Articles | Volume 19, issue 3
https://doi.org/10.5194/os-19-769-2023
© 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-19-769-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| Highlight paper
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06 Jun 2023
Research article | Highlight paper |
| 06 Jun 2023
| 06 Jun 2023
Seasonal overturning variability in the eastern North Atlantic subpolar gyre: a Lagrangian perspective
Oliver John Tooth
CORRESPONDING AUTHOR
Department of Earth Sciences, University of Oxford, Oxford, United Kingdom
Helen Louise Johnson
Department of Earth Sciences, University of Oxford, Oxford, United Kingdom
Chris Wilson
National Oceanography Centre, Liverpool, United Kingdom
Dafydd Gwyn Evans
National Oceanography Centre, Southampton, United Kingdom
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Nora Fried, Renske Gelderloos, Oliver J. Tooth, Caroline A. Katsman, and M. Femke de Jong
Ocean Sci., 22, 1763–1780, https://doi.org/10.5194/os-22-1763-2026, https://doi.org/10.5194/os-22-1763-2026, 2026
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This study investigates how much warm and saline subtropical-origin water flowing in the Irminger Current (IC) can enter the Irminger Sea convection region by releasing virtual particles in an ocean model. We show that one quarter of IC waters enter the convection region with the potential to increase local stratification. Our results suggest that changes in the water mass properties of the IC have the potential to influence the strength of deep convection in the Irminger Sea.
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This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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This paper presents a new large ensemble of climate model simulations: The CANARI HadGEM3 Large Ensemble (CANARI LE). The CANARI LE has a comparatively high resolution, provides sub-daily output on atmospheric pressure levels, and boundary conditions for driving regional model simulations. The CANARI LE is thus a community resource that lends itself for the study of physical coupled climate processes, weather systems, and impacts in a changing climate.
Nora Fried, Renske Gelderloos, Oliver J. Tooth, Caroline A. Katsman, and M. Femke de Jong
Ocean Sci., 22, 1763–1780, https://doi.org/10.5194/os-22-1763-2026, https://doi.org/10.5194/os-22-1763-2026, 2026
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This study investigates how much warm and saline subtropical-origin water flowing in the Irminger Current (IC) can enter the Irminger Sea convection region by releasing virtual particles in an ocean model. We show that one quarter of IC waters enter the convection region with the potential to increase local stratification. Our results suggest that changes in the water mass properties of the IC have the potential to influence the strength of deep convection in the Irminger Sea.
Jakob Dörr, Carlo Mans, Marius Årthun, Kristofer Döös, Dafydd Gwyn Evans, and Yanchun He
Ocean Sci., 22, 565–585, https://doi.org/10.5194/os-22-565-2026, https://doi.org/10.5194/os-22-565-2026, 2026
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The Arctic Ocean plays a key role in the global ocean circulation by producing dense waters that feed the lower limb of the Atlantic meridional overturning circulation (AMOC). We use a high-resolution ocean simulation to investigate the pathways and mechanisms through which these dense waters are formed in the Arctic. Our results show that surface cooling in the Barents Sea dominates the dense water production, but that internal mixing plays a role at high densities.
Oliver J. Tooth, Helen L. Johnson, and Chris Wilson
Ocean Sci., 21, 2101–2123, https://doi.org/10.5194/os-21-2101-2025, https://doi.org/10.5194/os-21-2101-2025, 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.
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.
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.
Marilena Oltmanns, N. Penny Holliday, James Screen, Ben I. Moat, Simon A. Josey, D. Gwyn Evans, and Sheldon Bacon
Weather Clim. Dynam., 5, 109–132, https://doi.org/10.5194/wcd-5-109-2024, https://doi.org/10.5194/wcd-5-109-2024, 2024
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The melting of land ice and sea ice leads to freshwater input into the ocean. Based on observations, we show that stronger freshwater anomalies in the subpolar North Atlantic in winter are followed by warmer and drier weather over Europe in summer. The identified link indicates an enhanced predictability of European summer weather at least a winter in advance. It further suggests that warmer and drier summers over Europe can become more frequent under increased freshwater fluxes in the future.
Dafydd Gwyn Evans, N. Penny Holliday, Sheldon Bacon, and Isabela Le Bras
Ocean Sci., 19, 745–768, https://doi.org/10.5194/os-19-745-2023, https://doi.org/10.5194/os-19-745-2023, 2023
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This study investigates the processes that form dense water in the high latitudes of the North Atlantic to determine how they affect the overturning circulation in the Atlantic. We show for the first time that turbulent mixing is an important driver in the formation of dense water, along with the loss of heat from the ocean to the atmosphere. We point out that the simulation of turbulent mixing in ocean–climate models must improve to better predict the ocean's response to climate change.
Noam S. Vogt-Vincent, Satoshi Mitarai, and Helen L. Johnson
EGUsphere, https://doi.org/10.5194/egusphere-2023-778, https://doi.org/10.5194/egusphere-2023-778, 2023
Preprint archived
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Coral larvae can drift through ocean currents between coral reefs, establishing connectivity, which plays an important role in coral reef resilience. However, larval transport is chaotic. We simulate coral spawning events across the tropical southwest Indian Ocean for almost three decades, and find that larval transport can vary massively from day-to-day. This variability is largely random, and this introduces a lot of uncertainty in connectivity predictions.
Noam S. Vogt-Vincent and Helen L. Johnson
Geosci. Model Dev., 16, 1163–1178, https://doi.org/10.5194/gmd-16-1163-2023, https://doi.org/10.5194/gmd-16-1163-2023, 2023
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Ocean currents transport things over large distances across the ocean surface. Predicting this transport is key for tackling many environmental problems, such as marine plastic pollution and coral reef resilience. However, doing this requires a good understanding ocean currents, which is currently lacking. Here, we present and validate state-of-the-art simulations for surface currents in the southwestern Indian Ocean, which will support future marine dispersal studies across this region.
Marilena Oltmanns, N. Penny Holliday, James Screen, D. Gwyn Evans, Simon A. Josey, Sheldon Bacon, and Ben I. Moat
Weather Clim. Dynam. Discuss., https://doi.org/10.5194/wcd-2021-79, https://doi.org/10.5194/wcd-2021-79, 2021
Revised manuscript not accepted
Short summary
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The Arctic is currently warming twice as fast as the global average. This results in enhanced melting and thus freshwater releases into the North Atlantic. Using a combination of observations and models, we show that atmosphere-ocean feedbacks initiated by freshwater releases into the North Atlantic lead to warmer and drier weather over Europe in subsequent summers. The existence of this dynamical link suggests that European summer weather can potentially be predicted months to years in advance.
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Editorial statement
The authors investigate the main contributors to the seasonal variability in the strength of the Atlantic Meridional Overturning Circulation in the eastern North Atlantic subpolar gyre using a Lagrangian approach. They analyze trajectories from a hindcast model that permits eddies. The insights gained from the study are important and of interest to the broader scientific community, as well as potentially to the public. Specifically, the study finds that the strong seasonality in the strength of the AMOC is explained by the rapid circulation of upper limb waters. Parcels with sufficiently long circulation times within the gyre experience a combination of surface buoyancy loss and interior mixing, which filters out their seasonal thermohaline variability.
The authors investigate the main contributors to the seasonal variability in the strength of the...
Short summary
This study uses the trajectories of water parcels traced within an ocean model simulation to identify the pathways responsible for the seasonal cycle of dense water formation (overturning) in the eastern subpolar North Atlantic. We show that overturning seasonality is due to the fastest water parcels circulating within the eastern basins in less than 8.5 months. Slower pathways set the average strength of overturning in this region since water parcels cannot escape intense wintertime cooling.
This study uses the trajectories of water parcels traced within an ocean model simulation to...
