Eddies observed by Argo floats. Part II: form stress and streamline length in the Southern Ocean

Eddies observed by Argo floats. Part II: form stress and streamline length in the Southern Ocean AbstractArgo floats measure horizontal current velocities at the parking depth and vertical profiles of temperature and salinity. These data were used to study the roles that eddies play in the dynamics of the Antarctic Circumpolar Current (ACC) in the Southern Ocean. A zonal momentum budget was quantified in a box spanning the latitudes of the Drake Passage and bounded by the sea surface and the 1000-dbar depth. The input of eastward zonal momentum from the wind (17.1 × 1011 N) was approximately twice the downward transfer of eastward momentum across the isopycnal whose mean depth was 1000 dbar, which was mediated via form stress carried by eddies ((8.1 ± 1.9) × 1011 N). The zonal momentum budget was closed to within uncertainty, meaning that the momentum not accounted for by eddies was explained by the Coriolis term associated with meridional transport. The form stress was spatially concentrated near meridional ridges, particularly on their eastern flanks. The localization was extreme: 7% of the total area contributed about 90% of the form stress. Lengths of streamlines were stretched around steady standing meanders. Seven major meanders were found at large topographic barriers along the ACC, with cyclonic meander collocated with the peaks of the topographic barriers. Eddies were found to lengthen the streamlines mostly on the eastern flanks of the meridional ridges, where the eddy transport was southward. Poleward eddy transport on the eastern flanks of meridional ridges is thus highlighted in the ACC dynamics in transferring eastward zonal momentum downward and in adjusting to wind changes by stretching streamlines. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Physical Oceanography American Meteorological Society

Eddies observed by Argo floats. Part II: form stress and streamline length in the Southern Ocean

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0485
D.O.I.
10.1175/JPO-D-17-0072.1
Publisher site
See Article on Publisher Site

Abstract

AbstractArgo floats measure horizontal current velocities at the parking depth and vertical profiles of temperature and salinity. These data were used to study the roles that eddies play in the dynamics of the Antarctic Circumpolar Current (ACC) in the Southern Ocean. A zonal momentum budget was quantified in a box spanning the latitudes of the Drake Passage and bounded by the sea surface and the 1000-dbar depth. The input of eastward zonal momentum from the wind (17.1 × 1011 N) was approximately twice the downward transfer of eastward momentum across the isopycnal whose mean depth was 1000 dbar, which was mediated via form stress carried by eddies ((8.1 ± 1.9) × 1011 N). The zonal momentum budget was closed to within uncertainty, meaning that the momentum not accounted for by eddies was explained by the Coriolis term associated with meridional transport. The form stress was spatially concentrated near meridional ridges, particularly on their eastern flanks. The localization was extreme: 7% of the total area contributed about 90% of the form stress. Lengths of streamlines were stretched around steady standing meanders. Seven major meanders were found at large topographic barriers along the ACC, with cyclonic meander collocated with the peaks of the topographic barriers. Eddies were found to lengthen the streamlines mostly on the eastern flanks of the meridional ridges, where the eddy transport was southward. Poleward eddy transport on the eastern flanks of meridional ridges is thus highlighted in the ACC dynamics in transferring eastward zonal momentum downward and in adjusting to wind changes by stretching streamlines.

Journal

Journal of Physical OceanographyAmerican Meteorological Society

Published: Jul 12, 2017

References

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