Modeling the Effect of a Submarine Canyon on Eddy Generation in Banderas Bay, Mexico

Banderas Bay is located at the tip of Cabo Corrientes, a coastal promontory near the entrance of the Gulf of California. In this area, the intensification and recirculation of the Mexican Coastal Current (MCC) interact with Banderas Bay and, more specifically, a submarine canyon within the bay, in a manner that generates eddies. This eddy formation was explored using the Regional Ocean Modeling System (ROMS) numerical model in a series of idealized experiments consisting of a northward coastal current simulating the MCC. Banderas Bay is prone to generate eddies due to a headland and the very steep topography of the canyon. When the intensity of the currents at the entrance of the bay reaches 0.4 m s(-1), the circulation exhibits detachments and then eddies. The eddies have azimuthal speeds of 0.1 to 0.3 m s(-1) and diameters that are constrained by the bay/canyon geometry of up to 30 km. Dynamically, the Froude number is Fr similar to 0.4, and the Rossby number (Ro) is >0.65, leading the Burger number (Bu = Ro(2)/Fr-2) to be similar to 2, showing that the eddy shedding is due to a separation process. These eddies are generated at the lee of the cape and shed to the center of the bay. As a result of the MCC intensification, the advection of vorticity is more intense, by similar to 15%, than the vertical stretching mechanism (which is commonly more significant in canyon dynamics). In addition, as the canyon narrows with depth, the dynamics change from a gradient-flow balance in the upper layers to less of a gradient-flow balance in the deeper layers, where the pressure gradient force dominates the circulation.