Generation of submesoscale frontal eddies in the Agulhas Current

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.

Keyword(s)

Submesoscale, Numerical Modelling, Barotropic Instability, Agulhas Current, Frontal Eddies

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Tedesco Pauline, Gula Jonathan, Ménesguen Claire, Penven Pierrick, Krug M. (2019). Generation of submesoscale frontal eddies in the Agulhas Current. Journal Of Geophysical Research-oceans. 124 (11). 7606-7625. https://doi.org/10.1029/2019JC015229, https://archimer.ifremer.fr/doc/00514/62520/

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