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Eddy stirring in the Southern Ocean

Eddy stirring in the Southern Ocean
Eddy stirring in the Southern Ocean
There is an ongoing debate concerning the distribution of eddy stirring across the Antarctic Circumpolar Current (ACC) and the nature of its controlling processes. The problem is addressed here by estimating the isentropic eddy diffusivity ? from a collection of hydrographic and altimetric observations, analyzed in a mixing length theoretical framework. It is shown that, typically, ? is suppressed by an order of magnitude in the upper kilometer of the ACC frontal jets relative to their surroundings, primarily as a result of a local reduction of the mixing length. This observation is reproduced by a quasi-geostrophic theory of eddy stirring across a broad barotropic jet based on the scaling law derived by Ferrari and Nikurashin (2010). The theory interprets the observed widespread suppression of the mixing length and ? in the upper layers of frontal jets as the kinematic consequence of eddy propagation relative to the mean flow within jet cores. Deviations from the prevalent regime of mixing suppression in the core of upper-ocean jets are encountered in a few special sites. Such ‘leaky jet’ segments appear to be associated with sharp stationary meanders of the mean flow that are generated by the interaction of the ACC with major topographic features. It is contended that the characteristic thermohaline structure of the Southern Ocean, consisting of multiple upper-ocean thermohaline fronts separated and underlaid by regions of homogenized properties, is largely a result of the widespread suppression of eddy stirring by parallel jets.
0148-0227
C09019
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Ferrari, R.
d785df74-e6bb-4f6f-bd27-50ca42032e42
Polzin, K.L.
a6ad08a3-7577-4b70-9db7-65926301df6f
Naveira Garabato, A.C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Ferrari, R.
d785df74-e6bb-4f6f-bd27-50ca42032e42
Polzin, K.L.
a6ad08a3-7577-4b70-9db7-65926301df6f

Naveira Garabato, A.C., Ferrari, R. and Polzin, K.L. (2011) Eddy stirring in the Southern Ocean. Journal of Geophysical Research, 116 (C9), C09019. (doi:10.1029/2010JC006818).

Record type: Article

Abstract

There is an ongoing debate concerning the distribution of eddy stirring across the Antarctic Circumpolar Current (ACC) and the nature of its controlling processes. The problem is addressed here by estimating the isentropic eddy diffusivity ? from a collection of hydrographic and altimetric observations, analyzed in a mixing length theoretical framework. It is shown that, typically, ? is suppressed by an order of magnitude in the upper kilometer of the ACC frontal jets relative to their surroundings, primarily as a result of a local reduction of the mixing length. This observation is reproduced by a quasi-geostrophic theory of eddy stirring across a broad barotropic jet based on the scaling law derived by Ferrari and Nikurashin (2010). The theory interprets the observed widespread suppression of the mixing length and ? in the upper layers of frontal jets as the kinematic consequence of eddy propagation relative to the mean flow within jet cores. Deviations from the prevalent regime of mixing suppression in the core of upper-ocean jets are encountered in a few special sites. Such ‘leaky jet’ segments appear to be associated with sharp stationary meanders of the mean flow that are generated by the interaction of the ACC with major topographic features. It is contended that the characteristic thermohaline structure of the Southern Ocean, consisting of multiple upper-ocean thermohaline fronts separated and underlaid by regions of homogenized properties, is largely a result of the widespread suppression of eddy stirring by parallel jets.

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More information

Published date: 2011
Organisations: Ocean and Earth Science, Physical Oceanography

Identifiers

Local EPrints ID: 153603
URI: http://eprints.soton.ac.uk/id/eprint/153603
ISSN: 0148-0227
PURE UUID: e7e03f26-b774-44bf-8ec7-bbcc9edcede1

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Date deposited: 20 May 2010 15:43
Last modified: 16 Jul 2019 23:58

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Contributors

Author: R. Ferrari
Author: K.L. Polzin

University divisions

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