Entrainment of Shelf Water by a Bifurcating Continental Boundary Current

Abstract

At the northeast corner of Taiwan the direction of the continental slope isobaths changes rapidly relative to the oncoming Kuroshio, so that the inertia of a small inshore fraction of this current causes it to cross the slope, while the main branch follows the isobaths. It is suggested that the portion of the bifurcated current entering the shelf displaces ambient water of relatively high potential vorticity as a countercurrent, which flows across the slope. The vortex stretching and subsequent entrainment of this water into the main branch of the Kuroshio increases its maximum cyclonic vorticity and helps to maintain the inshore shear of the western boundary current. This Idea is supported by simple initial value and steady-state models, and also by dye observations of the flow from a source on the wall of a rotating tank.