Time dependent mixing in a salt wedge estuary

Abstract Measurements of the profiles of salinity and velocity at a station in the Duwamish River estuary indicate that the turbulent mixing through the density interface is highly time dependent with the most intense mixing occurring at the maximum current speed during the ebb. Additional measurements of the turbulent kinetic energy and the turbulent flux of salt by the eddy correlation technique verify that interpretation. The vertical turbulent salt flux and the turbulent kinetic energy vary by an order of magnitude over the tidal cycle and approximately half of the total vertical salt transport takes place during a short time centered about the maximum ebb. Different mechanisms of turbulence generation operate at various times during the tidal cycle and the intense mixing periods are shown to coincide with conditions favorable for the formation of an internal hydraulic jump.