Influence of Topography on the Large-Scale Ocean Circulation

Abstract

Abstract The influence of the bottom topography on the large-scale ocean circulation is discussed and illustrated with a simple model based on the ideal-fluid thermocline equations. The requirement that fluid remains in linear vorticity balance while conserving its density leads to a coupled problem, but one that can be reduced to a single characteristic equation under an assumption of uniform potential vorticity on density surfaces. The characteristics are intermediate between the f/H contours found in a homogeneous ocean and the f contours found in an ocean with a motionless abyss. The extent to which topography influences the circulation in upper layers is quantified and is shown to depend on both the strength of the bottom currents and on the vertical profile of stratification. In a realistic limit, in which the abyssal waters are sluggish and weakly stratified, the circulation in surface layers is relatively indifferent to the topography beneath. The direction in which a current deflects around a top...