Articles | Volume 21, issue 4
https://doi.org/10.5194/os-21-1237-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-21-1237-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Local versus far-field control on South Pacific Subantarctic mode water variability
Ciara Pimm
CORRESPONDING AUTHOR
Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, Liverpool, UK
Woods Hole Oceanographic Institution, Woods Hole, MA, USA
Andrew J. S. Meijers
British Antarctic Survey, NERC, UKRI, Cambridge, UK
Dani C. Jones
British Antarctic Survey, NERC, UKRI, Cambridge, UK
Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan, Ann Arbor, MI, USA
Richard G. Williams
Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, Liverpool, UK
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Yavor Kostov, Paul R. Holland, Kelly A. Hogan, James A. Smith, Nicolas C. Jourdain, Pierre Mathiot, Anna Olivé Abelló, Andrew H. Fleming, and Andrew J. S. Meijers
EGUsphere, https://doi.org/10.5194/egusphere-2025-2423, https://doi.org/10.5194/egusphere-2025-2423, 2025
This preprint is open for discussion and under review for The Cryosphere (TC).
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Icebergs ground when they reach shallow topography such as Bear Ridge in the Amundsen Sea. Grounded icebergs can block the transport of sea-ice and create areas of higher and lower sea-ice concentration. We introduce a physically and observationally motivated representation of grounding in an ocean model. In addition, we improve the way simulated icebergs respond to winds, ocean currents, and density differences in sea water. We analyse the forces acting on freely floating and grounded icebergs.
Richard G. Williams, Philip Goodwin, Paulo Ceppi, Chris D. Jones, and Andrew MacDougall
EGUsphere, https://doi.org/10.5194/egusphere-2025-800, https://doi.org/10.5194/egusphere-2025-800, 2025
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How the climate system responds when carbon emissions cease is an open question: some climate models reveal a slight warming, whereas most models reveal a slight cooling. Their climate response is affected by how the planet takes up heat and radiates heat back to space, and how the land and ocean sequester carbon from the atmosphere. A framework is developed to connect the temperature response of the climate models to competing and opposing-signed thermal and carbon contributions.
Neill Mackay, Taimoor Sohail, Jan David Zika, Richard G. Williams, Oliver Andrews, and Andrew James Watson
Geosci. Model Dev., 17, 5987–6005, https://doi.org/10.5194/gmd-17-5987-2024, https://doi.org/10.5194/gmd-17-5987-2024, 2024
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The ocean absorbs carbon dioxide from the atmosphere, mitigating climate change, but estimates of the uptake do not always agree. There is a need to reconcile these differing estimates and to improve our understanding of ocean carbon uptake. We present a new method for estimating ocean carbon uptake and test it with model data. The method effectively diagnoses the ocean carbon uptake from limited data and therefore shows promise for reconciling different observational estimates.
Philip Goodwin, Richard Williams, Paulo Ceppi, and B. B. Cael
EGUsphere, https://doi.org/10.5194/egusphere-2023-2307, https://doi.org/10.5194/egusphere-2023-2307, 2023
Preprint archived
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Climate feedbacks are normally evaluated by considering the change over time for Earth's energy balance and surface temperatures in the climate system. However, we only have around 1 degree Celsius of temperature change to utilise. Here, climate feedbacks are instead evaluated from the change in latitude of Earth's energy balance and surface temperatures, where we have around 70 degrees Celsius of temperature change to utilise.
Dani C. Jones, Maike Sonnewald, Shenjie Zhou, Ute Hausmann, Andrew J. S. Meijers, Isabella Rosso, Lars Boehme, Michael P. Meredith, and Alberto C. Naveira Garabato
Ocean Sci., 19, 857–885, https://doi.org/10.5194/os-19-857-2023, https://doi.org/10.5194/os-19-857-2023, 2023
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Machine learning is transforming oceanography. For example, unsupervised classification approaches help researchers identify underappreciated structures in ocean data, helping to generate new hypotheses. In this work, we use a type of unsupervised classification to identify structures in the temperature and salinity structure of the Weddell Gyre, which is an important region for global ocean circulation and for climate. We use our method to generate new ideas about mixing in the Weddell Gyre.
Katherine E. Turner, Doug M. Smith, Anna Katavouta, and Richard G. Williams
Biogeosciences, 20, 1671–1690, https://doi.org/10.5194/bg-20-1671-2023, https://doi.org/10.5194/bg-20-1671-2023, 2023
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We present a new method for reconstructing ocean carbon using climate models and temperature and salinity observations. To test this method, we reconstruct modelled carbon using synthetic observations consistent with current sampling programmes. Sensitivity tests show skill in reconstructing carbon trends and variability within the upper 2000 m. Our results indicate that this method can be used for a new global estimate for ocean carbon content.
Negar Vakilifard, Richard G. Williams, Philip B. Holden, Katherine Turner, Neil R. Edwards, and David J. Beerling
Biogeosciences, 19, 4249–4265, https://doi.org/10.5194/bg-19-4249-2022, https://doi.org/10.5194/bg-19-4249-2022, 2022
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To remain within the Paris climate agreement, there is an increasing need to develop and implement carbon capture and sequestration techniques. The global climate benefits of implementing negative emission technologies over the next century are assessed using an Earth system model covering a wide range of plausible climate states. In some model realisations, there is continued warming after emissions cease. This continued warming is avoided if negative emissions are incorporated.
Anna Katavouta and Richard G. Williams
Biogeosciences, 18, 3189–3218, https://doi.org/10.5194/bg-18-3189-2021, https://doi.org/10.5194/bg-18-3189-2021, 2021
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Diagnostics of the latest-generation Earth system models reveal the ocean will continue to absorb a large fraction of the anthropogenic carbon released to the atmosphere in the next century, with the Atlantic Ocean storing a large amount of this carbon relative to its size. The ability of the ocean to absorb carbon will reduce in the future as the ocean warms and acidifies. This reduction is larger in the Atlantic Ocean due to a weakening of the meridional overturning with changes in climate.
Vivek K. Arora, Anna Katavouta, Richard G. Williams, Chris D. Jones, Victor Brovkin, Pierre Friedlingstein, Jörg Schwinger, Laurent Bopp, Olivier Boucher, Patricia Cadule, Matthew A. Chamberlain, James R. Christian, Christine Delire, Rosie A. Fisher, Tomohiro Hajima, Tatiana Ilyina, Emilie Joetzjer, Michio Kawamiya, Charles D. Koven, John P. Krasting, Rachel M. Law, David M. Lawrence, Andrew Lenton, Keith Lindsay, Julia Pongratz, Thomas Raddatz, Roland Séférian, Kaoru Tachiiri, Jerry F. Tjiputra, Andy Wiltshire, Tongwen Wu, and Tilo Ziehn
Biogeosciences, 17, 4173–4222, https://doi.org/10.5194/bg-17-4173-2020, https://doi.org/10.5194/bg-17-4173-2020, 2020
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Since the preindustrial period, land and ocean have taken up about half of the carbon emitted into the atmosphere by humans. Comparison of different earth system models with the carbon cycle allows us to assess how carbon uptake by land and ocean differs among models. This yields an estimate of uncertainty in our understanding of how land and ocean respond to increasing atmospheric CO2. This paper summarizes results from two such model intercomparison projects that use an idealized scenario.
Jan D. Zika, Jean-Baptiste Sallée, Andrew J. S. Meijers, Alberto C. Naveira-Garabato, Andrew J. Watson, Marie-Jose Messias, and Brian A. King
Ocean Sci., 16, 323–336, https://doi.org/10.5194/os-16-323-2020, https://doi.org/10.5194/os-16-323-2020, 2020
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The ocean can regulate climate by distributing heat and carbon dioxide into its interior. This work has resulted from a major experiment aimed at understanding how that distribution occurs. In the experiment an artificial tracer was released into the ocean. After release the tracer was tracked as it was distorted by ocean currents. Using novel methods we reveal how the tracer's distortions follow the movement of the underlying water masses in the ocean and we estimate the rate at which it mixes.
Related subject area
Approach: Numerical Models | Properties and processes: Overturning circulation, gyres and water masses
Stratification and overturning circulation are intertwined controls on ocean heat uptake efficiency in climate models
Controls on dense water formation along the path of the North Atlantic subpolar gyre
Long-term variability and trends in the Agulhas Leakage and its impacts on the global overturning
North Atlantic Subtropical Mode Water properties: intrinsic and atmospherically forced interannual variability
The formation and ventilation of an oxygen minimum zone in a simple model for latitudinally alternating zonal jets
Topographic modulation on the layered circulation in South China Sea
Persistent climate model biases in the Atlantic Ocean's freshwater transport
Surface factors controlling the volume of accumulated Labrador Sea Water
Dependency of simulated tropical Atlantic current variability on the wind forcing
Altered Weddell Sea warm- and dense-water pathways in response to 21st-century climate change
Assessing the drift of fish aggregating devices in the tropical Pacific Ocean
Assessment of Indonesian Throughflow transports from ocean reanalyses with mooring-based observations
Linus Vogt, Jean-Baptiste Sallée, and Casimir de Lavergne
Ocean Sci., 21, 1081–1103, https://doi.org/10.5194/os-21-1081-2025, https://doi.org/10.5194/os-21-1081-2025, 2025
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The ocean buffers human-induced climate change by taking up excess heat from the atmosphere. In this study, we use an ensemble of global climate models to study the physical processes which set the efficiency at which this heat is stored in the ocean. We reconcile previous attempts to explain controls on this efficiency and find that Southern Ocean stratification is a key model property due to its influence on the local overturning circulation and its connection to the subpolar North Atlantic.
Oliver John Tooth, Helen Louise Johnson, and Chris Wilson
EGUsphere, https://doi.org/10.5194/egusphere-2025-1132, https://doi.org/10.5194/egusphere-2025-1132, 2025
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The North Atlantic Subpolar Gyre (SPG) forms dense water as part of the Atlantic Meridional Overturning Circulation. To explore the factors controlling dense water formation around the SPG, we trace the pathways of virtual water parcels in a high-resolution ocean model. We show that the amount of dense water formed around the SPG depends principally on the availability of light waters flowing northward, such that a stronger SPG circulation results in more dense water formation along-stream.
Hendrik Großelindemann, Frederic S. Castruccio, Gokhan Danabasoglu, and Arne Biastoch
Ocean Sci., 21, 93–112, https://doi.org/10.5194/os-21-93-2025, https://doi.org/10.5194/os-21-93-2025, 2025
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This study investigates the Agulhas Leakage and examines its role in the global ocean circulation. It utilises a high-resolution Earth system model and a preindustrial climate to look at the response of the Agulhas Leakage to the wind field and the Atlantic Meridional Overturning Circulation (AMOC) and its evolution under climate change. The Agulhas Leakage could influence the stability of the AMOC, whose possible collapse would impact the climate in the Northern Hemisphere.
Olivier Narinc, Thierry Penduff, Guillaume Maze, Stéphanie Leroux, and Jean-Marc Molines
Ocean Sci., 20, 1351–1365, https://doi.org/10.5194/os-20-1351-2024, https://doi.org/10.5194/os-20-1351-2024, 2024
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This study examines how the ocean's chaotic variability and atmospheric fluctuations affect yearly changes in North Atlantic Subtropical Mode Water (STMW) properties, using an ensemble of realistic ocean simulations. Results show that while yearly changes in STMW properties are mostly paced by the atmosphere, a notable part of these changes are random in phase. This study also illustrates the value of ensemble simulations over single runs in understanding oceanic fluctuations and their causes.
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.
Qibang Tang, Zhongya Cai, and Zhiqiang Liu
EGUsphere, https://doi.org/10.5194/egusphere-2024-2995, https://doi.org/10.5194/egusphere-2024-2995, 2024
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The South China Sea is the largest semi-enclosed marginal sea in the western Pacific, features with unique layered circulation with rotating currents in its upper, middle, and deep layers. This study uses simulations to explore how stronger currents in the upper layer influence circulation across the entire basin. The vorticity analysis show that the enhanced upper currents increase the strength of middle and deep currents, driven by changes in bottom pressure and cross-slope movements.
René M. van Westen and Henk A. Dijkstra
Ocean Sci., 20, 549–567, https://doi.org/10.5194/os-20-549-2024, https://doi.org/10.5194/os-20-549-2024, 2024
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The Atlantic Meridional Overturning Circulation (AMOC) is an important component in the global climate system. Observations of the present-day AMOC indicate that it may weaken or collapse under global warming, with profound disruptive effects on future climate. However, AMOC weakening is not correctly represented because an important feedback is underestimated due to biases in the Atlantic's freshwater budget. Here we address these biases in several state-of-the-art climate model simulations.
Yavor Kostov, Marie-José Messias, Herlé Mercier, David P. Marshall, and Helen L. Johnson
Ocean Sci., 20, 521–547, https://doi.org/10.5194/os-20-521-2024, https://doi.org/10.5194/os-20-521-2024, 2024
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We examine factors affecting variability in the volume of Labrador Sea Water (LSW), a water mass that is important for the uptake and storage of heat and carbon in the Atlantic Ocean. We find that LSW accumulated in the Labrador Sea exhibits a lagged response to remote conditions: surface wind stress, heat flux, and freshwater flux anomalies, especially along the pathways of the North Atlantic Current branches. We use our results to reconstruct and attribute historical changes in LSW volume.
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.
Cara Nissen, Ralph Timmermann, Mathias van Caspel, and Claudia Wekerle
Ocean Sci., 20, 85–101, https://doi.org/10.5194/os-20-85-2024, https://doi.org/10.5194/os-20-85-2024, 2024
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The southeastern Weddell Sea is important for global ocean circulation due to the cross-shelf-break exchange of Dense Shelf Water and Warm Deep Water, but their exact circulation pathways remain elusive. Using Lagrangian model experiments in an eddy-permitting ocean model, we show how present circulation pathways and transit times of these water masses on the continental shelf are altered by 21st-century climate change, which has implications for local ice-shelf basal melt rates and ecosystems.
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.
Magdalena Fritz, Michael Mayer, Leopold Haimberger, and Susanna Winkelbauer
Ocean Sci., 19, 1203–1223, https://doi.org/10.5194/os-19-1203-2023, https://doi.org/10.5194/os-19-1203-2023, 2023
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The interaction between the Indonesian Throughflow (ITF) and regional climate phenomena indicates the high relevance for monitoring the ITF. Observations remain temporally and spatially limited; hence near-real-time monitoring is only possible with reanalyses. We assess how well ocean reanalyses depict the intensity of the ITF via comparison to observations. The results show that reanalyses agree reasonably well with in situ observations; however, some aspects require higher-resolution products.
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This paper highlights a new implementation of density co-ordinate functionality within an adjoint ocean model, the MITgcm ECCO adjoint. This is illustrated accordingly with a science application investigating the variability of Subantarctic Mode Water. The use of adjoints helps to trace causal links within the ocean, and the density-following feature is of particular interest for the ocean community with many possible further applications.
This paper highlights a new implementation of density co-ordinate functionality within an...
Short summary
Subantarctic mode water in the South Pacific Ocean is important due to its role in the uptake and transport of anthropogenic heat and carbon. The Subantarctic mode water region can be split into two pools using mixed-layer-depth properties. Sensitivity experiments are used to understand the effects of heating and wind on each pool. It is found that the optimal conditions to form large amounts of Subantarctic mode water in the South Pacific are local cooling and upstream warming combined.
Subantarctic mode water in the South Pacific Ocean is important due to its role in the uptake...