Modeling the impacts of the Loop Current on circulation and water properties over the Pulley Ridge region on the Southwest Florida shelf

Abstract

A high-resolution (∼1.5km) regional ocean model was developed for the southern Florida Shelf and Florida Straits. A two-year (2011–12) simulation was conducted and the model results were generally in good agreement with available satellite and in situ data. Model results show that the meandering of the Gulf of Mexico Loop Current (LC) exerts strong impacts on the dynamics over Pulley Ridge on the southwest Florida shelf, where the LC turns into the Florida Straits to become the Florida Current (FC). In particular, the northward migration of the LC/FC front often drives strong on-shelf (eastward) transport of the slope water onto the shelf of southern Pulley Ridge, an important mesophotic coral reef at depths between 60 and 90m. Frequent remotely or locally generated eddies over the western slope of Pulley Ridge may be blocked by the northern LC/FC front when it is closely in contact with the shelf break, a phenomenon documented in previous studies. These eddies drive strong upwelling of slope water toward the shelf break, which sometimes can extend 20–30km onto the shelf, strongly affecting the Pulley Ridge region. A narrow return flow, largely along the shelf edge from Florida Keys to Pulley Ridge, may be produced when the FC impinges upon the continental slope during late fall to early spring. The results from an experiment without the surface winds suggest that wind forcing contributes to the westward flow but is not the determining factor for its generation.