The Frictional Nearshore Response to Forcing by Synoptic Scale Winds

Abstract

Abstract An analytic barotropic model was used to study the nearshore frictional response to synoptic-scale wind forcing. The results depend only on the region where the surface and bottom Ekman layers interact strongly and the water is consequently well mixed. Thus, the conclusions apply even to shelves where baroclinic effects are not negligible father offshore. The main findings are as follows. (i) The “blocking” of the surface Ekman flux which drives the shelf flow is a consequence of the interaction of Ekwan layers in the nearshore region. The interaction transfers progressively more of the surface stress directly to bottom stress as the depth decreases. The consequent decrease in Ekman flux toward the shore creates an Ekman flux divergence which drives the interior flow. (ii) The region over which the shelf is effectively forced is narrow. It extends, approximately, from where the depth divided by the Ekman layer e-folding scale is 0.2 to where it is 2.5. (iii) Simple equations for pressure and the ...