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142582 - Southern Ocean heat storage, reemergence, and winter sea ice decline induced.pdf (4.73 MB)

Southern Ocean heat storage, reemergence, and winter sea ice decline induced by summertime winds

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journal contribution
posted on 2023-05-20, 20:32 authored by Edward DoddridgeEdward Doddridge, Marshall, J, Song, H, Campin, J-M, Kelley, M
The observational record shows a substantial 40-yr upward trend in summertime westerly winds over the Southern Ocean, as characterized by the southern annular mode (SAM) index. Enhanced summertime westerly winds have been linked to cold summertime sea surface temperature (SST) anomalies. Previous studies have suggested that Ekman transport or upwelling is responsible for this seasonal cooling. Here, another process is presented in which enhanced vertical mixing, driven by summertime wind anomalies, moves heat downward, cooling the sea surface and simultaneously warming the subsurface waters. The anomalously cold SSTs draw heat from the atmosphere into the ocean, leading to increased depth-integrated ocean heat content. The subsurface heat is returned to the surface mixed layer during the autumn and winter as the mixed layer deepens, leading to anomalously warm SSTs and potentially reducing sea ice cover. Observational analyses and numerical experiments support our proposed mechanism, showing that enhanced vertical mixing produces subsurface warming and cools the surface mixed layer. Nevertheless, the dominant driver of surface cooling remains uncertain; the relative importance of advective and mixing contributions to the surface cooling is model dependent. Modeling results suggest that sea ice volume is more sensitive to summertime winds than sea ice extent, implying that enhanced summertime westerly winds may lead to thinner sea ice in the following winter, if not lesser ice extent. Thus, strong summertime winds could precondition the sea ice cover for a rapid retreat in the following melt season.

History

Publication title

Journal of Climate

Volume

34

Issue

4

Pagination

1403-1415

ISSN

0894-8755

Department/School

Institute for Marine and Antarctic Studies

Publisher

Amer Meteorological Soc

Place of publication

45 Beacon St, Boston, USA, Ma, 02108-3693

Rights statement

Copyright 2021 American Meteorological Society

Repository Status

  • Restricted

Socio-economic Objectives

Antarctic and Southern Ocean ice dynamics; Antarctic and Southern Ocean oceanic processes

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