The effect of varying bathymetry on steady, zonal equivalent-barotropic jets

Abstract

The influence of sudden changes in bathymetry on zonal, equivalent-barotropic, steady oceanic jets on a β plane is considered. Solutions to the perturbations induced by a step-like change in bathymetry yield the well-known results that an eastward-flowing jet will oscillate about the mean axis downstream of the step; upstream the perturbation results in a shear re-adjustment. However, the amplitude of an individual streamlined oscillation depends upon its lateral position in the incident jet. For westward-flowing jets, the perturbation results in a northward or southward migration of streamlines, accompanied by a shear adjustment. Both eastward and westward jets intensity on entering a deeper region and broaden on entering a shallower region. This change in width arises from the opposite sense of the shear vorticities on the two flanks of the jet. The hitherto unexplained broadening of the Kuroshio over the Izu Ridge has been shown to be quantitatively determined by the simple model presented.