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Stirring of Sea‐Ice Meltwater Enhances Submesoscale Fronts in the Southern Ocean

Giddy, I. and Swart, S. and du Plessis, M. and Thompson, A. F. and Nicholson, S. A. (2021) Stirring of Sea‐Ice Meltwater Enhances Submesoscale Fronts in the Southern Ocean. Journal of Geophysical Research. Oceans, 126 (4). Art. No. e2020JC016814. ISSN 2169-9275. doi:10.1029/2020JC016814.

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In the sea‐ice‐impacted Southern Ocean, the spring sea‐ice melt and its impact on physical processes set the rate of surface water mass modification. These modified waters will eventually subduct near the polar front and enter the global overturning circulation. Submesoscale processes modulate the stratification of the mixed layer (ML) and ML properties. Sparse observations in polar regions mean that the role of submesoscale motions in the exchange of properties across the base of the ML is not well understood. The goal of this study is to determine the interplay between sea‐ice melt, surface boundary layer forcing, and submesoscale flows in setting properties of the surface ML in the Antarctic marginal ice zone. High‐resolution observations suggest that fine‐scale lateral fronts arise from either/both mesoscale and submesoscale stirring of sea‐ice meltwater anomalies. The strong salinity‐driven stratification at the base of the ML confines these fronts to the upper ocean, limiting submesoscale vertical fluxes across the ML base. This strong stratification prevents the local subduction of modified waters by submesoscale flows, suggesting that the subduction site that links to the global overturning circulation does not correspond with the location of sea‐ice melt. However, surface‐enhanced fronts increase the potential for Ekman‐driven cross‐frontal flow to modulate the stability of the ML and ML properties. The parameterization of submesoscale processes in coupled‐climate models, particularly those contributing to the Ekman buoyancy flux, may improve the representation of ML heat and freshwater transport in the ice‐impacted Southern Ocean during summer.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
ftp://ssh.roammiz.comRelated ItemData - giddy 2020 ItemCopernicus Climate Change Service Information
Giddy, I.0000-0002-8926-3311
Swart, S.0000-0002-2251-8826
du Plessis, M.0000-0003-2759-2467
Thompson, A. F.0000-0003-0322-4811
Nicholson, S. A.0000-0002-1226-1828
Additional Information:© 2021. The Authors. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. Issue Online: 26 March 2021; Version of Record online: 26 March 2021; Accepted manuscript online: 10 March 2021; Manuscript accepted: 02 March 2021; Manuscript revised: 27 February 2021; Manuscript received: 22 September 2020. This work was supported by the following grants of S. Swart: Wallenberg Academy Fellowship (WAF 2015.0186), Swedish Research Council (VR 2019‐04400), STINT‐NRF Mobility Grant (STNT180910357293). S. A. Nicholson and S. Swart: NRF‐SANAP (SNA170522231782, SANAP200324510487) and S. A. Nicholson, the Young Researchers Establishment Fund (YREF 2019 0000007361). S. Swart and M. du Plessis have received funding from the European Union's Horizon 2020 research and innovation program under Grant agreement no. 821001 (SO‐CHIC). A. F. Thompson is supported by ONR (N00014‐19‐1‐2421), NSF (1756956, 1829969), and a Linde Center Discovery Fund grant. The authors thank Sea Technology Services (STS), SANAP, the captain, and crew of the S.A. Agulhas II for their field‐work/technical assistance. Zach Erickson, Mar Flexas, and Giuliana Viglione (Caltech) contributed to glider piloting throughout the deployment. S. Swart is grateful to Geoff Shilling and Craig Lee (APL, University of Washington) for hosting gliders on IOP. B. Queste is thanked for insightful discussions on glider processing and thermal lag corrections, which was made possible through the UCT‐UEA Newton Fund. Special thanks is extended to Isabelle Ansorge for the generous support of I. Giddy in her doctoral studies and training, from which this paper is derived (SANAP 110733 SAMOC‐SA). I. Giddy is further supported by the Oppenheimer Memorial Trust. The authors are grateful to the insightful and constructive reviews of Dr. Balwada and one anonymous reviewer, which greatly improved this manuscript. Data Availability Statement: ERA5 data are generated using Copernicus Climate Change Service Information, available online ( All the data used for this analysis can be accessed online ( via anonymous login and navigate to giddy_2020. The code used to produce this analysis is available at
Funding AgencyGrant Number
Knut and Alice Wallenberg FoundationWAF 2015.0186
Swedish Research CouncilVR 2019‐04400
National Research Foundation (South Africa)STNT180910357293
National Research Foundation (South Africa)SNA170522231782
National Research Foundation (South Africa)SANAP200324510487
Council for Scientific and Industrial Research (South Africa)2019 0000007361
European Research Council (ERC)821001
Office of Naval Research (ONR)N00014-19-1-2421
Ronald And Maxine Linde Center for Global Environmental ScienceUNSPECIFIED
South African National Antarctic Programme (SANAP)SANAP 110733 SAMOC-SA
Oppenheimer Memorial TrustUNSPECIFIED
Subject Keywords:marginal ice zone; Seaglider observations; sea‐ice meltwater; submesoscale eddies; upper ocean; wind‐front interactions
Issue or Number:4
Record Number:CaltechAUTHORS:20201023-141150937
Persistent URL:
Official Citation:Giddy, I., Swart, S., du Plessis, M., Thompson, A. F., & Nicholson, S.‐A. (2021). Stirring of sea‐ice meltwater enhances submesoscale fronts in the Southern Ocean. Journal of Geophysical Research: Oceans, 126, e2020JC016814.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106266
Deposited By: Tony Diaz
Deposited On:23 Oct 2020 21:44
Last Modified:09 Jul 2021 20:47

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