydifferences in effective basal boundary friction related to different algorithms for modelling boundaryfriction. The third experiment examines stacking of forward thrusts that are translated upward along abackward thrust. The results of the seven codes that run this experiment show variability in deformationstyle, number of thrusts, thrust dip angles and surface slope. Overall, our experiments show that nu-merical models run with different numerical techniques can successfully simulate laboratory brittlethrust wedge models at the cm-scale. In more detail, however, we find that it is challenging to reproducesandbox-type setups numerically, because of frictional boundary conditions and velocity discontinuities.We recommend that future numerical-analogue comparisons use simple boundary conditions and thatthe numerical Earth Science community de fines a plasticity test to resolve the variability in model shearzones

Published
2016

3. Laboratory studies of aeolian sediment transport processes on planetary surfaces

Author

Keld Rømer Rasmussen, Jonathan Merrison, Alexandre Valance, Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Aarhus], We acknowledge Andreas Boes Jakobsen and Jens Jacob Iversen for their help and support with the experimental work in the Aarhus wind tunnel. We would like to thank Pascal Dupont, Ahmed Ould El Mochtar, and Marc Lämmel for fruitful discussion during the workshop ‘Fluid-Mediated Particle Transport in Geophysical Flows’, 2013-09-23 to 2013-12-20 at the Kavli Institute, UCSB. Marc Lämmel also derived Fig. 17B from our experimental data. We also acknowledge two anonymous reviewers for the valuable comments and suggestions., and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
splash, Dust detachment, 010504 meteorology & atmospheric sciences, Saltation, Splash, 010502 geochemistry & geophysics, 01 natural sciences, Aeolian laboratory studies, Shields parameter, Wind speed, ripple spacing, Particle tracking velocimetry, Saltation (geology), saltation, Particle velocity, Shear velocity, Particle trajectory, Geomorphology, 0105 earth and related environmental sciences, Earth-Surface Processes, Wind tunnel, Mechanics, Ripple spacing, dust detachment, particle trajectory, Aeolian processes, [PHYS.COND.CM-SCM]Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft], Geology
Abstract

International audience; We review selected experimental saltation studies performed in laboratory wind tunnels and collision experiments performed in (splash-) laboratory facilities that allow detailed observations between impinging particles on a stationary bed.We also discuss progress in understanding aeolian transport in nonterrestrial environments. Saltation studies in terrestrial wind tunnels can be divided into two groups. The first group comprises studies using a short test bed, typically 1–4m long, and focuses on the transitional behavior near the upwind roughness discontinuity where saltation starts. The other group focuses on studies using long test beds — typically 6 m or more — where the saturated saltation takes place under equilibrium conditions between wind flow and the underlying rough bed. Splash studies using upscaled model experiments allow collision simulations with large spherical particles to be recorded with a high speed video camera. The findings indicate that the number of ejected particles per impact scales linearlywith the impact velocity of the saltating particles. Studies of saturated saltation in several facilities using predominantly Particle Tracking Velocimetry or Laser Doppler Velocimetry indicate that the velocity of the (few) particles having high trajectories increases with increasing friction velocity. However, the speed of the majority of particles that do not reachmuch higher than Bagnold's focal point is virtually independent of Shields parameter—at least for lowor intermediate u⁎-values. In this case mass flux depends on friction velocity squared and not cubed as originally suggested by Bagnold. Over short beds particle velocity shows stronger dependence on friction velocity and profiles of particle velocity deviate from those obtained over long beds. Measurements using horizontally segmented traps give average saltation jump-lengths near 60–70 mm and appear to be only weakly dependent on friction velocity, which is in agreement with some, but not all, older or recent wind tunnel observations. Similarly some measurements performed with uniform sand samples having grain diameters of the order of 0.25–0.40mmindicate that ripple spacing depends on friction velocity in a similar way as particle jump length. The observations are thus in agreementwith a recent ripple model that link the typical jump length to ripple spacing. A possible explanation for contradictory observations in some experiments may be that long observation sequences are required in order to assure that equilibrium exists between ripple geometry and wind flow.Quantitative understanding of saltation characteristics onMars still lacks important elements. Based upon image analysis and numerical predictions, aeolian ripples have been thought to consist of relatively large grains (diameter N 0.6mm) and that saltation occurs at high wind speeds (N26 m/s) involving trajectories that are significantly longer than those on Earth (by a factor of 10–100). However, this is not supported by recent observations from the surface of Mars, which shows that active ripples in their geometry and composition have characteristics compatible with those of terrestrial ripples (Sullivan et al., 2008). Also the highest average wind speeds on Mars have been measured to be b20 m/s, with even turbulent gusts not exceeding 25 m/s. Electrification is seen as a dominant factor in the transport dynamics of dust onMars, affecting the structure, adhesive properties and detachment/entrainment mechanisms specifically through the formation of aggregates (Merrison et al., 2012). Conversely for terrestrial conditions electric fields typically observed are not intense enough to significantly affect sand transport rates while little is known in the case of extra-terrestrial environments.

Published
2015

4. Saltating particles in a turbulent boundary layer: experiment and theory

Author

Keld Rømer Rasmussen, Pascal Dupont, José Miguel Pasini, J. T. Jenkins, M. Creyssels, Isabelle Cantat, A. Ould El Moctar, Alexandre Valance, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA), Laboratoire de thermocinétique [Nantes] (LTN), Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS), Granulaires - Mousses, Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Department of Theoretical and Applied Mechanics [Ithaca], Cornell University [New York], Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES), Centre National de la Recherche Scientifique (CNRS)-Université de Nantes (UN), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn], Splash, Materials science, 010504 meteorology & atmospheric sciences, Computer simulation, Meteorology, Mechanical Engineering, Mechanics, Velocimetry, 010502 geochemistry & geophysics, Condensed Matter Physics, 01 natural sciences, Wind speed, Physics::Fluid Dynamics, Boundary layer, Particle image velocimetry, Mechanics of Materials, Boundary value problem, saltation, boundary layer, 0105 earth and related environmental sciences, Wind tunnel
Abstract

International audience; The work presented here focuses on the analysis of a turbulent boundary layer saturated with saltating particles. Experiments were carried out in a wind tunnel 15m long and 0.6m wide at the University of Aarhus in Denmark with sand grains 242 μm in size for wind speeds ranging from the threshold speed to twice its value. The saltating particles were analysed using particle image velocimetry (PIV) and particletracking velocimetry (PTV), and vertical profiles of particle concentration and velocity were extracted. The particle concentration was found to decrease exponentially with the height above the bed, and the characteristic decay height was independent of the wind speed. In contrast with the logarithmic profile of the wind speed, the grain velocity was found to vary linearly with the height. In addition, the measurements indicated that the grain velocity profile depended only slightly on the wind speed. These results are shown to be closely related to the features of the splash function that characterizes the impact of the saltating particles on a sandbed. A numerical simulation is developed that explicitly incorporates low-velocity moments of the splash function in a calculation of the boundary conditions that apply at the bed. The overall features of the experimental measurements are reproduced by simulation.

Published
2009

5. Decadal variability of sea surface temperatures off North Iceland over the last 2000 years

Author

Jón Eiríksson, Marie-Alexandrine Sicre, Sonia Rousse, Karen Luise Knudsen, Ullah Ezat, Jérémy Jacob, Pascal Yiou, Eystein Jansen, Jean-Louis Turon, Catherine Kissel, 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), Paléocéanographie (PALEOCEAN), 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 Sciences de la Terre d'Orléans (ISTO), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Climat et Magnétisme (CLIMAG), Extrèmes : Statistiques, Impacts et Régionalisation (ESTIMR), University of Iceland [Reykjavik], Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences [Bergen] (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Departement de Géologie et Océanographie, Université Sciences et Technologies - Bordeaux 1, PACLIVA European Commission 5th Framework Program (Contract EVK2-2002-00143)., 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), Université Sciences et Technologies - Bordeaux 1 (UB), 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), and University of Bergen (UIB)

Subjects
010506 paleontology, Alkenone, 010504 meteorology & atmospheric sciences, Sea surface temperature, Iceland, Decadal variability, 01 natural sciences, VARIATION TEMPORELLE, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Sea ice, 14. Life underwater, TEMPERATURE, GEOCHRONOLOGIE, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Alkenones, North Atlantic, Medieval Warm Period, SURFACE MARINE, Current (stream), Geophysics, Oceanography, 13. Climate action, Space and Planetary Science, North Atlantic oscillation, [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology, Temporal resolution, Climatology, CHANGEMENT CLIMATIQUE, GLACIER, Period (geology), Little Ice Age, Tephrochronology, Geology
Abstract

International audience; Ocean variability at decadal time-scales remains poorly described partly because of the scarcity of high temporal resolution marine records. Here, we present a reconstruction of Sea Surface Temperatures (SSTs) over the past twomillennia at unprecedented temporal resolution (2 to 5 years), from a marine core located off North Iceland. Alkenone paleothermometry was used to infer SST variability, and tephrochronology to build the age model. Spectral analyses of the SSTsignal indicate intermittent 20–25 year oscillations, with periods of strong and weak power, that are likely reflecting the ocean response to wind forcing, presumably the North Atlantic Oscillation (NAO). Warmer SSTs and paleo-magnetic proxy data, between 1000 and 1350 year A.D., overlapping theMedievalWarm Period (MWP), suggest enhanced heat transport across the Denmark Strait by the North Icelandic IrmingerCurrent (NIIC). This is in contrast with the subsequent period, which includes the Little IceAge (LIA), showing continuous cooling towards the 20th century.Reduced NIIC flow through theDenmark Strait likely resulting from higher freshwater and sea ice export from the Arctic would account for the observed colder conditions.

Published
2008

6. Barchan dune mobility in Mauritania related to dune and interdune sand fluxes

Author

Pascal Dupont, Keld Rømer Rasmussen, A. Ould El Moctar, A. Ould Mahfoudh, Alexandre Valance, D. Ould Ahmedou, Département de Physique [Nouakchott], Université de Nouakchott Al-Aasriya (UNA), Laboratoire de thermocinétique [Nantes] (LTN), Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS), Groupe matière condensée et matériaux (GMCM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], université de Nouakchott, Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Atmospheric Science, Mass transport, Standard sample, 010504 meteorology & atmospheric sciences, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Soil Science, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Aquatic Science, 010502 geochemistry & geophysics, Oceanography, 01 natural sciences, West africa, Small field, Flux (metallurgy), barchan dunes, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Geomorphology, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Wind strength, Ecology, Paleontology, Forestry, geomorphology, Geophysics, Barchan, Space and Planetary Science, aolian sand transport, Crest, Geology
Abstract

We present a 1 year study of 50 dunes in a small field of barchan dunes in Mauritania. We documented the morphological evolution of the dunes and their migration rates and measured at 10 min intervals the interdune sand transport, the wind strength, and its direction for the same interval of time. The dune heights H 0 range between 2 and 5 m, and their celerity c is found to be well approximated by the standard migration law: c = Q 0/H 0, with Q 0 ≈ 50 m3/m yr. From both the interdune sand flux and the migration rate of the dunes we were able to estimate the spatially averaged sand flux at the dune crest as well as the bulk sand flux associated with the mass of sand transported by the dune. We found that the sand flux at the crest was about 3 times greater than the interdune mass transport rate, whereas the bulk sand flux was surprisingly of the same order as the interdune flux. Moreover, we analyzed carefully the interdune sand transport data, which can be well described by the Sorensen law. The cumulative mass of sand transported during moderate wind events within 1 year was much greater than that transported during strong wind events.

Published
2007

7. Holocene centennial to millennial-scale climatic variability: Evidence from high-resolution magnetic analyses of the last 10 cal kyr off North Iceland (core MD99-2275)

Author

Carlo Laj, Jón Eiríksson, Sonia Rousse, Karen Luise Knudsen, Cathrine Kissel, 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), Institute of Earth Sciences [Reykjavik], University of Iceland [Reykjavik], Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], 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
Polar front, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 010506 paleontology, 010504 meteorology & atmospheric sciences, North Atlantic Deep Water, Holocene climatic optimum, Climate change, Westerlies, 01 natural sciences, Geophysics, 13. Climate action, Space and Planetary Science, Geochemistry and Petrology, North Atlantic oscillation, Climatology, Earth and Planetary Sciences (miscellaneous), Thermohaline circulation, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Holocene, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

High-resolution magnetic analysis has been performed on the top ∼25 m of core MD99-2275 (66°33.06′N, 17°41.59′W; 440 m water depth) from the mid-outer shelf off North Iceland. This is a key boundary region for climate changes related to atmospheric and oceanographic variations influenced by the moving limit between the cold and warm water masses at the Polar Front and the low depression track with its associated westerlies situated across Iceland. An age model based on tephrochronology was previously reported for this core and has allowed precise timing of significant variations in the magnetic mineral concentration and grain size over the last 10 cal kyr. The ‘Holocene climatic optimum’ identified in North Iceland between ∼ 10 and 6 cal kyr BP is characterized by minor variations in the magnetic record, while there is a clear increase in oceanographic instability from ∼ 6 cal kyr BP to the present. At large scale, a decreasing trend in the magnetic mineral content toward the present is presumably associated with a change in the circulation pattern and coincides in time with decreasing North Atlantic Deep Water formation. Short-term intervals of decreased magnetic mineral content are also identified at 5.2–4.9, 3.77–3.41, 3.01–2.7 and 0.93–0.62 cal kyr BP, the youngest one (AD 1020 to 1330) corresponding in time to the Medieval Warm Period. These events are interpreted to reflect periods of increased activity of the relatively warm, high salinity surface Irminger Current related to stronger input of North Atlantic waters into the Nordic Seas. In addition, spectral analysis of selected magnetic parameters demonstrates centennial-scale periodicities of ∼715, 240, 170 and 100 yr, which are more clearly expressed in the last 6 cal kyr BP than in the previous period. These periodicities might be attributed to intervals of persistence in the North Atlantic Oscillation (NAO) mode at centennial timescales. This record, therefore, indicates that the Holocene climate was more unstable than is often assumed, and it demonstrates the importance of high-resolution climatic studies for this recent time period to improve climate model predictions.

Published
2006

8. Climate records and changes in deep outflow from the Norwegian Sea ~150-55 ka

Author

E. Balbon, Tine Lander Rasmussen, Laurent Labeyrie, T.C.E. van Weering, Erik Thomsen, Department of Geology [Lund], Lund University [Lund], 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), Department of Earth Sciences [Aarhus], Aarhus University [Aarhus], Royal Netherlands Institute for Sea Research (NIOZ), 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, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, biology, Ocean current, Geology, 010502 geochemistry & geophysics, biology.organism_classification, 01 natural sciences, Foraminifera, Oceanography, Ice core, 13. Climate action, Stage (stratigraphy), Benthic zone, Outflow, 14. Life underwater, Stadial, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Channel (geography), ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

In order to contribute to our understanding of the linkage between climate and ocean circulation we have studied benthic foraminifera from near the northern end of the Faeroe–Shetland Channel covering isotope stages 6 to lower stage 3 (∼150–55 ka). Our records demonstrate shifts between recurring assemblages, which on millennial timescales monitor the outflow history of Norwegian Sea Deep Water. The records show that the outflow is closely linked to the climate of the region as documented in the Greenland ice cores. Outflow was relatively strong during all major warmer interstadials whereas there was no outflow during the colder stadials. During isotope substage 5e outflow was stable for ∼10–12 kyr with significant changes at the beginning and end only.

Published
1999

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