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On the export of Antarctic bottom water from the Weddell Sea

On the export of Antarctic bottom water from the Weddell Sea
On the export of Antarctic bottom water from the Weddell Sea
A survey of the current field over the South Scotia Ridge, obtained with a lowered Acoustic Doppler Current Profiler (LADCP), is presented. There is a pattern of northward (southward) flow on the western (eastern) side of each of four deep passages in the ridge, which is supported by tracer measurements. The net full-depth LADCP-referenced geostrophic transport over the ridge is 22 ± 7 Sv (1 Sv = 10-6 m3 s-1) northward, with the jets on either side of the passages transporting 5–10 Sv in alternating directions. The corresponding Weddell Sea Deep Water (WSDW) transport over the ridge is 6.7 ± 1.7 Sv. This is a factor of 4 larger than the only previous estimate in the literature, and suggests that a significant proportion of the Antarctic Bottom Water (AABW) invading the world ocean abyss escapes the Weddell Sea via the Scotia Sea.
The net full-depth and WSDW transports over the ridge are modified to 7 ± 6 and 4.7 ± 0.7 Sv, respectively, by a box inverse model of the western Weddell Gyre. The model incorporates the WOCE A23 crossing of the central part of the gyre and a set of five constraints synthesizing our previous oceanographic knowledge of the region. It diagnoses that 9.7 ± 3.7 Sv of AABW are formed in the Weddell Sea, and that comparable amounts are exported over the South Scotia Ridge (~48%) and further east (~52%) assuming that no AABW enters the Weddell Gyre from the Indian Ocean. The WSDW fraction with neutral density > 28.31 kg m-3 transported over the ridge upwells in the Scotia Sea at a rate of 6 x 10-6 m s-1, an order of magnitude larger than many basin-scale estimates of deep upwelling in the literature. In contrast, the Weddell Sea Bottom Water exported to the eastern Weddell Gyre entrains upward at a rate of 8 x 10-7 m s-1, more typical of other open-ocean regions. When their different ventilation histories are considered, the comparable transports and disparate upwelling rates of the AABW exported over the South Scotia Ridge and farther east may be crucial to our understanding of teleconnections between the Weddell Sea and the global ocean.
0967-0645
4715-4742
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6
McDonagh, E.L.
47e26eeb-b774-4068-af07-31847e42b977
Stevens, D.P.
9b78fd18-9ea2-409d-b78f-61ac70555905
Heywood, K.J.
4eeebe72-3857-4729-8d6a-7ece46d37cd5
Sanders, R.J.
02c163c1-8f5e-49ad-857c-d28f7da66c65
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6
McDonagh, E.L.
47e26eeb-b774-4068-af07-31847e42b977
Stevens, D.P.
9b78fd18-9ea2-409d-b78f-61ac70555905
Heywood, K.J.
4eeebe72-3857-4729-8d6a-7ece46d37cd5
Sanders, R.J.
02c163c1-8f5e-49ad-857c-d28f7da66c65

Naveira Garabato, A.C., McDonagh, E.L., Stevens, D.P., Heywood, K.J. and Sanders, R.J. (2002) On the export of Antarctic bottom water from the Weddell Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 49 (21), 4715-4742. (doi:10.1016/S0967-0645(02)00156-X).

Record type: Article

Abstract

A survey of the current field over the South Scotia Ridge, obtained with a lowered Acoustic Doppler Current Profiler (LADCP), is presented. There is a pattern of northward (southward) flow on the western (eastern) side of each of four deep passages in the ridge, which is supported by tracer measurements. The net full-depth LADCP-referenced geostrophic transport over the ridge is 22 ± 7 Sv (1 Sv = 10-6 m3 s-1) northward, with the jets on either side of the passages transporting 5–10 Sv in alternating directions. The corresponding Weddell Sea Deep Water (WSDW) transport over the ridge is 6.7 ± 1.7 Sv. This is a factor of 4 larger than the only previous estimate in the literature, and suggests that a significant proportion of the Antarctic Bottom Water (AABW) invading the world ocean abyss escapes the Weddell Sea via the Scotia Sea.
The net full-depth and WSDW transports over the ridge are modified to 7 ± 6 and 4.7 ± 0.7 Sv, respectively, by a box inverse model of the western Weddell Gyre. The model incorporates the WOCE A23 crossing of the central part of the gyre and a set of five constraints synthesizing our previous oceanographic knowledge of the region. It diagnoses that 9.7 ± 3.7 Sv of AABW are formed in the Weddell Sea, and that comparable amounts are exported over the South Scotia Ridge (~48%) and further east (~52%) assuming that no AABW enters the Weddell Gyre from the Indian Ocean. The WSDW fraction with neutral density > 28.31 kg m-3 transported over the ridge upwells in the Scotia Sea at a rate of 6 x 10-6 m s-1, an order of magnitude larger than many basin-scale estimates of deep upwelling in the literature. In contrast, the Weddell Sea Bottom Water exported to the eastern Weddell Gyre entrains upward at a rate of 8 x 10-7 m s-1, more typical of other open-ocean regions. When their different ventilation histories are considered, the comparable transports and disparate upwelling rates of the AABW exported over the South Scotia Ridge and farther east may be crucial to our understanding of teleconnections between the Weddell Sea and the global ocean.

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Published date: 2002

Identifiers

Local EPrints ID: 37570
URI: http://eprints.soton.ac.uk/id/eprint/37570
ISSN: 0967-0645
PURE UUID: e407ee4b-7496-4fee-a5a9-e0f20444104e

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Date deposited: 25 May 2006
Last modified: 09 Nov 2021 08:09

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Contributors

Author: E.L. McDonagh
Author: D.P. Stevens
Author: K.J. Heywood
Author: R.J. Sanders

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