Lagrangian surface circulation in the Gulf of California from a 3D numerical model

The surface circulation of the Gulf of California was studied from a Lagrangian point of view using the results of a 3D numerical model. The advection of particles, whose depth is fixed, was carried out for annual and monthly periods with 710 particles homogeneously distributed over the gulf. An anticyclonic circulation was found at the northern region from October to May and in the central and southern regions during May and from October to November; cyclonic circulation was found in the entire gulf from July to August. This circulation pattern agrees with direct measurements of drifters in the northern region. During the cyclonic period the particles from the central and southern regions travel to the northern basin where they are trapped by a gyre for more than a month. On the other hand, during the anticyclonic period the particles flow to the southern part of the gulf. Some particles escape to the Pacific Ocean and others remain in the gulf and return to the northern part during the cyclonic period. The principal gyre that appears on the center of the northern gulf in both cyclonic and anticyclonic periods traps particles for more than 30 days in a radius of 50 km. In the central and southern regions, a trapping zone was found in the peninsula side, where the particles travel less than 100 km in 30 days. On the other hand, over the continental coast there is a rapid transit zone. The particles escape only during the anticyclonic period.