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3. Global sea-level budget 1993–present

Author

Group, WCRP Global Sea Level Budget, Cazenave, Anny, Meyssignac, Benoit, Ablain, Michael, Balmaseda, Magdalena, Bamber, Jonathan, Barletta, Valentina Roberta, Beckley, Brian, Benveniste, Jérôme, Berthier, Etienne, Blazquez, Alejandro, Boyer , Tim, Caceres , Denise, Chambers, Don P., Champollion, Nicolas, Chao , Ben, Chen , Jianli, Cheng , Lijing, Church , John A., Chuter, Stephen, Cogley , J. Graham, Dangendorf , Soenke, Desbruyères , Damien, Döll , Petra, Domingues, Catia, Falk , Ulrike, Famiglietti , James, Fenoglio-Marc, Luciana, Forsberg, René, Galassi , Gaia, Gardner, Alex, Groh, Andreas, Hamlington , Benjamin, Hogg, Anna, Horwath, Martin, Humphrey , Vincent, Husson , Laurent, Ishii , Masayoshi, Jaeggi , Adrian, Jevrejeva , Svetlana, Johnson , Gregory, Kolodziejczyk , Nicolas, Kusche , Jürgen, Lambeck , Kurt, Landerer , Felix, Leclercq , Paul, Legresy , Benoit, Leuliette , Eric, Llovel, William, Longuevergne , Laurent, Loomis , Bryant D., Luthcke, Scott B, Marcos, Marta, Marzeion , Ben, Merchant , Chris, Merrifield , Mark, Milne, Glenn, Mitchum , Gary, Mohajerani, Yara, Monier , Maeva, Monselesan , Didier, Nerem , Steve, Palanisamy , Hindumathi, Paul, Frank, Pérez, Begona, Piecuch , Christopher G., Ponte , Rui M., Purkey , Sarah G., Reager , John T., Rietbroek , Roelof, Rignot, Eric, Riva, Riccardo, Roemmich , Dean H., Sørensen, Louise Sandberg, Sasgen, Ingo, Schram, E.J.O., Seneviratne , Sonia I., Shum, C.K., Spada, Giorgio, Stammer, Detlef, van de Wal , Roderic, Velicogna, Isabella, von Schuckmann, Karina, Wada, Yoshihide, Wang , Yiguo, Watson, Christopher S., Wiese, David, Wijffels , Susan, Westaway , Richard, Woppelmann, Guy, Wouters, Bert, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), International Space Science Institute [Bern] (ISSI), Géosciences Rennes (GR), 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 Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Collecte Localisation Satellites (CLS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales [Toulouse] (CNES), European Centre for Medium-Range Weather Forecasts (ECMWF), University of New South Wales [Sydney] (UNSW), Universität Siegen [Siegen], Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), National Oceanographic Centre [Liverpool] (NOC ), Australian National University (ANU), CSIRO Marine and Atmosphere Research [Hobart], Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Institut Mediterrani d'Estudis Avancats (IMEDEA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de las Islas Baleares (UIB), University of Tasmania [Hobart, Australia] (UTAS), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Hubrecht Institute [Utrecht, Netherlands], University Medical Center [Utrecht]-Royal Netherlands Academy of Arts and Sciences (KNAW), 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), Cazenave, Anny, Meyssignac, Benoit, Ablain, Michael, Balmaseda, Magdalena, Bamber, Jonathan, Barletta, Valentina, Beckley, Brian, Benveniste, Jérôme, Berthier, Etienne, Blazquez, Alejandro, Boyer, Tim, Caceres, Denise, Chambers, Don, Champollion, Nicola, Chao, Ben, Chen, Jianli, Cheng, Lijing, Church, John A., Chuter, S., Cogley, J., Dangendorf, Soenke, Desbruyères, Damien, Döll, Petra, Domingues, Catia, Falk, Ulrike, Famiglietti, Jame, Fenoglio-Marc, Luciana, Forsberg, Rene, Galassi, Gaia, Gardner, Alex, Groh, Andrea, Hamlington, Benjamin, Hogg, Anna, Horwath, Martin, Humphrey, Vincent, Husson, Laurent, Ishii, Masayoshi, Jaeggi, Adrian, Jevrejeva, Svetlana, Johnson, Gregory, Kolodziejczyk, Nicola, Kusche, Jürgen, Lambeck, Kurt, Landerer, Felix, Leclercq, Paul, Legresy, Benoit, Leuliette, Eric, Llovel, William, Longuevergne, Laurent, Loomis, Bryant D., Luthcke, Scott B., Marcos, Marta, Marzeion, Ben, Merchant, Chri, Merrifield, Mark, Milne, Glenn, Mitchum, Gary, Mohajerani, Yara, Monier, Maeva, Monselesan, Didier, Nerem, Steve, Palanisamy, Hindumathi, Paul, Frank, Perez, Begoña, Piecuch, Christopher G., Ponte, Rui M., Purkey, Sarah G., Reager, John T., Rietbroek, Roelof, Rignot, Eric, Riva, Riccardo, Roemmich, Dean H., Sandberg Sørensen, Louise, Sasgen, Ingo, Schrama, E. J. O., Seneviratne, Sonia I., Shum, C. K., Spada, Giorgio, Stammer, Detlef, van de Wal, Roderic, Velicogna, Isabella, von Schuckmann, Karina, Wada, Yoshihide, Wang, Yiguo, Watson, Christopher, Wiese, David, Wijffels, Susan, Westaway, Richard, Woppelmann, Guy, and Wouters, Bert

Subjects
010504 meteorology & atmospheric sciences, Climate change, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Context (language use), sea level, 010502 geochemistry & geophysics, 01 natural sciences, Deep sea, SDG 13 - Climate Action, sea level, sea level change, gauge records, 14. Life underwater, Altimeter, Sea level, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, lcsh:Environmental sciences, 0105 earth and related environmental sciences, lcsh:GE1-350, geography, geography.geographical_feature_category, 520 Astronomy, Global warming, lcsh:QE1-996.5, Glacier, lcsh:Geology, 13. Climate action, Climatology, gauge records, General Earth and Planetary Sciences, Environmental science, GlobalMass, Ice sheet, sea level change
Abstract

Global mean sea level is an integral of changes occurring in the climate system in response to unforced climate variability as well as natural and anthropogenic forcing factors. Its temporal evolution allows changes (e.g., acceleration) to be detected in one or more components. Study of the sea-level budget provides constraints on missing or poorly known contributions, such as the unsurveyed deep ocean or the still uncertain land water component. In the context of the World Climate Research Programme Grand Challenge entitledRegional Sea Level and Coastal Impacts, an international effort involving the sea-level community worldwide has been recently initiated with the objective of assessing the various datasets used to estimate components of the sea-level budget during the altimetry era (1993 to present). These datasets are based on the combination of a broad range of space-based and in situ observations, model estimates, and algorithms. Evaluating their quality, quantifying uncertainties and identifying sources of discrepancies between component estimates is extremely useful for various applications in climate research. This effort involves several tens of scientists from about 50 research teams/institutions worldwide (www.wcrp-climate.org/grand-challenges/gc-sea-level, last access: 22 August 2018). The results presented in this paper are a synthesis of the first assessment performed during 2017–2018. We present estimates of the altimetry-based global mean sea level (average rate of 3.1 ± 0.3 mm yr−1and acceleration of 0.1 mm yr−2over 1993–present), as well as of the different components of the sea-level budget (http://doi.org/10.17882/54854, last access: 22 August 2018). We further examine closure of the sea-level budget, comparing the observed global mean sea level with the sum of components. Ocean thermal expansion, glaciers, Greenland and Antarctica contribute 42 %, 21 %, 15 % and 8 % to the global mean sea level over the 1993–present period. We also study the sea-level budget over 2005–present, using GRACE-based ocean mass estimates instead of the sum of individual mass components. Our results demonstrate that the global mean sea level can be closed to within 0.3 mm yr−1(1σ). Substantial uncertainty remains for the land water storage component, as shown when examining individual mass contributions to sea level.

Published
2018

4. Unabated Bottom Water Warming and Freshening in the South Pacific Ocean.

Author

Purkey, Sarah G., Johnson, Gregory C., Talley, Lynne D., Sloyan, Bernadette M., Wijffels, Susan E., Smethie, William, Mecking, Sabine, and Katsumata, Katsuro

Subjects
BOTTOM water (Oceanography), OCEAN circulation, GLOBAL warming, SEA level
Abstract

Abyssal ocean warming contributed substantially to anthropogenic ocean heat uptake and global sea level rise between 1990 and 2010. In the 2010s, several hydrographic sections crossing the South Pacific Ocean were occupied for a third or fourth time since the 1990s, allowing for an assessment of the decadal variability in the local abyssal ocean properties among the 1990s, 2000s, and 2010s. These observations from three decades reveal steady to accelerated bottom water warming since the 1990s. Strong abyssal (z > 4,000 m) warming of 3.5 (±1.4) m°C/year (m°C = 10−3 °C) is observed in the Ross Sea, directly downstream from bottom water formation sites, with warming rates of 2.5 (±0.4) m°C/year to the east in the Amundsen‐Bellingshausen Basin and 1.3 (±0.2) m°C/year to the north in the Southwest Pacific Basin, all associated with a bottom‐intensified descent of the deepest isotherms. Warming is consistently found across all sections and their occupations within each basin, demonstrating that the abyssal warming is monotonic, basin‐wide, and multidecadal. In addition, bottom water freshening was strongest in the Ross Sea, with smaller amplitude in the Amundsen‐Bellingshausen Basin in the 2000s, but is discernible in portions of the Southwest Pacific Basin by the 2010s. These results indicate that bottom water freshening, stemming from strong freshening of Ross Shelf Waters, is being advected along deep isopycnals and mixed into deep basins, albeit on longer timescales than the dynamically driven, wave‐propagated warming signal. We quantify the contribution of the warming to local sea level and heat budgets. Plain Language Summary: Over 90% of the excess energy gained by Earth's climate system has been absorbed by the oceans, with about 10% found deeper than 2,000 m. The rates and patterns of deep and abyssal (deeper than 4,000 m) ocean warming, while vital for understanding how this heat sink might behave in the future, are poorly known owing to limited data. Here we use highly accurate data collected by ships along oceanic transects with decadal revisits to quantify how much heat and freshwater has entered the South Pacific Ocean between the 1990s and 2010s. We find widespread warming throughout the deep basins there and evidence that the warming rate has accelerated in the 2010s relative to the 1990s. The warming is strongest near Antarctica where the abyssal ocean is ventilated by surface waters that sink to the sea floor and hence become bottom water, but abyssal warming is observed everywhere. In addition, we observe an infusion of freshwater propagating along the pathway of the bottom water as it moves northward from Antarctica. We quantify the deep ocean warming contributions to heat uptake as well as sea level rise through thermal expansion. Key Points: Bottom waters in the South Pacific Ocean have warmed steadily since the 1990s, based on data from multiple repeat oceanographic transectsMaximum warming of 0.04 degrees C/decade is found within the deep Ross Sea, with the signal weakening to the northAntarctic Bottom Water freshening, limited to around Antarctica in previous decades, has reached the Southwest Pacific Basin in the 2010s [ABSTRACT FROM AUTHOR]

Published
2019
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5. Deep Caribbean Sea warming

Author

Johnson, Gregory C. and Purkey, Sarah G.

Subjects
*DEEP-sea temperature, *HYDROGRAPHY, *GLOBAL warming, *CLIMATE change, *ABSOLUTE sea level change, *OCEAN temperature, *WATER depth, *THERMAL conductivity
Abstract

Abstract: Data collected from hydrographic stations occupied within the Venezuelan and Columbian basins of the Caribbean Sea from 1922 through 2003 are analyzed to study the decadal variability of deep temperature in the region. The analysis focuses on waters below the 1815-m sill depth of the Anegada–Jungfern Passage. Relatively dense waters (compared to those in the deep Caribbean) from the North Atlantic spill over this sill to ventilate the deep Caribbean Sea. Deep warming at a rate of over 0.01°Cdecade–1 below this sill depth appears to have commenced in the 1970s after a period of relatively constant deep Caribbean Sea temperatures extending at least as far back as the 1920s. Conductivity–temperature–depth station data from World Ocean Circulation Experiment Section A22 along 66°W taken in 1997 and again in 2003 provide an especially precise, albeit geographically limited, estimate of this warming over that 6-year period. They also suggest a small (0.001 PSS-78, about the size of expected measurement biases) deep freshening. The warming is about 10 times larger than the size of geothermal heating in the region, and is of the same magnitude as the average global upper-ocean heat uptake over a recent 50-year period. Together with the freshening, the warming contributes about 0.012mdecade–1 of sea level rise in portions of the Caribbean Sea with bottom depths around 5000m. [Copyright &y& Elsevier]

Published
2009
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6. Warming and Freshening in the Abyssal Southeastern Indian Ocean.

Author

Johnson, Gregory C., Purkey, Sarah G., and Bullister, John L.

Subjects
*GLOBAL warming, *ABYSSAL zone, *HYDROGRAPHIC surveying, *SEAWATER, *OCEAN, *SALINITY
Abstract

Warming and freshening of abyssal waters in the eastern Indian Ocean between 1994/95 and 2007 are quantified using data from two closely sampled high-quality occupations of a hydrographic section extending from Antarctica northward to the equator. These changes are limited to abyssal waters in the Princess Elizabeth Trough and the Australian–Antarctic Basin, with little abyssal change evident north of the Southeast Indian Ridge. As in previous studies, significant cooling and freshening is observed in the bottom potential temperature–salinity relations in these two southern basins. In addition, analysis on pressure surfaces shows abyssal warming of about 0.05°C and freshening of about 0.01 Practical Salinity Scale 1978 (PSS-78) in the Princess Elizabeth Trough, and warming of 0.1°C with freshening of about 0.005 in the abyssal Australian–Antarctic Basin. These 12-yr differences are statistically significant from zero at 95% confidence intervals over the bottom few to several hundred decibars of the water column in both deep basins. Both warming and freshening reduce the density of seawater, contributing to the vertical expansion of the water column. The changes below 3000 dbar in these basins suggest local contributions approaching 1 and 4 cm of sea level rise, respectively. Transient tracer data from the 2007 occupation qualitatively suggest that the abyssal waters in the two southern basins exhibiting changes have significant components that have been exposed to the ocean surface within the last few decades, whereas north of the Southeast Indian Ridge, where changes are not found, the component of abyssal waters that have undergone such ventilation is much reduced. [ABSTRACT FROM AUTHOR]

Published
2008
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