Articles | Volume 22, issue 8
https://doi.org/10.5194/bg-22-1947-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-22-1947-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
23 Apr 2025
Research article |
| 23 Apr 2025
| 23 Apr 2025
Anomalous summertime CO2 sink in the subpolar Southern Ocean promoted by early 2021 sea ice retreat
Kirtana Naëck
CORRESPONDING AUTHOR
LOCEAN, Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, LOCEAN/IPSL, 75005 Paris, France
Jacqueline Boutin
CORRESPONDING AUTHOR
LOCEAN, Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, LOCEAN/IPSL, 75005 Paris, France
Sebastiaan Swart
Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
Marcel du Plessis
Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
Liliane Merlivat
LOCEAN, Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, LOCEAN/IPSL, 75005 Paris, France
Laurence Beaumont
DT-INSU, Meudon, France
Antonio Lourenco
LOCEAN, Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, LOCEAN/IPSL, 75005 Paris, France
Francesco d'Ovidio
LOCEAN, Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, LOCEAN/IPSL, 75005 Paris, France
Louise Rousselet
LOCEAN, Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, LOCEAN/IPSL, 75005 Paris, France
Brian Ward
AirSea Laboratory, School of Physics and Ryan Institute, University of Galway, Galway, Ireland
Jean-Baptiste Sallée
LOCEAN, Sorbonne Université, CNRS, IRD, MNHN, Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, LOCEAN/IPSL, 75005 Paris, France
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Estel Font, Esther Portela, Sebastiaan Swart, Mauro Pinto-Juica, and Bastien Y. Queste
EGUsphere, https://doi.org/10.5194/egusphere-2025-3782, https://doi.org/10.5194/egusphere-2025-3782, 2025
This preprint is open for discussion and under review for Ocean Science (OS).
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In the Sea of Oman, mode waters form at the surface in winter and are trapped beneath a warmer surface layer in spring, linking the surface ocean and the oxygen minimum zone. Using data from ocean gliders, our study examines how this layer evolves. Changes occur along layers of equal density, with brief episodes of vertical mixing, enhanced by eddies. Glider data reveal more variability than monthly means, showing the need for sustained glider observations to understand future ecosystem impacts.
Léa Olivier, Jacqueline Boutin, Gilles Reverdin, Christopher Hunt, Thomas Linkowski, Alison Chase, Nils Haentjens, Pedro C. Junger, Stéphane Pesant, and Douglas Vandemark
Earth Syst. Sci. Data, 17, 3583–3598, https://doi.org/10.5194/essd-17-3583-2025, https://doi.org/10.5194/essd-17-3583-2025, 2025
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The air–sea CO2 flux in coastal waters plays a key role in the global carbon budget but remains poorly understood. In 2021, the Tara schooner collected 14 000 km of CO2 fugacity (fCO2) data along the South American coast. This dataset improves our understanding of fCO2 in the under-sampled Brazilian coastal region and provides a unique insight into the complex biogeochemistry of the Amazon River–ocean continuum.
Estel Font, Sebastiaan Swart, Puthenveettil Narayana Vinayachandran, and Bastien Y. Queste
Ocean Sci., 21, 1349–1368, https://doi.org/10.5194/os-21-1349-2025, https://doi.org/10.5194/os-21-1349-2025, 2025
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Mode water is formed annually and sits between the warm surface water and deeper older waters. In the Arabian Sea, it plays a crucial role in regulating ocean heat and oxygen variability by acting as a doorway between the surface and deeper waters. Using observations and models, we show that its formation is primarily driven by atmospheric forcing, though ocean currents, eddies, and biological heating also influence its life cycle. This water mass contributes up to 40 % of the region's oxygen content.
Renske Koets, Sebastiaan Swart, Kathleen Donohue, and Marcel du Plessis
EGUsphere, https://doi.org/10.5194/egusphere-2025-3112, https://doi.org/10.5194/egusphere-2025-3112, 2025
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The Cape Basin is a dynamic region where warm, salty Indian Ocean waters meet cooler Atlantic waters. Mixing between these waters drives ventilation, the transport of surface waters to deeper layers in the ocean. Using high-resolution observations from an autonomous Seaglider combined with satellite altimetry we provide new evidence on how small-scale ocean dynamics contribute to ventilation in the Cape Basin, with broader implications on ocean circulation.
Linus Vogt, Jean-Baptiste Sallée, and Casimir de Lavergne
Ocean Sci., 21, 1081–1103, https://doi.org/10.5194/os-21-1081-2025, https://doi.org/10.5194/os-21-1081-2025, 2025
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The ocean buffers human-induced climate change by taking up excess heat from the atmosphere. In this study, we use an ensemble of global climate models to study the physical processes which set the efficiency at which this heat is stored in the ocean. We reconcile previous attempts to explain controls on this efficiency and find that Southern Ocean stratification is a key model property due to its influence on the local overturning circulation and its connection to the subpolar North Atlantic.
Alex Nalivaev, Francesco d'Ovidio, Laurent Bopp, Maristella Berta, Louise Rousselet, Clara Azarian, and Stéphane Blain
EGUsphere, https://doi.org/10.5194/egusphere-2025-2145, https://doi.org/10.5194/egusphere-2025-2145, 2025
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The Kerguelen region hosts a phytoplankton bloom influenced by several iron sources. In particular, glaciers supply iron to the coastal waters. However, the importance of glacial iron for the bloom is not known. Here we calculate iron transport pathways from glaciers to the open ocean using in situ and satellite data, showing that one third of the offshore bloom is reached by glacial iron. These results are important in the context of the melting of the Kerguelen ice cap under climate change.
Linus Vogt, Casimir de Lavergne, Jean-Baptiste Sallée, Lester Kwiatkowski, Thomas L. Frölicher, and Jens Terhaar
EGUsphere, https://doi.org/10.21203/rs.3.rs-3982037/v2, https://doi.org/10.21203/rs.3.rs-3982037/v2, 2025
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Ocean heat uptake (OHU) accounts for over 90% of the Earth's excess energy storage due to climate change, but future (OHU) projections strongly differ between climate models. Here, we reveal an observational constraint on future OHU using historical Antarctic sea ice extent observations. This emergent constraint is based on a coupling between sea ice, deep and surface ocean temperatures, and cloud feedback. It implies an upward correction of 2024–2100 global OHU projections by up to 14%.
Nicolas Metzl, Jonathan Fin, Claire Lo Monaco, Claude Mignon, Samir Alliouane, Bruno Bombled, Jacqueline Boutin, Yann Bozec, Steeve Comeau, Pascal Conan, Laurent Coppola, Pascale Cuet, Eva Ferreira, Jean-Pierre Gattuso, Frédéric Gazeau, Catherine Goyet, Emilie Grossteffan, Bruno Lansard, Dominique Lefèvre, Nathalie Lefèvre, Coraline Leseurre, Sébastien Petton, Mireille Pujo-Pay, Christophe Rabouille, Gilles Reverdin, Céline Ridame, Peggy Rimmelin-Maury, Jean-François Ternon, Franck Touratier, Aline Tribollet, Thibaut Wagener, and Cathy Wimart-Rousseau
Earth Syst. Sci. Data, 17, 1075–1100, https://doi.org/10.5194/essd-17-1075-2025, https://doi.org/10.5194/essd-17-1075-2025, 2025
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This work presents a new synthesis of 67 000 total alkalinity and total dissolved inorganic carbon observations obtained between 1993 and 2023 in the global ocean, coastal zones, and the Mediterranean Sea. We describe the data assemblage and associated quality control and discuss some potential uses of this dataset. The dataset is provided in a single format and includes the quality flag for each sample.
Blandine Jacob, Bastien Y. Queste, and Marcel D. du Plessis
Ocean Sci., 21, 359–379, https://doi.org/10.5194/os-21-359-2025, https://doi.org/10.5194/os-21-359-2025, 2025
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Few observations exist in the Amundsen Sea. Consequently, studies rely on reanalysis (e.g., ERA5) to investigate how the atmosphere affects ocean variability (e.g., sea-ice formation and melt). We use data collected along ice shelves to show that cold, dry air blowing from Antarctica triggers large ocean heat loss, which is underestimated by ERA5. We then use an ocean model to show that this bias has an important impact on the ocean, with implications for sea-ice forecasts.
Clovis Thouvenin-Masson, Jacqueline Boutin, Vincent Échevin, Alban Lazar, and Jean-Luc Vergely
Ocean Sci., 20, 1547–1566, https://doi.org/10.5194/os-20-1547-2024, https://doi.org/10.5194/os-20-1547-2024, 2024
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We focus on understanding the impact of river runoff and precipitation on sea surface salinity (SSS) in the eastern North Tropical Atlantic (e-NTA) region off northwestern Africa. By analyzing regional simulations and observational data, we find that river flows significantly influence SSS variability, particularly after the rainy season. Our findings underscore that a main source of uncertainty representing SSS variability in this region is from river runoff estimates.
Jean-Baptiste Sallée, Lucie Vignes, Audrey Minière, Nadine Steiger, Etienne Pauthenet, Antonio Lourenco, Kevin Speer, Peter Lazarevich, and Keith W. Nicholls
Ocean Sci., 20, 1267–1280, https://doi.org/10.5194/os-20-1267-2024, https://doi.org/10.5194/os-20-1267-2024, 2024
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In the Weddell Sea, we investigated how warm deep currents and cold waters containing freshwater released from the Antarctic are connected. We used autonomous observation devices that have never been used in this region previously and that allow us to track the movement and characteristics of water masses under the sea ice. Our findings show a dynamic interaction between warm masses, providing key insights to understand climate-related changes in the region.
Nicolas Metzl, Jonathan Fin, Claire Lo Monaco, Claude Mignon, Samir Alliouane, David Antoine, Guillaume Bourdin, Jacqueline Boutin, Yann Bozec, Pascal Conan, Laurent Coppola, Frédéric Diaz, Eric Douville, Xavier Durrieu de Madron, Jean-Pierre Gattuso, Frédéric Gazeau, Melek Golbol, Bruno Lansard, Dominique Lefèvre, Nathalie Lefèvre, Fabien Lombard, Férial Louanchi, Liliane Merlivat, Léa Olivier, Anne Petrenko, Sébastien Petton, Mireille Pujo-Pay, Christophe Rabouille, Gilles Reverdin, Céline Ridame, Aline Tribollet, Vincenzo Vellucci, Thibaut Wagener, and Cathy Wimart-Rousseau
Earth Syst. Sci. Data, 16, 89–120, https://doi.org/10.5194/essd-16-89-2024, https://doi.org/10.5194/essd-16-89-2024, 2024
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This work presents a synthesis of 44 000 total alkalinity and dissolved inorganic carbon observations obtained between 1993 and 2022 in the Global Ocean and the Mediterranean Sea at the surface and in the water column. Seawater samples were measured using the same method and calibrated with international Certified Reference Material. We describe the data assemblage, quality control and some potential uses of this dataset.
Ria Oelerich, Karen J. Heywood, Gillian M. Damerell, Marcel du Plessis, Louise C. Biddle, and Sebastiaan Swart
Ocean Sci., 19, 1465–1482, https://doi.org/10.5194/os-19-1465-2023, https://doi.org/10.5194/os-19-1465-2023, 2023
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At the southern boundary of the Antarctic Circumpolar Current, relatively warm waters encounter the colder waters surrounding Antarctica. Observations from underwater vehicles and altimetry show that medium-sized cold-core eddies influence the southern boundary's barrier properties by strengthening the slopes of constant density lines across it and amplifying its associated jet. As a result, the ability of exchanging properties, such as heat, across the southern boundary is reduced.
Stéphanie Barrillon, Robin Fuchs, Anne A. Petrenko, Caroline Comby, Anthony Bosse, Christophe Yohia, Jean-Luc Fuda, Nagib Bhairy, Frédéric Cyr, Andrea M. Doglioli, Gérald Grégori, Roxane Tzortzis, Francesco d'Ovidio, and Melilotus Thyssen
Biogeosciences, 20, 141–161, https://doi.org/10.5194/bg-20-141-2023, https://doi.org/10.5194/bg-20-141-2023, 2023
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Extreme weather events can have a major impact on ocean physics and biogeochemistry, but their study is challenging. In May 2019, an intense storm occurred in the north-western Mediterranean Sea, during which in situ multi-platform measurements were performed. The results show a strong impact on the surface phytoplankton, highlighting the need for high-resolution measurements coupling physics and biology during these violent events that may become more common in the context of global change.
Yona Silvy, Clément Rousset, Eric Guilyardi, Jean-Baptiste Sallée, Juliette Mignot, Christian Ethé, and Gurvan Madec
Geosci. Model Dev., 15, 7683–7713, https://doi.org/10.5194/gmd-15-7683-2022, https://doi.org/10.5194/gmd-15-7683-2022, 2022
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A modeling framework is introduced to understand and decompose the mechanisms causing the ocean temperature, salinity and circulation to change since the pre-industrial period and into 21st century scenarios of global warming. This framework aims to look at the response to changes in the winds and in heat and freshwater exchanges at the ocean interface in global climate models, throughout the 1850–2100 period, to unravel their individual effects on the changing physical structure of the ocean.
Liliane Merlivat, Michael Hemming, Jacqueline Boutin, David Antoine, Vincenzo Vellucci, Melek Golbol, Gareth A. Lee, and Laurence Beaumont
Biogeosciences, 19, 3911–3920, https://doi.org/10.5194/bg-19-3911-2022, https://doi.org/10.5194/bg-19-3911-2022, 2022
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We use in situ high-temporal-resolution measurements of dissolved inorganic carbon and atmospheric parameters at the air–sea interface to analyse phytoplankton bloom initiation identified as the net rate of biological carbon uptake in the Mediterranean Sea. The shift from wind-driven to buoyancy-driven mixing creates conditions for blooms to begin. Active mixing at the air–sea interface leads to the onset of the surface phytoplankton bloom due to the relaxation of wind speed following storms.
Michael P. Hemming, Jan Kaiser, Jacqueline Boutin, Liliane Merlivat, Karen J. Heywood, Dorothee C. E. Bakker, Gareth A. Lee, Marcos Cobas García, David Antoine, and Kiminori Shitashima
Ocean Sci., 18, 1245–1262, https://doi.org/10.5194/os-18-1245-2022, https://doi.org/10.5194/os-18-1245-2022, 2022
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An underwater glider mission was carried out in spring 2016 near a mooring in the northwestern Mediterranean Sea. The glider deployment served as a test of a prototype ion-sensitive field-effect transistor pH sensor. Mean net community production rates were estimated from glider and buoy measurements of dissolved oxygen and inorganic carbon concentrations before and during the spring bloom. Incorporating advection is important for accurate mass budgets. Unexpected metabolic quotients were found.
Léa Olivier, Jacqueline Boutin, Gilles Reverdin, Nathalie Lefèvre, Peter Landschützer, Sabrina Speich, Johannes Karstensen, Matthieu Labaste, Christophe Noisel, Markus Ritschel, Tobias Steinhoff, and Rik Wanninkhof
Biogeosciences, 19, 2969–2988, https://doi.org/10.5194/bg-19-2969-2022, https://doi.org/10.5194/bg-19-2969-2022, 2022
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We investigate the impact of the interactions between eddies and the Amazon River plume on the CO2 air–sea fluxes to better characterize the ocean carbon sink in winter 2020. The region is a strong CO2 sink, previously underestimated by a factor of 10 due to a lack of data and understanding of the processes responsible for the variability in ocean carbon parameters. The CO2 absorption is mainly driven by freshwater from the Amazon entrained by eddies and by the winter seasonal cooling.
Gilles Reverdin, Claire Waelbroeck, Catherine Pierre, Camille Akhoudas, Giovanni Aloisi, Marion Benetti, Bernard Bourlès, Magnus Danielsen, Jérôme Demange, Denis Diverrès, Jean-Claude Gascard, Marie-Noëlle Houssais, Hervé Le Goff, Pascale Lherminier, Claire Lo Monaco, Herlé Mercier, Nicolas Metzl, Simon Morisset, Aïcha Naamar, Thierry Reynaud, Jean-Baptiste Sallée, Virginie Thierry, Susan E. Hartman, Edward W. Mawji, Solveig Olafsdottir, Torsten Kanzow, Anton Velo, Antje Voelker, Igor Yashayaev, F. Alexander Haumann, Melanie J. Leng, Carol Arrowsmith, and Michael Meredith
Earth Syst. Sci. Data, 14, 2721–2735, https://doi.org/10.5194/essd-14-2721-2022, https://doi.org/10.5194/essd-14-2721-2022, 2022
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The CISE-LOCEAN seawater stable isotope dataset has close to 8000 data entries. The δ18O and δD isotopic data measured at LOCEAN have uncertainties of at most 0.05 ‰ and 0.25 ‰, respectively. Some data were adjusted to correct for evaporation. The internal consistency indicates that the data can be used to investigate time and space variability to within 0.03 ‰ and 0.15 ‰ in δ18O–δD17; comparisons with data analyzed in other institutions suggest larger differences with other datasets.
Roxane Tzortzis, Andrea M. Doglioli, Stéphanie Barrillon, Anne A. Petrenko, Francesco d'Ovidio, Lloyd Izard, Melilotus Thyssen, Ananda Pascual, Bàrbara Barceló-Llull, Frédéric Cyr, Marc Tedetti, Nagib Bhairy, Pierre Garreau, Franck Dumas, and Gérald Gregori
Biogeosciences, 18, 6455–6477, https://doi.org/10.5194/bg-18-6455-2021, https://doi.org/10.5194/bg-18-6455-2021, 2021
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This work analyzes an original high-resolution data set collected in the Mediterranean Sea. The major result is the impact of a fine-scale frontal structure on the distribution of phytoplankton groups, in an area of moderate energy with oligotrophic conditions. Our results provide an in situ confirmation of the findings obtained by previous modeling studies and remote sensing about the structuring effect of the fine-scale ocean dynamics on the structure of the phytoplankton community.
Anastasiia Tarasenko, Alexandre Supply, Nikita Kusse-Tiuz, Vladimir Ivanov, Mikhail Makhotin, Jean Tournadre, Bertrand Chapron, Jacqueline Boutin, Nicolas Kolodziejczyk, and Gilles Reverdin
Ocean Sci., 17, 221–247, https://doi.org/10.5194/os-17-221-2021, https://doi.org/10.5194/os-17-221-2021, 2021
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Data from the ARKTIKA-2018 expedition and new satellite data help us to follow rapid changes in the upper layer of the Laptev and East Siberian seas (LS, ESS) in summer 2018. With satellite-derived surface temperature, an improved SMOS salinity, and wind, we study how the fresh river water is mixed with cold sea water and ice-melted water at small time and spatial scales. The wind pushes fresh water northward and northeastward, close to and under the ice, forcing it into the deep Arctic Ocean.
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Short summary
In summer 2022, a CARbon Interface OCean Atmosphere (CARIOCA) drifting buoy observed an anomalously strong ocean carbon sink in the subpolar Southern Ocean associated with large plumes of chlorophyll a. Lagrangian backward trajectories indicate that these waters originated from the sea ice edge in spring 2021. Our study highlights the northward migration of the CO2 sink associated with early sea ice retreat.
In summer 2022, a CARbon Interface OCean Atmosphere (CARIOCA) drifting buoy observed an...
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