Dynamics of Mesoscale Eddies Interacting With a Western Boundary Current Flowing by a Gap

Abstract

AbstractThe propagation of cyclonic and anticyclonic mesoscale eddies through a wide meridional gap with a crossing western boundary current (WBC) is studied using a 1.5‐layer quasi‐geostrophic ocean circulation model. The results of the numerical experiments suggest that a steady, leaping WBC blocks nearly completely all eddies from propagating westward through the gap. In comparison, both cyclonic and anticyclonic eddies propagate westward nearly uninterrupted through the gap if the WBC is in a penetrating state. Interactions of mesoscale eddies with a critical‐state WBC trigger regime transitions of the WBC between leaping and penetrating states, resulting in dramatic changes of the circulation west of the gap. The radiation of the circulation plumes from the gap into the western basin due to the WBC regime transition is found to be independent of the size and the initial location of the perturbing eddy in the eastern basin, provided that the WBC path shift is induced successfully by the eddy.