Current response at the shelf break to transient wind forcing

Abstract

An analysis of current meter and hydrographic data collected from an array of moorings situated at the shelf break off Nova Scotia is presented. In particular, the focus is on the ocean response to moderate (10 to 20m s−1) transient winds of two or more days duration blowing parallel to the local bathymetry. Under these conditions, upwelling occurs at the shelf break from depths of 400 m and with peak vertical velocities of about 2 mm s−1. The upwelling appears to be confined to within 10 km of the slope. Acceleration, Coriolis, and pressure‐gradient terms are important for the along‐ and cross‐slope momentum balances. Local topographic variations contribute to the anomalously large bottom currents on the shoreward side of the shelf break. Both coastal sea level and the shelf break circulation respond coherently to synoptic wind forcing, but quantitative agreement with two‐layer shelf models is poor.