Surface water mass transformation in the Southern Ocean: The role of eddies revisited
The water mass transformation (WMT) framework describes how water of one class, such as a discrete interval of density, is converted into another class via air-sea fluxes or interior mixing processes. This paper investigates how this process is modified at the surface when mesoscale ocean eddies are...
Published in: | Journal of Physical Oceanography |
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Language: | English |
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Online Access: | https://doi.org/10.1175/JPO-D-21-0087.1 |
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ftncar:oai:drupal-site.org:articles_25824 2024-04-14T08:19:59+00:00 Surface water mass transformation in the Southern Ocean: The role of eddies revisited Small, R. Justin (author) Bryan, Frank O. (author) Bishop, Stuart P. (author) 2022-06-01 https://doi.org/10.1175/JPO-D-21-0087.1 en eng Journal of Physical Oceanography--0022-3670--1520-0485 Argo float data and metadata from Global Data Assembly Centre (Argo GDAC)--10.17882/42182 articles:25824 doi:10.1175/JPO-D-21-0087.1 ark:/85065/d70005wv Copyright 2022 American Meteorological Society (AMS). article Text 2022 ftncar https://doi.org/10.1175/JPO-D-21-0087.1 2024-03-21T18:00:26Z The water mass transformation (WMT) framework describes how water of one class, such as a discrete interval of density, is converted into another class via air-sea fluxes or interior mixing processes. This paper investigates how this process is modified at the surface when mesoscale ocean eddies are present, using a state-of-the-art high-resolution climate model with reasonable fidelity in the Southern Ocean. The method employed is to coarse-grain the high-resolution model fields to remove eddy signatures, and compare the results with those from the full model fields. This method shows that eddies reduced the WMT by 2-4 Sv (10%-20%; 1 Sv 10(6) m(3) s(-1)) over a wide range of densities, from typical values of 20 Sv in the smoothed case. The corresponding water mass formation was reduced by 40% at one particular density increment, namely, between 1026.4 and 1026.5 kg m(-3), which corresponds to the lighter end of the range of Indian Ocean Mode Water in the model. The effect of eddies on surface WMT is decomposed into three terms: direct modulation of the density outcrops, then indirectly, by modifying the air-sea density flux, and the combined effect of the two, akin to a covariance. It is found that the first and third terms dominate, i.e., smoothing the outcrops alone has a significant effect, as does the combination of smoothing both outcrops and density flux distributions, but smoothing density flux fields alone has little effect. Results from the coarse-graining method are compared to an alternative approach of temporally averaging the data. Implications for climate model resolution are also discussed. 1852977 80NSSC18K0769 80NSSC20K0890 DE-SC0006743 Article in Journal/Newspaper Southern Ocean OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) Southern Ocean Indian Journal of Physical Oceanography 52 5 789 804 |
institution |
Open Polar |
collection |
OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) |
op_collection_id |
ftncar |
language |
English |
description |
The water mass transformation (WMT) framework describes how water of one class, such as a discrete interval of density, is converted into another class via air-sea fluxes or interior mixing processes. This paper investigates how this process is modified at the surface when mesoscale ocean eddies are present, using a state-of-the-art high-resolution climate model with reasonable fidelity in the Southern Ocean. The method employed is to coarse-grain the high-resolution model fields to remove eddy signatures, and compare the results with those from the full model fields. This method shows that eddies reduced the WMT by 2-4 Sv (10%-20%; 1 Sv 10(6) m(3) s(-1)) over a wide range of densities, from typical values of 20 Sv in the smoothed case. The corresponding water mass formation was reduced by 40% at one particular density increment, namely, between 1026.4 and 1026.5 kg m(-3), which corresponds to the lighter end of the range of Indian Ocean Mode Water in the model. The effect of eddies on surface WMT is decomposed into three terms: direct modulation of the density outcrops, then indirectly, by modifying the air-sea density flux, and the combined effect of the two, akin to a covariance. It is found that the first and third terms dominate, i.e., smoothing the outcrops alone has a significant effect, as does the combination of smoothing both outcrops and density flux distributions, but smoothing density flux fields alone has little effect. Results from the coarse-graining method are compared to an alternative approach of temporally averaging the data. Implications for climate model resolution are also discussed. 1852977 80NSSC18K0769 80NSSC20K0890 DE-SC0006743 |
author2 |
Small, R. Justin (author) Bryan, Frank O. (author) Bishop, Stuart P. (author) |
format |
Article in Journal/Newspaper |
title |
Surface water mass transformation in the Southern Ocean: The role of eddies revisited |
spellingShingle |
Surface water mass transformation in the Southern Ocean: The role of eddies revisited |
title_short |
Surface water mass transformation in the Southern Ocean: The role of eddies revisited |
title_full |
Surface water mass transformation in the Southern Ocean: The role of eddies revisited |
title_fullStr |
Surface water mass transformation in the Southern Ocean: The role of eddies revisited |
title_full_unstemmed |
Surface water mass transformation in the Southern Ocean: The role of eddies revisited |
title_sort |
surface water mass transformation in the southern ocean: the role of eddies revisited |
publishDate |
2022 |
url |
https://doi.org/10.1175/JPO-D-21-0087.1 |
geographic |
Southern Ocean Indian |
geographic_facet |
Southern Ocean Indian |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
Journal of Physical Oceanography--0022-3670--1520-0485 Argo float data and metadata from Global Data Assembly Centre (Argo GDAC)--10.17882/42182 articles:25824 doi:10.1175/JPO-D-21-0087.1 ark:/85065/d70005wv |
op_rights |
Copyright 2022 American Meteorological Society (AMS). |
op_doi |
https://doi.org/10.1175/JPO-D-21-0087.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
52 |
container_issue |
5 |
container_start_page |
789 |
op_container_end_page |
804 |
_version_ |
1796298156633227264 |