Spinup of Source-driven Circulation in an Abyssal Basin in the Presence of Bottom Topography

Abstract

Spinup of the circulation driven by an inflow into an abyssal basin containing a simple large-scale topographic feature is studied, using an inverted one-and-a-half-layer shallow-water model. Two types of topography, one a plateau and the other a depression, are considered. In both cases, the topography gives rise to a region of closed geostrophic contours. The character of the adjustment and the resultant flow differ markedly between the closed geostrophic contour region and the region outside. Long-wave processes set up a modified Stommel?Arons flow outside the closed contour region, while inside the closed contour region ?frictional spinup? leads to a vigorous recirculation. It is shown that the ratio of the velocity of the recirculation to that of the Stommet?Arons flow is equal to half the ratio of the radius of the closed contour region to the Stommel boundary-layer thickness. Moreover, it is shown that the recirculation inside the closed contour region is always cyclonic, whether the topography is a plateau or a depression. The shape of the topography is important, however, to the formation of meanders in the flow around the rim of the closed contour region.