On the dynamics of an idealised bottom density current overflowing in a semi-enclosed basin: mesoscale and submesoscale eddies generation

Type Article
Date 2020-09
Language English
Author(s) Morvan Mathieu1, Carton Xavier1, L'Hégaret Pierre1, de Marez Charly1, Corréard Stéphanie2, Louazel Stephanie3
Affiliation(s) 1 : LOPS, Univ. Brest-CNRS-IFREMER-IRD, IUEM, Plouzané, France
2 : SHOM/DOPS/STM/DTO, Toulouse Cedex 5, France
3 : SHOM/DOPS/STM/DTO, Brest Cedex 2, France
Source Geophysical And Astrophysical Fluid Dynamics (0309-1929) (Informa UK Limited), 2020-09 , Vol. 114 , N. 4-5 , P. 607-630
DOI 10.1080/03091929.2020.1747058
WOS© Times Cited 4
Note Issue 4-5: Geophysical and Astrophysical Vortex
Keyword(s) Bottom density current, Red Sea outflow, submesoscale eddies, current instability, mesoscale eddies
Abstract

The Red Sea Water enters the Gulf of Aden through the Strait of Bab El Mandeb as a density current. The Red Sea Water subsequently spreads into the Gulf of Aden under the influence of surface mesoscale eddies, which dominate the surface flow, of topographic features such as rift and capes, and of the monsoon regimes. The dynamics of a bottom density current overflowing in a semi-enclosed basin, as the Red Sea Water outflows in the Gulf of Aden, is investigated by performing idealised numerical simulations, at submesoscale resolution, in which we progressively add topographic and dynamical elements. The rift and cape play an important role, respectively, on the vertical and the horizontal mixing as well as baroclinic and barotropic instabilities undergone by the bottom density current. Mesoscale and submesoscale eddies are generated depending on the model configuration. In the presence of surface mesoscale eddies, the bottom density current water is mainly advected at their periphery. In winter, both mesoscale and submesoscale eddies are generated, while in summer only submesoscale eddies are present. Finally, to put our results based on idealised numerical simulations and Lagrangian experiments in perspective, we analyse the trajectories of three Argo floats, deployed in the Rift of Tadjurah. Clues of submesoscale eddies generation at capes are observed which is in agreement with our idealised numerical simulations.

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Morvan Mathieu, Carton Xavier, L'Hégaret Pierre, de Marez Charly, Corréard Stéphanie, Louazel Stephanie (2020). On the dynamics of an idealised bottom density current overflowing in a semi-enclosed basin: mesoscale and submesoscale eddies generation. Geophysical And Astrophysical Fluid Dynamics, 114(4-5), 607-630. Publisher's official version : https://doi.org/10.1080/03091929.2020.1747058 , Open Access version : https://archimer.ifremer.fr/doc/00627/73918/