Modeling of wind-driven interaction at the estuary/ocean transition

Earlier studies on estuarine dynamics mostly have been focused on the impact of river discharge and tidal oscillation. Some studies have been done by accumulating field data from several estuaries, and others by using numerical simulation. Several prior studies suggest that the bathymetry could affect the estuarine dynamics, and its' effect could be characterized by the ratio between friction and the Earth's rotation effect, and the width of the estuary and internal Rossby radius. However, it still remains unclear that the importance of shape of bathymetry in the estuary and shelf bathymetry on the estuarine circulations. In addition, most studies separately focused on the in-estuary and out-estuary hydrodynamics. However, the region between an estuary and open ocean (estuary mouth) could have different flow characteristics with in-estuary and out-estuary having both boundary effects. The estuary/ocean transition region often meets wide open ocean and a narrow estuary channel, and this specific geometry could have an affect on the flow characteristics differing in-estuary flow characters. For this reason, this study focuses on the reciprocal influence that an estuary and its adjacent shelf exert under the influence of wind forcing especially depending on the channel and shelf bathymetry. To perform this specific study, 21 types of channel are ideally designed under four directional winds effects, and the Regional Ocean Modeling System (ROMS) is used.;Distinct simulations are performed to compare wind-driven patterns resulting over each bathymetry under weak wind stress. The effects of density gradients are added to the patterns that arise for wind-driven flow over bathymetry. Finally, the effects of tidal forcing are assessed. The model results show that (1) vertically sheared flow pattern changes into laterally sheared pattern as channel width increased and depth decreased, (2) the channel width does not effect much on salinity intrusion but the channel depth does, (3) the extended channel toward offshore strengthens stratification, (4) plume can be located more offshore with a flat shelf than a sloping shelf, and (5) plume expansion can be restricted by flow curtain effects near the edge of a channel. It is concluded that channel shape in the estuary and existence of the underneath channel at the offshore plays a crucial role in flow and plume dynamics at an estuary/ocean transition.