TOPOGRAPHY AND GROUNDING IN A SIMPLE BOTTOM LAYER MODEL

A reduced-gravity model for a dense bottom layer under a motionless de ep layer is used to investigate bottom layer flow with topography. The two competing effects in the model are topography, which introduces a topographic beta effect, and strong layer thickness variation, which allows for the possibility of zero-layer thickness or grounding. The g oal is to arrive at a simple, observationally relevant characterizatio n of the model which can help to distinguish different dynamical mecha nisms operating in the ocean. Several regimes are identified, includin g situations for which the layer depth goes to zero with and without t opography. Ways of distinguishing observationally between competing ef fects are suggested. The study is motivated by the observed shift of A ntarctic Bottom Water in the western North Atlantic Ocean from the wes t to the east; this phenomenon is used to discriminate key elements of the model.