Articles | Volume 22, issue 2
https://doi.org/10.5194/os-22-1023-2026
© Author(s) 2026. 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-22-1023-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
26 Mar 2026
Research article |
| 26 Mar 2026
| 26 Mar 2026
Characterisation of past marine heatwaves around South Pacific Island countries: what really matters?
Université de Toulouse, LEGOS (IRD/CNES/CNRS/UT3), 31400 Toulouse, France
Institut de Recherche pour le Développement (IRD) Centre de Nouvelle Calédonie, Nouméa, New Caledonia
Sophie Cravatte
Université de Toulouse, LEGOS (IRD/CNES/CNRS/UT3), 31400 Toulouse, France
Institut de Recherche pour le Développement (IRD) Centre de Nouvelle Calédonie, Nouméa, New Caledonia
Christophe Menkes
ENTROPIE, UMR 9220, IRD, Université de la Nouvelle-Calédonie, Université de la Réunion, CNRS, IFREMER, BP 32078, 98897 Nouméa CEDEX, New Caledonia
Jed Macdonald
Oceanic Fisheries Programme, Fisheries Aquaculture and Marine Ecosystems Division, Pacific Community (SPC), 98848 Noumea, New Caledonia
Romain Le Gendre
Université de Toulouse, LEGOS (IRD/CNES/CNRS/UT3), 31400 Toulouse, France
ENTROPIE, UMR 9220, IRD, Université de la Nouvelle-Calédonie, Université de la Réunion, CNRS, IFREMER, BP 32078, 98897 Nouméa CEDEX, New Caledonia
Ines Mangolte
ENTROPIE, UMR 9220, IRD, Université de la Nouvelle-Calédonie, Université de la Réunion, CNRS, IFREMER, BP 32078, 98897 Nouméa CEDEX, New Caledonia
Cyril Dutheil
MARBEC, University of Montpellier, CNRS, IFREMER, IRD, Sète, France
Neil J. Holbrook
Institute for Marine and Antarctic Studies and ARC Centre of Excellence for Climate Extremes, University of Tasmania, Hobart, Tasmania, Australia
Simon Nicol
Oceanic Fisheries Programme, Fisheries Aquaculture and Marine Ecosystems Division, Pacific Community (SPC), 98848 Noumea, New Caledonia
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Carla Chevillard, Romain Le Gendre, Christophe Menkes, Takeshi Izumo, Bastien Pagli, Simon Van Wynsberge, and Sophie Cravatte
Ocean Sci., 22, 1213–1236, https://doi.org/10.5194/os-22-1213-2026, https://doi.org/10.5194/os-22-1213-2026, 2026
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To detect past marine heatwaves events and analyse their characteristics, scientists use one of the available sea surface temperature products, relying on different data ingested and procedures. Here, we compare marine heatwaves statistics computed using six products in the tropical Pacific over 1993–2021. We highlight significant differences and provide uncertainties. Our results advocate for the use of multiple products in marine heatwaves studies to increase the robustness of the conclusions.
Jules Victor Lehodey, Alexandre Mignot, Alexandre Ganachaud, Sarah Albernhe, and Simon Nicol
EGUsphere, https://doi.org/10.5194/egusphere-2026-711, https://doi.org/10.5194/egusphere-2026-711, 2026
This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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Marine zooplankton transfer energy from microscopic algae to fish and larger predators. Understanding their distribution helps predict how oceans respond to climate change. We developed SeapoPym, a freely available model that simulates zooplankton using ocean temperature and plant productivity. This tool lets scientists test biological hypotheses and estimate parameters from observations.
Chenhui Jin, Elizabeth A. Ritchie, and Neil J. Holbrook
EGUsphere, https://doi.org/10.5194/egusphere-2025-6321, https://doi.org/10.5194/egusphere-2025-6321, 2026
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Tropical cyclones that move into the midlatitudes become extratropical cyclones, so-called extratropical transition. In this study, we detected transition events in the Southern Hemisphere based on the model data. We found that weather patterns during the transition are different from case to case. In some cases, strong tropical cyclones interact with the midlaltitude flow and lead to great changes in weather nearby.
Inès Mangolte, Sophie Cravatte, Alexandre Ganachaud, and Christophe Menkès
EGUsphere, https://doi.org/10.5194/egusphere-2025-5995, https://doi.org/10.5194/egusphere-2025-5995, 2025
This preprint is open for discussion and under review for Ocean Science (OS).
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Marine heatwaves pose a serious threat to marine ecosystems that will become increasingly important with climate change. Here we show in the Southwest Pacific that dynamical forecasting systems are able to forecast long, large-scale marine heatwaves occurring in austral winter, but have less skill in predicting smaller, shorter events, and summer events. We discuss the implications for operational forecasts dedicated to help marine managers to prepare and mitigate some of their impacts.
Daneeja Mawren, Julia Araujo, Romain Le Gendre, Jessica A. Benthuysen, Franck Eitel Kemgang Ghomsi, Jayanthi S. Saranya, and Amandine Schaeffer
EGUsphere, https://doi.org/10.5194/egusphere-2025-6045, https://doi.org/10.5194/egusphere-2025-6045, 2025
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Using sixteen years of ocean glider observations, we show that marine heatwaves shoal the mixed layer and alter subsurface biogeochemistry across Australia’s continental shelf. While surface chlorophyll generally declined, strong stratification and event severity promoted deeper, intensified chlorophyll maxima while subsurface oxygen responses varied. These findings underscore the importance of region-specific dynamics in shaping ecological responses to marine heatwaves.
Esther Ladet, Carla Chevillard, Romain Le Gendre, Thomas Trophime, Sébastien Petton, and Simon Van Wynsberge
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2025-692, https://doi.org/10.5194/essd-2025-692, 2025
Revised manuscript under review for ESSD
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This dataset on Reao atoll provides an unprecedented record of thermal dynamics and lagoon circulation in a semi-closed atoll of French Polynesia, including full coverage of the extreme 2024 marine heatwave that caused mass bleaching. Collected over six monitoring periods between 2016 and 2025, it offers a critical basis for analysing thermal exposure of giant clams, identifying potential refugia, and supporting modelling of atoll responses to climate change.
Florian Börgel, Itzel Ruvalcaba Baroni, Leonie Barghorn, Leonard Borchert, Bronwyn Cahill, Cyril Dutheil, Leonie Esters, Malgorzata Falarz, Helena L. Filipsson, Matthias Gröger, Jari Hänninen, Magnus Hieronymus, Erko Jakobsen, Mehdi Pasha Karami, Karol Kulinski, Taavi Liblik, H. E. Markus Meier, Gabriele Messori, Lev Naumov, Thomas Neumann, Piia Post, Gregor Rehder, Anna Rutgersson, and Georg Sebastian Voelker
EGUsphere, https://doi.org/10.5194/egusphere-2025-5496, https://doi.org/10.5194/egusphere-2025-5496, 2025
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This review explains how weather patterns, guided by the polar jet stream, influence the Baltic Sea’s climate and ecosystem. It covers the NAO, blocking events and other processes and discusses how they affect temperature, rainfall, and storms from days to decades. These shifts then impact oxygen levels, productivity, and acidification in the Baltic Sea. Physical links are fairly well known, but biogeochemical pathways remain uncertain.
John Reilly, Chris Chapman, Courtney Quinn, Jules Kajtar, Ashley Barnes, and Neil Holbrook
EGUsphere, https://doi.org/10.5194/egusphere-2025-4226, https://doi.org/10.5194/egusphere-2025-4226, 2025
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Recent advancements in regional ocean modelling allow higher resolution simulations providing improved estimates of the large-scale ocean state, while also revealing new insights into the fine-scale processes connecting the open ocean to the continental shelf seas. Our study highlights the importance of increased model resolution in regions of the ocean that are particularly turbulent while in quasi-stable circulation regions (e.g., jets), the current state-of-the-art global models do suffice.
Romain Le Gendre, David Varillon, Sylvie Fiat, Régis Hocdé, Antoine de Ramon N'Yeurt, Serge Andréfouët, Jérôme Aucan, Sophie Cravatte, Maxime Duphil, Alexandre Ganachaud, Baptiste Gaudron, Elodie Kestenare, Vetea Liao, Bernard Pelletier, Alexandre Peltier, Anne-Lou Schaefer, Thomas Trophime, Simon Van Wynsberge, Yves Dandonneau, Michel Allenbach, and Christophe Menkes
Earth Syst. Sci. Data, 17, 5277–5301, https://doi.org/10.5194/essd-17-5277-2025, https://doi.org/10.5194/essd-17-5277-2025, 2025
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Due to ocean warming, coral reef ecosystems are strongly impacted by dystrophic events and corals experiencing increasing frequencies of bleaching events. In situ observation remains the best alternative for accurate characterization of trends and extremes in these shallow environments. This paper presents the coastal temperature dataset of the ReefTEMPS monitoring network, which spreads over multiple Pacific Island countries and territories (PICTs) in the western and central South Pacific.
Sarah Albernhe, Thomas Gorgues, Olivier Titaud, Patrick Lehodey, Christophe Menkes, and Anna Conchon
State Planet, 6-osr9, 4, https://doi.org/10.5194/sp-6-osr9-4-2025, https://doi.org/10.5194/sp-6-osr9-4-2025, 2025
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Micronekton are marine organisms gathering a wide diversity of taxa (crustaceans, fish, cephalopods) 2 to 20 cm in size. They are responsible for an important carbon export to the deep ocean and are the main prey for marine predators. We define provinces of homogeneous environmental parameters, representing areas of common micronekton biomass and vertical structure. We observe the evolution of the provinces in time from 1998 to 2023 to account for the seasonal to interannual variability.
Arne Bendinger, Sophie Cravatte, Lionel Gourdeau, Clément Vic, and Florent Lyard
Ocean Sci., 21, 1943–1966, https://doi.org/10.5194/os-21-1943-2025, https://doi.org/10.5194/os-21-1943-2025, 2025
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Temporal variability of the semidiurnal internal tide around New Caledonia is investigated using regional modeling. An important contribution to temporal variability not linked to the spring–neap tide cycle is due to the presence of mesoscale eddies both at the generation sites and in the propagation direction. The incoherent tide has a widespread signature in sea surface height (SSH), challenging the SSH observability of mesoscale to submesoscale dynamics.
Bastien Pagli, Takeshi Izumo, Alexandre Barboni, Carla Chevillard, Cyril Dutheil, Raphael Legrand, Christophe Menkes, Claire Rocuet, and Sophie Cravatte
EGUsphere, https://doi.org/10.5194/egusphere-2025-4166, https://doi.org/10.5194/egusphere-2025-4166, 2025
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Marine heatwaves—periods of unusually warm ocean temperatures—are becoming more frequent and intense with climate change. These events can harm marine ecosystems, especially in vulnerable regions like French Polynesia. Here, we used satellite sea surface temperature data and ocean reanalysis to characterize past events. We investigated their characteristics, variability linked to ENSO, and the physical mechanisms driving their onset and decay across the region.
Arne Bendinger, Sophie Cravatte, Lionel Gourdeau, Luc Rainville, Clément Vic, Guillaume Sérazin, Fabien Durand, Frédéric Marin, and Jean-Luc Fuda
Ocean Sci., 20, 945–964, https://doi.org/10.5194/os-20-945-2024, https://doi.org/10.5194/os-20-945-2024, 2024
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A unique dataset of glider observations reveals tidal beams south of New Caledonia – an internal-tide-generation hot spot in the southwestern tropical Pacific. Observations are in good agreement with numerical modeling output, highlighting the glider's capability to infer internal tides while assessing the model's realism of internal-tide dynamics. Discrepancies are in large part linked to eddy–internal-tide interactions. A methodology is proposed to deduce the internal-tide surface signature.
Oriane Bruyère, Romain Le Gendre, Vetea Liao, and Serge Andréfouët
Earth Syst. Sci. Data, 16, 667–679, https://doi.org/10.5194/essd-16-667-2024, https://doi.org/10.5194/essd-16-667-2024, 2024
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During 2019–2020, the lagoon and forereefs of Gambier Island (French Polynesia) were monitored with oceanographic instruments to measure lagoon hydrodynamics and ocean–lagoon water exchanges. Gambier Island is a key black pearl producer and the study goal was to understand the processes influencing spat collection of pearl oyster Pinctada margaritifera, the species used to produce black pearls. The data set is provided to address local pearl farming questions and other investigations as well.
Philippe F. V. W. Frankemölle, Peter D. Nooteboom, Joe Scutt Phillips, Lauriane Escalle, Simon Nicol, and Erik van Sebille
Ocean Sci., 20, 31–41, https://doi.org/10.5194/os-20-31-2024, https://doi.org/10.5194/os-20-31-2024, 2024
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Tuna fisheries in the Pacific often use drifting fish aggregating devices (dFADs) to attract fish that are advected by subsurface flow through underwater appendages. Using a particle advection model, we find that virtual particles advected by surface flow are displaced farther than virtual dFADs. We find a relation between El Niño–Southern Oscillation and circular motion in some areas, influencing dFAD densities. This information helps us to understand processes that drive dFAD distribution.
Oriane Bruyère, Romain Le Gendre, Mathilde Chauveau, Bertrand Bourgeois, David Varillon, John Butscher, Thomas Trophime, Yann Follin, Jérôme Aucan, Vetea Liao, and Serge Andréfouët
Earth Syst. Sci. Data, 15, 5553–5573, https://doi.org/10.5194/essd-15-5553-2023, https://doi.org/10.5194/essd-15-5553-2023, 2023
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During 2018–2022, four pearl farming Tuamotu atolls (French Polynesia) were studied with oceanographic instruments to measure lagoon hydrodynamics and ocean-lagoon water exchanges. The goal was to gain knowledge on the processes influencing the spat collection of the pearl oyster Pinctada margaritifera, the species used to produce black pearls. A worldwide unique oceanographic atoll data set is provided to address local pearl farming questions and other fundamental and applied investigations.
Arne Bendinger, Sophie Cravatte, Lionel Gourdeau, Laurent Brodeau, Aurélie Albert, Michel Tchilibou, Florent Lyard, and Clément Vic
Ocean Sci., 19, 1315–1338, https://doi.org/10.5194/os-19-1315-2023, https://doi.org/10.5194/os-19-1315-2023, 2023
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New Caledonia is a hot spot of internal-tide generation due to complex bathymetry. Regional modeling quantifies the coherent internal tide and shows that most energy is converted in shallow waters and on very steep slopes. The region is a challenge for observability of balanced dynamics due to strong internal-tide sea surface height (SSH) signatures at similar wavelengths. Correcting the SSH for the coherent internal tide may increase the observability of balanced motion to < 100 km.
Oriane Bruyère, Benoit Soulard, Hugues Lemonnier, Thierry Laugier, Morgane Hubert, Sébastien Petton, Térence Desclaux, Simon Van Wynsberge, Eric Le Tesson, Jérôme Lefèvre, Franck Dumas, Jean-François Kayara, Emmanuel Bourassin, Noémie Lalau, Florence Antypas, and Romain Le Gendre
Earth Syst. Sci. Data, 14, 5439–5462, https://doi.org/10.5194/essd-14-5439-2022, https://doi.org/10.5194/essd-14-5439-2022, 2022
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From 2014 to 2021, extensive monitoring of hydrodynamics was deployed within five contrasted lagoons of New Caledonia during austral summers. These coastal physical observations encompassed unmonitored lagoons and captured eight major atmospheric events ranging from tropical depression to category 4 cyclone. The main objectives were to characterize the processes controlling hydrodynamics of these lagoons and record the signature of extreme events on land–lagoon–ocean continuum functioning.
Xi Wei, Josette Garnier, Vincent Thieu, Paul Passy, Romain Le Gendre, Gilles Billen, Maia Akopian, and Goulven Gildas Laruelle
Biogeosciences, 19, 931–955, https://doi.org/10.5194/bg-19-931-2022, https://doi.org/10.5194/bg-19-931-2022, 2022
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Estuaries are key reactive ecosystems along the land–ocean aquatic continuum and are often strongly impacted by anthropogenic activities. We calculated nutrient in and out fluxes by using a 1-D transient model for seven estuaries along the French Atlantic coast. Among these, large estuaries with high residence times showed higher retention rates than medium and small ones. All reveal coastal eutrophication due to the excess of diffused nitrogen from intensive agricultural river basins.
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Short summary
This paper characterizes historical (1981–2023) marine heatwaves in the tropical southwestern Pacific, where they pose a challenge for marine resource dependent Islands. Heatwaves are distinguished as a function of their spatial extent, signature at the coast, and seasonality, to allow a better understanding of their impacts on ecosystems. Marine heatwaves are getting longer and more frequent, with greater spatial extents. Our results aim to inform the Pacific Islands on their vulnerability.
This paper characterizes historical (1981–2023) marine heatwaves in the tropical southwestern...
