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Longshore Currents and the Onset of Upwelling over Bottom Slope

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  • 1 Dipt. of Geophysical Sciences, The University of Chicago
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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:

  1. 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.

  2. Within a Rossby radius of deformation of the coast a swift equatorward longshore current with a pole-ward countercurrent is formed.

  3. 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.

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:

  1. 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.

  2. Within a Rossby radius of deformation of the coast a swift equatorward longshore current with a pole-ward countercurrent is formed.

  3. 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.

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