CIRCULATION IN THE ENSENADA FRONT - SEPTEMBER 1988

The 3-D circulation of the Ensenada Front, located off southern California and northern Baja California, is examined using hydrographic and mixed-layer drifter measurements. The measurements resolve sub-mesoscale motions (10 km scale) and trace the flow over a 400 km extent, from deep water into the continental margin. Along the Ensenada Front, the cool, relatively fresh, southeastward-flowing waters of the California Current were observed to turn abruptly onshore and flow eastward for approximately 200 km before resuming a southeastward trajectory. Embedded in the onshore flow was a 60 km wide, surface-intensified (>30 cm s(-1)), high speed filament, which bifurcated after resuming a southeastward course, and appeared to feed into a complex set of flows that were strongly influenced by the mesoscale eddy field. Various water mass properties are used to trace the along-front evolution of the filament and its demise. Estimates of vorticity and divergence in the filament are made on the scale of drifter clusters, deployed in diamond patterns with a separation of 10 km. Potential vorticity appears to be conserved along drifter trajectories, and suggests a divergent, upwelling (5 m day(-1)) filament with convergent flow along the sides. Such a pattern is consistent with a model of constant wind stress blowing along the filament.