Geostrophic Departure, Local Turning, Speed Change, and Eddy Flux: A New Perspective

Abstract

Conjunctions of meander passages and cross-stream eddy momentum fluxes are common in western boundary currents. To explore the mechanism linking them, we offer a diagnostic equation of their time-dependent motions. The equation is embodied in the more explicit form of a hodograph with two characteristics: a tilt and a veering/backing. The veering/backing is in response to the changing geostrophic departure, and the tilt to the change in the speed of the flow, which can be zero, positive, or negative. This direct approach to the kinematic field?its pattern and its change?led to a hypothesis on the linkage that the cross-stream eddy momentum flux is driven by the downstream pressure gradient force in the supergeostrophic segment of the meandering flow.