Dynamics of mesoscale anticyclones in the California Current System off the Northern Baja California Coast

Abstract:

Subsurface eddies are ubiquitous features in eastern boundary current systems. They tend to modulate the across-shore transport of heat and tracers. In the California Current System they have been observed using different field techniques. Using shipboard measurements, an anticyclonic subsurface eddy was observed in October 2009 off the northern Baja California coast. The genesis, evolution, and turbulent heat transport of the anticyclonic eddy are addressed in this study using a realistic regional model. The oceanic response to the synoptic wind variations acts as finite amplitude perturbation. The hydrodynamic stability of the California Undercurrent is compromised, through baroclinic instability, this lead to the formation of subthermocline eddy that detach from the coast and move out toward the open ocean. The potential vorticity associated to the eddy is eroded by the irregularities of the bottom topography and it is dissipated in the northern Baja California offshore. Once the anticyclonic eddy is weakened, the eddy heat anomaly is reincorporated into the transitional zone by the mean flow. This study shows evidence of reinstatement of the thermal anomalies toward the transitional zone of the southern region of the California Current, helping to keep its water mass relatively warmer than the adjacent sea.