Effect of the Coriolis Force on Salt Dynamics in Convergent Partially Mixed Estuaries

Abstract

AbstractIn this study, we numerically investigate the effect of the Earth's rotation on the salt dynamics in an idealized convergent partially mixed estuary. The effect of the Coriolis force on salt transport is shown to vary in different parts of the estuary. Near the estuary mouth and in the upper estuary, compared with nonrotating environments, the Coriolis force weakens the longitudinal estuarine circulation and salinity stratification, thus decreasing the landward salt transport induced by the steady shear. On the other hand, the Coriolis force increases the magnitudes of the tidal variations of current and salinity, and decreases the phase shift between these two variables, resulting in enhanced landward transport of salt by the tidal oscillatory. In the middle estuary, the Coriolis force has less effect on the steady shear and tidal oscillatory transport. The Coriolis force decreases the salinity along the channel bottom by decreasing the vertical advection and increasing the vertical mixing, which results in a decreased salt intrusion. Sensitivity experiments show that in partially mixed estuaries with landward salt transport dominated by steady shear, the effect of the Coriolis force is proportional to the Coriolis parameter, and is more prominent for moderate tidal mixing and higher river discharge scenarios. However, when the tidal mixing is further increased and the estuary transits into a state of well‐mixed with landward salt transport dominated by tidal dispersion, the Coriolis force is shown to increase the stratification and estuarine circulation, and consequently enhances the salt intrusion.