Features of the Observed Annual Ocean–Atmosphere Flux Variability on the West Florida Shelf

Abstract

The annual cycle of sea surface temperature and ocean?atmosphere fluxes on the west Florida shelf is described using in situ measurements and climatology. Seasonal reversals in water temperature tendency occur when the net surface heat flux changes sign in boreal spring and fall. Synoptic-scale variability is also important. Momentum and heat flux variations result in successive water column stratification and destratification events, particularly at shallower depths during spring. Fall is characterized by destratification of the water column and a series of steplike decreases in the temperature. These are in response to both tropical storms and extratropical fronts. Tropical storms are responsible for the largest momentum fluxes, but not necessarily for the largest surface heat fluxes. A one-dimensional analysis of the temperature equation suggests that surface heat flux is primarily responsible for the spring and fall seasonal ocean temperature changes, but that synoptic-scale variability is also controlled by the ocean circulation dynamics. During summer, the situation is reversed and the major influence on water temperature is ocean dynamics, with the heat flux contributing to the synoptic-scale variability. There is also evidence of interannual variability: the wintertime temperatures get increasingly colder from 1998 to 2000, and the greatest stratification and coldest subsurface temperatures occur in 1998. NCEP?NCAR reanalysis fields do not reproduce the high spatial flux variability observed in situ or with satellite measurements. Reconciling these differences and their impacts on the climate variability of this region provides challenges to coupled ocean?atmosphere models and their supporting observing systems.