The Baroclinic Structure of the Abyssal Circulation

Abstract

A simple baroclinic model of the abyssal ocean circulation is formulated in which the reversals of the meridional velocity with depth, and hence the layering of the abyss, is explained by the longitudinal variation of upwelling into the main thermocline. Since the barotropic meridional velocity is connected to the local upwelling velocity by the Sverdrup relation, regions of weak upwelling have meridional velocity fields that are essentially baroclinic. The baroclinic velocities are driven by thermal anomalies that propagate westward by stationary diffusive Rossby waves from regions of vertical strong upwelling in the eastern portion of the basin. These dynamically driven, internally generated vertical velocities produce the layered baroclinic structure in the western interior of the basin. A simple linear model, continuous in the vertical, is developed to illustrate these elements of the conceptual picture.