Analysis of the mesoscale structure in the IMECOCAL region (off Baja California) from hydrographic, ADCP and altimetry data

We present geostrophic velocities obtained using hydrographic-altimeter data and direct measurements of currents from 11 cruises offshore of Baja California from January 2000 to July 2002. The study area was dominated by meanders and eddies in geostrophic balance. Two mechanisms of eddy generation were observed; the first associated with the geometry of the coastline, and the second a product of the cooling of the California Current and the California Undercurrent from the South. There were two persistent eddies observed during the study. The first eddy was offshore of Bahia Vizcaino and had an anticyclonic circulation. Situated in the southern region, the rotation of the second eddy was dependant on which current was first to enter the transition zone along the coast. Spring was a transition period characterized by the formation of meanders. The summer brought a period of eddy generation along the coast. Autumn and winter were marked by a separation of eddies from the coast and their subsequent drift towards the west. The phase velocity of the mesoscale eddies was in accordance with the theory of the linear propagation of a Rossby wave.