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Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic
Author(s) -
Buckingham Christian E.,
Khaleel Zammath,
Lazar Ayah,
Martin Adrian P.,
Allen John T.,
Naveira Garabato Alberto C.,
Thompson Andrew F.,
Vic Clément
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc012910
Subject(s) - eddy , baroclinity , geology , barotropic fluid , sea surface height , climatology , buoyancy , hydrography , rossby number , instability , vortex , ocean current , geophysics , gulf stream , oceanography , sea surface temperature , turbulence , meteorology , physics , mechanics
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 ∼ 390 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.