Articles | Volume 21, issue 4
https://doi.org/10.5194/os-21-1575-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Special issue:
https://doi.org/10.5194/os-21-1575-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
29 Jul 2025
Research article |
| 29 Jul 2025
| 29 Jul 2025
Ventilation of the Bay of Bengal oxygen minimum zone by the Southwest Monsoon Current
Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom
Benjamin G. M. Webber
Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom
Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom
Alejandra Sanchez-Franks
National Oceanography Centre, Southampton, United Kingdom
Bastien Y. Queste
Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
Related authors
Peter M. F. Sheehan, Gillian M. Damerell, Philip J. Leadbitter, Karen J. Heywood, and Rob A. Hall
Ocean Sci., 19, 77–92, https://doi.org/10.5194/os-19-77-2023, https://doi.org/10.5194/os-19-77-2023, 2023
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We calculate the rate of turbulent kinetic energy dissipation, i.e. the mixing driven by small-scale ocean turbulence, in the western tropical Atlantic Ocean via two methods. We find good agreement between the results of both. A region of elevated mixing is found between 200 and 500 m, and we calculate the associated heat and salt fluxes. We find that double-diffusive mixing in salt fingers, a common feature of the tropical oceans, drives larger heat and salt fluxes than the turbulent mixing.
Peter M. F. Sheehan, Barbara Berx, Alejandro Gallego, Rob A. Hall, Karen J. Heywood, Sarah L. Hughes, and Bastien Y. Queste
Ocean Sci., 14, 225–236, https://doi.org/10.5194/os-14-225-2018, https://doi.org/10.5194/os-14-225-2018, 2018
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We calculate tidal velocities using observations of ocean currents collected by an underwater glider. We use these velocities to investigate the location of sharp boundaries between water masses in shallow seas. Narrow currents along these boundaries are important transport pathways around shallow seas for pollutants and organisms. Tides are an important control on boundary location in summer, but seawater salt concentration can also influence boundary location, especially in winter.
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.
Daisy Drew Pickup, Dorothee C. E. Bakker, Karen J. Heywood, Francis Glassup, Emily Hammermeister, Sharon E. Stammerjohn, Gareth A. Lee, Socratis Loucaides, Bastien Y. Queste, Benjamin G. M. Webber, and Patricia L. Yager
EGUsphere, https://doi.org/10.5194/egusphere-2025-2441, https://doi.org/10.5194/egusphere-2025-2441, 2025
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Autonomous platforms in the Amundsen Sea have allowed for detection of isolated water masses that are colder, saltier and denser than overlying water. They are also associated with a higher dissolved inorganic carbon concentration and lower pH. The water masses, referred to as lenses, could have implications for the transfer of heat and storage of carbon in the region. We hypothesise that they form in surrounding areas that experience intense cooling and sea ice formation in autumn/winter.
Siyu Meng, Xun Gong, Benjamin Webber, Manoj Joshi, Xiaokun Ding, Xiang Gong, Mingliang Gu, and Huiwang Gao
EGUsphere, https://doi.org/10.5194/egusphere-2025-13, https://doi.org/10.5194/egusphere-2025-13, 2025
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The North Pacific Ocean Desert (NPOD), with low phytoplankton biomass, covers about 40 % of the North Pacific. The variations in NPOD seasonal cycle, which have a greater impact than its annual mean changes, are influenced by the El Niño-Southern Oscillation from 1998 to 2021. However, from 2021 to 2100, a weakened NPOD seasonal cycle is expected due to climate change. These changes in NPOD seasonal cycle could affect fisheries and marine ecosystems.
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.
Helene Asbjørnsen, Tor Eldevik, Johanne Skrefsrud, Helen L. Johnson, and Alejandra Sanchez-Franks
Ocean Sci., 20, 799–816, https://doi.org/10.5194/os-20-799-2024, https://doi.org/10.5194/os-20-799-2024, 2024
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The Gulf Stream system is essential for northward ocean heat transport. Here, we use observations along the path of the extended Gulf Stream system and an observationally constrained ocean model to investigate variability in the Gulf Stream system since the 1990s. We find regional differences in the variability between the subtropical, subpolar, and Nordic Seas regions, which warrants caution in using observational records at a single latitude to infer large-scale circulation change.
Peter M. F. Sheehan, Gillian M. Damerell, Philip J. Leadbitter, Karen J. Heywood, and Rob A. Hall
Ocean Sci., 19, 77–92, https://doi.org/10.5194/os-19-77-2023, https://doi.org/10.5194/os-19-77-2023, 2023
Short summary
Short summary
We calculate the rate of turbulent kinetic energy dissipation, i.e. the mixing driven by small-scale ocean turbulence, in the western tropical Atlantic Ocean via two methods. We find good agreement between the results of both. A region of elevated mixing is found between 200 and 500 m, and we calculate the associated heat and salt fluxes. We find that double-diffusive mixing in salt fingers, a common feature of the tropical oceans, drives larger heat and salt fluxes than the turbulent mixing.
Alan D. Fox, Patricia Handmann, Christina Schmidt, Neil Fraser, Siren Rühs, Alejandra Sanchez-Franks, Torge Martin, Marilena Oltmanns, Clare Johnson, Willi Rath, N. Penny Holliday, Arne Biastoch, Stuart A. Cunningham, and Igor Yashayaev
Ocean Sci., 18, 1507–1533, https://doi.org/10.5194/os-18-1507-2022, https://doi.org/10.5194/os-18-1507-2022, 2022
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Observations of the eastern subpolar North Atlantic in the 2010s show exceptional freshening and cooling of the upper ocean, peaking in 2016 with the lowest salinities recorded for 120 years. Using results from a high-resolution ocean model, supported by observations, we propose that the leading cause is reduced surface cooling over the preceding decade in the Labrador Sea, leading to increased outflow of less dense water and so to freshening and cooling of the eastern subpolar North Atlantic.
Elise S. Droste, Mario Hoppema, Melchor González-Dávila, Juana Magdalena Santana-Casiano, Bastien Y. Queste, Giorgio Dall'Olmo, Hugh J. Venables, Gerd Rohardt, Sharyn Ossebaar, Daniel Schuller, Sunke Trace-Kleeberg, and Dorothee C. E. Bakker
Ocean Sci., 18, 1293–1320, https://doi.org/10.5194/os-18-1293-2022, https://doi.org/10.5194/os-18-1293-2022, 2022
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Tides affect the marine carbonate chemistry of a coastal polynya neighbouring the Ekström Ice Shelf by movement of seawater with different physical and biogeochemical properties. The result is that the coastal polynya in the summer can switch between being a sink or a source of CO2 multiple times a day. We encourage consideration of tides when collecting in polar coastal regions to account for tide-driven variability and to avoid overestimations or underestimations of air–sea CO2 exchange.
Benjamin R. Loveday, Timothy Smyth, Anıl Akpinar, Tom Hull, Mark E. Inall, Jan Kaiser, Bastien Y. Queste, Matt Tobermann, Charlotte A. J. Williams, and Matthew R. Palmer
Earth Syst. Sci. Data, 14, 3997–4016, https://doi.org/10.5194/essd-14-3997-2022, https://doi.org/10.5194/essd-14-3997-2022, 2022
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Using a new approach to combine autonomous underwater glider data and satellite Earth observations, we have generated a 19-month time series of North Sea net primary productivity – the rate at which phytoplankton absorbs carbon dioxide minus that lost through respiration. This time series, which spans 13 gliders, allows for new investigations into small-scale, high-frequency variability in the biogeochemical processes that underpin the carbon cycle and coastal marine ecosystems in shelf seas.
Yixi Zheng, David P. Stevens, Karen J. Heywood, Benjamin G. M. Webber, and Bastien Y. Queste
The Cryosphere, 16, 3005–3019, https://doi.org/10.5194/tc-16-3005-2022, https://doi.org/10.5194/tc-16-3005-2022, 2022
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New observations reveal the Thwaites gyre in a habitually ice-covered region in the Amundsen Sea for the first time. This gyre rotates anticlockwise, despite the wind here favouring clockwise gyres like the Pine Island Bay gyre – the only other ocean gyre reported in the Amundsen Sea. We use an ocean model to suggest that sea ice alters the wind stress felt by the ocean and hence determines the gyre direction and strength. These processes may also be applied to other gyres in polar oceans.
Helen E. Phillips, Amit Tandon, Ryo Furue, Raleigh Hood, Caroline C. Ummenhofer, Jessica A. Benthuysen, Viviane Menezes, Shijian Hu, Ben Webber, Alejandra Sanchez-Franks, Deepak Cherian, Emily Shroyer, Ming Feng, Hemantha Wijesekera, Abhisek Chatterjee, Lisan Yu, Juliet Hermes, Raghu Murtugudde, Tomoki Tozuka, Danielle Su, Arvind Singh, Luca Centurioni, Satya Prakash, and Jerry Wiggert
Ocean Sci., 17, 1677–1751, https://doi.org/10.5194/os-17-1677-2021, https://doi.org/10.5194/os-17-1677-2021, 2021
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Over the past decade, understanding of the Indian Ocean has progressed through new observations and advances in theory and models of the oceanic and atmospheric circulation. This review brings together new understanding of the ocean–atmosphere system in the Indian Ocean, describing Indian Ocean circulation patterns, air–sea interactions, climate variability, and the critical role of the Indian Ocean as a clearing house for anthropogenic heat.
Alejandra Sanchez-Franks, Eleanor Frajka-Williams, Ben I. Moat, and David A. Smeed
Ocean Sci., 17, 1321–1340, https://doi.org/10.5194/os-17-1321-2021, https://doi.org/10.5194/os-17-1321-2021, 2021
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In the North Atlantic, ocean currents carry warm surface waters northward and return cooler deep waters southward. This type of ocean circulation, known as overturning, is important for the Earth’s climate. This overturning has been measured using a mooring array at 26° N in the North Atlantic since 2004. Here we use these mooring data and global satellite data to produce a new method for monitoring the overturning over longer timescales, which could potentially be applied to different latitudes.
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.
Jack Giddings, Karen J. Heywood, Adrian J. Matthews, Manoj M. Joshi, Benjamin G. M. Webber, Alejandra Sanchez-Franks, Brian A. King, and Puthenveettil N. Vinayachandran
Ocean Sci., 17, 871–890, https://doi.org/10.5194/os-17-871-2021, https://doi.org/10.5194/os-17-871-2021, 2021
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Little is known about the impact of chlorophyll on SST in the Bay of Bengal (BoB). Solar irradiance measured by an ocean glider and three Argo floats is used to determine the effect of chlorophyll on BoB SST during the 2016 summer monsoon. The Southwest Monsoon Current has high chlorophyll concentrations (∼0.5 mg m−3) and shallow solar penetration depths (∼14 m). Ocean mixed layer model simulations show that SST increases by 0.35°C per month, with the potential to influence monsoon rainfall.
Jack Giddings, Adrian J. Matthews, Nicholas P. Klingaman, Karen J. Heywood, Manoj Joshi, and Benjamin G. M. Webber
Weather Clim. Dynam., 1, 635–655, https://doi.org/10.5194/wcd-1-635-2020, https://doi.org/10.5194/wcd-1-635-2020, 2020
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The impact of chlorophyll on the southwest monsoon is unknown. Here, seasonally varying chlorophyll in the Bay of Bengal was imposed in a general circulation model coupled to an ocean mixed layer model. The SST increases by 0.5 °C in response to chlorophyll forcing and shallow mixed layer depths in coastal regions during the inter-monsoon. Precipitation increases significantly to 3 mm d-1 across Myanmar during June and over northeast India and Bangladesh during October, decreasing model bias.
Ben I. Moat, David A. Smeed, Eleanor Frajka-Williams, Damien G. Desbruyères, Claudie Beaulieu, William E. Johns, Darren Rayner, Alejandra Sanchez-Franks, Molly O. Baringer, Denis Volkov, Laura C. Jackson, and Harry L. Bryden
Ocean Sci., 16, 863–874, https://doi.org/10.5194/os-16-863-2020, https://doi.org/10.5194/os-16-863-2020, 2020
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The RAPID 26° N array has been measuring the Atlantic meridional overturning circulation (AMOC) since 2004. Since 2009 the AMOC has, compared with previous years, been in a low state. In 2013–2015, in the northern North Atlantic, strong cooling was observed in the ocean and anticipated to intensify the strength of the AMOC some years later. Here, we analyse the latest results from 26° N and conclude that while the AMOC has increased since 2009, this increase is not statistically significant.
Venugopal Thushara, Puthenveettil Narayana Menon Vinayachandran, Adrian J. Matthews, Benjamin G. M. Webber, and Bastien Y. Queste
Biogeosciences, 16, 1447–1468, https://doi.org/10.5194/bg-16-1447-2019, https://doi.org/10.5194/bg-16-1447-2019, 2019
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Chlorophyll distribution in the ocean remains to be explored in detail, despite its climatic significance. Here, we document the vertical structure of chlorophyll in the Bay of Bengal using observations and a model. The shape of chlorophyll profiles, characterized by prominent deep chlorophyll maxima, varies in dynamically different regions, controlled by the monsoonal forcings. The present study provides new insights into the vertical distribution of chlorophyll, rarely observed by satellites.
Reiner Onken, Heinz-Volker Fiekas, Laurent Beguery, Ines Borrione, Andreas Funk, Michael Hemming, Jaime Hernandez-Lasheras, Karen J. Heywood, Jan Kaiser, Michaela Knoll, Baptiste Mourre, Paolo Oddo, Pierre-Marie Poulain, Bastien Y. Queste, Aniello Russo, Kiminori Shitashima, Martin Siderius, and Elizabeth Thorp Küsel
Ocean Sci., 14, 321–335, https://doi.org/10.5194/os-14-321-2018, https://doi.org/10.5194/os-14-321-2018, 2018
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In June 2014, high-resolution oceanographic data were collected in the
western Mediterranean Sea by two research vessels, 11 gliders, moored
instruments, drifters, and one profiling float. The objective
of this article is to provide an overview of the data set which
is utilised by various ongoing studies, focusing on (i) water masses and circulation, (ii) operational forecasting, (iii) data assimilation, (iv) variability of the ocean, and (v) new payloads
for gliders.
Peter M. F. Sheehan, Barbara Berx, Alejandro Gallego, Rob A. Hall, Karen J. Heywood, Sarah L. Hughes, and Bastien Y. Queste
Ocean Sci., 14, 225–236, https://doi.org/10.5194/os-14-225-2018, https://doi.org/10.5194/os-14-225-2018, 2018
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We calculate tidal velocities using observations of ocean currents collected by an underwater glider. We use these velocities to investigate the location of sharp boundaries between water masses in shallow seas. Narrow currents along these boundaries are important transport pathways around shallow seas for pollutants and organisms. Tides are an important control on boundary location in summer, but seawater salt concentration can also influence boundary location, especially in winter.
Michaela Knoll, Ines Borrione, Heinz-Volker Fiekas, Andreas Funk, Michael P. Hemming, Jan Kaiser, Reiner Onken, Bastien Queste, and Aniello Russo
Ocean Sci., 13, 889–904, https://doi.org/10.5194/os-13-889-2017, https://doi.org/10.5194/os-13-889-2017, 2017
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The hydrography and circulation west of Sardinia, observed in June 2014 during REP14-MED by means of various measuring platforms, are presented and compared with previous knowledge. So far, the circulation of this area is not well-known and the hydrography is subject to long-term changes. The different water masses are characterized and temporal changes are emphasized. The observed eddies are specified and geostrophic transports in the upper ocean are presented.
Bastien Y. Queste, Liam Fernand, Timothy D. Jickells, Karen J. Heywood, and Andrew J. Hind
Biogeosciences, 13, 1209–1222, https://doi.org/10.5194/bg-13-1209-2016, https://doi.org/10.5194/bg-13-1209-2016, 2016
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In stratified shelf seas, physical and biological conditions can lead to seasonal oxygen depletion when consumption exceeds supply. An ocean glider obtained a high-resolution 3-day data set of biochemical and physical properties in the central North Sea. The data revealed very high oxygen consumption rates, far exceeding previously reported rates. A consumption–supply oxygen budget indicates a localized or short-lived resuspension event causing rapid remineralization of benthic organic matter.
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Ocean Sci., 21, 1549–1573, https://doi.org/10.5194/os-21-1549-2025, https://doi.org/10.5194/os-21-1549-2025, 2025
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The Southern Ocean Time Series acquires observations in subantarctic waters south of Australia. We present the seasonality in hydrography, biogeochemistry, phytoplankton community composition, and particulate organic and inorganic carbon export to the deep sea using observations collected between 1997 and 2022. We also review recent research underpinned by these observations and emphasize the value of long time series for understanding ocean processes and responses to a changing climate.
Susana Flecha, Mercedes de la Paz, Fiz Fernández Pérez, Núria Marbà, Carlos Morell, Eva Alou-Font, Joaquín Tintoré, and Iris E. Hendriks
Ocean Sci., 21, 1515–1532, https://doi.org/10.5194/os-21-1515-2025, https://doi.org/10.5194/os-21-1515-2025, 2025
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Nitrous oxide (N2O), a potent greenhouse gas, is understudied in coastal zones. We present N2O concentrations and air–sea fluxes from the Balearic coast (2018–2023). Concentrations varied slightly across sites, with areas acting as weak sources or being near equilibrium. Temperature was the main driver of seasonal changes. These findings improve our understanding of coastal N2O emissions.
Meredith G. Meyer, Esther Portela, Walker O. Smith Jr., and Karen J. Heywood
Ocean Sci., 21, 1223–1236, https://doi.org/10.5194/os-21-1223-2025, https://doi.org/10.5194/os-21-1223-2025, 2025
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During the annual phytoplankton bloom, rates of primary production and carbon export in the Ross Sea, Antarctica, are uncoupled from each other and from oxygen and carbon stocks. These biogeochemical rates support the high-productivity, low-export classification of the region and suggest that environmental factors influence these stocks and rates differently and make projections under future climate change scenarios difficult.
Megan Jeffers, Christopher C. Chapman, Bernadette M. Sloyan, and Helen Bostock
Ocean Sci., 21, 537–554, https://doi.org/10.5194/os-21-537-2025, https://doi.org/10.5194/os-21-537-2025, 2025
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This study analyses physical and biogeochemical data collected in the East Australian Current (EAC) to understand variability in the nutrient-poor surface waters. The distribution of nutrients in the water column is influenced by seasonal flow and the EAC's position. An inshore EAC has a deeper nutricline and lower nutrient concentrations compared to an offshore EAC position. This has implications for the marine ecosystems along the coastline.
Detong Tian, Xuegang Li, Jinming Song, Jun Ma, Huamao Yuan, and Liqin Duan
EGUsphere, https://doi.org/10.5194/egusphere-2024-3467, https://doi.org/10.5194/egusphere-2024-3467, 2024
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Particulate organic carbon plays a vital role in the ocean carbon cycle, yet its transformation involves complex processes that are not fully understood. This study examines the vertical distribution the stable carbon isotopes in the tropical Northwestern Pacific, identifying three distinct biogeochemical layers of POC transformation, which contribute to a deeper understanding of the ocean carbon cycle.
Mona Norbisrath, Justus E. E. van Beusekom, and Helmuth Thomas
Ocean Sci., 20, 1423–1440, https://doi.org/10.5194/os-20-1423-2024, https://doi.org/10.5194/os-20-1423-2024, 2024
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We present an observational study investigating total alkalinity (TA) in the Dutch Wadden Sea. Discrete water samples were used to identify the TA spatial distribution patterns and locate and shed light on TA sources. By observing a tidal cycle, the sediments and pore water exchange were identified as local TA sources. We assumed metabolically driven CaCO3 dissolution as the TA source in the upper, oxic sediments and anaerobic metabolic processes as TA sources in the deeper, anoxic ones.
Nicolas Metzl, Claire Lo Monaco, Coraline Leseurre, Céline Ridame, Gilles Reverdin, Thi Tuyet Trang Chau, Frédéric Chevallier, and Marion Gehlen
Ocean Sci., 20, 725–758, https://doi.org/10.5194/os-20-725-2024, https://doi.org/10.5194/os-20-725-2024, 2024
Short summary
Short summary
In the southern Indian Ocean, south of the polar front, an observed increase of sea surface fCO2 and a decrease of pH over 1985–2021 are mainly driven by anthropogenic CO2 uptake, but in the last decade (2010–2020) fCO2 and pH were stable in summer, highlighting the competitive balance between anthropogenic CO2 and primary production. In the water column the increase of anthropogenic CO2 concentrations leads to migration of the aragonite saturation state from 600 m in 1985 up to 400 m in 2021.
Cited articles
Armstrong McKay, D. I., Cornell, S. E., Richardson, K., and Rockström, J.: Resolving ecological feedbacks on the ocean carbon sink in Earth system models, Earth Syst. Dynam., 12, 797–818, https://doi.org/10.5194/esd-12-797-2021, 2021. a
Asdar, S., Jacobs, Z. L., Popova, E., Noyon, M., Sauer, W. H., and Roberts, M. J.: Projected climate change impacts on the ecosystems of the Agulhas Bank, South Africa, Deep-Sea Res. Pt. II, 200, 105092, https://doi.org/10.1016/j.dsr2.2022.105092, 2022. a
Bange, H. W., Wajih, A., Naqvi, S., and Codispoti, L. A.: The nitrogen cycle in the Arabian Sea, Prog. Oceanogr., 65, 145–158, 2005. a
Bittig, H., Körtzinger, A., Johnson, K., Claustre, H., Emerson, S., Fennel, K., Garcia, H., Gilbert, D., Gruber, N., Kang, D.-J., Naqvi, W., Prakash, S., Riser, S., Thierry, V., Tilbrook, B., Uchida, H., Ulloa, O., and Xing, X.: SCOR WG 142: Quality control procedures for oxygen and other biogeochemical sensors on floats and gliders. Recommendations on the conversion between oxygen quantities for Bio-Argo floats and other autonomous platforms, Ifremer, https://doi.org/10.13155/45915, 2018. a
Bittig, H. C., Maurer, T. L., Plant, J. L., Schmechtig, C., Wong, A. P. S., Claustre, H., Trull, T. W., Udaya Bhaskar, T. V. S., Boss, E., Dall'Olmo, G., Organelli, E., Poteau, A., Johnson, K. S., Hanstein, C., Leymarie, E., Le Reste, S., Riser, S. C., Rupan, A. R., Taillandier, V., Thierry, V., and Xing, X.: A BGC-Argo guide: planning, deployment, data handling and usage, Front. Mar. Sci., 6, 502, https://doi.org/10.3389/fmars.2019.00502, 2019. a
Bristow, L. A., Callbeck, C. M., Larsen, M., Altabet, M. A., Dekaezemacker, J., Forth, M., Gauns, M., Glud, R. N., Kuypers, M. M. M., Lavik, G., Milucka, J., Naqvi, S. W. A., Pratihary, A., Revsbech, N. P., Thamdrup, B., Treusch, A. H., and Canfield, D. E.: N2 production rates limited by nitrite availability in the Bay of Bengal oxygen minimum zone, Nat. Geosci., 10, 24–31, 2017. a, b
Brodeau, L., Barnier, B., Penduff, T., Treguier, A. M., and Gulev, S.: An ERA40-based atmospheric forcing for global ocean circulation models, Ocean Model., 31, 88–104, 2010. a
Busecke, J. J. M., Resplandy, L., Ditkovsky, S., and John, J. G.: Diverging fates of the Pacific Ocean oxygen minimum zone and its core in a warming world, AGU Adv., 3, e2021AV000470, https://doi.org/10.1029/2021AV000470, 2022. a
CLS: Global Ocean Gridded L 4 Sea Surface Heights And Derived Variables Reprocessed 1993 Ongoing, CLS [data set], https://doi.org/10.48670/moi-00148, 2024. a
D'Asaro, E., Altaet, M., Suresh Kumar, N., and Ravichandran, M.: Structure of the Bay of Bengal oxygen deficient zone, Deep-Sea Rese. Pt. II, 179, 104650, https://doi.org/10.1016/j.dsr2.2019.104650, 2020. a, b, c, d
Ditkovsky, S., Resplandy, L., and Busecke, J.: Unique ocean circulation pathways reshape the Indian Ocean oxygen minimum zone with warming, Biogeosciences, 20, 4711–4736, https://doi.org/10.5194/bg-20-4711-2023, 2023. a, b
Eriksen, C. C., James Osse, T., Light, R. D., Wen, T., Lehman, T., Sabin, P. L., Ballard, J. W., and Chiodi, A. M.: Seaglider: a long-range autonomous underwater vehicle for oceanographic research, IEEE J. Ocean. Eng., 26, 424–436, 2001. a
Font, E., Swart, S., Bruss, G., Sheehan, P. M. F., Heywood, K. J., and Queste, B. Y.: Ventilation of the Arabian Sea oxygen minimum zone by Persian Gulf Water, J. Geophys. Res.-Oceans, 129, e2023JC020668, https://doi.org/10.1029/2023JC020668, 2024. a
Frajka-Williams, E., Eriksen, C. C., Rhines, P. B., and Harcourt, R. R.: Determining vertical water velocities from Seaglider, J. Atmos. Ocean. Tech., 28, 1641–1656, 2011. a
Garau, B., Ruiz, S., Zhang, W. G., Pascual, A., Heslop, E., Kerfoot, J., and Tintoré, J.: Thermal lag correction on Slocum CTD glider data, J. Atmos. Ocean. Tech., 28, 1065–1071, 2011. a
Garcia, H. E., Wang, Z., Bouchard, C., Cross, S. L., Paver, C. R., Reagan, J. R., Boyer, T. P., Locarnini, R. A., Mishonov, A. V., Baranova, O. K., Seidov, D., and Dukhovskoy, D.: World Ocean Atlas 2023, Volume 3: Dissolved Oxygen, Apparent Oxygen Utilization, and Oxygen Saturation, NOAA Atlas NESDID 91, NOAA, https://www.ncei.noaa.gov/products/world-ocean-atlas (last access: 23 July 2025), 2024. a, b
Gruber, N.: The marine nitrogen cycle: overview and challenges, in: Nitrogen in the marine environment, edited by: Capone, D. G., Bronk, D. A., Mulholland, M. R., and Carpenter, E. J., Burlington, USA, 1–50, ISBN 978-0-12-372522-6, 2008. a
Hofmann, A. F., Peltzer, E. T., Walz, P. M., and Brewer, P. G.: Hypoxia by degrees: establishing definitions for a changing ocean, Deep-Sea Res. Pt. I, 58, 1212–1226, 2011. a
Jacobs, Z. L., Jebri, F., Raitsos, D. E., Popova, E., Srokosz, M., Painter, S. C., Nencioli, F., Roberts, M., Kamau, J., Palmer, M., and Wihsgott, J.: Shelf-break upwelling and productivity over the North Kenya Banks: the importance of large-scale ocean dynamics, J. Geophys. Res.-Oceans, 125, e2019JC015519, https://doi.org/10.1029/2019JC015519, 2020. a
Jebri, F., Jacobs, Z. L., Raitsos, D. E., Srokosz, M., Painter, S. C., Kelly, S., Roberts, M. J., Scott, L., Taylor, S. F. W., Palmer, M. R., Kizenger, H., Shaghude, Y., and Popova, E.: Interannual monsoon wind variability as a key driver of East African small pelagic fisheries, Sci. Rep., 10, 13247, https://doi.org/10.1038/s41598-020-70275-9, 2020. a
Kwiatkowski, L., Torres, O., Bopp, L., Aumont, O., Chamberlain, M., Christian, J. R., Dunne, J. P., Gehlen, M., Ilyina, T., John, J. G., Lenton, A., Li, H., Lovenduski, N. S., Orr, J. C., Palmieri, J., Santana-Falcón, Y., Schwinger, J., Séférian, R., Stock, C. A., Tagliabue, A., Takano, Y., Tjiputra, J., Toyama, K., Tsujino, H., Watanabe, M., Yamamoto, A., Yool, A., and Ziehn, T.: Twenty-first century ocean warming, acidification, deoxygenation, and upper-ocean nutrient and primary production decline from CMIP6 model projections, Biogeosciences, 17, 3439–3470, https://doi.org/10.5194/bg-17-3439-2020, 2020. a
Lachkar, Z., Lévy, M., Hailegeorgis, D., and Vallivattathillam, P.: Differences in recent and future trends in the Arabian Sea oxygen minimum zone: processes and uncertainties, Front. Mar. Sci., 10, 1122043, https://doi.org/10.3389/fmars.2023.1122043, 2023. a, b
Lellouche, J.-M., Grenier, E., Romain, B.-B., Garric, G., Melet, A., Drévillon, M., Bricaud, C., Hamon, M., Le Galloudec, O., Regnier, C., Candela, T., Testut, C.-E., Gasparin, F., Ruggiero, G., Benkiran, M., Drillet, Y., and Le Traon, P.-Y.: The Copernicus global 1/12° oceanic and sea ice GLORYS12 re-analysis, Front. Mar. Sci., 9, 698876, https://doi.org/10.3389/feart.2021.698876, 2021. a, b
Lévy, M., Couespel, D., Haëck, C., Keerthi, M. G., Mangolte, I., and Prend, C. J.: The impact of fine-scale currents on biogeochemcial cycles in a changing ocean, Annu. Rev. Mar. Sci., 16, 191–215, 2024. a
Locarnini, R. A., Mishonov, A. V., Baranova, O. K., Reagan, J. R., Boyer, T. P., Seidov, D., Wang, Z., Garcia, H. E., Bouchard, C., Cross, S. L., Paver, C. R., and Dukhovskoy, D.: World Ocean Atlas 2023, Volume 1: Temperature, NOAA Atlas NESDID 89, NOAA, https://www.ncei.noaa.gov/products/world-ocean-atlas (last access: 23 July 2025), 2024. a, b
Madec, G.: NEMO ocean engine. Note du Pôle de modélisation, Tech. Rep. 27, Institute Pierre-Simon Laplace, France, https://www.nemo-ocean.eu/doc/ (last access: 23 July 2025), 2016. a
Mercator Ocean International: Global Ocean Physics Reanalysis, Mercator Ocean International [data set], https://doi.org/10.48670/moi-00021, 2023. a
Murtugudde, R., McCreary, J. P., and Busalacchi, A. J.: Oceanic processes associated with anomalous events in the Indian Ocean with relevance to 1997–1998, J. Geophys. Res., 105, 3295–3306, 2000. a
Nayak, A. A., Vinayachandran, P. N., and George, J. V.: Arabian Sea high salinity core supplies oxygen to the Bay of Bengal, Deep-Sea Res. Pt. II, 221, 105477, https://doi.org/10.1016/j.dsr2.2025.105477, 2025. a, b, c, d
NOAA: Index of /data/oceans/woa/WOA23/DATA, NOAA [data set], https://www.ncei.noaa.gov/data/oceans/woa/WOA23/DATA/ (last access: 23 July 2025), 2025. a
Popova, E., Yool, A., Byfield, V., Cochrane, K., Coward, A. C., Salim, S. S., Gasalla, M. A., Henson, S. E., Hobday, A. J., Pecl, G. T., Sauer, W. H., and Roberts, M. J.: From global to regional and back again: common climate stressors of marine ecosystems relevant for adaptation across five ocean warming hotspots, Global Change Biol., 22, 2038–2053, 2016. a
Reagan, J. R., Seidov, D., Wang, Z., Dukhovskoy, D., Boyer, T. P., Locarnini, R. A., Baranova, O. K., Mishonov, A. V., Garcia, H. E., Bouchard, C., Cross, S. L., and Paver, C. R.: World Ocean Atlas 2023, Volume 2: Salinity, NOAA Atlas NESDID, NOAA Atlas NESDID 90, NOAA, https://www.ncei.noaa.gov/products/world-ocean-atlas (last access: 23 July 2025), 2024. a, b
Rixen, T., Cowie, G., Gaye, B., Goes, J., do Rosário Gomes, H., Hood, R. R., Lachkar, Z., Schmidt, H., Segschneider, J., and Singh, A.: Reviews and syntheses: Present, past, and future of the oxygen minimum zone in the northern Indian Ocean, Biogeosciences, 17, 6051–6080, https://doi.org/10.5194/bg-17-6051-2020, 2020. a, b, c
Sheehan, P. M. F., Webber, B. G. M., Sanchez-Franks, A., Matthews, A. J., Heywood, K. J., and Vinayachandran, P. N.: Injection of oxygenated Persian Gulf Water into the southern Bay of Bengal, Geophys. Res. Lett., 47, e2020GL087773, https://doi.org/10.1029/2020GL087773, 2020. a, b, c, d
Vinayachandran, P. N., Masumoto, Y., Mikawa, T., and Yamagata, T.: Intrusion of the Southwest Monsoon Current into the Bay of Bengal, J. Geophys. Res., 104, 11077–11085, 1999. a
Vinayachandran, P. N., Shankar, D., Vernekar, S., Sandeep, K. K., Amol, P., Neema, C. P., and Chatterjee, A.: A summer monsoon pump to keep the Bay of Bengal salty, Geophys. Res. Lett., 40, 1777–1782, 2013. a
Vinayachandran, P. N., Matthews, A. J., Vijay Kumar, K., Sanchez-Franks, A., Thushara, V., George, J., Vijith, V., Webber, B. G. M., Queste, B. Y., Roy, R., Sarkar, A., Baranowski, D. B., Bhat, G. S., Klingaman, N. P., Peatman, S. C., Parida, C., Heywood, K. J., Hall, R. A., King, B., Kent, E. C., Nayak, A. A., Neema, C. P., Amol, P., Lotliker, A., Kankonkar, A., Gracias, D. G., Vernekar, S., Souza, A. C. D. Valluvan, G., Pargaonkar, S. M., Dinesh, K., Giddings, J., and Joshi, M.: BoBBLE (Bay of Bengal Boundary Layer Experiment): ocean-atmosphere interaction and its impact of the South Asian monsoon, B. Am. Meteorol. Soc., 99, 1569–1587, 2018. a
Webber, B. G. M., Matthews, A. J., Vinayachandran, P. N., Neema, C. P., Sanchez-Franks, A., Vijith, V., Amol, P., and Baranowski, D. B.: The dynamics of the Southwest Monsoon Current in 2016 from high-resolution observations and models, J. Phys. Oceanogr., 48, 2259–2282, 2018. a, b, c, d, e, f, g, h
Webber, B. G. M., Matthews, A. J., Queste, B. Y., Lee, G. A., Cobas-Garcia, M., Heywood, K. J., and Vinayachandran, P. N.: Ocean glider data from five Seagliders deployed in the Bay of Bengal during the BoBBLE (Bay of Bengal Boundary Layer Experiment) project in July 2016, British Oceanographic Data Centre, National Oceanography Centre, NERC [data set], https://doi.org/10.5285/996bf53d-5448-297a-e053-6c86abc0b996, 2019. a, b
Yool, A., Popova, E. E., and Anderson, T. R.: MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies, Geosci. Model Dev., 6, 1767–1811, https://doi.org/10.5194/gmd-6-1767-2013, 2013a. a, b, c, d
Yool, A., Popova, E. E., Coward, A. C., Bernie, D., and Anderson, T. R.: Climate change and ocean acidification impacts on lower trophic levels and the export of organic carbon to the deep ocean, Biogeosciences, 10, 5831–5854, https://doi.org/10.5194/bg-10-5831-2013, 2013b. a
Zhou, Y., Gong, H., and Zhou, F.: Responses of horizontally expanding oceanic oxygen minimum zones to climate change based on observations, Geophys. Res. Lett., 49, e2022GL097724, https://doi.org/10.1029/2022GL097724, 2022. a
Short summary
Using measurements and computer models, we identify a large flux of oxygen within the Southwest Monsoon Current, which flows north into the Bay of Bengal between June and September each year. Oxygen levels in the bay are very low, but they are not quite low enough for key nutrient cycles to be as dramatically altered as in other low-oxygen regions. We suggest that the flux which we identify contributes to keeping oxygen levels in the bay above the threshold below which dramatic changes would occur.
Using measurements and computer models, we identify a large flux of oxygen within the Southwest...
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