Continental shelf eddies forced by cooling and modified by winds

When surface cooling occurs uniformly in an ocean with a sloping bottom, water mixes vertically due to convection, and the nearshore, shallower, water column becomes colder than the offshore, deeper, water column. It is well-known that this surface cooling can lead to cross-shelf density gradients, hence baroclinic instability and an eddy field. How is this process affected by alongshore wind stress? Idealized numerical model experiments are conducted with surface cooling and sustained, spatially uniform winds in an alongshore-cyclic channel. Downwelling-favorable winds carry lighter water onshore near the surface, and deeper water offshore. The density field becomes more nearly stable, and the eddy field is suppressed by a factor dependent on Earth rotation, water depth and wind stress amplitude, among other factors. Upwelling- favorable winds, on the other hand, cause further gravitational instability (vertical mixing) but do not affect lateral density gradients strongly. Thus, upwelling-favorable winds have a weaker effect on the shelf’s cross-shelf density gradient, hence eddy field.