The M 2 tide on the West Florida Shelf

Abstract

The M 2 tide on the West Florida Shelf was analyzed with data from five arrays of current meter and bottom pressure sensors spanning a 2-year period. The observations of the tidal fluctuations are consistent with a linear barotropic flow model. Internal tides do not contribute significantly to the variance. Consequently, the tidal currents do not change substantially (±25%) over the course of a year and the temperature fluctuations are caused by horizontal advection of the mean thermal gradients. Estimates of energy flux onto the shelf revealed that energy propagates at an angle oblique to the wave crests. The dissipation of tidal energy occurs primarily near shore (depth < 50 m), where the quadratic drag law for bottom friction with drag coefficient γ = 0.002 underestimates the observed dissipation rate. The energy loss over the mid-shelf region is small and consistent with a drag coefficient of 0.002. A one-dimensional model was developed to predict tidal sea level and current amplitudes across the shelf. The model requires only the coastal sea level and the cross-shelf topography. Results of the model are consistent with the observed tidal coefficients.