Particle Drift in the Surface Layer off Southwest Nova Scotia; Description and Evaluation of a Model

Abstract

A two-dimensional (horizontal) surface layer particle dispersion model for the Southwest Nova Scotia region is described and evaluated. The model is based on a barotropic M2 tidal model and wind-driven response model. It includes a constant residual current field plus time varying M2 tidal and wind-driven currents. Tidal currents are shown to cause particle trajectories to vary with the time of particle release. Constant winds are shown to have an important influence on particle trajectories, although periodic winds have little effect. Comparisons between simulated particle trajectories and satellite-tracked drogue trajectories show the model can qualitatively reproduce drogue trajectories on the western, but not on the eastern portion of Browns Bank. However, the model consistently underestimates the observed displacements. These discrepancies are probably due to (1) unmodeiled baroclinic components of the circulation and/or (2) the inability of the model to resolve strong topographic gradients and the resulting rectified currents over the steep flanks of the Bank. The use of a previous empirically-defined circulation does not significantly improve the model's performance.