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Eddy heat flux in the Southern Ocean: response to variable wind forcing

Hogg, Andrew McC.; Meredith, Michael P.; Blundell, Jeffrey R; Wilson, Christopher. 2008 Eddy heat flux in the Southern Ocean: response to variable wind forcing. Journal of Climate, 21 (4). 608-620. 10.1175/2007JCLI1925.1

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Abstract/Summary

We assess the role of time-dependent eddy variability in the Antarctic Circumpolar Current (ACC) in influencing warming of the Southern Ocean. For this, we use an eddy-resolving quasigeostrophic model of the wind-driven circulation, and quantify the response of circumpolar transport, eddy kinetic energy and eddy heat transport to changes in winds. On interannual timescales, the model exhibits the behaviour of an "eddy saturated" ocean state, where increases in wind stress do not signicantly change the circumpolar transport, but instead enhance the eddy eld. This is in accord with previous dynamical arguments, and a recent observational study. The instantaneous response to increased wind stress is to cool temperatures through increased northward Ekman transport of cool water. But, in the longer term, the enhanced eddy state is more ecient at transporting heat, leading to a warming of the ocean. The total eddy heat flux response is greater than the Ekman transport heat flux in this model by a factor of 2, indicating that coarse (non-eddy resolving) models may fail to adequately capture the key processes. We also test the model response to long-term changes in wind forcing, including steadily-increasing circumpolar wind strength over a 30 year period. The model shows a response in eddy heat flux, and a change in ocean temperature not dissimilar from observed Southern Ocean warming. These findings suggest that eddy heat flux, energised by increasing wind stress, may be a significant contributor to the observed warming of the Southern Ocean.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1175/2007JCLI1925.1
Programmes: POL Programmes > Shallow coastal seas - function and impacts of change
BAS Programmes > Global Science in the Antarctic Context (2005-2009) > DISCOVERY 2010 - Integrating Southern Ocean Ecosystems into the Earth System
ISSN: 0894-8755
Additional Information. Not used in RCUK Gateway to Research.: Copyright 2007 American Meteorological Society (AMS). Permission to use figures, tables and BRIEF excerpts from this work in scientific and educational works is hereby granted provided that is determined to be "fair use" under section 107 of the US Copyright Act or that it satisfies the conditions specified in 108 of the US Copyright Act (17 USC Section 108 as revised by P.L. 94-553) does not require the AMS's permission. Or in a searchable database, or other uses if this material, except as exempted in the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS website located at http://www.ametsoc.org/ or from the AMS at 617-227-2425 or copyright@ametsoc.org
Additional Keywords: Eddy variability, Antarctic Circumpolar Current, Southern Ocean Warming, Southern Annular Mode
NORA Subject Terms: Marine Sciences
Meteorology and Climatology
Date made live: 07 Mar 2008 13:19
URI: http://nora.nerc.ac.uk/id/eprint/1683

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