Articles | Volume 19, issue 3
https://doi.org/10.5194/os-19-581-2023
© Author(s) 2023. 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-19-581-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Review article
| 
11 May 2023
Review article |
| 11 May 2023
| 11 May 2023
Physical processes and biological productivity in the upwelling regions of the tropical Atlantic
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Faculty of Mathematics and Natural Sciences, Kiel University, Kiel, Germany
Gaël Alory
LEGOS, CNES/CNRS/IRD/UPS, Toulouse, France
Founi Mesmin Awo
Nansen-Tutu Centre for Marine Environmental Research, Department of Oceanography, University of Cape Town, Cape Town, South Africa
Marcus Dengler
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Sandrine Djakouré
LASMES, UFR SSMT, Felix Houphouët-Boigny University, Abidjan, Côte d'Ivoire
Rodrigue Anicet Imbol Koungue
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Julien Jouanno
LEGOS, CNES/CNRS/IRD/UPS, Toulouse, France
Mareike Körner
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Marisa Roch
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
Mathieu Rouault
Nansen-Tutu Centre for Marine Environmental Research, Department of Oceanography, University of Cape Town, Cape Town, South Africa
deceased
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Alexandra Andrae, Peter Brandt, Franz Philip Tuchen, Rebecca Hummels, and Joke F. Lübbecke
EGUsphere, https://doi.org/10.5194/egusphere-2026-4390, https://doi.org/10.5194/egusphere-2026-4390, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
Short summary
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Trajectories of surface drifters reveal the presence wind-forced intraseasonal Yanai (mixed Rossby–gravity) waves superimposed on the mean background circulation in the western equatorial Atlantic. Three drifters deployed in May 2023 exhibited circular trajectories centered on the equator, consistent with a 14-day Yanai wave. Numerical experiments reproduce the observation, indicating wave amplitudes of 0.6–0.7 m/s and demonstrating how the North Brazil Current modulates the wave-induced motion.
Anna Christina Hans, Rebecca Hummels, Peter Brandt, Franziska U. Schwarzkopf, and Stephan Juricke
EGUsphere, https://doi.org/10.5194/egusphere-2026-2983, https://doi.org/10.5194/egusphere-2026-2983, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
Short summary
Short summary
We mimic an observational array at 11°S in an ocean model to assess its capability to compute the temporal variability of the Atlantic Meridional Overturning Circulation. The current approaches based on bottom pressure sensors and measurements of the boundary currents explain large parts of the transport variability. Improvements can be achieved by also considering temperature and salinity data, while the potential of self-calibrating pressure sensors and inverted echo sounders is limited.
Florian Schütte, Johannes Hahn, Ivy Frenger, Arne Bendinger, Ahmad Fehmi Dilmahamod, Marco Schulz, and Peter Brandt
Ocean Sci., 22, 119–143, https://doi.org/10.5194/os-22-119-2026, https://doi.org/10.5194/os-22-119-2026, 2026
Short summary
Short summary
We found extreme drops in oxygen levels in the tropical Atlantic linked to surprisingly long-lived, small subsurface eddies. These eddies are hidden beneath the surface (undetectable by satellites) and are unusually stable, even in the highly dynamic ocean near the equator. Using long-term measurements and computer models, we show that these features can strongly influence oxygen supply and potentially impact marine ecosystems.
Joelle Habib, Lars Stemmann, Alexandre Accardo, Alberto Baudena, Franz Philip Tuchen, Peter Brandt, and Rainer Kiko
Biogeosciences, 22, 7985–8003, https://doi.org/10.5194/bg-22-7985-2025, https://doi.org/10.5194/bg-22-7985-2025, 2025
Short summary
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This study investigates how carbon moves from the ocean surface to the depths in the equatorial Atlantic, contributing to long-term carbon storage. Using an Argo float equipped with a camera, we captured two periods with major carbon export events. By identifying particle types and their sinking behaviors, we found that smaller, compact particles are key drivers of carbon transport. Our findings underscore the value of using imaging tools on autonomous platforms in tracking carbon sequestration.
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
Short summary
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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.
Léo C. Aroucha, Joke F. Lübbecke, Peter Brandt, Franziska U. Schwarzkopf, and Arne Biastoch
Ocean Sci., 21, 661–678, https://doi.org/10.5194/os-21-661-2025, https://doi.org/10.5194/os-21-661-2025, 2025
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The west African coastal region sustains highly productive fisheries and marine ecosystems influenced by sea surface temperature. We use oceanic models to show that the freshwater input from land to ocean strengthens a surface northward (southward) coastal current north (south) of the Congo River mouth, promoting a transfer of cooler (warmer) waters to north (south) of the Congo discharge location. We highlight the significant impact of river discharge on ocean temperatures and circulation.
Eike E. Köhn, Richard J. Greatbatch, Peter Brandt, and Martin Claus
Ocean Sci., 20, 1281–1290, https://doi.org/10.5194/os-20-1281-2024, https://doi.org/10.5194/os-20-1281-2024, 2024
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The latitudinally alternating zonal jets are a ubiquitous feature of the ocean. We use a simple model to illustrate the potential role of these jets in the formation, maintenance, and multidecadal variability in the oxygen minimum zones, using the eastern tropical North Atlantic oxygen minimum zone as an example.
Kristin Burmeister, Franziska U. Schwarzkopf, Willi Rath, Arne Biastoch, Peter Brandt, Joke F. Lübbecke, and Mark Inall
Ocean Sci., 20, 307–339, https://doi.org/10.5194/os-20-307-2024, https://doi.org/10.5194/os-20-307-2024, 2024
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We apply two different forcing products to a high-resolution ocean model to investigate their impact on the simulated upper-current field in the tropical Atlantic. Where possible, we compare the simulated results to long-term observations. We find large discrepancies between the two simulations regarding the wind and current fields. We propose that long-term observations, once they have reached a critical length, need to be used to test the quality of wind-driven simulations.
Swantje Bastin, Martin Claus, Richard J. Greatbatch, and Peter Brandt
Ocean Sci., 19, 923–939, https://doi.org/10.5194/os-19-923-2023, https://doi.org/10.5194/os-19-923-2023, 2023
Short summary
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Equatorial deep jets are ocean currents that flow along the Equator in the deep oceans. They are relevant for oxygen transport and tropical surface climate, but their dynamics are not yet entirely understood. We investigate different factors leading to the jets being broader than theory predicts. Mainly using an ocean model, but corroborating the results with shipboard observations, we show that loss of momentum is the main factor for the broadening but that meandering also contributes.
Mareike Körner, Peter Brandt, and Marcus Dengler
Ocean Sci., 19, 121–139, https://doi.org/10.5194/os-19-121-2023, https://doi.org/10.5194/os-19-121-2023, 2023
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The coastal waters off Angola host a productive ecosystem. Surface waters at the coast are colder than further offshore. We find that surface heat fluxes warm the coastal region more strongly than the offshore region and cannot explain the differences. The influence of horizontal heat advection is minor on the surface temperature change. In contrast, ocean turbulence data suggest that cooling associated with vertical mixing is an important mechanism to explain the near-coastal cooling.
Rainer Kiko, Marc Picheral, David Antoine, Marcel Babin, Léo Berline, Tristan Biard, Emmanuel Boss, Peter Brandt, Francois Carlotti, Svenja Christiansen, Laurent Coppola, Leandro de la Cruz, Emilie Diamond-Riquier, Xavier Durrieu de Madron, Amanda Elineau, Gabriel Gorsky, Lionel Guidi, Helena Hauss, Jean-Olivier Irisson, Lee Karp-Boss, Johannes Karstensen, Dong-gyun Kim, Rachel M. Lekanoff, Fabien Lombard, Rubens M. Lopes, Claudie Marec, Andrew M. P. McDonnell, Daniela Niemeyer, Margaux Noyon, Stephanie H. O'Daly, Mark D. Ohman, Jessica L. Pretty, Andreas Rogge, Sarah Searson, Masashi Shibata, Yuji Tanaka, Toste Tanhua, Jan Taucher, Emilia Trudnowska, Jessica S. Turner, Anya Waite, and Lars Stemmann
Earth Syst. Sci. Data, 14, 4315–4337, https://doi.org/10.5194/essd-14-4315-2022, https://doi.org/10.5194/essd-14-4315-2022, 2022
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The term
marine particlescomprises detrital aggregates; fecal pellets; bacterioplankton, phytoplankton and zooplankton; and even fish. Here, we present a global dataset that contains 8805 vertical particle size distribution profiles obtained with Underwater Vision Profiler 5 (UVP5) camera systems. These data are valuable to the scientific community, as they can be used to constrain important biogeochemical processes in the ocean, such as the flux of carbon to the deep sea.
Gaël Many, Julien Jouanno, Marc Lucas, Audrey Hasson, Jean-Michel Lellouche, and Yann Drillet
State Planet Discuss., https://doi.org/10.5194/sp-2026-30, https://doi.org/10.5194/sp-2026-30, 2026
Preprint under review for SP
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Large Sargassum blooms have become a recurring feature of the Tropical Atlantic, affecting coastal areas and ecosystems. We studied satellite observations from 2002 to 2025 to understand how bloom size and severity vary through time and across regions. We developed two simple indicators to compare years and areas. The results reveal strong regional differences and show that 2025 was an exceptional basin-wide bloom, highlighting the value of consistent monitoring for tracking future events.
Arnaud Bertrand, Monique Simier, Gabriel Vinicius Felix Afonso, Gael Alory, Alejandro Ariza, Ramilla Assunção, Jean-Christophe Auguet, François Baurand, Beatrice Bec, Delphine Bonnet, Léandro Ferreira Cabanez, Claire Carré, Alexis Chaigneau, Adilma de Lourdes Montenegro Cocentino, Isis Amalia Cordeiro, Alex Costa da Silva, Martin Coubard, Mauro de Melo Junior, Juan-Carlos Molinero, Jeremy Devesa, Gilles Domalain, Leandro Nole Eduardo, Gérard Eldin, Gabriel Bittencourt Farias, Guilherme Ferreira, Gabriela Guerra Araújo Abrantes Figueiredo, Thierry Frédou, Diaz Xiomara Garcia, Everton Giachini Tosetto, Júlio Guazzelli Gonzalez, Jacques Grelet, Sandrine Hillion, Anne Justino, Marina Cavalcanti Jales, Sírleis Rodrigues Lacerda, François Le Loc'h, Anne Lebourges-Dhaussy, Rayssa Siqueira Lima, Nathalia Lins-Silva, Alex Souza Lira, Simone Maria de Albuquerque Lira, Catarina Marcolin da Rocha, Júlia Rodrigues Martins, Anais Médieu, Catarina Melo, Pedro Augusto Mendes de Castro Melo, Michael Maia Mincarone, Magali Monnier, Jean-Marie Munaron, Sigrid Neumann-Leitão, Junior Miodeli Nogueira, Matheus Oliveira, Beatrice Padovani Ferreira, Latifa Pelage, David Point, Ulisses Pinheiro, Fabrice Roubaud, Gildas Roudaut, Pierre Rousselot, Julianna de Lemos Santana, Ralf Schwamborn, Maria da Glória Gonçalves Silva-Cunha, Andrey Soares, Jesser Fidelis Souza Filho, Jean-François Ternon, Paulo Travassos, Gary Vargas, Teodoro Vaske Jr., Renata P. S. Campelo, Bárbara Teixeira Villarins, and Flávia Lucena-Frédou
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2026-512, https://doi.org/10.5194/essd-2026-512, 2026
Preprint under review for ESSD
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Understanding marine ecosystems requires observing environment, organisms, and interactions. Off Northeast Brazil, we conducted expeditions in 2015 and 2017 to measure ocean conditions, map distributions with acoustics, and sample from plankton to deep-sea fish. We identified 172,000 specimens, analysed food webs using chemical tracers, and measured contaminants. This dataset connects ocean physics to biodiversity across depths, providing an integrated view of a tropical marine ecosystem.
Alexandra Andrae, Peter Brandt, Franz Philip Tuchen, Rebecca Hummels, and Joke F. Lübbecke
EGUsphere, https://doi.org/10.5194/egusphere-2026-4390, https://doi.org/10.5194/egusphere-2026-4390, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
Short summary
Short summary
Trajectories of surface drifters reveal the presence wind-forced intraseasonal Yanai (mixed Rossby–gravity) waves superimposed on the mean background circulation in the western equatorial Atlantic. Three drifters deployed in May 2023 exhibited circular trajectories centered on the equator, consistent with a 14-day Yanai wave. Numerical experiments reproduce the observation, indicating wave amplitudes of 0.6–0.7 m/s and demonstrating how the North Brazil Current modulates the wave-induced motion.
Hans Segura, Allison A. Wing, Heike Kalesse-Los, Ruben Carrasco, James H. Ruppert Jr., Anna Trosits, Louise Nuijens, Felix Ament, Daniel Blandfort, Michael M. Bell, Pierre Bosser, Delián Colón-Burgos, Geet George, Joelle Habib, Jochen Horstmann, Friedhelm Jansen, Lukas Kluft, Robert Kopte, Klas Ove Möller, Peristera Paschou, Hauke Schmidt, Michael Schlundt, Ilya Serikov, Martin Stelzner, Elizabeth J. Thompson, Werenfrid Wimmer, Marcus Dengler, and Daniel Klocke
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2026-343, https://doi.org/10.5194/essd-2026-343, 2026
Preprint under review for ESSD
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BOWTIE (Beobachtung von Ozean und Wolken - Das Trans ITCZ Experiment) was an observational campaign occurring in summer 2024, which intensively took measurements from the upper ocean to the upper troposphere in the wettest region of the tropical Atlantic. Here, we provide an overview of the measurements and instrumentation, including remote sensing and conventional, which targeted small-scale processes under different weather regimes, from calm doldrums to gusty, precipitating events.
Anna Christina Hans, Rebecca Hummels, Peter Brandt, Franziska U. Schwarzkopf, and Stephan Juricke
EGUsphere, https://doi.org/10.5194/egusphere-2026-2983, https://doi.org/10.5194/egusphere-2026-2983, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
Short summary
Short summary
We mimic an observational array at 11°S in an ocean model to assess its capability to compute the temporal variability of the Atlantic Meridional Overturning Circulation. The current approaches based on bottom pressure sensors and measurements of the boundary currents explain large parts of the transport variability. Improvements can be achieved by also considering temperature and salinity data, while the potential of self-calibrating pressure sensors and inverted echo sounders is limited.
Clovis Thouvenin-Masson and Julien Jouanno
EGUsphere, https://doi.org/10.5194/egusphere-2026-2727, https://doi.org/10.5194/egusphere-2026-2727, 2026
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We studied why floating Sargassum seaweed repeatedly reaches the northern Gulf of Guinea, where it affects coastal activities such as fishing. By combining satellite observations with computer simulations, we found two main arrival seasons, in spring and autumn. Most events are driven by seaweed transported from the eastern tropical Atlantic, while winds push it toward the coast and beaching limits how long it persists. Year-to-year changes are linked to shifts in Atlantic climate.
Marc Kakante Mendy, Florent Gasparin, Manon Gévaudan, Moussa Diakhaté, Issa Sakho, and Julien Jouanno
Ocean Sci., 22, 1745–1762, https://doi.org/10.5194/os-22-1745-2026, https://doi.org/10.5194/os-22-1745-2026, 2026
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The North Tropical Atlantic plays an important role in shaping climate in the region. In our study we examined how African Easterly Waves influence the ocean surface. Using numerical modelling and buoy records, we found that these waves can warm or cool the sea by more than half a degree. The faster waves have the strongest impact. Because sea temperature affects rainfall and storms, understanding these waves can help improve weather and climate forecasts.
Landry Junior Mbang Essome, Gaël Alory, Casimir Yelognissé Da-Allada, Isabelle Dadou, Roy Dorgeless Ngakala, and Guillaume Morvan
Ocean Sci., 22, 1279–1309, https://doi.org/10.5194/os-22-1279-2026, https://doi.org/10.5194/os-22-1279-2026, 2026
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We used a high-resolution model to study how ocean currents and waves, especially coastal trapped waves, control nitrate variability in the Gabon-Congo upwelling system. This nutrient availability drives seasonal marine productivity, with the Congo River also adding significant nitrate. Our research clarifies the complex interplay of physical and biological factors, offering crucial insights for managing regional fisheries and assessing climate change impacts on this vital ecosystem.
Gabriela Martinez Balbontin, Julien Jouanno, Rachid Benshila, Julien Lamouroux, Coralie Perruche, and Stefano Ciavatta
Biogeosciences, 23, 2601–2620, https://doi.org/10.5194/bg-23-2601-2026, https://doi.org/10.5194/bg-23-2601-2026, 2026
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This study uses machine learning to predict global sea surface chlorophyll a, which is important for monitoring marine ecosystems and the carbon cycle. Using forecasts of sea surface temperature, salinity, height, and mixed layer depth, we generate global predictions up to six months ahead in just minutes. Our approach matches state-of-the-art numerical methods while being faster and more resource-efficient.
Arthur Prigent, Riccardo Farneti, Manfredi Manizza, and Rodrigue Anicet Imbol Koungue
EGUsphere, https://doi.org/10.5194/egusphere-2026-2021, https://doi.org/10.5194/egusphere-2026-2021, 2026
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Using a suite of ocean model simulations scaling chlorophyll-a from 0.01–2× climatology, we show that low chlorophyll ("clear-ocean") warms the eastern equatorial Atlantic by 0.15 °C, weakens the vertical temperature gradient, deepens the mixed layer and thermocline, and reduces upwelling. These mean-state changes reduce the SST seasonal cycle by 14 % and interannual variability by 12.9 %. Our results suggests that the observed decreasing tropical Atlantic chlorophyll may weaken SST variability.
Marco Larrañaga, Julien Jouanno, Eric P. Chassignet, Giovanni Durante, Ilkyeong Ma, Julio Sheinbaum, and Lionel Renault
Ocean Sci., 22, 821–841, https://doi.org/10.5194/os-22-821-2026, https://doi.org/10.5194/os-22-821-2026, 2026
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We analyze 29 years of satellite altimetry to investigate the detachment of Loop Current Eddies in the Gulf of Mexico. Over half of the Loop Current eddies reattach within a month, while 42 % separate and drift westward. Detachment requires the Loop Current to reach the Mississippi Fan and is strongly influenced by cyclonic eddies, whose configuration determines whether an eddy separates or reattaches to the Loop Current.
Florian Schütte, Johannes Hahn, Ivy Frenger, Arne Bendinger, Ahmad Fehmi Dilmahamod, Marco Schulz, and Peter Brandt
Ocean Sci., 22, 119–143, https://doi.org/10.5194/os-22-119-2026, https://doi.org/10.5194/os-22-119-2026, 2026
Short summary
Short summary
We found extreme drops in oxygen levels in the tropical Atlantic linked to surprisingly long-lived, small subsurface eddies. These eddies are hidden beneath the surface (undetectable by satellites) and are unusually stable, even in the highly dynamic ocean near the equator. Using long-term measurements and computer models, we show that these features can strongly influence oxygen supply and potentially impact marine ecosystems.
Joelle Habib, Lars Stemmann, Alexandre Accardo, Alberto Baudena, Franz Philip Tuchen, Peter Brandt, and Rainer Kiko
Biogeosciences, 22, 7985–8003, https://doi.org/10.5194/bg-22-7985-2025, https://doi.org/10.5194/bg-22-7985-2025, 2025
Short summary
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This study investigates how carbon moves from the ocean surface to the depths in the equatorial Atlantic, contributing to long-term carbon storage. Using an Argo float equipped with a camera, we captured two periods with major carbon export events. By identifying particle types and their sinking behaviors, we found that smaller, compact particles are key drivers of carbon transport. Our findings underscore the value of using imaging tools on autonomous platforms in tracking carbon sequestration.
Hans Segura, Xabier Pedruzo-Bagazgoitia, Philipp Weiss, Sebastian K. Müller, Thomas Rackow, Junhong Lee, Edgar Dolores-Tesillos, Imme Benedict, Matthias Aengenheyster, Razvan Aguridan, Gabriele Arduini, Alexander J. Baker, Jiawei Bao, Swantje Bastin, Eulàlia Baulenas, Tobias Becker, Sebastian Beyer, Hendryk Bockelmann, Nils Brüggemann, Lukas Brunner, Suvarchal K. Cheedela, Sushant Das, Jasper Denissen, Ian Dragaud, Piotr Dziekan, Madeleine Ekblom, Jan Frederik Engels, Monika Esch, Richard Forbes, Claudia Frauen, Lilli Freischem, Diego García-Maroto, Philipp Geier, Paul Gierz, Álvaro González-Cervera, Katherine Grayson, Matthew Griffith, Oliver Gutjahr, Helmuth Haak, Ioan Hadade, Kerstin Haslehner, Shabeh ul Hasson, Jan Hegewald, Lukas Kluft, Aleksei Koldunov, Nikolay Koldunov, Tobias Kölling, Shunya Koseki, Sergey Kosukhin, Josh Kousal, Peter Kuma, Arjun U. Kumar, Rumeng Li, Nicolas Maury, Maximilian Meindl, Sebastian Milinski, Kristian Mogensen, Bimochan Niraula, Jakub Nowak, Divya Sri Praturi, Ulrike Proske, Dian Putrasahan, René Redler, David Santuy, Domokos Sármány, Reiner Schnur, Patrick Scholz, Dmitry Sidorenko, Dorian Spät, Birgit Sützl, Daisuke Takasuka, Adrian Tompkins, Alejandro Uribe, Mirco Valentini, Menno Veerman, Aiko Voigt, Sarah Warnau, Fabian Wachsmann, Marta Wacławczyk, Nils Wedi, Karl-Hermann Wieners, Jonathan Wille, Marius Winkler, Yuting Wu, Florian Ziemen, Janos Zimmermann, Frida A.-M. Bender, Dragana Bojovic, Sandrine Bony, Simona Bordoni, Patrice Brehmer, Marcus Dengler, Emanuel Dutra, Saliou Faye, Erich Fischer, Chiel van Heerwaarden, Cathy Hohenegger, Heikki Järvinen, Markus Jochum, Thomas Jung, Johann H. Jungclaus, Noel S. Keenlyside, Daniel Klocke, Heike Konow, Martina Klose, Szymon Malinowski, Olivia Martius, Thorsten Mauritsen, Juan Pedro Mellado, Theresa Mieslinger, Elsa Mohino, Hanna Pawłowska, Karsten Peters-von Gehlen, Abdoulaye Sarré, Pajam Sobhani, Philip Stier, Lauri Tuppi, Pier Luigi Vidale, Irina Sandu, and Bjorn Stevens
Geosci. Model Dev., 18, 7735–7761, https://doi.org/10.5194/gmd-18-7735-2025, https://doi.org/10.5194/gmd-18-7735-2025, 2025
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The Next Generation of Earth Modeling Systems project (nextGEMS) developed two Earth system models that use horizontal grid spacing of 10 km and finer, giving more fidelity to the representation of local phenomena, globally. In its fourth cycle, nextGEMS simulated the Earth System climate over the 2020–2049 period under the SSP3-7.0 scenario. Here, we provide an overview of nextGEMS, insights into the model development, and the realism of multi-decadal, kilometer-scale simulations.
Rosmery Sosa-Gutierrez, Julien Jouanno, and Leo Berline
Ocean Sci., 21, 1505–1514, https://doi.org/10.5194/os-21-1505-2025, https://doi.org/10.5194/os-21-1505-2025, 2025
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Since 2010, pelagic Sargassum spp. blooms have increased in several tropical Atlantic regions, causing socioeconomic and ecosystem impacts. Offshore structuration of Sargassum by mesoscale dynamics may influence transport and growth. Sargassum stays afloat, constantly interacting with currents, waves, winds, and mesoscale eddies. We find that anticyclones and cyclones effectively trap Sargassum throughout its propagation, with a greater tendency for cyclones to accumulate Sargassum.
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
Short summary
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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.
Léo C. Aroucha, Joke F. Lübbecke, Peter Brandt, Franziska U. Schwarzkopf, and Arne Biastoch
Ocean Sci., 21, 661–678, https://doi.org/10.5194/os-21-661-2025, https://doi.org/10.5194/os-21-661-2025, 2025
Short summary
Short summary
The west African coastal region sustains highly productive fisheries and marine ecosystems influenced by sea surface temperature. We use oceanic models to show that the freshwater input from land to ocean strengthens a surface northward (southward) coastal current north (south) of the Congo River mouth, promoting a transfer of cooler (warmer) waters to north (south) of the Congo discharge location. We highlight the significant impact of river discharge on ocean temperatures and circulation.
Swantje Bastin, Aleksei Koldunov, Florian Schütte, Oliver Gutjahr, Marta Agnieszka Mrozowska, Tim Fischer, Radomyra Shevchenko, Arjun Kumar, Nikolay Koldunov, Helmuth Haak, Nils Brüggemann, Rebecca Hummels, Mia Sophie Specht, Johann Jungclaus, Sergey Danilov, Marcus Dengler, and Markus Jochum
Geosci. Model Dev., 18, 1189–1220, https://doi.org/10.5194/gmd-18-1189-2025, https://doi.org/10.5194/gmd-18-1189-2025, 2025
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Vertical mixing is an important process, for example, for tropical sea surface temperature, but cannot be resolved by ocean models. Comparisons of mixing schemes and settings have usually been done with a single model, sometimes yielding conflicting results. We systematically compare two widely used schemes with different parameter settings in two different ocean models and show that most effects from mixing scheme parameter changes are model-dependent.
Eike E. Köhn, Richard J. Greatbatch, Peter Brandt, and Martin Claus
Ocean Sci., 20, 1281–1290, https://doi.org/10.5194/os-20-1281-2024, https://doi.org/10.5194/os-20-1281-2024, 2024
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The latitudinally alternating zonal jets are a ubiquitous feature of the ocean. We use a simple model to illustrate the potential role of these jets in the formation, maintenance, and multidecadal variability in the oxygen minimum zones, using the eastern tropical North Atlantic oxygen minimum zone as an example.
Kristin Burmeister, Franziska U. Schwarzkopf, Willi Rath, Arne Biastoch, Peter Brandt, Joke F. Lübbecke, and Mark Inall
Ocean Sci., 20, 307–339, https://doi.org/10.5194/os-20-307-2024, https://doi.org/10.5194/os-20-307-2024, 2024
Short summary
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We apply two different forcing products to a high-resolution ocean model to investigate their impact on the simulated upper-current field in the tropical Atlantic. Where possible, we compare the simulated results to long-term observations. We find large discrepancies between the two simulations regarding the wind and current fields. We propose that long-term observations, once they have reached a critical length, need to be used to test the quality of wind-driven simulations.
Swantje Bastin, Martin Claus, Richard J. Greatbatch, and Peter Brandt
Ocean Sci., 19, 923–939, https://doi.org/10.5194/os-19-923-2023, https://doi.org/10.5194/os-19-923-2023, 2023
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Equatorial deep jets are ocean currents that flow along the Equator in the deep oceans. They are relevant for oxygen transport and tropical surface climate, but their dynamics are not yet entirely understood. We investigate different factors leading to the jets being broader than theory predicts. Mainly using an ocean model, but corroborating the results with shipboard observations, we show that loss of momentum is the main factor for the broadening but that meandering also contributes.
Roy Dorgeless Ngakala, Gaël Alory, Casimir Yélognissè Da-Allada, Olivia Estelle Kom, Julien Jouanno, Willi Rath, and Ezinvi Baloïtcha
Ocean Sci., 19, 535–558, https://doi.org/10.5194/os-19-535-2023, https://doi.org/10.5194/os-19-535-2023, 2023
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Surface heat flux is the main driver of the heat budget in the Senegal, Angola, and Benguela regions but not in the equatorial region. In the Senegal and Benguela regions, freshwater flux governs the salt budget, while in equatorial and Angola regions, oceanic processes are the main drivers. Results from numerical simulation show the important role of mesoscale advection for temperature and salinity variations in the mixed layer. Nonlinear processes unresolved by observations play a key role.
Sarah Berthet, Julien Jouanno, Roland Séférian, Marion Gehlen, and William Llovel
Earth Syst. Dynam., 14, 399–412, https://doi.org/10.5194/esd-14-399-2023, https://doi.org/10.5194/esd-14-399-2023, 2023
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Phytoplankton absorbs the solar radiation entering the ocean surface and contributes to keeping the associated energy in surface waters. This natural effect is either not represented in the ocean component of climate models or its representation is simplified. An incomplete representation of this biophysical interaction affects the way climate models simulate ocean warming, which leads to uncertainties in projections of oceanic emissions of an important greenhouse gas (nitrous oxide).
Mareike Körner, Peter Brandt, and Marcus Dengler
Ocean Sci., 19, 121–139, https://doi.org/10.5194/os-19-121-2023, https://doi.org/10.5194/os-19-121-2023, 2023
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The coastal waters off Angola host a productive ecosystem. Surface waters at the coast are colder than further offshore. We find that surface heat fluxes warm the coastal region more strongly than the offshore region and cannot explain the differences. The influence of horizontal heat advection is minor on the surface temperature change. In contrast, ocean turbulence data suggest that cooling associated with vertical mixing is an important mechanism to explain the near-coastal cooling.
Michel Tchilibou, Ariane Koch-Larrouy, Simon Barbot, Florent Lyard, Yves Morel, Julien Jouanno, and Rosemary Morrow
Ocean Sci., 18, 1591–1618, https://doi.org/10.5194/os-18-1591-2022, https://doi.org/10.5194/os-18-1591-2022, 2022
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This high-resolution model-based study investigates the variability in the generation, propagation, and sea height signature (SSH) of the internal tide off the Amazon shelf during two contrasted seasons. ITs propagate further north during the season characterized by weak currents and mesoscale eddies and a shallow and strong pycnocline. IT imprints on SSH dominate those of the geostrophic motion for horizontal scales below 200 km; moreover, the SSH is mainly incoherent below 70 km.
Rainer Kiko, Marc Picheral, David Antoine, Marcel Babin, Léo Berline, Tristan Biard, Emmanuel Boss, Peter Brandt, Francois Carlotti, Svenja Christiansen, Laurent Coppola, Leandro de la Cruz, Emilie Diamond-Riquier, Xavier Durrieu de Madron, Amanda Elineau, Gabriel Gorsky, Lionel Guidi, Helena Hauss, Jean-Olivier Irisson, Lee Karp-Boss, Johannes Karstensen, Dong-gyun Kim, Rachel M. Lekanoff, Fabien Lombard, Rubens M. Lopes, Claudie Marec, Andrew M. P. McDonnell, Daniela Niemeyer, Margaux Noyon, Stephanie H. O'Daly, Mark D. Ohman, Jessica L. Pretty, Andreas Rogge, Sarah Searson, Masashi Shibata, Yuji Tanaka, Toste Tanhua, Jan Taucher, Emilia Trudnowska, Jessica S. Turner, Anya Waite, and Lars Stemmann
Earth Syst. Sci. Data, 14, 4315–4337, https://doi.org/10.5194/essd-14-4315-2022, https://doi.org/10.5194/essd-14-4315-2022, 2022
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The term
marine particlescomprises detrital aggregates; fecal pellets; bacterioplankton, phytoplankton and zooplankton; and even fish. Here, we present a global dataset that contains 8805 vertical particle size distribution profiles obtained with Underwater Vision Profiler 5 (UVP5) camera systems. These data are valuable to the scientific community, as they can be used to constrain important biogeochemical processes in the ocean, such as the flux of carbon to the deep sea.
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Short summary
Tropical upwelling systems are among the most productive ecosystems globally. The tropical Atlantic upwelling undergoes a strong seasonal cycle that is forced by the wind. Local wind-driven upwelling and remote effects, particularly via the propagation of equatorial and coastal trapped waves, lead to an upward and downward movement of the nitracline. Turbulent mixing results in upward supply of nutrients. Here, we review the different physical processes responsible for biological productivity.
Tropical upwelling systems are among the most productive ecosystems globally. The tropical...
