On the relation between the deep circulation and the Gulf Stream

Abstract A kinematic argument is used to estimate the direction and amplitude of the recirculating gyre in the deep water associated with the Gulf Stream. The model consists of two layers separated by the thermocline. In the region between Cape Hatteras and the Grand Banks of Newfoundland the depth of the bottom increases offshore, so the thickness of the lower layer also generally increases offshore. The exception is in the region of the Gulf Stream near the foot of the Continental Rise where the thermocline deepens so abruptly that the thickness of the lower layer decreases locally offshore. The amplitude and shape of a freely circulating gyre of uniform potential vorticity in the lower layer are determined by the horizontal distribution of its thickness (pattern of isopachs), and are compared to those inferred by other authors from observations. A similar argument is used to explore the manner in which the Deep Western Boundary Current crosses under the Gulf Stream at Cape Hatteras.