Articles | Volume 22, issue 4
https://doi.org/10.5194/os-22-2425-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-22-2425-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Thermohaline gradients and frontal regimes in the northwestern Tropical Atlantic
Dante C. Napolitano
CORRESPONDING AUTHOR
Univ. Brest, CNRS, Ifremer, IRD, Laboratoire d’Océanographie Physique et Spatiale (LOPS), IUEM, 29280, Plouzané, France
Jonathan Gula
Univ. Brest, CNRS, Ifremer, IRD, Laboratoire d’Océanographie Physique et Spatiale (LOPS), IUEM, 29280, Plouzané, France
Institut Universitaire de France (IUF), Paris, France
Solange Coadou-Chaventon
LMD/IPSL, ENS, PSL University, École Polytechnique, Institut Polytechnique de Paris, Sorbonne Université, CNRS, Paris, France
Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
Sabrina Speich
LMD/IPSL, ENS, PSL University, École Polytechnique, Institut Polytechnique de Paris, Sorbonne Université, CNRS, Paris, France
Cesar B. Rocha
Instituto Oceanográfico, Universidade de São Paulo, São Paulo, Brazil
James C. McWilliams
Department of Atmospheric and Ocean Sciences, University of California Los Angeles, Los Angeles, California, USA
Dongxiao Zhang
CICOES/University of Washington and NOAA Pacific Marine Environmental Laboratory, Seattle, Washington, USA
Xavier Carton
Univ. Brest, CNRS, Ifremer, IRD, Laboratoire d’Océanographie Physique et Spatiale (LOPS), IUEM, 29280, Plouzané, France
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Delphine Hypolite, Daniel Dauhajre, Minna Ho, Leonel Romero, and James McWilliams
EGUsphere, https://doi.org/10.5194/egusphere-2026-2942, https://doi.org/10.5194/egusphere-2026-2942, 2026
This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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As ocean waves break on the beach, they push water along the shore and drag against the seafloor, sculpting the currents that flow past our shores. We built a computer model that captures these wave-driven effects together with the broader ocean circulation, at a resolution fine enough to see how the surf zone connects to the open sea. On the California coast, the model shows how breaking waves and seafloor friction together drive a vertical overturning loop and fast currents along the shore.
Yonglin Huang, Annalisa Bracco, Kurt Polzin, and Jonathan Gula
EGUsphere, https://doi.org/10.5194/egusphere-2026-2869, https://doi.org/10.5194/egusphere-2026-2869, 2026
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We compared four high-resolution simulations with observations from the Brazil Basin to test how models represent deep-ocean mixing above rough seafloor. By tracking virtual particles, we found that the simulations reproduce strong mixing near the bottom, and higher resolution produces enhanced mixing in the ocean interior. Our results indicate that smoothed seafloor details weaken wave breaking and leave too much energy in eddies, making them more intense than they likely are in the real ocean.
Audrey Minière, Karina von Schuckmann, and Sabrina Speich
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2026-106, https://doi.org/10.5194/essd-2026-106, 2026
Revised manuscript under review for ESSD
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This study assesses the sensitivity of global ocean heat content estimates to key methodological choices. Global trends are robust across methodological configurations. Most of the spread comes from the choice of temperature dataset, while other methodological impacts remain small. Our results show that both research and operational indicators consistently track global ocean warming, supporting their reliability and traceability for climate monitoring and Earth energy budget assessments.
Pablo Fernández, Sabrina Speich, Guillaume Lapeyre, Claudia Pasquero, Carlos Conejero, Lionel Renault, and Fabien Desbiolles
Ocean Sci., 22, 699–725, https://doi.org/10.5194/os-22-699-2026, https://doi.org/10.5194/os-22-699-2026, 2026
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We use a high-resolution ocean-atmosphere coupled simulation to assess the effects of fine-scale sea surface temperature, surface currents, and ocean vertical stratification on the spatial variability of latent heat flux in the Northwest Tropical Atlantic. The results show significant impacts from these three variables in latent heat flux. They stress the need to account for fine-scale ocean processes in the coarser global coupled models even in relatively quiescent regions like the tropics.
Iury Simoes-Sousa, Cesar Rocha, Amit Tandon, and Andre Schmidt
Earth Syst. Sci. Data, 18, 1089–1101, https://doi.org/10.5194/essd-18-1089-2026, https://doi.org/10.5194/essd-18-1089-2026, 2026
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This research combines ocean profile data with satellite-tracked ocean vortex data to explore the vertical structure of ocean vortices globally. It integrates over 4 million vertical profiles with 35 million vortex observations. The dataset, processed using advanced computing, is openly accessible and offers a foundation for studying the role of ocean vortices on weather, climate, and ecosystems.
Yan Barabinot, Sabrina Speich, and Xavier Carton
Ocean Sci., 21, 2527–2553, https://doi.org/10.5194/os-21-2527-2025, https://doi.org/10.5194/os-21-2527-2025, 2025
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Mesoscale eddies, characterized by rotating currents, are ubiquitous in the ocean. However, their three-dimensional structure remains poorly observed and analyzed, with transport estimates often relying on approximations. To better quantify their shape, we propose a new theoretical framework based on geophysical fluid dynamics and apply it to field observations.
Yan Barabinot, Sabrina Speich, Xavier Carton, Pierre L'Hégaret, Corentin Subirade, Rémi Laxenaire, and Johannes Karstensen
Ocean Sci., 21, 1849–1872, https://doi.org/10.5194/os-21-1849-2025, https://doi.org/10.5194/os-21-1849-2025, 2025
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Mesoscale eddies are rotating oceanic currents key to ocean variability. Off Brazil’s northeast coast, the North Brazil Current generates on average 4.5 eddies per year, which drift towards the West Indies, transporting waters from the Southern Hemisphere. Using data collected at sea by the EUREC4A-OA cruise, this study reveals that deep eddies transport 5 times more water than surface ones, reshaping our understanding of the regional water transport.
Théo Picard, Chelsey A. Baker, Jonathan Gula, Ronan Fablet, Laurent Mémery, and Richard Lampitt
Biogeosciences, 22, 4309–4331, https://doi.org/10.5194/bg-22-4309-2025, https://doi.org/10.5194/bg-22-4309-2025, 2025
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Ocean sediment traps measure the sequestrated sinking organic carbon. While sinking, the particles are affected by local currents, which presents a challenge with regard to linking the deep flux with the surface. We present a machine learning tool that predicts the source location of the sinking particles based on satellite data. The predictions demonstrate a stronger correlation between surface and deep carbon fluxes, allowing a more comprehensive understanding of the deep carbon sequestration drivers.
Yawouvi Dodji Soviadan, Miriam Beck, Joelle Habib, Alberto Baudena, Laetitia Drago, Alexandre Accardo, Remi Laxenaire, Sabrina Speich, Peter Brandt, Rainer Kiko, and Stemmann Lars
Biogeosciences, 22, 3485–3501, https://doi.org/10.5194/bg-22-3485-2025, https://doi.org/10.5194/bg-22-3485-2025, 2025
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Key parameters representing the gravity flux in global models are sinking speed and vertical attenuation of exported material. We calculate, for the first time, these parameters in situ in the ocean for six intermittent blooms followed by export events using high-resolution (3 d) time series of 0–1000 m depth profiles from imaging sensors mounted on an Argo float. We show that sinking speed depends not only on size but also on the morphology of the particles, with density being an important property.
Alexandre Accardo, Rémi Laxenaire, Alberto Baudena, Sabrina Speich, Rainer Kiko, and Lars Stemmann
Biogeosciences, 22, 1183–1201, https://doi.org/10.5194/bg-22-1183-2025, https://doi.org/10.5194/bg-22-1183-2025, 2025
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The open ocean helps mitigate climate change by storing CO2 via the biological carbon pump (BCP), which involves processes like organic carbon production at the surface and transferring it to the deep ocean via various pathways. By deploying an autonomous platform, we found significant marine snow accumulation from the surface to the mesopelagic zone in frontal regions between eddies. We suggest that the coupling of hydrodynamics at eddy edges and biological activity may enhance this process.
Yan Barabinot, Sabrina Speich, and Xavier Carton
Ocean Sci., 21, 151–179, https://doi.org/10.5194/os-21-151-2025, https://doi.org/10.5194/os-21-151-2025, 2025
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Mesoscale eddies are ubiquitous rotating currents in the ocean. Some eddies, called "materially coherent", are able to transport a different water mass from the surrounding water. By analyzing 3D eddy structures sampled during oceanographic cruises, we found that eddies can be nonmaterially coherent, accounting only for their surface properties, but materially coherent considering their properties at depth. Future studies cannot rely solely on satellite data to evaluate heat and salt transport.
Théo Picard, Jonathan Gula, Ronan Fablet, Jeremy Collin, and Laurent Mémery
Ocean Sci., 20, 1149–1165, https://doi.org/10.5194/os-20-1149-2024, https://doi.org/10.5194/os-20-1149-2024, 2024
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The biological carbon pump plays a key role in the climate system. Plankton absorb and transform CO2 into organic carbon, forming particles that sink to the ocean floor. Sediment traps catch these particles and measure the carbon stored in the abyss. However, the particles' surface origin is unknown as ocean currents alter their paths. Here, we train an AI model to predict the origin of these particles. This new tool enables a better link between deep-ocean observations and satellite images.
Jonathan Andrew Baker, Richard Renshaw, Laura Claire Jackson, Clotilde Dubois, Doroteaciro Iovino, Hao Zuo, Renellys C. Perez, Shenfu Dong, Marion Kersalé, Michael Mayer, Johannes Mayer, Sabrina Speich, and Tarron Lamont
State Planet, 1-osr7, 4, https://doi.org/10.5194/sp-1-osr7-4-2023, https://doi.org/10.5194/sp-1-osr7-4-2023, 2023
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We use ocean reanalyses, in which ocean models are combined with observations, to infer past changes in ocean circulation and heat transport in the South Atlantic. Comparing these estimates with other observation-based estimates, we find differences in their trends, variability, and mean heat transport but closer agreement in their mean overturning strength. Ocean reanalyses can help us understand the cause of these differences, which could improve estimates of ocean transports in this region.
Saeed Hariri, Sabrina Speich, Bruno Blanke, and Marina Lévy
Ocean Sci., 19, 1183–1201, https://doi.org/10.5194/os-19-1183-2023, https://doi.org/10.5194/os-19-1183-2023, 2023
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This work presents a series of studies conducted by the authors on the application of the Lagrangian approach for the connectivity analysis between different ocean locations in an idealized open-ocean model. We assess how the connectivity properties of typical oceanic flows are affected by the fine-scale circulation and discuss the challenges facing ocean connectivity estimates related to the spatial resolution. Our results are important to improve the understanding of marine ecosystems.
Pierre L'Hégaret, Florian Schütte, Sabrina Speich, Gilles Reverdin, Dariusz B. Baranowski, Rena Czeschel, Tim Fischer, Gregory R. Foltz, Karen J. Heywood, Gerd Krahmann, Rémi Laxenaire, Caroline Le Bihan, Philippe Le Bot, Stéphane Leizour, Callum Rollo, Michael Schlundt, Elizabeth Siddle, Corentin Subirade, Dongxiao Zhang, and Johannes Karstensen
Earth Syst. Sci. Data, 15, 1801–1830, https://doi.org/10.5194/essd-15-1801-2023, https://doi.org/10.5194/essd-15-1801-2023, 2023
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In early 2020, the EUREC4A-OA/ATOMIC experiment took place in the northwestern Tropical Atlantic Ocean, a dynamical region where different water masses interact. Four oceanographic vessels and a fleet of autonomous devices were deployed to study the processes at play and sample the upper ocean, each with its own observing capability. The article first describes the data calibration and validation and second their cross-validation, using a hierarchy of instruments and estimating the uncertainty.
Alexandre Barboni, Solange Coadou-Chaventon, Alexandre Stegner, Briac Le Vu, and Franck Dumas
Ocean Sci., 19, 229–250, https://doi.org/10.5194/os-19-229-2023, https://doi.org/10.5194/os-19-229-2023, 2023
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Mesoscale eddies are ubiquitous turbulent structures in the ocean, influencing the upper mixed layer. The mixed layer is the ocean surface layer mixed through air–sea exchanges. Using Argo profiling floats inside large Mediterranean anticyclones, we investigate the induced winter mixed-layer depth anomalies. Mixed-layer depth was observed to be greatly influenced by the eddy preexisting subsurface structure to which it possibly connects and can also create double-core anticyclones.
Adriana Bailey, Franziska Aemisegger, Leonie Villiger, Sebastian A. Los, Gilles Reverdin, Estefanía Quiñones Meléndez, Claudia Acquistapace, Dariusz B. Baranowski, Tobias Böck, Sandrine Bony, Tobias Bordsdorff, Derek Coffman, Simon P. de Szoeke, Christopher J. Diekmann, Marina Dütsch, Benjamin Ertl, Joseph Galewsky, Dean Henze, Przemyslaw Makuch, David Noone, Patricia K. Quinn, Michael Rösch, Andreas Schneider, Matthias Schneider, Sabrina Speich, Bjorn Stevens, and Elizabeth J. Thompson
Earth Syst. Sci. Data, 15, 465–495, https://doi.org/10.5194/essd-15-465-2023, https://doi.org/10.5194/essd-15-465-2023, 2023
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One of the novel ways EUREC4A set out to investigate trade wind clouds and their coupling to the large-scale circulation was through an extensive network of isotopic measurements in water vapor, precipitation, and seawater. Samples were taken from the island of Barbados, from aboard two aircraft, and from aboard four ships. This paper describes the full collection of EUREC4A isotopic in situ data and guides readers to complementary remotely sensed water vapor isotope ratios.
Takaya Uchida, Julien Le Sommer, Charles Stern, Ryan P. Abernathey, Chris Holdgraf, Aurélie Albert, Laurent Brodeau, Eric P. Chassignet, Xiaobiao Xu, Jonathan Gula, Guillaume Roullet, Nikolay Koldunov, Sergey Danilov, Qiang Wang, Dimitris Menemenlis, Clément Bricaud, Brian K. Arbic, Jay F. Shriver, Fangli Qiao, Bin Xiao, Arne Biastoch, René Schubert, Baylor Fox-Kemper, William K. Dewar, and Alan Wallcraft
Geosci. Model Dev., 15, 5829–5856, https://doi.org/10.5194/gmd-15-5829-2022, https://doi.org/10.5194/gmd-15-5829-2022, 2022
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Ocean and climate scientists have used numerical simulations as a tool to examine the ocean and climate system since the 1970s. Since then, owing to the continuous increase in computational power and advances in numerical methods, we have been able to simulate increasing complex phenomena. However, the fidelity of the simulations in representing the phenomena remains a core issue in the ocean science community. Here we propose a cloud-based framework to inter-compare and assess such simulations.
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.
Kai Wang, Xiujun Wang, Raghu Murtugudde, Dongxiao Zhang, and Rong-Hua Zhang
Geosci. Model Dev., 15, 1017–1035, https://doi.org/10.5194/gmd-15-1017-2022, https://doi.org/10.5194/gmd-15-1017-2022, 2022
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We use observational data of dissolved oxygen (DO) and organic nitrogen to calibrate a basin-scale model (OGCM-DEMC V1.4) and then evaluate model capacity for simulating mid-depth DO in the tropical Pacific. Sensitivity studies show that enhanced vertical mixing combined with reduced biological consumption performs well in reproducing asymmetric oxygen minimum zones (OMZs). We find that DO is more sensitive to biological processes in the upper OMZs but to physical processes in the lower OMZs.
Bjorn Stevens, Sandrine Bony, David Farrell, Felix Ament, Alan Blyth, Christopher Fairall, Johannes Karstensen, Patricia K. Quinn, Sabrina Speich, Claudia Acquistapace, Franziska Aemisegger, Anna Lea Albright, Hugo Bellenger, Eberhard Bodenschatz, Kathy-Ann Caesar, Rebecca Chewitt-Lucas, Gijs de Boer, Julien Delanoë, Leif Denby, Florian Ewald, Benjamin Fildier, Marvin Forde, Geet George, Silke Gross, Martin Hagen, Andrea Hausold, Karen J. Heywood, Lutz Hirsch, Marek Jacob, Friedhelm Jansen, Stefan Kinne, Daniel Klocke, Tobias Kölling, Heike Konow, Marie Lothon, Wiebke Mohr, Ann Kristin Naumann, Louise Nuijens, Léa Olivier, Robert Pincus, Mira Pöhlker, Gilles Reverdin, Gregory Roberts, Sabrina Schnitt, Hauke Schulz, A. Pier Siebesma, Claudia Christine Stephan, Peter Sullivan, Ludovic Touzé-Peiffer, Jessica Vial, Raphaela Vogel, Paquita Zuidema, Nicola Alexander, Lyndon Alves, Sophian Arixi, Hamish Asmath, Gholamhossein Bagheri, Katharina Baier, Adriana Bailey, Dariusz Baranowski, Alexandre Baron, Sébastien Barrau, Paul A. Barrett, Frédéric Batier, Andreas Behrendt, Arne Bendinger, Florent Beucher, Sebastien Bigorre, Edmund Blades, Peter Blossey, Olivier Bock, Steven Böing, Pierre Bosser, Denis Bourras, Pascale Bouruet-Aubertot, Keith Bower, Pierre Branellec, Hubert Branger, Michal Brennek, Alan Brewer, Pierre-Etienne Brilouet, Björn Brügmann, Stefan A. Buehler, Elmo Burke, Ralph Burton, Radiance Calmer, Jean-Christophe Canonici, Xavier Carton, Gregory Cato Jr., Jude Andre Charles, Patrick Chazette, Yanxu Chen, Michal T. Chilinski, Thomas Choularton, Patrick Chuang, Shamal Clarke, Hugh Coe, Céline Cornet, Pierre Coutris, Fleur Couvreux, Susanne Crewell, Timothy Cronin, Zhiqiang Cui, Yannis Cuypers, Alton Daley, Gillian M. Damerell, Thibaut Dauhut, Hartwig Deneke, Jean-Philippe Desbios, Steffen Dörner, Sebastian Donner, Vincent Douet, Kyla Drushka, Marina Dütsch, André Ehrlich, Kerry Emanuel, Alexandros Emmanouilidis, Jean-Claude Etienne, Sheryl Etienne-Leblanc, Ghislain Faure, Graham Feingold, Luca Ferrero, Andreas Fix, Cyrille Flamant, Piotr Jacek Flatau, Gregory R. Foltz, Linda Forster, Iulian Furtuna, Alan Gadian, Joseph Galewsky, Martin Gallagher, Peter Gallimore, Cassandra Gaston, Chelle Gentemann, Nicolas Geyskens, Andreas Giez, John Gollop, Isabelle Gouirand, Christophe Gourbeyre, Dörte de Graaf, Geiske E. de Groot, Robert Grosz, Johannes Güttler, Manuel Gutleben, Kashawn Hall, George Harris, Kevin C. Helfer, Dean Henze, Calvert Herbert, Bruna Holanda, Antonio Ibanez-Landeta, Janet Intrieri, Suneil Iyer, Fabrice Julien, Heike Kalesse, Jan Kazil, Alexander Kellman, Abiel T. Kidane, Ulrike Kirchner, Marcus Klingebiel, Mareike Körner, Leslie Ann Kremper, Jan Kretzschmar, Ovid Krüger, Wojciech Kumala, Armin Kurz, Pierre L'Hégaret, Matthieu Labaste, Tom Lachlan-Cope, Arlene Laing, Peter Landschützer, Theresa Lang, Diego Lange, Ingo Lange, Clément Laplace, Gauke Lavik, Rémi Laxenaire, Caroline Le Bihan, Mason Leandro, Nathalie Lefevre, Marius Lena, Donald Lenschow, Qiang Li, Gary Lloyd, Sebastian Los, Niccolò Losi, Oscar Lovell, Christopher Luneau, Przemyslaw Makuch, Szymon Malinowski, Gaston Manta, Eleni Marinou, Nicholas Marsden, Sebastien Masson, Nicolas Maury, Bernhard Mayer, Margarette Mayers-Als, Christophe Mazel, Wayne McGeary, James C. McWilliams, Mario Mech, Melina Mehlmann, Agostino Niyonkuru Meroni, Theresa Mieslinger, Andreas Minikin, Peter Minnett, Gregor Möller, Yanmichel Morfa Avalos, Caroline Muller, Ionela Musat, Anna Napoli, Almuth Neuberger, Christophe Noisel, David Noone, Freja Nordsiek, Jakub L. Nowak, Lothar Oswald, Douglas J. Parker, Carolyn Peck, Renaud Person, Miriam Philippi, Albert Plueddemann, Christopher Pöhlker, Veronika Pörtge, Ulrich Pöschl, Lawrence Pologne, Michał Posyniak, Marc Prange, Estefanía Quiñones Meléndez, Jule Radtke, Karim Ramage, Jens Reimann, Lionel Renault, Klaus Reus, Ashford Reyes, Joachim Ribbe, Maximilian Ringel, Markus Ritschel, Cesar B. Rocha, Nicolas Rochetin, Johannes Röttenbacher, Callum Rollo, Haley Royer, Pauline Sadoulet, Leo Saffin, Sanola Sandiford, Irina Sandu, Michael Schäfer, Vera Schemann, Imke Schirmacher, Oliver Schlenczek, Jerome Schmidt, Marcel Schröder, Alfons Schwarzenboeck, Andrea Sealy, Christoph J. Senff, Ilya Serikov, Samkeyat Shohan, Elizabeth Siddle, Alexander Smirnov, Florian Späth, Branden Spooner, M. Katharina Stolla, Wojciech Szkółka, Simon P. de Szoeke, Stéphane Tarot, Eleni Tetoni, Elizabeth Thompson, Jim Thomson, Lorenzo Tomassini, Julien Totems, Alma Anna Ubele, Leonie Villiger, Jan von Arx, Thomas Wagner, Andi Walther, Ben Webber, Manfred Wendisch, Shanice Whitehall, Anton Wiltshire, Allison A. Wing, Martin Wirth, Jonathan Wiskandt, Kevin Wolf, Ludwig Worbes, Ethan Wright, Volker Wulfmeyer, Shanea Young, Chidong Zhang, Dongxiao Zhang, Florian Ziemen, Tobias Zinner, and Martin Zöger
Earth Syst. Sci. Data, 13, 4067–4119, https://doi.org/10.5194/essd-13-4067-2021, https://doi.org/10.5194/essd-13-4067-2021, 2021
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The EUREC4A field campaign, designed to test hypothesized mechanisms by which clouds respond to warming and benchmark next-generation Earth-system models, is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. It was the first campaign that attempted to characterize the full range of processes and scales influencing trade wind clouds.
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Short summary
The Amazon River plume interaction with the North Brazil Current creates sharp temperature-salinity differences called fronts that are important for modulating air-sea interactions and biogeochemical cycles. This study uses data from robotic sailboats and a numerical model to provide a comprehensive picture of these fronts associated with the local dynamics. We characterize three distinct frontal regimes and the temperature-salinity relations linked to the Amazon discharge and current strength.
The Amazon River plume interaction with the North Brazil Current creates sharp...