Journal article
A geometric interpretation of Southern Ocean eddy form stress
- Abstract:
- An interpretation of eddy form stress via the geometry described by the Eliassen-Palm flux tensor is explored. Complimentary to previous works on eddy Reynolds stress geometry, this study shows that eddy form stress is fully described by a vertical ellipse, whose size, shape and orientation with respect to the mean-flow shear determine the strength and direction of vertical momentum transfers. Following a recent proposal, this geometric framework is here used to form a Gent-McWilliams eddy transfer coefficient which depends on eddy energy and a non-dimensional geometric parameter α, bounded in magnitude by unity. α expresses the efficiency by which eddies exchange energy with baroclinic mean-flow via along-gradient eddy buoyancy flux - a flux equivalent to eddy form stress along mean buoyancy contours. An eddy-resolving ocean general circulation model is used to estimate the spatial structure of α in the Southern Ocean and assess its potential to form a basis for parameterization. α averages to a low but positive value of 0.043 within the Antarctic Circumpolar Current, consistent with an inefficient eddy field extracting energy from the mean-flow. It is found that the low eddy efficiency is mainly the result of that eddy buoyancy fluxes are weakly anisotropic on average. α is subject to pronounced vertical structure and is maximum at ∼ 3 km depth where eddy buoyancy fluxes tend to be directed most downgradient. Since α partly sets the eddy form stress in the Southern Ocean, a parameterization for α must reproduce its vertical structure to provide a faithful representation of vertical stress divergence and eddy forcing.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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(Preview, Version of record, pdf, 3.1MB, Terms of use)
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- Publisher copy:
- 10.1175/JPO-D-18-0220.1
Authors
- Publisher:
- American Meteorological Society
- Journal:
- Journal of Physical Oceanography More from this journal
- Volume:
- 49
- Pages:
- 2553-2570
- Publication date:
- 2019-07-30
- Acceptance date:
- 2019-07-22
- DOI:
- EISSN:
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1520-0485
- ISSN:
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0022-3670
- Pubs id:
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pubs:1034455
- UUID:
-
uuid:a295c859-6c38-41a1-b28d-04805755e2fb
- Local pid:
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pubs:1034455
- Source identifiers:
-
1034455
- Deposit date:
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2019-07-24
Terms of use
- Copyright holder:
- American Meteorological Society
- Copyright date:
- 2019
- Notes:
- © 2019 American Meteorological Society. This article is licensed under a Creative Commons Attribution 4.0 license (http://creativecommons.org/licenses/by/4.0/).
- Licence:
- CC Attribution (CC BY)
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