Abyssal Circulation in a Circumpolar Basin Driven by Discrete Sources of Buoyancy

Abstract

The response of the deep ocean to periodic and steady forcing by mass sources is considered, in the presence of fluid loss, diffusion, and topography, which may or may not have regions of closed planetary vorticity. There can be a preexisting deep layer, or the forcing may produce one. The long-time response to forcing, which varies annually, is shown to have only a small periodic component, essentially because the mass loss by diapycnic transfer is weak. This is in qualitative agreement with observations of overflows, which show little seasonal signal. Ridges do not form an effective block to the flow, which can bypass the ridges, approximately following lines of constant planetary vorticity. A brief discussion of how fluid leaks out of closed planetary vorticity regions by diffusion is included.