Barotropic Response of the Labrador/Newfoundland Shelf to a Moving Storm

Abstract

The barotropic response of the Labrador and Newfoundland shelves to a moving storm over the Labrador Sea is investigated using a linear barotropic ocean model with realistic coastline and topography. The model results show that the storm generates motions of different time–space scales. Four types of motions are identified:directly wind-forced motion, shelf waves with distinctive frequency and wavelength, low-frequency shelf waves, and trapped inertio–gravity waves. The strongest currents are directly wind-forced currents occurring in areas of maximum wind stress over the shelf. The spatial pattern and temporal change of the current field are strongly influenced by the time history of the storm and the geometry of the coastline. Continental shelf waves are generated in the shelf region south of the storm track. Maximum amplitude occurs along the shelf edge at a wavelength of 800 km and a period of 20 h. This wavelength and period are close to the maximum frequency point of the dispersion curve for the first-mode shelf waves. On the northeast Newfoundland shelf and Grand Banks, the most energetic motion is associated with low-frequency shelf waves with no definitive frequency and wavelength. The currents are rectilinear and parallel to the bathymetry contours at the shelf break and clockwise circular in the shelf interior. Inertio–gravity waves with signatures in both current and sea surface elevation are trapped in the northern Labrador Sea and the Davis Strait. The implications of the model results for current observation on the shelf are discussed.