Longshore Currents and the Onset of Upwelling over Bottom Slope

Abstract

The evolution of longshore currents produced by upwelling on an f-plane over shelf-like bottom topography for times long compared to a barotropic spin-up time, but short compared to a diffusion time, reveals in a linear, time-dependent, three-dimensional model that: The topographic constraints yield a steady topographic boundary layer on these short time scales similar in structure to the layer found in an earlier steady-state model. Within a Rossby radius of deformation of the coast a swift equatorward longshore current with a pole-ward countercurrent is formed. Wind-stress forcing with large north-south scales are the most efficient in driving longshore currents, but do not effectively produce internal Kelvin waves, as do the shorter longshore scales of forcing.