This article analyzes the barotropic circulation in the Southwestern Atlantic Shelf using
a three-dimensional numerical model forced with winds and tides. South of 40°S, the shelf
circulation is dominated by the propagation of the semidiurnal tides. In this region the
diurnal tides are generally weak, except at the shelf edge where they resonate with northward
propagating, continental shelf waves. North of 40°S, the tidal circulation is relatively weak,
and the circulation is mainly driven by the winds. The wind-driven annual mean circulation
is characterized by a broad northeastward flow south of approximately 40°S and is
characterized by a southwestward flow farther north. The intense mixing associated with the
Patagonian tides enhances the bottom friction that balances the energy input from the wind
stress forcing. In contrast with previous results our simulation shows a detrainment of the
northward volume transport with latitude due to an offshore flow along the edge of the
Patagonian shelf break. The largest seasonal variations of the shelf circulation are observed
in the region between 45°S and 25°S where, during the fall, there is a development of a
clockwise gyre and a northeastward flow north of 40°S. The gyre weakens toward the
winter, and the northeastward flow reverses directions