SYNOPTIC BOTTOM PRESSURE VARIABILITY ON THE LABRADOR AND NEWFOUNDLANDCONTINENTAL SHELVES

A high-resolution, barotropic model of the North Atlantic is used to i nvestigate bottom pressure variability on the Labrador and Newfoundlan d Shelves. The model has a free surface and is forced by surface atmos pheric pressure and wind stress derived from twice-daily analyses from the European Centre for Medium-Range Weather Forecasts. Model output is compared with a yearlong set of bottom pressure data (1985-1986). C oherence squared between model and observations is significant at the 95% confidence level at almost all stations and exceeds 0.6 over most of the inner shelf, with good agreement in the phase. The model shows a tendency to overestimate the autospectral energy at periods less tha n 10 days but to underestimate the energy at longer periods. The model does less well at the outer shelf, where coherence squared is only ma rginally significant. The weaker performance of the model near the she lf break may indicate a role for physical processes not accounted for in the model (e.g., eddies, stratification) or, alternatively, might b e due to the low signal-to-noise ratio in the bottom pressure measurem ents made at the shelf break. Model/data comparisons show that wind fo rcing dominates over pressure forcing, except at the northern end of t he Labrador Shelf, where both forcings are important. Model experiment s run with and without Hudson Bay in the model domain demonstrate that Hudson Bay influences the Labradr Shelf in the 2 to 10-day period ran ge.