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Observing the local emergence of the Southern Ocean residual-mean circulation

Observing the local emergence of the Southern Ocean residual-mean circulation
Observing the local emergence of the Southern Ocean residual-mean circulation

The role of mesoscale turbulence in maintaining the mean buoyancy structure and overturning circulation of the Southern Ocean is investigated through a 2-year-long, single-mooring record of measurements in Drake Passage. The buoyancy budget of the area is successively assessed within the Eulerian and the Temporal-Residual-Mean frameworks. We find that a regime change occurs on time scales of 1 to 100 days, characteristic of mesoscale dynamics, whereby the eddy-induced turbulent horizontal advection balances the vertical buoyancy advection by the mean flow. We use these diagnostics to reconstruct the region's overturning circulation, which is found to entail an equatorward downwelling of Antarctic Intermediate and Bottom Waters and a poleward upwelling of Circumpolar Deep Water. The estimated eddy-induced flow can be accurately parameterized via the Gent-McWilliams closure by adopting a diffusivity of ∼2,000 m 2  s −1 with a middepth increase to 2,500 m 2  s −1 at 2,100 m, immediately underneath the maximum interior stratification.

Eulerian circulation, meridional overturning, mesoscale turbulence, mooring measurements, residual-mean circulation, Southern Ocean
0094-8276
3862-3870
Sévellec, F.
01569d6c-65b0-4270-af2a-35b0a77c9140
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Vic, C.
408e7f4a-468f-4139-90a6-3a95228ad758
Ducousso, N.
a9918eba-476c-4997-adb6-7319be1fa14c
Sévellec, F.
01569d6c-65b0-4270-af2a-35b0a77c9140
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Vic, C.
408e7f4a-468f-4139-90a6-3a95228ad758
Ducousso, N.
a9918eba-476c-4997-adb6-7319be1fa14c

Sévellec, F., Naveira Garabato, A.C., Vic, C. and Ducousso, N. (2019) Observing the local emergence of the Southern Ocean residual-mean circulation. Geophysical Research Letters, 46 (7), 3862-3870. (doi:10.1029/2018GL081382).

Record type: Article

Abstract

The role of mesoscale turbulence in maintaining the mean buoyancy structure and overturning circulation of the Southern Ocean is investigated through a 2-year-long, single-mooring record of measurements in Drake Passage. The buoyancy budget of the area is successively assessed within the Eulerian and the Temporal-Residual-Mean frameworks. We find that a regime change occurs on time scales of 1 to 100 days, characteristic of mesoscale dynamics, whereby the eddy-induced turbulent horizontal advection balances the vertical buoyancy advection by the mean flow. We use these diagnostics to reconstruct the region's overturning circulation, which is found to entail an equatorward downwelling of Antarctic Intermediate and Bottom Waters and a poleward upwelling of Circumpolar Deep Water. The estimated eddy-induced flow can be accurately parameterized via the Gent-McWilliams closure by adopting a diffusivity of ∼2,000 m 2  s −1 with a middepth increase to 2,500 m 2  s −1 at 2,100 m, immediately underneath the maximum interior stratification.

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More information

Accepted/In Press date: 4 March 2019
e-pub ahead of print date: 7 March 2019
Published date: 16 April 2019
Keywords: Eulerian circulation, meridional overturning, mesoscale turbulence, mooring measurements, residual-mean circulation, Southern Ocean

Identifiers

Local EPrints ID: 430530
URI: http://eprints.soton.ac.uk/id/eprint/430530
ISSN: 0094-8276
PURE UUID: a1d91c0d-9f21-48ae-b218-eb96fa89cd6e

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Date deposited: 03 May 2019 16:30
Last modified: 07 Oct 2020 06:39

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