Separation of an Advectively Trapped Buoyancy Current at a Bathymetric Bend*

Abstract

Abstract The coastal current system along the east coast of North America, from the Labrador shelf to Cape Hatteras, must negotiate complex bathymetry with numerous sharp bends and large cross-shelf channels. The behavior of these shelf currents is studied here using an advectively trapped buoyancy current (ATBC) model, in which a coastal buoyancy current on a sloping bottom forms a surface-to-bottom density front that becomes trapped along an isobath by offshore advection of buoyancy in the bottom boundary layer. Alongfront flow is concentrated in a nearly geostrophic surface-intensified frontal jet. Trapping occurs where the cross-shelf bottom velocity vanishes on the shoreward side of the front, thus terminating offshore buoyancy advection and causing the bottom boundary layer to detach and to flow upward along frontal isopycnals. The dynamics of an ATBC at a sharp bend in bathymetry and at a cross-shelf channel are investigated using a primitive equation numerical model, focusing on the separation of ...