Wind and Tide Response in Florida Bay

Florida Bay is a shallow estuarine environment located between the Everglades freshwater wetlands and a chain of islands called the Florida Keys. The assimilation, transformation and transport of biogeochemical elements in the bay are important in influencing the health of the regional ecosystem. This system includes extensive live coral reefs seaward of the Keys, the only such reefs in the continental U.S. Distinct compartmentalisation by partially submerged banks and multiple islands cause extraordinary damping of diurnal and semidiurnal tides within the bay. The reduced circulation has resulted in partial isolation of water masses in subregions and strong gradients in salinity. We have collected and analyzed wind data from Miami Airport, Key West, Flamingo, and a CMAN station at Molasses Reef for 1989–1991. Although, seasonal variations and sea-breeze effects are more pronounced in the mainland stations, spatial coherence is high throughout. Correlation of water surface fluctuations with wind observations are used to determine the wind-forced dynamic response and water exchange. The main responses are distributed within three period bands: diurnal and semidiurnal tides, 3–5 d-period wind forcing, and long period (about 14.7 d) astronomical tides. Numerical model simulation shows that tides are strongly influenced by a combination of bottom friction and obstruction to flow from chained islands and submerged banks. The damping of the progressive tidal wave is the source of a mean sealevel rise of approximately 0.01–0.02 m within the bay. A large part of the wind response is due to remote forcing and results in long wave surges in the bay. Model results also indicate a net southward exchange between the bay and the Atlantic Ocean driven by the elevated mean sealevel inside the bay. This net southward exchange is supported by results of field measurements (Smith, 1993).