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Transport and variability of the Antarctic Circumpolar Current in Drake Passage

Transport and variability of the Antarctic Circumpolar Current in Drake Passage
Transport and variability of the Antarctic Circumpolar Current in Drake Passage
The baroclinic transport of the Antarctic Circumpolar Current (ACC) above 3000 m through Drake Passage is 107.3 ± 10.4 Sv and has been steady between 1975 and 2000. For six hydrographic sections (1993–2000) along the World Ocean Circulation Experiment (WOCE) line SR1b, the baroclinic transport relative to the deepest common level is 136.7 ± 7.8 Sv. The ACC transport is carried in two jets, the Subantarctic Front 53 ± 10 Sv and the Polar Front (PF) 57.5 ± 5.7 Sv. Southward of the ACC the Southern Antarctic Circumpolar Current transports 9.3 ± 2.4 Sv. We observe the PF at two latitudes separated by 90 km. This bimodal distribution is related to changes in the circulation and properties of Antarctic Bottom Water. Three realizations of the instantaneous velocity field were obtained with lowered ADCPs. From these observations we obtain near-bottom reference velocities for transport calculations. Net transport due to these reference velocities ranges from -28 to 43 Sv, consistent with previous estimates of variability. The transport in density layers shows systematic variations due to seasonal heating in near-surface layers. Volume transport-weighted mean temperatures vary by 0.40°C from spring to summer; a seasonal variation in heat flux of about 0.22 PW. Finally, we review a series of papers from the International Southern Ocean Studies Program. The average yearlong absolute transport is 134 Sv, and the standard deviation of the average is 11.2 Sv; the error of the average transport is 15 to 27 Sv. We emphasize that baroclinic variability is an important contribution to net variability in the ACC.
Drake Passage, Antarctic Circumpolar Current, hydrography, acoustic Doppler current profiler, transport, ISOS.
0148-0227
8084
Cunningham, S.A.
07f1bd78-d92f-478b-a016-b92f530142c3
Alderson, S.G.
01a82dea-f358-433f-8228-9c72e65026ef
King, B.A.
960f44b4-cc9c-4f77-b3c8-775530ac0061
Brandon, M.A.
ebede00e-6706-4880-9ecc-3364b9da6a5b
Cunningham, S.A.
07f1bd78-d92f-478b-a016-b92f530142c3
Alderson, S.G.
01a82dea-f358-433f-8228-9c72e65026ef
King, B.A.
960f44b4-cc9c-4f77-b3c8-775530ac0061
Brandon, M.A.
ebede00e-6706-4880-9ecc-3364b9da6a5b

Cunningham, S.A., Alderson, S.G., King, B.A. and Brandon, M.A. (2003) Transport and variability of the Antarctic Circumpolar Current in Drake Passage. Journal of Geophysical Research, 108 (C5), 8084. (doi:10.1029/2001JC001147).

Record type: Article

Abstract

The baroclinic transport of the Antarctic Circumpolar Current (ACC) above 3000 m through Drake Passage is 107.3 ± 10.4 Sv and has been steady between 1975 and 2000. For six hydrographic sections (1993–2000) along the World Ocean Circulation Experiment (WOCE) line SR1b, the baroclinic transport relative to the deepest common level is 136.7 ± 7.8 Sv. The ACC transport is carried in two jets, the Subantarctic Front 53 ± 10 Sv and the Polar Front (PF) 57.5 ± 5.7 Sv. Southward of the ACC the Southern Antarctic Circumpolar Current transports 9.3 ± 2.4 Sv. We observe the PF at two latitudes separated by 90 km. This bimodal distribution is related to changes in the circulation and properties of Antarctic Bottom Water. Three realizations of the instantaneous velocity field were obtained with lowered ADCPs. From these observations we obtain near-bottom reference velocities for transport calculations. Net transport due to these reference velocities ranges from -28 to 43 Sv, consistent with previous estimates of variability. The transport in density layers shows systematic variations due to seasonal heating in near-surface layers. Volume transport-weighted mean temperatures vary by 0.40°C from spring to summer; a seasonal variation in heat flux of about 0.22 PW. Finally, we review a series of papers from the International Southern Ocean Studies Program. The average yearlong absolute transport is 134 Sv, and the standard deviation of the average is 11.2 Sv; the error of the average transport is 15 to 27 Sv. We emphasize that baroclinic variability is an important contribution to net variability in the ACC.

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More information

Published date: 2003
Keywords: Drake Passage, Antarctic Circumpolar Current, hydrography, acoustic Doppler current profiler, transport, ISOS.

Identifiers

Local EPrints ID: 1384
URI: http://eprints.soton.ac.uk/id/eprint/1384
ISSN: 0148-0227
PURE UUID: 7f20494a-8145-4f8a-87b0-8506c94e4d40

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Date deposited: 06 May 2004
Last modified: 27 Apr 2022 12:15

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Contributors

Author: S.A. Cunningham
Author: S.G. Alderson
Author: B.A. King
Author: M.A. Brandon

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