Can mesoscale eddy kinetic energy sources and sinks be inferred from sea surface height in the Agulhas Current ?

Type Article
Acceptance Date 2022-07-05 IN PRESS
Language English
Author(s) Tedesco PaulineORCID1, 2, Gula JonathanORCID1, 3, Penven PierrickORCID5, Menesguen ClaireORCID6, Jamet QuentinORCID4, Vic ClementORCID6
Affiliation(s) 1 : Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Oceanographie Physique et Spatiale (LOPS), IUEM, 5 6 29280, Brest, France
2 : Imperial College of London, London, UK
3 : Institut Universitaire de France (IUF), Paris, France
4 : Institut des Geosciences de l’Environnement (IGE), Grenoble, France
5 : Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Oceanographie Physique et Spatiale (LOPS), IUEM, 5 6 29280, Brest, France
6 : Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Oceanographie Physique et Spatiale (LOPS), IUEM, 5 6 29280, Brest, France
Source under consideration at Journal of Geophysical Research - Oceans. (Wiley) In Press
DOI 10.1002/essoar.10511782.1
Abstract

Western boundaries (WB) have been suggested to be hotspots of mesoscale eddy decay, using an eddy kinetic energy (EKE) flux divergence based on sea surface height (η). The η-based diagnostic requires approximations, including the use of geostrophic velocities. Here, we assess to what extent mesoscale EKE flux divergence can be inferred from η using a numerical simulation of the Agulhas Current. The EKE flux divergence is composed of two terms: the eddy-pressure work (linear component) and the advection of EKE (nonlinear component). Both are mainly positive in the WB region (net EKE sources). However, it is not reliably accounted by both η-based diagnostics. The η-based eddy-pressure work has a net contribution in the WB region of the opposite sign than the true one. Ageostrophic eddy-pressure work dominates the geostrophic one (corresponding to a β-contribution). It is explained by mesoscale eddies’s scale to fall below the scale of ζ/β (ζ: root mean square of normalized relative vorticity for mesoscale eddies; β: latitudinal variations of Coriolis parameter). The advection done by geostrophic EKE flux dominates the EKE flux divergence in the WB region. It results in the EKE flux divergence to be qualitatively estimable using η (up to 54 % of the net EKE source). Our results in the Agulhas Current show a mesoscale eddy dynamics in contrast with the decay's paradigm at western boundaries. Further analysis in other western boundaries are required to complete our understanding of mesoscale eddies dynamics.

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Tedesco Pauline, Gula Jonathan, Penven Pierrick, Menesguen Claire, Jamet Quentin, Vic Clement Can mesoscale eddy kinetic energy sources and sinks be inferred from sea surface height in the Agulhas Current ? under consideration at Journal of Geophysical Research - Oceans. IN PRESS. Publisher's official version : https://doi.org/10.1002/essoar.10511782.1 , Open Access version : https://archimer.ifremer.fr/doc/00783/89477/