Three-dimensional island wakes in the field, laboratory experiments and numerical models

Results of field, laboratory and numerical studies are used to describe the three-dimensional circulation in a barotropic island wake in shallow waters. Bottom friction generates a closed circulation characterized by a strong upwelling (typically 10–20 m h−1) in the bulk of the eddy and an even larger downwelling velocity in a narrow zone along the edges of the eddy. This downwelling exists at the solid boundaries of the island and also all along the separation streamline. This circulation can be realistically modeled numerically provided the intense turbulence in the free shear layers is explicitly parameterized. This secondary circulation aggregates buoyant material along the edges of the eddy even in well-mixed coastal waters.