On the sea level forcing of the Mid‐Atlantic Bight

Abstract

The Mid‐Atlantic Bight circulation is discussed with particular comment directed toward the role of the parabathic pressure gradient. A distinction is made between external and local sea level forcing. External forcing consists of an oceanic boundary condition on the sea level gradient. The shelf response to this is geostrophic: the diabathic component drives the parabathic flow, and the parabathic component drives diabathic flow. The latter, together with the bottom stress generated by the former and the physical dimensions of the shelf, determine the degree of convergence or divergence within the shelf volume, which, in turn, determines the sea level dependence required to satisfy continuity over the shelf. Local forcing due to the wind stress, the internal field of mass, and the total bottom stress, in conjunction with local bathymetry, determines the extent of local convergence or divergence, and as a consequence, generates additional sea level distortion. Conceptually, local and external forcing can be considered as independent although they are, in fact, coupled through bottom stress and internal field of mass adjustment.