EFFECTS OF WIND ON A STRATIFIED ESTUARY

Before the onset of wind in the Krka Estuary, a sharp halocline extends from 2.5 to 4 m below the surface, separating the upper brackish water layer from the lower marine layer. Strong wind (20 m s-1) induces a tilt of the halocline surface so that downwind (5-km wind fetch) the halocline is pushed to 4.6 m below the surface. Wind-driven surface currents induce a vertical gyre within the upper layer and a gyre in the opposite direction in the lower marine layer. As a consequence, the halocline close to the coast on the downwind side is not only deeper but is also steepened. The entrainment of marine water into the upper brackish water layer is intensified on the windward side. The possible role of wind in oxygenating the bottom layer is discussed.