Mesoscale Eddies Detached from Spatially Growing Meanders in an Eastward-Flowing Oceanic jet Using a Two-Layer Quasi-Geostrophic Model

Abstract

Abstract The process of eddy detachment from a strong, eastward-flowing oceanic jet, which is modeled after the Gulf Stream, is studied using a two-layer quasi-geostrophic model. Numerical calculations are performed, in which an initial perturbation having a small amplitude is superimposed on a basic flow consisting of the eastward jet in the upper layer. The initial perturbation is located in the western part of the jet and consists of one wavelength of meanders. The initial perturbation propagates eastward and grows rapidly, for the most part because of a baroclinic instability. The extremes of large-amplitude meanders are forced to go along the edges of recirculating gyres which are generated on both sides of the jet in the western part, and as a result the meanders are cut off and form eddies. In some cases, meander interactions—by which an upstream meander overtakes the nearest downstream meander—precedes the detachment. The meander growth, which is the basic condition for the detachment, is highly d...