The Estuarine Circulation

Recent research in estuaries challenges the long-standing paradigm of the gravitationally driven estuarine circulation. In estuaries with relatively strong tidal forcing and modest buoyancy forcing, the tidal variation in stratification leads to a tidal straining circulation driven by tidal variation in vertical mixing, with a magnitude that may significantly exceed the gravitational circulation. For weakly stratified estuaries, vertical and lateral advection are also important contributors to the tidally driven residual circulation. The apparent contradiction with the conventional paradigm is resolved when the estuarine parameter space is mapped with respect to a mixing parameter M that is based on the ratio…