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


Downes, SM and Langlais, C and Brook, JP and Spence, P, Regional impacts of the westerly winds on Southern Ocean mode and intermediate water subduction, Journal of Physical Oceanography, 47, (10) pp. 2521-2530. ISSN 0022-3670 (2017) [Refereed Article]

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DOI: doi:10.1175/JPO-D-17-0106.1


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 Details

Item Type:Refereed Article
Keywords:mass fluxes/transport, ocean dynamics, upwelling/downwelling, wind stress
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical Oceanography
Objective Division:Environment
Objective Group:Other Environment
Objective Field:Antarctic and Sub-Antarctic Oceanography
Author:Downes, SM (Dr Stephanie Downes)
ID Code:123572
Year Published:2017
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2018-01-11
Last Modified:2018-04-23

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