Tides on the West Florida Shelf

Abstract

The principal semidiurnal (M2 and S2) and diurnal (K1 and O1) tidal constituents are described on the west Florida continental shelf (WFS) using a combination of in situ measurements and a three-dimensional, primitive equation numerical model. The measurements are of sea level and currents along the coastline and across the shelf, respectively. The model extends from west of the Mississippi River to the Florida Keys with an open boundary arcing between. It is along this open boundary that the regional model is forced by a global tide model. Standard barotropic tidal analyses are performed for both the data and the model, and quantifiable metrics are provided for comparison. Based on these comparisons, the authors present coamplitude and cophase charts for sea level and velocity hodographs for currents. The semidiurnal constituents show marked spatial variability, whereas the diurnal constituents are spatially more uniform. Apalachicola Bay is a demarcation point for the semidiurnal tides that are well developed to the southeast along the WFS but are minimal to the west. The largest semidiurnal tides are in the Florida Big Bend and Florida Bay regions with a relative minimum in between just to the south of Tampa Bay. These spatial distributions may be explained on the basis of local geometry. A Lagrangian Stokes drift, coherently directed toward the northwest, is identified but is of relatively small magnitude when compared with the potential for particle transport by seasonal and synoptic-scale forcing. Bottom stress-induced tidal mixing is examined and estimates are made of the bottom logarithmic layer height by the M2 tidal currents.