Generation of submesoscale frontal eddies in the Agulhas Current

Type Article
Date 2019-11
Language English
Author(s) Tedesco Pauline1, Gula Jonathan5, Ménesguen ClaireORCID1, Penven Pierrick5, Krug M.2, 3, 4
Affiliation(s) 1 : Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM Brest ,France
2 : Council for Scientific and Industrial Research, Natural Resources and the Environment Cape Town ,South Africa
3 : Department of OceanographyMa‐re Institute, University of Cape Town, South Africa
4 : Nansen‐Tutu Centre for Marine Environmental Research, Department of OceanographyUniversity of Cape Town ,South Africa
5 : Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM Brest ,France
Source Journal Of Geophysical Research-oceans (2169-9275) (American Geophysical Union (AGU)), 2019-11 , Vol. 124 , N. 11 , P. 7606-7625
DOI 10.1029/2019JC015229
WOS© Times Cited 27
Keyword(s) Submesoscale, Numerical Modelling, Barotropic Instability, Agulhas Current, Frontal Eddies

This study addresses the dynamics of the Agulhas inshore front in the submesoscale range upstream of 26°E. Submesoscale frontal eddies are observed in the vicinity of Port Elizabeth (26°E) from satellite images and in observations collected from under‐water gliders. Using a submesoscale‐resolving numerical model (dx ~ 0.75 km) we are able to simulate similar submesoscale eddies. Barotropic instability is confirmed as the generation mechanism by a 1D linear stability analysis and an eddy kinetic energy budget. Kinetic energy is transferred from the mean flow to the eddies through the mean horizontal shear, which is a signature of barotropic instability. When the Agulhas Current is in a non‐meandering state, submesoscale eddy generation is a recurrent process which locally drives the front's variability. Along the front, the spatial variability of barotropic instability is shaped by the background strain. A large strain aligned with the frontal axis intensifies the frontal shear upstream of 28°E while a weakening of the strain allows for barotropic instability to be triggered downstream. Although an intermittent process, the barotropic instability shows a dominant period of variability comparable with the variability of the Agulhas Current and Undercurrent.

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