Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing
We examine the sensitivity of the Weddell and Ross seas to vertical mixing and surface freshwater forcing using an ocean–sea ice model. The high latitude Southern Ocean is very weakly stratified, with a winter salinity difference across the pycnocline of only ?0.2 PSU. We find that insufficient vert...
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ftsouthampton:oai:eprints.soton.ac.uk:383331 2023-07-30T03:59:16+02:00 Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing Kjellsson, Joakim Holland, Paul R. Marshall, Gareth J. Mathiot, Pierre Aksenov, Yevgeny Coward, Andrew C. Bacon, Sheldon Megann, Alex P. Ridley, Jeff 2015-10 text https://eprints.soton.ac.uk/383331/ https://eprints.soton.ac.uk/383331/1/1-s2.0-S1463500315001560-main.pdf en English eng https://eprints.soton.ac.uk/383331/1/1-s2.0-S1463500315001560-main.pdf Kjellsson, Joakim, Holland, Paul R., Marshall, Gareth J., Mathiot, Pierre, Aksenov, Yevgeny, Coward, Andrew C., Bacon, Sheldon, Megann, Alex P. and Ridley, Jeff (2015) Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing. Ocean Modelling, 94, 141-152. (doi:10.1016/j.ocemod.2015.08.003 <http://dx.doi.org/10.1016/j.ocemod.2015.08.003>). cc_by_4 Article PeerReviewed 2015 ftsouthampton https://doi.org/10.1016/j.ocemod.2015.08.003 2023-07-09T22:02:30Z We examine the sensitivity of the Weddell and Ross seas to vertical mixing and surface freshwater forcing using an ocean–sea ice model. The high latitude Southern Ocean is very weakly stratified, with a winter salinity difference across the pycnocline of only ?0.2 PSU. We find that insufficient vertical mixing, freshwater supply from the Antarctic Ice Sheet, or initial sea ice causes a high salinity bias in the mixed layer which erodes the stratification and causes excessive deep convection. This leads to vertical homogenisation of the Weddell and Ross seas, opening of polynyas in the sea ice and unrealistic spin-up of the subpolar gyres and Antarctic Circumpolar Current. The model freshwater budget shows that a ?30% error in any component can destratify the ocean in about a decade. We find that freshwater forcing in the model should be sufficient along the Antarctic coastline to balance a salinity bias caused by dense coastal water that is unable to sink to the deep ocean. We also show that a low initial sea ice area introduces a salinity bias in the marginal ice zone. We demonstrate that vertical mixing, freshwater forcing and initial sea ice conditions need to be constrained simultaneously to reproduce the Southern Ocean hydrography, circulation and sea ice in a model. As an example, insufficient vertical mixing will cause excessive convection in the Weddell and Ross seas even in the presence of large surface freshwater forcing and initial sea ice cover. Article in Journal/Newspaper Antarc* Antarctic Antarctica Ice Sheet Sea ice Southern Ocean University of Southampton: e-Prints Soton Antarctic Southern Ocean The Antarctic Weddell Ocean Modelling 94 141 152 |
institution |
Open Polar |
collection |
University of Southampton: e-Prints Soton |
op_collection_id |
ftsouthampton |
language |
English |
description |
We examine the sensitivity of the Weddell and Ross seas to vertical mixing and surface freshwater forcing using an ocean–sea ice model. The high latitude Southern Ocean is very weakly stratified, with a winter salinity difference across the pycnocline of only ?0.2 PSU. We find that insufficient vertical mixing, freshwater supply from the Antarctic Ice Sheet, or initial sea ice causes a high salinity bias in the mixed layer which erodes the stratification and causes excessive deep convection. This leads to vertical homogenisation of the Weddell and Ross seas, opening of polynyas in the sea ice and unrealistic spin-up of the subpolar gyres and Antarctic Circumpolar Current. The model freshwater budget shows that a ?30% error in any component can destratify the ocean in about a decade. We find that freshwater forcing in the model should be sufficient along the Antarctic coastline to balance a salinity bias caused by dense coastal water that is unable to sink to the deep ocean. We also show that a low initial sea ice area introduces a salinity bias in the marginal ice zone. We demonstrate that vertical mixing, freshwater forcing and initial sea ice conditions need to be constrained simultaneously to reproduce the Southern Ocean hydrography, circulation and sea ice in a model. As an example, insufficient vertical mixing will cause excessive convection in the Weddell and Ross seas even in the presence of large surface freshwater forcing and initial sea ice cover. |
format |
Article in Journal/Newspaper |
author |
Kjellsson, Joakim Holland, Paul R. Marshall, Gareth J. Mathiot, Pierre Aksenov, Yevgeny Coward, Andrew C. Bacon, Sheldon Megann, Alex P. Ridley, Jeff |
spellingShingle |
Kjellsson, Joakim Holland, Paul R. Marshall, Gareth J. Mathiot, Pierre Aksenov, Yevgeny Coward, Andrew C. Bacon, Sheldon Megann, Alex P. Ridley, Jeff Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing |
author_facet |
Kjellsson, Joakim Holland, Paul R. Marshall, Gareth J. Mathiot, Pierre Aksenov, Yevgeny Coward, Andrew C. Bacon, Sheldon Megann, Alex P. Ridley, Jeff |
author_sort |
Kjellsson, Joakim |
title |
Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing |
title_short |
Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing |
title_full |
Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing |
title_fullStr |
Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing |
title_full_unstemmed |
Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing |
title_sort |
model sensitivity of the weddell and ross seas, antarctica, to vertical mixing and freshwater forcing |
publishDate |
2015 |
url |
https://eprints.soton.ac.uk/383331/ https://eprints.soton.ac.uk/383331/1/1-s2.0-S1463500315001560-main.pdf |
geographic |
Antarctic Southern Ocean The Antarctic Weddell |
geographic_facet |
Antarctic Southern Ocean The Antarctic Weddell |
genre |
Antarc* Antarctic Antarctica Ice Sheet Sea ice Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctica Ice Sheet Sea ice Southern Ocean |
op_relation |
https://eprints.soton.ac.uk/383331/1/1-s2.0-S1463500315001560-main.pdf Kjellsson, Joakim, Holland, Paul R., Marshall, Gareth J., Mathiot, Pierre, Aksenov, Yevgeny, Coward, Andrew C., Bacon, Sheldon, Megann, Alex P. and Ridley, Jeff (2015) Model sensitivity of the Weddell and Ross seas, Antarctica, to vertical mixing and freshwater forcing. Ocean Modelling, 94, 141-152. (doi:10.1016/j.ocemod.2015.08.003 <http://dx.doi.org/10.1016/j.ocemod.2015.08.003>). |
op_rights |
cc_by_4 |
op_doi |
https://doi.org/10.1016/j.ocemod.2015.08.003 |
container_title |
Ocean Modelling |
container_volume |
94 |
container_start_page |
141 |
op_container_end_page |
152 |
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1772810009700204544 |