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Acceleration and overturning of the Antarctic Slope Current by winds, eddies, and tides

Citation

Stewart, AL and Klocker, A and Menemenlis, D, Acceleration and overturning of the Antarctic Slope Current by winds, eddies, and tides, Journal of Physical Oceanography, 49 pp. 2043-2074. ISSN 0022-3670 (2019) [Refereed Article]


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DOI: doi:10.1175/JPO-D-18-0221.1

Abstract

All exchanges between the open ocean and the Antarctic continental shelf must cross the Antarctic Slope Current (ASC). Previous studies indicate that these exchanges are strongly influenced by mesoscale and tidal variability, yet the mechanisms responsible for setting the ASC’s transport and structure have received relatively little attention. In this study the roles of winds, eddies, and tides in accelerating the ASC are investigated using a global ocean–sea ice simulation with very high resolution (1/48° grid spacing). It is found that the circulation along the continental slope is accelerated both by surface stresses, ultimately sourced from the easterly winds, and by mesoscale eddy vorticity fluxes. At the continental shelf break, the ASC exhibits a narrow (~30–50 km), swift (>0.2 m s−1) jet, consistent with in situ observations. In this jet the surface stress is substantially reduced, and may even vanish or be directed eastward, because the ocean surface speed matches or exceeds that of the sea ice. The shelfbreak jet is shown to be accelerated by tidal momentum advection, consistent with the phenomenon of tidal rectification. Consequently, the shoreward Ekman transport vanishes and thus the mean overturning circulation that steepens the Antarctic Slope Front (ASF) is primarily due to tidal acceleration. These findings imply that the circulation and mean overturning of the ASC are not only determined by near-Antarctic winds, but also depend crucially on sea ice cover, regionally-dependent mesoscale eddy activity over the continental slope, and the amplitude of tidal flows across the continental shelf break.

Item Details

Item Type:Refereed Article
Keywords:Antarctic Slope Current, eddies, tides, Antarctic margins, ocean model
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical Oceanography
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Climate Change Models
UTAS Author:Klocker, A (Dr Andreas Klocker)
ID Code:134357
Year Published:2019
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2019-08-08
Last Modified:2019-08-14
Downloads:0

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