Laboratory experiments on coastal current separation and vortex formation in front of Cabo Corrientes and Bahia de Banderas, Mexico

A series of rotating tank experiments are carried out to study the behaviour of a coastal current when encountering a cape and an adjacent bay. The experiments are designed to represent some essential dynamics of the interaction of the Mexican Coastal Current with Cabo Corrientes and Bahia de Banderas on the western coast of Mexico. The experiments show that the current surrounds the cape and accumulates negative relative vorticity in front of the downstream bay. For sufficiently strong currents, the flow separates from the coast and the accumulated vorticity develops an anticyclonic eddy that drifts away from the generation region. Afterwards, the current is re-established and the process is repeated. The periodicity is about 16 periods of the rotating system. The current separation and vortex formation depend on the ratio between the inertial length of the current (defined as the characteristic speed over the Coriolis parameter) and the coastal radius of curvature associated with the cape. Another mechanism for vortex formation is verified when the coastal current is switched off. The current separation and eventual vortex shedding are further studied in additional experiments without the cape or the bay, thus increasing the effective coastal radius of curvature. It is verified that the absence of any of these two features inhibits the current separation. The results illustrate the dynamical conditions that may help to explain the emergence of mesoscale oceanic eddies observed on the lee side of Cabo Corrientes, especially during the summer. This assertion is explored by examining historical data from the GLORYS12V1 reanalysis, in which current separation and eddy-shedding events are found and compared with the experimental observations.

Automated summary

A series of rotating tank experiments were conducted to study the behavior of a coastal current encountering a cape and a bay. The experiments revealed that the current surrounds the cape and accumulates negative relative vorticity in front of the downstream bay. The periodicity of the current separation and vortex formation was found to be approximately 16 periods of the rotating system.