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.
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
Related authors
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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
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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.
Related subject area
Approach: Numerical Models | Properties and processes: Overturning circulation | Depth range: All Depths | Geographical range: Deep Seas: North Atlantic | Challenges: Oceans and climate
On the ocean's response to enhanced Greenland runoff in model experiments: relevance of mesoscale dynamics and atmospheric coupling
Regional imprints of changes in the Atlantic Meridional Overturning Circulation in the eddy-rich ocean model VIKING20X
Torge Martin and Arne Biastoch
Ocean Sci., 19, 141–167, https://doi.org/10.5194/os-19-141-2023, https://doi.org/10.5194/os-19-141-2023, 2023
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How is the ocean affected by continued Greenland Ice Sheet mass loss? We show in a systematic set of model experiments that atmospheric feedback needs to be accounted for as the large-scale ocean circulation is more than twice as sensitive to the meltwater otherwise. Coastal winds, boundary currents, and ocean eddies play a key role in redistributing the meltwater. Eddy paramterization helps the coarse simulation to perform better in the Labrador Sea but not in the North Atlantic Current region.
Arne Biastoch, Franziska U. Schwarzkopf, Klaus Getzlaff, Siren Rühs, Torge Martin, Markus Scheinert, Tobias Schulzki, Patricia Handmann, Rebecca Hummels, and Claus W. Böning
Ocean Sci., 17, 1177–1211, https://doi.org/10.5194/os-17-1177-2021, https://doi.org/10.5194/os-17-1177-2021, 2021
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The Atlantic Meridional Overturning Circulation (AMOC) quantifies the impact of the ocean on climate and climate change. Here we show that a high-resolution ocean model is able to realistically simulate ocean currents. While the mean representation of the AMOC depends on choices made for the model and on the atmospheric forcing, the temporal variability is quite robust. Comparing the ocean model with ocean observations, we able to identify that the AMOC has declined over the past two decades.
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Co-editor-in-chief
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...