Flow near a Continental Boundary Driven by an Oceanic Jet

Abstract

To provide possible dynamical interpretations of the GulfStream-induced circulation in the Middle Atlantic Bight (MAB), the inshore flow driven by a steady and straight jet in a homogeneous ocean is considered via similarity solutions. To isolate the curvature effect of the coastal boundary, the author first considers the case of a constant-depth ocean, from which various nonlinear flow regimes are discerned. When applied to the MAB, the model can explain the observed intrusion of the Gulf Stream water just downstream of Cape Hatteras where the coastline curves convexly. Over larger scales of the MAB, the scale analysis suggests the importance of the topography in the vorticity balance. When the topography is included, the similarity solution shows the strong flow to be confined offshore, flanked inshore by a weak counterflow, consistent with the observed slope sea gyre. There is in addition a flow convergence toward the inshore edge of the jet, consistent with the observed occurrence of the shelf water there and the inferred shoreward flux of nutrients across the jet axis.