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Bathymetric Control of Subpolar Gyres and the Overturning Circulation in the Southern Ocean

Wilson, Earle A. and Thompson, Andrew F. and Stewart, Andrew L. and Sun, Shantong (2022) Bathymetric Control of Subpolar Gyres and the Overturning Circulation in the Southern Ocean. Journal of Physical Oceanography, 52 (2). pp. 205-223. ISSN 0022-3670. doi:10.1175/jpo-d-21-0136.1. https://resolver.caltech.edu/CaltechAUTHORS:20220721-7922000

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Abstract

The subpolar gyres of the Southern Ocean form an important dynamical link between the Antarctic Circumpolar Current (ACC) and the coastline of Antarctica. Despite their key involvement in the production and export of bottom water and the poleward transport of oceanic heat, these gyres are rarely acknowledged in conceptual models of the Southern Ocean circulation, which tend to focus on the zonally averaged overturning across the ACC. To isolate the effect of these gyres on the regional circulation, we carried out a set of numerical simulations with idealized representations of the Weddell Sea sector in the Southern Ocean. A key result is that the zonally oriented submarine ridge along the northern periphery of the subpolar gyre plays a fundamental role in setting the stratification and circulation across the entire region. In addition to sharpening and strengthening the horizontal circulation of the gyre, the zonal ridge establishes a strong meridional density front that separates the weakly stratified subpolar gyre from the more stratified circumpolar flow. Critically, the formation of this front shifts the latitudinal outcrop position of certain deep isopycnals such that they experience different buoyancy forcing at the surface. Additionally, the zonal ridge modifies the mechanisms by which heat is transported poleward by the ocean, favoring heat transport by transient eddies while suppressing that by stationary eddies. This study highlights the need to characterize how bathymetry at the subpolar gyre–ACC boundary may constrain the transient response of the regional circulation to changes in surface forcing. Significance Statement: This study explores the impact of seafloor bathymetry on the dynamics of subpolar gyres in the Southern Ocean. The subpolar gyres are major circulation features that connect the Antarctic Circumpolar Current (ACC) and the coastline of Antarctica. This work provides deeper insight for how the submarine ridges that exist along the northern periphery of these gyres shape the vertical distribution of tracers and overturning circulation in these regions. These findings highlight an underappreciated yet fundamentally important topographical constraint on the three-dimensional cycling of heat and carbon in the Southern Ocean—processes that have far-reaching implications for the global climate. Future work should explore how the presence of these ridges affect the time-evolving response of the Southern Ocean to changes in surface conditions.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1175/JPO-D-21-0136.1DOIArticle
https://github.com/MITgcm/Related ItemSource code for MITgcm
https://doi.org/10.5281/zenodo.1409237DOIversion of MITgcm used in this study
https://doi.org/10.5281/zenodo.5057219DOIInput files for the MITgcm runs
https://cchdo.ucsd.edu/cruise/06AQANTX_4Related ItemHydrographic sections of the Weddell Sea collected by the R/V Polarstern on the 1992 ANT/X cruise
https://doi.org/10/dtg3DOISouthern Ocean Bathymetry data
ORCID:
AuthorORCID
Wilson, Earle A.0000-0003-2329-5115
Thompson, Andrew F.0000-0003-0322-4811
Stewart, Andrew L.0000-0001-5861-4070
Sun, Shantong0000-0002-6932-5589
Additional Information:© 2022 American Meteorological Society. (Manuscript received 1 July 2021, in final form 11 November 2021) EAW, AFT, and SS were supported by NSF Awards OCE-1756956 and OPP-2023259. EAW also acknowledges support from Caltech’s Terrestrial Hazard Observations and Reporting (THOR) Center. ALS was supported by NSF Award OPP-2023244. Numerical simulations were carried out at the Resnick High Performance Computing Center at Caltech. The authors graciously thank the MITgcm modelling team for their invaluable efforts. The authors also thank two anonymous reviewers for their insightful and constructive feedback, which substantially improved this manuscript. Data availability statement. Source code for MITgcm is available at https://github.com/MITgcm/. The version of MITgcm used in this study is archived at https://doi.org/10.5281/zenodo.1409237. Input files for the MITgcm runs described in this study are archived at https://doi.org/10.5281/zenodo.5057219. Hydrographic sections of the Weddell Sea collected by the R/V Polarstern on the 1992 ANT/X cruise are available at https://cchdo.ucsd.edu/cruise/06AQANTX_4. Southern Ocean Bathymetry data were compiled and made available by the GEBCO Bathymetric Compilation Group 2020, which may be retrieved at https://doi.org/10/dtg3. Publisher's Note: This article was revised on 28 February 2022 to include better resolution versions of Figs. 7, 11, and 12.
Group:Resnick Sustainability Institute
Funders:
Funding AgencyGrant Number
NSFOCE-1756956
NSFOPP-2023259
Caltech Terrestrial Hazard Observation and Reporting (THOR) CenterUNSPECIFIED
NSFOPP-2023244
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:Southern Ocean; Eddies; Ocean dynamics; Gyres; General circulation models; Idealized models
Issue or Number:2
DOI:10.1175/jpo-d-21-0136.1
Record Number:CaltechAUTHORS:20220721-7922000
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20220721-7922000
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115716
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:26 Jul 2022 17:15
Last Modified:26 Jul 2022 17:15

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