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A Greenland Sea perspective on the dynamics of postconvective eddies

A Greenland Sea perspective on the dynamics of postconvective eddies
A Greenland Sea perspective on the dynamics of postconvective eddies
Open ocean deep convection contributes to the formation of the dense waters that fill the global deep ocean. The dynamics of post–convective vortices are key to understanding the role of convection in ocean circulation. Submesoscale coherent vortices (SCVs) observed in convective regions are likely to be the anticyclonic components of hetons. Hetons are dipoles, consisting of a surface cyclone and a weakly stratified subsurface anticyclone, that can be formed by convection. Here, key post-convective processes are investigated using numerical experiments of increasing sophistication, with two primary goals: (1) to understand how the ambient hydrography and topography influence the propagation of hetons; (2) to provide a theoretical context for recent observations of SCVs in the Greenland Sea. It is found that the alignment of hetons is controlled by ambient horizontal density gradients, and that hetons self-propagate into lighter waters as a result. This provides a mechanism for transporting convected water out of a cyclonic gyre, but the propagation is arrested if the heton meets large amplitude topography. Upon interaction with topography, hetons usually separate, and the surface cyclone returns towards denser water. The anti-cyclone usually remains close to topography and may become trapped for several hundred days. These findings may explain the observed accumulation and longevity of SCVs at the Greenland Fracture Zone, on the rim of the Greenland Sea gyre. The separation and sorting of cyclones from anticyclones have likely implications for the density and vorticity budgets of convective regions.
0022-3670
2755-2771
Oliver, K.I.C.
588b11c6-4d0c-4c59-94e2-255688474987
Eldevik, T.
e5cd116e-a17d-4787-b785-168f88ce5e3b
Stevens, D.P.
9b78fd18-9ea2-409d-b78f-61ac70555905
Watson, A.J.
22b78032-6022-4ed3-bea8-d1bfefcf599c
Oliver, K.I.C.
588b11c6-4d0c-4c59-94e2-255688474987
Eldevik, T.
e5cd116e-a17d-4787-b785-168f88ce5e3b
Stevens, D.P.
9b78fd18-9ea2-409d-b78f-61ac70555905
Watson, A.J.
22b78032-6022-4ed3-bea8-d1bfefcf599c

Oliver, K.I.C., Eldevik, T., Stevens, D.P. and Watson, A.J. (2008) A Greenland Sea perspective on the dynamics of postconvective eddies. Journal of Physical Oceanography, 38 (12), 2755-2771. (doi:10.1175/2008JPO3844.1).

Record type: Article

Abstract

Open ocean deep convection contributes to the formation of the dense waters that fill the global deep ocean. The dynamics of post–convective vortices are key to understanding the role of convection in ocean circulation. Submesoscale coherent vortices (SCVs) observed in convective regions are likely to be the anticyclonic components of hetons. Hetons are dipoles, consisting of a surface cyclone and a weakly stratified subsurface anticyclone, that can be formed by convection. Here, key post-convective processes are investigated using numerical experiments of increasing sophistication, with two primary goals: (1) to understand how the ambient hydrography and topography influence the propagation of hetons; (2) to provide a theoretical context for recent observations of SCVs in the Greenland Sea. It is found that the alignment of hetons is controlled by ambient horizontal density gradients, and that hetons self-propagate into lighter waters as a result. This provides a mechanism for transporting convected water out of a cyclonic gyre, but the propagation is arrested if the heton meets large amplitude topography. Upon interaction with topography, hetons usually separate, and the surface cyclone returns towards denser water. The anti-cyclone usually remains close to topography and may become trapped for several hundred days. These findings may explain the observed accumulation and longevity of SCVs at the Greenland Fracture Zone, on the rim of the Greenland Sea gyre. The separation and sorting of cyclones from anticyclones have likely implications for the density and vorticity budgets of convective regions.

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Published date: December 2008

Identifiers

Local EPrints ID: 68797
URI: http://eprints.soton.ac.uk/id/eprint/68797
ISSN: 0022-3670
PURE UUID: e1171c79-31a5-4b80-aac7-7f00e387c63a

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Date deposited: 05 Oct 2009
Last modified: 13 Mar 2024 19:09

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Contributors

Author: K.I.C. Oliver
Author: T. Eldevik
Author: D.P. Stevens
Author: A.J. Watson

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