Tidal-driven dynamics and mixing processes in a coastal ocean model with wetting and drying |
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| Authors: | Suriyan Saramul Tal Ezer |
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| Institution: | (1) Center for Coastal Physical Oceanography, Old Dominion University, 4111 Monarch Way, Norfolk, VA 23508, USA |
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| Abstract: | A three-dimensional sigma coordinate numerical model with wetting and drying (WAD) and a Mellor–Yamada turbulence closure
scheme has been used in an idealized island configuration to evaluate how tidally driven dynamics and mixing are affected
by inundation processes. Comprehensive sensitivity experiments evaluate the influence of various factors, including tidal
amplitudes (from 1- to 9-m range), model grid size (from 2 to 16 km), stratification, wind, rotation, and the impact of WAD
on the mixing. The dynamics of the system involves tidally driven basin-scale waves (propagating anticlockwise in the northern
hemisphere) and coastally trapped waves propagating around the island in an opposite direction. The evolutions of the surface
mixed layer (SML) and the bottom boundary layer (BBL) under different forcing have been studied. With small amplitude tides,
wind-driven mixing dominates and the thickness of the SML increases with time, while with large-amplitude tides, tidal mixing
dominates and the thickness of the BBL increases with time. The inclusion of WAD in the simulations increases bottom stress
and impacts the velocities, the coastal waves, and the mixing. However, the impact of WAD is complex and non-linear. For example,
WAD reduces near-coast currents during flood but increases currents during ebb as water drains from the island back to the
sea. The impacts of WAD, forcing, and model parameters on the dynamics are summarized by an analysis of the vorticity balance
for the different sensitivity experiments. |
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