A Simple Model of Abyssal Circulation, Including Effects of Wind, Buoyancy and Topography

Abstract

We examine problems of steady abyssal circulation using an inviscid planetary geostrophic layered model. The model includes an active wind-driven upper layer and arbitrary topography; forcing is in the form of specified interlayer mass fluxes from which we model global upwelling and geothermal heating. The results considered in this study are appropriate to the shadow zone of a Pacific-sized, moderately wind-forced oceanic basin. It is found that topographic effects, global upwelling and geothermal heating may all control the abyssal circulation, at least locally, within realistic values of their parameter ranges, suggesting that a better understanding of the geothermal and interior buoyancy flux fields is necessary for an understanding of abyssal circulation in the ocean. The model reduces to a nonlinear extension of the one-layer abyssal circulation model of Stommel and Arons, generalized to include mass flux structure and topography, and this limit is shown to be valid in an oceanic shadow zone for moderate topography and weak to moderate buoyancy forcing.