A Coupled-mode Shallow Water model for tidal analysis: Internal-tide reflection and refraction by the Gulf Stream
A novel hydrostatic coupled-mode shallow water model (CSW) is developed
and used to simulate tides in the greater Middle Atlantic Bight region.
The model incorporates realistic stratification and topography, an internal
tide generating function (ITGF) that provides internal tide forcing from existing
surface tide parameters, and dynamical terms that describe linearized
wave- mean-flow and mean-density interactions. Several idealized and realistic
simulations are used to verify the model. These verification simulations
include internal-tide interactions involving topographic coupling and mean-flow
coupling, and comparisons with other simpler and more complex nonlinear
primitive-equation models. Then, twenty-four simulations of internal
tide generation and propagation in the greater Middle Atlantic Bight region
are used to identify significant internal-tide interactions with the Gulf Stream.
The simulations indicate that locally generated mode-1 internal tides can refract
and/or reflect at the Gulf Stream. The redirected internal tides often
re-appear at the shelfbreak, where they produce onshore energy fluxes that
are intermittent (i.e., noncoherent) because meanders in the Gulf Stream alter
their precise location, phase, and amplitude. These results provide an explanation
for the anomalous onshore energy fluxes previously observed at the
New Jersey Shelfbreak and linked with the generation of nonlinear internal
waves.