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A microscale view of mixing and overturning across the Antarctic Circumpolar Current

A microscale view of mixing and overturning across the Antarctic Circumpolar Current
A microscale view of mixing and overturning across the Antarctic Circumpolar Current
The relative roles of isoneutral stirring by mesoscale eddies and dianeutral stirring by small-scale turbulence in setting the large-scale temperature–salinity relation of the Southern Ocean against the action of the overturning circulation are assessed by analyzing a set of shear and temperature microstructure measurements across Drake Passage in a “triple decomposition” framework. It is shown that a picture of mixing and overturning across a region of the Antarctic Circumpolar Current (ACC) may be constructed from a relatively modest number of microstructure profiles. The rates of isoneutral and dianeutral stirring are found to exhibit distinct, characteristic, and abrupt variations: most notably, a one to two orders of magnitude suppression of isoneutral stirring in the upper kilometer of the ACC frontal jets and an order of magnitude intensification of dianeutral stirring in the subpycnocline and deepest layers of the ACC. These variations balance an overturning circulation with meridional flows of O(1) mm s?1 across the ACC’s mean thermohaline structure. Isoneutral and dianeutral stirring play complementary roles in balancing the overturning, with isoneutral processes dominating in intermediate waters and the Upper Circumpolar Deep Water and dianeutral processes prevailing in lighter and denser layers.
0022-3670
233-254
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Polzin, Kurt L.
2424c950-d9b0-471c-95c0-b7b9d44132a1
Ferrari, Raffaele
2dfe7e2b-caf5-4a6a-8db5-7a2c8839a3f5
Zika, Jan D.
1843cce7-77ce-4ef6-9f79-bcf4f9db30e5
Forryan, Alexander
4e753ae9-7f12-495f-933a-2c5a1f554a0e
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Polzin, Kurt L.
2424c950-d9b0-471c-95c0-b7b9d44132a1
Ferrari, Raffaele
2dfe7e2b-caf5-4a6a-8db5-7a2c8839a3f5
Zika, Jan D.
1843cce7-77ce-4ef6-9f79-bcf4f9db30e5
Forryan, Alexander
4e753ae9-7f12-495f-933a-2c5a1f554a0e

Naveira Garabato, Alberto C., Polzin, Kurt L., Ferrari, Raffaele, Zika, Jan D. and Forryan, Alexander (2016) A microscale view of mixing and overturning across the Antarctic Circumpolar Current. Journal of Physical Oceanography, 46 (1), 233-254. (doi:10.1175/JPO-D-15-0025.1).

Record type: Article

Abstract

The relative roles of isoneutral stirring by mesoscale eddies and dianeutral stirring by small-scale turbulence in setting the large-scale temperature–salinity relation of the Southern Ocean against the action of the overturning circulation are assessed by analyzing a set of shear and temperature microstructure measurements across Drake Passage in a “triple decomposition” framework. It is shown that a picture of mixing and overturning across a region of the Antarctic Circumpolar Current (ACC) may be constructed from a relatively modest number of microstructure profiles. The rates of isoneutral and dianeutral stirring are found to exhibit distinct, characteristic, and abrupt variations: most notably, a one to two orders of magnitude suppression of isoneutral stirring in the upper kilometer of the ACC frontal jets and an order of magnitude intensification of dianeutral stirring in the subpycnocline and deepest layers of the ACC. These variations balance an overturning circulation with meridional flows of O(1) mm s?1 across the ACC’s mean thermohaline structure. Isoneutral and dianeutral stirring play complementary roles in balancing the overturning, with isoneutral processes dominating in intermediate waters and the Upper Circumpolar Deep Water and dianeutral processes prevailing in lighter and denser layers.

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Accepted/In Press date: 27 October 2015
Published date: January 2016
Organisations: Physical Oceanography

Identifiers

Local EPrints ID: 390050
URI: http://eprints.soton.ac.uk/id/eprint/390050
ISSN: 0022-3670
PURE UUID: 1c0f0ca7-f112-4e98-a49c-19a6a0bce6cd
ORCID for Alberto C. Naveira Garabato: ORCID iD orcid.org/0000-0001-6071-605X

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Date deposited: 17 Mar 2016 13:52
Last modified: 15 Mar 2024 03:24

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Contributors

Author: Kurt L. Polzin
Author: Raffaele Ferrari
Author: Jan D. Zika
Author: Alexander Forryan

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