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Response of the Southern Ocean overturning circulation to extreme Southern Annular Mode conditions
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  • Kial Douglas Stewart,
  • Andrew McC. Hogg,
  • Matthew H. England,
  • Darryn W. Waugh
Kial Douglas Stewart
Australian National University

Corresponding Author:[email protected]

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Andrew McC. Hogg
Australian National University
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Matthew H. England
University of New South Wales
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Darryn W. Waugh
Johns Hopkins University
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The positive trend of the Southern Annular Mode (SAM) will impact the Southern Ocean’s role in Earth’s climate, however the details of the Southern Ocean’s response remain uncertain. We introduce a methodology to examine the influence of SAM on the Southern Ocean, and apply this method to a global ocean–sea-ice model run at three resolutions (1$^{\circ}$, 1/4$^{\circ}$ and 1/10$^{\circ}$). Our methodology drives perturbation simulations with realistic atmospheric forcing of extreme SAM conditions. The thermal response agrees with previous studies; positive SAM perturbations warm the upper ocean north of the windspeed maximum and cool it to the south, with the opposite response for negative SAM. The overturning circulation exhibits a rapid response that increases/decreases for positive/negative SAM perturbations and is insensitive to model resolution. The longer term adjustment of the overturning circulation, however, depends on the representation of eddies, and is faster at higher resolutions.
28 Nov 2020Published in Geophysical Research Letters volume 47 issue 22. 10.1029/2020GL091103