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Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic

Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic
Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic
A high-resolution satellite image that reveals a train of coherent, submesoscale (6 km) vortices along the edge of an ocean front is examined in concert with hydrographic measurements in an effort to understand formation mechanisms of the submesoscale eddies. The infrared satellite image consists of ocean surface temperatures at inline image m resolution over the midlatitude North Atlantic (48.69°N, 16.19°W). Concomitant altimetric observations coupled with regular spacing of the eddies suggest the eddies result from mesoscale stirring, filamentation, and subsequent frontal instability. While horizontal shear or barotropic instability (BTI) is one mechanism for generating such eddies (Munk's hypothesis), we conclude from linear theory coupled with the in situ data that mixed layer or submesoscale baroclinic instability (BCI) is a more plausible explanation for the observed submesoscale vortices. Here we assume that the frontal disturbance remains in its linear growth stage and is accurately described by linear dynamics. This result likely has greater applicability to the open ocean, i.e., regions where the gradient Rossby number is reduced relative to its value along coasts and within strong current systems. Given that such waters comprise an appreciable percentage of the ocean surface and that energy and buoyancy fluxes differ under BTI and BCI, this result has wider implications for open-ocean energy/buoyancy budgets and parameterizations within ocean general circulation models. In summary, this work provides rare observational evidence of submesoscale eddy generation by BCI in the open ocean.
2169-9275
6725–6745
Buckingham, Christian E.
dba7c776-a8c6-4617-ad40-7919dd4ab3dc
Khaleel, Zammath
0b06a7c3-28f0-4fc6-bb12-95b9d837f390
Lazar, Ayah
df385613-a17f-4e77-beaf-1b07014dad5d
Martin, Adrian P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Allen, John T.
17bc259e-c288-4d19-b23b-35bb3926e679
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Thompson, Andrew F.
e75ef46b-cd1b-46d9-9e8f-b5d128f186ab
Vic, Clément
408e7f4a-468f-4139-90a6-3a95228ad758
Buckingham, Christian E.
dba7c776-a8c6-4617-ad40-7919dd4ab3dc
Khaleel, Zammath
0b06a7c3-28f0-4fc6-bb12-95b9d837f390
Lazar, Ayah
df385613-a17f-4e77-beaf-1b07014dad5d
Martin, Adrian P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Allen, John T.
17bc259e-c288-4d19-b23b-35bb3926e679
Naveira Garabato, Alberto C.
97c0e923-f076-4b38-b89b-938e11cea7a6
Thompson, Andrew F.
e75ef46b-cd1b-46d9-9e8f-b5d128f186ab
Vic, Clément
408e7f4a-468f-4139-90a6-3a95228ad758

Buckingham, Christian E., Khaleel, Zammath, Lazar, Ayah, Martin, Adrian P., Allen, John T., Naveira Garabato, Alberto C., Thompson, Andrew F. and Vic, Clément (2017) Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic. Journal of Geophysical Research: Oceans, 122 (8), 6725–6745. (doi:10.1002/2017JC012910).

Record type: Article

Abstract

A high-resolution satellite image that reveals a train of coherent, submesoscale (6 km) vortices along the edge of an ocean front is examined in concert with hydrographic measurements in an effort to understand formation mechanisms of the submesoscale eddies. The infrared satellite image consists of ocean surface temperatures at inline image m resolution over the midlatitude North Atlantic (48.69°N, 16.19°W). Concomitant altimetric observations coupled with regular spacing of the eddies suggest the eddies result from mesoscale stirring, filamentation, and subsequent frontal instability. While horizontal shear or barotropic instability (BTI) is one mechanism for generating such eddies (Munk's hypothesis), we conclude from linear theory coupled with the in situ data that mixed layer or submesoscale baroclinic instability (BCI) is a more plausible explanation for the observed submesoscale vortices. Here we assume that the frontal disturbance remains in its linear growth stage and is accurately described by linear dynamics. This result likely has greater applicability to the open ocean, i.e., regions where the gradient Rossby number is reduced relative to its value along coasts and within strong current systems. Given that such waters comprise an appreciable percentage of the ocean surface and that energy and buoyancy fluxes differ under BTI and BCI, this result has wider implications for open-ocean energy/buoyancy budgets and parameterizations within ocean general circulation models. In summary, this work provides rare observational evidence of submesoscale eddy generation by BCI in the open ocean.

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Buckingham_et_al-2017-Journal_of_Geophysical_Research__Oceans - Version of Record
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Accepted/In Press date: 18 July 2017
e-pub ahead of print date: 28 August 2017
Published date: 15 September 2017

Identifiers

Local EPrints ID: 413609
URI: https://eprints.soton.ac.uk/id/eprint/413609
ISSN: 2169-9275
PURE UUID: 31efa0cb-8736-49dc-8886-658929552135

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Date deposited: 30 Aug 2017 16:31
Last modified: 14 Aug 2019 17:20

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Contributors

Author: Christian E. Buckingham
Author: Zammath Khaleel
Author: Ayah Lazar
Author: Adrian P. Martin
Author: John T. Allen
Author: Andrew F. Thompson
Author: Clément Vic

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