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Regional impacts of the westerly winds on Southern Ocean mode and intermediate water subduction

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Downes, SM ORCID: 0000-0002-5595-7243, Langlais, C, Brook, JP and Spence, P 2017 , 'Regional impacts of the westerly winds on Southern Ocean mode and intermediate water subduction' , Journal of Physical Oceanography, vol. 47, no. 10 , pp. 2521-2530 , doi: 10.1175/JPO-D-17-0106.1.

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Abstract

Subduction processes in the Southern Ocean transfer oxygen, heat, and anthropogenic carbon into the ocean interior. The future response of upper-ocean subduction, in the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) classes, is dependent on the evolution of the combined surface buoyancy forcing and overlying westerly wind stress. Here, the recently observed pattern of a poleward intensification of the westerly winds is divided into its shift and increase components. SAMW and AAIW formation occurs in regional "hot spots" in deep mixed layer zones, primarily in the southeast Indian and Pacific. It is found that the mixed layer depth responds differently to wind stress perturbations across these regional formation zones. An increase only in the westerly winds in the Indian sector steepens isopycnals and increases the local circulation, driving deeper mixed layers and increased subduction. Conversely, in the same region, a poleward shift and poleward intensification of the westerly winds reduces heat loss and increases freshwater input, thus decreasing the mixed layer depth and consequently the associated SAMW and AAIW subduction. In the Pacific sector, all wind stress perturbations lead to increases in heat loss and decreases in freshwater input, resulting in a net increase in SAMW and AAIW subduction. Overall, the poleward shift in the westerly wind stress dominates the SAMWsubduction changes, rather than the increase in wind stress. The net decrease in SAMW subduction across all basins would likely decrease anthropogenic carbon sequestration; however, the net AAIWsubduction changes across the Southern Ocean are overall minor.

Item Type: Article
Authors/Creators:Downes, SM and Langlais, C and Brook, JP and Spence, P
Keywords: mass fluxes/transport, ocean dynamics, upwelling/downwelling, wind stress
Journal or Publication Title: Journal of Physical Oceanography
Publisher: Amer Meteorological Soc
ISSN: 0022-3670
DOI / ID Number: 10.1175/JPO-D-17-0106.1
Copyright Information:

© Copyright 2017 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 the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center (http://www.copyright.com). Questions about permission to use materials for which AMS holds the copyright can also be directed to permissions@ametsoc.org. Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (http://www.ametsoc.org/CopyrightInformation).

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