Wind effects on a front over the continental shelf slope

Abstract

A continuously stratified, two‐dimensional (vertical and seaward) model is used to study the effects of alongshore wind on a front between lighter water over the continental shelf and heavier water in the offshore ocean. The model produces three components of alongshore flows: one component associated with the horizontal density front and two wind‐driven components, one near the coast and one over the shelf break. The cross‐shore circulation has two near‐surface features; a seaward component resulting from the offshore density gradient and a shoreward (seaward) component resulting from the right‐hand (left‐hand) alongshore wind stress, which has the coast to the right (left), facing downstream. These two components contribute to the maintenance of the front. With no wind, low‐density water over the shelf tends to move toward the offshore ocean associated with the near‐surface seaward flow, resulting in flatter isopycnal surfaces. A moderate right‐hand alongshore wind suppresses the density‐driven surface flow and constrains the shelf water, while a strong wind in the same direction pushes the front shoreward and makes isopycnal surfaces steeper, resulting in increased exchange of the shelf water. A left‐hand alongshore wind contributes to more rapid frontal relaxation and a seaward shift in its position. These results are applied to the Labrador Shelf.