On the Influence of Bottom Topography on the Agulhas Eddy

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Abstract
A series of numerical experiments with a two-layer primitive equation model is presented to study the dynamics of Agulhas eddies. The main goal of the paper is to examine the influence of an underwater meridional ridge (modeled after the Walvis Ridge) on an Agulhas eddy hitting it. First, the propagation of an eddy of the specified vertical structure over a flat bottom is considered, varying the initial eddy horizontal scale from 40 to 120 km. Unlike small nonlinear eddies, large nonlinear eddies (on the scale of Agulhas eddies) do not rapidly evolve into a compensated state (no motion in the lower layer). Second, the influence of a ridge on eddies of differing vertical structures having a specified intensity in the upper layer and a prescribed horizontal scale is analyzed. Significantly baroclinic eddies can cross the Walvis Ridge, but barotropic or near-barotropic ones cannot. The evolution of eddies crossing the ridge is compared with that of initially identical eddies moving over a flat botto... Abstract A series of numerical experiments with a two-layer primitive equation model is presented to study the dynamics of Agulhas eddies. The main goal of the paper is to examine the influence of an underwater meridional ridge (modeled after the Walvis Ridge) on an Agulhas eddy hitting it. First, the propagation of an eddy of the specified vertical structure over a flat bottom is considered, varying the initial eddy horizontal scale from 40 to 120 km. Unlike small nonlinear eddies, large nonlinear eddies (on the scale of Agulhas eddies) do not rapidly evolve into a compensated state (no motion in the lower layer). Second, the influence of a ridge on eddies of differing vertical structures having a specified intensity in the upper layer and a prescribed horizontal scale is analyzed. Significantly baroclinic eddies can cross the Walvis Ridge, but barotropic or near-barotropic ones cannot. The evolution of eddies crossing the ridge is compared with that of initially identical eddies moving over a flat botto...

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