CIRCULATION, MIXING, AND EXCHANGE PROCESSES IN THE VICINITY OF TIDAL INLETS - A NUMERICAL STUDY

The circulation in the vicinity of an idealized tidal inlet connecting a continental shelf and a coastal sound is examined. The circulation is forced by an M(2) tide and a weakly buoyant discharge. The buoyant discharge forms a plume in the coastal ocean and induces a distinct an ticyclonic circulation at the plume edge that is maintained throughout the tidal cycle. We focus on the plume's onset and its evolution over 5-10 tidal cycles. Over the timescales considered, the plume was roug hly circular, slightly skewed in the along-coast direction. The model solution yielded high vertical Ekman numbers E(v) similar to O(5) in t he vicinity of the inlet mouth, decreasing seaward from the inlet to a n order of magnitude smaller (E(v) similar to 0.25) at the seaward edg e of the plume. Passive particles released in the region seaward of th e inlet mouth were used to describe the exchange between the coastal r egion and the inlet. A marked asymmetry between ebb and hood hows is o bserved in the vicinity of the inlet, with jet-like ebbing currents an d weaker potential-flow-like flooding currents. Over a tidal cycle, ne t exchanges between the coastal ocean and the inlet are found to be sp atially and temporally dependent; that is, particle trajectories depen d on the release point and the time of the release in the tidal cycle. The near,inlet residual circulation shows significant differences in the absence of stratification.