The responses of the west Florida shelf to forcing at tidal, synoptic, seasonal and inter-annual time scales

Observations and numerical models are used to study the responses of the west Florida shelf to forcing at tidal, synoptic, seasonal and inter-annual time scales. The observations include coastal sea level and moored current meter data, and hydrographic and current data taken from ship surveys. The model is a regional adaptation of three dimensional, primitive equations, Princeton Ocean Model (POM) that uses an orthogonal curvilinear coordinate system in the horizontal and a sigma coordinate system in the vertical.; The west Florida shelf tides, especially the semi-diurnal constituents, are found to be primarily barotropic. Tides on the shelf are generally weak and minor contributors to the shelf water mixing and material property transports when compared with water motions occurring at synoptic and seasonal time scales.; The west Florida shelf circulations at synoptic and seasonal scales respond primarily to the shelf wide local forcing by winds, surface heat fluxes, and river runoffs. Shelf wide winds and surface heat fluxes are most important and they act together to modulate the shelf circulation and produce some unique, yearly-occurring physical and biological shelf water features (e.g., the spring “cold tongue” and the “green river”).; Interactions between the west Florida shelf water and the deep ocean Loop Current are constrained by the bottom topography. There are two types of interactions between the Loop Current and the shelf: (1) Loop Current impacts in the north that have relatively small effect on the shelf circulation and (2) Loop Current impacts at the southwest corner (west of the Florida Keys) that can set the shelf water in motion.; Comparisons of the shelf circulations in 1998 and 1999 indicate that the interannual variability between those two years is due to anomalies in both shelf wide local forcing and interactions with the Loop Current. In either case, the bottom Ekman layer provides the conduit for transporting cold, nutrient rich deep water onshore, thereby contributing to near-shore ecological variations.; Temperature budget analyses are performed for both the spring and fall seasonal transitions. Shelf water temperature balances in both seasonal transitions are found to be fully three-dimensional. Counter-intuitively, upwelling in the fall can provide a warming effect, thereby lengthening the fall transition.