Topographically Controlled Flow Around a Deep Trough Transecting the Shelf off Kodiak Island, Alaska

Abstract

Current measurements core the axis of a deep trough normal to the coast and from the adjacent shelf show that the mean flow is barotropic and follows depth contours, conserving potential vorticity, to form a cyclonic vortex or meander over the trough. The data are interpreted as an example of an inertial Taylor-Proudman column on the continental shelf. The scale of the topographic variations dominates the potential vorticity balance and a simple steady-state numerical model is in good agreement with the data when the vorticity balance approaches the limit U · BH = 0. Streamlines following isobaths converge over steeper topography and current speeds are nearly proportional to the local topographic gradient. Estimates from the data support this behavior and indicate that the ?20 cm s?1 mean current around the trough is driven by a typical cross-shelf-averaged velocity scale of ?5 cm s?1.