A Numerical Study of Circulation in the Western Caribbean Sea

Abstract

A three-dimensional ocean circulation model is used to study circulation and month-to-month variability in the western Caribbean Sea. The domain covers the area between 72° and 90°W and between 8° and 24°N, with a horizontal resolution of roughly 18 km. The western Caribbean Sea model is forced by the monthly mean Comprehensive Ocean?Atmosphere Data Set (COADS) wind stress and surface heat flux and monthly mean volume transports through the model open boundaries calculated by a (1/3)° Atlantic Ocean model. The model sea surface salinity is restored to the monthly mean climatology. The semiprognostic method suggested by Sheng et al. is used to reduce the model errors by assimilating the hydrographic data into the momentum equations. The model reproduces many well-known circulation features in the region, including the warm and persistent throughflow known as the Caribbean Current, the highly variable Panama?Colombia Gyre, and moderate seasonal variations of temperature and salinity in the surface mixed layer. The overall features of the model-calculated 10-yr mean near-surface circulation are in good agreement with the decadal-mean currents inferred from the trajectories of the satellite-tracked 15-m drogued drifters by Fratantoni. The vertical distributions of the time-mean model currents across the Yucatan Strait qualitatively agree with the time-mean observed currents made by Sheinbaum et al. The model results demonstrate that nonlinear dynamics play a very important role in simulating month-to-month and mesoscale variability in the western Caribbean, particularly over the southern Colombian Basin and eastern Cayman and Yucatan Basins. The monthly varying wind stress and boundary flows also play an important role in simulating general circulation and variability in the region. The monthly varying surface heat and freshwater fluxes are largely responsible for the seasonal cycle of temperature and salinity in the surface mixed layer.