Agulhas Leakage Predominantly Responds to the Southern Hemisphere Westerlies.

Durgadoo, Jonathan V. , Loveday, Benjamin R., Reason, Chris J. C., Penven, Pierrick and Biastoch, Arne (2013) Agulhas Leakage Predominantly Responds to the Southern Hemisphere Westerlies. Open Access Journal of Physical Oceanography, 43 (10). pp. 2113-2131. DOI 10.1175/JPO-D-13-047.1.

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Abstract

The Agulhas Current plays a crucial role in the thermohaline circulation through its leakage into the South Atlantic. Under both past and present climates, the trade winds and westerlies could have the ability to modulate the amount of Indian-Atlantic inflow. Compelling arguments have been put forward suggesting that trade winds alone have little impact on the magnitude of Agulhas leakage. Here, employing three ocean models for robust analysis – a global coarse resolution, a regional eddy-permitting and a nested high-resolution eddy-resolving configuration – and systematically altering the position and intensity of the westerly wind belt in a series of sensitivity experiments, it is shown that the westerlies, in particular their intensity, control the leakage. Leakage responds proportionally to the westerlies intensity up to a certain point. Beyond this, through the adjustment of the large-scale circulation, energetic interactions occur between the Agulhas Return Current and the Antarctic Circumpolar Current that result in a state where leakage no longer increases. This adjustment takes place within 1 to 2 decades. Contrary to previous assertions, our results further show that an equatorward (poleward) shift in westerlies increases (decreases) leakage. This occurs due to the redistribution of momentum input by the winds. It is concluded that the reported present-day leakage increase could therefore reflect an unadjusted oceanic response mainly to the strengthening westerlies over the last few decades.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/238512
Additional Information: WOS:000325534400005
Keywords: Boundary currents; Meridional overturning circulation; Wind stress; Mesoscale models; Numerical analysis; modeling
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/JPO-D-13-047.1
ISSN: 0022-3670
Projects: GATEWAYS, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 01 Oct 2013 09:29
Last Modified: 12 Apr 2018 12:37
URI: http://oceanrep.geomar.de/id/eprint/22060

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