The influence of merger and convection on an anticyclonic eddy trapped in a bowl

• Published in: Ocean Modelling
• Main Authors: de Marez, Charly, Le Corre, Mathieu, Gula, Jonathan
• Other Authors: Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), ANR-19-CE01-0002,DEEPER,Impacts de la turbulence de sous-mésoéchelle profonde sur la circulation océanique(2019)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: Mesoscale; Vortex; Merger; Convection; [SDU]Sciences of the Universe [physics]; Lofoten; Rockall Trough
• Online Access: https://insu.hal.science/insu-03683248; https://insu.hal.science/insu-03683248/document; https://insu.hal.science/insu-03683248/file/S146350032100127X.pdf; https://doi.org/10.1016/j.ocemod.2021.101874

International audience We investigate the impact of several parameters on the lifecycle of an anticyclonic eddy lying in a topographic depression (a bowl), similar to the Lofoten Vortex and the Rockall Trough eddy cases. We observe that the vortex merger with submesoscale coherent vortices generated at depth allows the eddy to grow in size, and intensify at depth. Wintertime convection is also shown to directly intensify the eddy by deepening isopycnals. Also, convection indirectly affects the shape of the eddy. It enhances the number of merger (1) at the surface, with small vortices generated in the convectively-deepened surface mixed-layer, and (2) at depth, because the vertical distance between the main eddy's core and small companion vortices is reduced, thus increasing the merging efficiency. These processes altogether contribute to the maintaining of the eddy. On the other hand, the bottom drag is the main process contributing to the decay of the eddy. Our study thus shows that the sustaining for several years of such eddies trapped in a bowl is mainly due to the balance between merger and bottom drag.