Generation of the internal pycnocline in the subpolar southern ocean by wintertime sea ice melting
Generation of the internal pycnocline in the subpolar southern ocean by wintertime sea ice melting
The ocean's internal pycnocline is a layer of elevated stratification that separates the well-ventilated upper ocean from the more slowly renewed deep ocean. Despite its pivotal role in organizing ocean circulation, the processes governing the formation of the internal pycnocline remain little understood. Classical theories on pycnocline formation have been couched in terms of temperature and it is not clear how the theory applies in the high-latitude Southern Ocean, where stratification is dominated by salinity. Here we assess the mechanisms generating the internal pycnocline at southern high latitudes through the analysis of a high-resolution, realistic, global sea ice–ocean model. We show evidence suggesting that the internal pycnocline's formation is associated with sea ice-ocean interactions in two distinct ice-covered regions, fringing the Antarctic continental slope and the winter sea-ice edge. In both areas, winter-persistent sea-ice melt creates strong, salinity-based stratification at the base of the winter mixed layer. The resulting sheets of high stratification subsequently descend into the ocean interior at fronts of the Antarctic Circumpolar Current, and connect seamlessly to the internal pycnocline in areas further north in which pycnocline stratification is determined by temperature. Our findings thus suggest an important role of localized sea ice-ocean interactions in configuring the vertical structure of the Southern Ocean.
Southern Ocean, ice-ocean interaction, pycnocline, sea ice
Klocker, A.
eb2cada3-1587-4262-983b-74b41734f5b8
Naveira Garabato, A. C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Roquet, F.
92998487-4f5f-42e8-8873-453e268d065e
De Lavergne, C.
5cd9bf80-0659-4ed5-9cc1-4d611b422759
Rintoul, S. R.
ff078a21-d6cd-45bf-8c8f-f81f2e8ae410
21 March 2023
Klocker, A.
eb2cada3-1587-4262-983b-74b41734f5b8
Naveira Garabato, A. C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Roquet, F.
92998487-4f5f-42e8-8873-453e268d065e
De Lavergne, C.
5cd9bf80-0659-4ed5-9cc1-4d611b422759
Rintoul, S. R.
ff078a21-d6cd-45bf-8c8f-f81f2e8ae410
Klocker, A., Naveira Garabato, A. C., Roquet, F., De Lavergne, C. and Rintoul, S. R.
(2023)
Generation of the internal pycnocline in the subpolar southern ocean by wintertime sea ice melting.
Journal of Geophysical Research: Oceans, 128 (3), [e2022JC019113].
(doi:10.1029/2022JC019113).
Abstract
The ocean's internal pycnocline is a layer of elevated stratification that separates the well-ventilated upper ocean from the more slowly renewed deep ocean. Despite its pivotal role in organizing ocean circulation, the processes governing the formation of the internal pycnocline remain little understood. Classical theories on pycnocline formation have been couched in terms of temperature and it is not clear how the theory applies in the high-latitude Southern Ocean, where stratification is dominated by salinity. Here we assess the mechanisms generating the internal pycnocline at southern high latitudes through the analysis of a high-resolution, realistic, global sea ice–ocean model. We show evidence suggesting that the internal pycnocline's formation is associated with sea ice-ocean interactions in two distinct ice-covered regions, fringing the Antarctic continental slope and the winter sea-ice edge. In both areas, winter-persistent sea-ice melt creates strong, salinity-based stratification at the base of the winter mixed layer. The resulting sheets of high stratification subsequently descend into the ocean interior at fronts of the Antarctic Circumpolar Current, and connect seamlessly to the internal pycnocline in areas further north in which pycnocline stratification is determined by temperature. Our findings thus suggest an important role of localized sea ice-ocean interactions in configuring the vertical structure of the Southern Ocean.
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pycnocline_grl-2
- Accepted Manuscript
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JGR Oceans - 2023 - Klocker - Generation of the Internal Pycnocline in the Subpolar Southern Ocean by Wintertime Sea Ice
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Accepted/In Press date: 9 March 2023
Published date: 21 March 2023
Additional Information:
Funding Information:
The authors thank the Consortium for Ocean‐Sea Ice Modeling in Australia (COSIMA; www.cosima.org.au ) for making the ACCESS‐OM2 suite of models available at github.com/COSIMA/access-om2 . Model runs were undertaken with the assistance of resources from the National Computational Infrastructure (NCI), which is supported by the Australian Government. This research was supported under Australian Research Council's Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001). This project received grant funding from the Australian Government as part of the Antarctic Science Collaboration Initiative program. The work was supported in part by the Centre for Southern Hemisphere Oceans Research, a partnership between CSIRO, the Qingdao National Laboratory for Marine Science and Technology, the University of New South Wales and the University of Tasmania and by the Australian Antarctic Program Partnership.
Publisher Copyright:
© 2023. American Geophysical Union. All Rights Reserved.
Keywords:
Southern Ocean, ice-ocean interaction, pycnocline, sea ice
Identifiers
Local EPrints ID: 477624
URI: http://eprints.soton.ac.uk/id/eprint/477624
ISSN: 2169-9275
PURE UUID: afe8355c-44eb-42d3-9ff4-44046c8e2966
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Date deposited: 09 Jun 2023 16:54
Last modified: 17 Mar 2024 03:04
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Contributors
Author:
A. Klocker
Author:
F. Roquet
Author:
C. De Lavergne
Author:
S. R. Rintoul
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