Nonlinear Tidal Dynamics in Florida Coastal Waters

This study investigated the dynamics of nonlinear tidal constituents, i.e., compound and shallow-water (C&S) tides, in Florida coastal waters. We simulated barotropic tides and depth-averaged tidal currents using a high-resolution, two-dimensional version of the Advanced Circulation (ADCIRC-2DDI) model. The model domain includes both the eastern Gulf of Mexico and the South Atlantic Bight. The model grid consists of 353,718 nodes and 622,367 triangular elements, with spatial resolutions ranging from 16 m to 41 km. We focused on analyzing two major compound tides, M4 and M6 of M2, and two shallow-water tides, MS4 and MK3. For each tidal constituent, we derived co-tidal charts, co-range charts, and atlases of tidal current ellipses, energy fluxes, and dissipation rates. We identified energy flux pathways of various C&S tides. We found that their energy fluxes follow different pathways than those of the astronomical constituents. The differences are attributed to differing genesis mechanisms. The astronomical tide originates from the deep-ocean equilibrium tide potential, while the C&S tides are predominantly generated in near-shore shallow waters due to nonlinear tidal interactions. Nonlinear tidal interactions were most intense in near-shore areas of the eastern Straits of Florida, the Big Bend and Florida Bay along the west Florida coast, and Biscayne Bay along the east Florida coast. In these areas, C&S energies are generated nearly equally by two mechanisms: local nonlinear interactions and energy influxes from far fields. In addition, coastline geometry exerts appreciable influence on tidal energetics. For instance, in Florida Bay, a funneling effect from the convergence of opposite shorelines overwhelms the damping effect of bottom friction and enhances the local tidal range. This study provides insight into the nonlinear tidal dynamics and energetics of Florida coastal waters.