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On the circulation of bottom water in the region of the Vema Channel

On the circulation of bottom water in the region of the Vema Channel
On the circulation of bottom water in the region of the Vema Channel
The circulation and transport of Antarctic Bottom Water (4<45.87) in the region of the Vema Channel are studied along three WOCE hydrographic lines, the geostrophic velocities referenced to previously published direct current measurements. The primary supply of water to the deep Vema Channel is from the Argentine Basin's deep western boundary current, with no indication of an inflow from the southeast. In the northern Argentine Basin, detachment of lower North Atlantic Deep Water from the continental slope is associated with a deep thermohaline front near 34°S. To the north of this front, the upper part of the AABW bound for the Vema Channel (4<46.01) exhibits a significant NADW influence. Further modification of the throughflow water occurs near 30°30?S, where the channel orientation changes by ~50°. Southward flow of bottom water on the eastern flank of the Vema Channel, amounting to ~1.5 Sv, represents a significant countercurrent to the deep channel transport. Inclusion of this countercurrent reduces the net flow of AABW through the Vema Channel from 3.2±0.7 to 1.7±1.1 Sv. Water properties imply that the near-zero net flow over the Santos Plateau results from a near-closed cyclonic circulation fed by the deep Vema Channel throughflow. A disruption of the northward boundary current in the upper AABW (lower circumpolar water) is required by this flow pattern. The extension of the cyclonic circulation on the Santos Plateau enters the Brazil Basin as a ~1 Sv flow distinct from the outflow in the Vema Channel Extension (6.2 Sv). The high magnitude of the latter suggests a southward recirculation of bottom water near the western boundary to the north of the region of study.
abyssal circulation, deep front, antarctic bottom water, north atlantic deep water, vema channel, argentine basin, brazil basin, south atlantic
0967-0637
1119-1139
McDonagh, E.L.
47e26eeb-b774-4068-af07-31847e42b977
Arhan, M.
7f2a83d2-e8b8-4e60-a460-2e8190286562
Heywood, K.J.
4eeebe72-3857-4729-8d6a-7ece46d37cd5
McDonagh, E.L.
47e26eeb-b774-4068-af07-31847e42b977
Arhan, M.
7f2a83d2-e8b8-4e60-a460-2e8190286562
Heywood, K.J.
4eeebe72-3857-4729-8d6a-7ece46d37cd5

McDonagh, E.L., Arhan, M. and Heywood, K.J. (2002) On the circulation of bottom water in the region of the Vema Channel. Deep Sea Research Part I: Oceanographic Research Papers, 49 (7), 1119-1139. (doi:10.1016/S0967-0637(02)00016-X).

Record type: Article

Abstract

The circulation and transport of Antarctic Bottom Water (4<45.87) in the region of the Vema Channel are studied along three WOCE hydrographic lines, the geostrophic velocities referenced to previously published direct current measurements. The primary supply of water to the deep Vema Channel is from the Argentine Basin's deep western boundary current, with no indication of an inflow from the southeast. In the northern Argentine Basin, detachment of lower North Atlantic Deep Water from the continental slope is associated with a deep thermohaline front near 34°S. To the north of this front, the upper part of the AABW bound for the Vema Channel (4<46.01) exhibits a significant NADW influence. Further modification of the throughflow water occurs near 30°30?S, where the channel orientation changes by ~50°. Southward flow of bottom water on the eastern flank of the Vema Channel, amounting to ~1.5 Sv, represents a significant countercurrent to the deep channel transport. Inclusion of this countercurrent reduces the net flow of AABW through the Vema Channel from 3.2±0.7 to 1.7±1.1 Sv. Water properties imply that the near-zero net flow over the Santos Plateau results from a near-closed cyclonic circulation fed by the deep Vema Channel throughflow. A disruption of the northward boundary current in the upper AABW (lower circumpolar water) is required by this flow pattern. The extension of the cyclonic circulation on the Santos Plateau enters the Brazil Basin as a ~1 Sv flow distinct from the outflow in the Vema Channel Extension (6.2 Sv). The high magnitude of the latter suggests a southward recirculation of bottom water near the western boundary to the north of the region of study.

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More information

Published date: 2002
Keywords: abyssal circulation, deep front, antarctic bottom water, north atlantic deep water, vema channel, argentine basin, brazil basin, south atlantic

Identifiers

Local EPrints ID: 6056
URI: http://eprints.soton.ac.uk/id/eprint/6056
ISSN: 0967-0637
PURE UUID: b18f5b43-e5fd-4c8f-a2ac-a156534554c9

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Date deposited: 10 Jun 2004
Last modified: 15 Mar 2024 04:47

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Contributors

Author: E.L. McDonagh
Author: M. Arhan
Author: K.J. Heywood

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