A laboratory study of floating lenticular anticyclones

Abstract

Oceanic vortices play an important role in the redistribution of heat, salt and momentum in the oceans. Among these vortices, floating lenses or rings are often met in the meanders of warm currents. In order to better describe these vortices, we propose here a laboratory study of floating anticyclonic lenses. A small volume of fresh water is gently injected near the surface of a rotating layer of homogeneous salted water. Because of the opposite effects of rotation that tends to generate columnar structures and density stratification that spreads light water on the surface, the vortices take after a rapid transient, a quasi-stationary lenticular, finite-sized three dimensional typical shape given by the hydrostatic and geostrophic balances. Visualization and measurements of this equilibrium shape, aspect ratios and vorticity fields are performed. These measurements permit to compare our laboratory anticyclones to analytical predictions that use first a simple solid body rotation model and then a more realistic isolated Gaussian vorticity field. Finally, a comparison of our models with oceanographic lenses described in the literature is discussed.