Wind-driven barotropic circulation off Newfoundland and Labrador

Three-dimensional (3-D) finite element models are used to investigate barotropic wind-driven circulation over the Newfoundland and Labrador Shelf, including its 3-D structure and seasonal and interannual variability, roles of regional vs. remote wind forcing, and importance of the wind-driven circulation. Long-term monthly mean and individual seasonal-mean wind-driven circulation is computed with wind stresses from the NCEP–NCAR reanalysis data (1990–1999) prescribed at the sea surface and corresponding large-scale remote forcing specified at the open boundary determined from a North Atlantic model. The shelf model solutions are discussed for annual-mean circulation features, for seasonal and interannual variations and for relative importance of regional to remote forcing. The model solutions show a shelf-edge current and an inshore current, both of which directed equatorward. The cross-shelf flows and anticyclonic circulation over shallow banks are evident as a consequence of topographic steering. There are prominent seasonal variations in the two branches of the Labrador Current, strongest in December and weakest in July. The interannual changes are also significant in the 1990s, with larger winter transport in the early 1990s and smallest winter transport in 1996. The model shelf-edge Labrador Current is predominated by the remote forcing, while the regional wind forcing plays a significant role in the inshore Current. The model transport for the primary shelf-scale flows is examined against previous model results and in situ observations. Importance of wind-driven currents in the overall circulation is evaluated, which indicates that the wind forcing contributes significantly to the inshore branch of the Labrador Current and less to the shelf-edge branch.