Simulated shelf-break processes in the northern Gulf of Mexico

Simulations that use the HYbrid Coordinate Ocean Model (HYCOM) configured for the Gulf of Mexico are used to elucidate the dynamics of the Gulf and explore the sensitivity to parameter space. HYCOM uses isopycnal coordinates in the deep stratified ocean, pressure coordinates in unstratified regions including the mixed layer, and terrain-following coordinates in shallow coastal regions. The simulations have 20 layers in the vertical and 1/12 or 1/25 degree horizontal resolution and are forced with 6-hourly NOGAPS winds and fluxes and boundary conditions from a 1/12 HYCOM Atlantic simulation during 2000 and 2001. Several different vertical mixing schemes have been examined and will be discussed. All simulations depict a realistic Loop Current and realistic Loop Current Eddy shedding. Upwelling is observed near the Yucatan consistent with observations. Emphasis is placed on the role of cyclones in cross-shelf exchange in the northeastern Gulf. The cyclones tend to orbit around the anticyclonic Loop Current eddies and seldom cross the shelf-break front, although filaments associated with baroclinically unstable eddies do genetrate cross-shelf exchange and interact with largely barotropic flows that tend to follow the shelf-break front.