Subsurface eddies in the northern Baja California oxygen minimum zone

Abstract:

Subthermocline (subsurface) eddies might be a common feature in eastern boundary currents. During October 2009 a high-resolution survey was carried out off northern Baja California to investigate subsurface eddies. Ocean currents velocities were obtained with a ship-mounted ADCP and with a Lowered-ADCP that was deployed with the Rosette-CTD system. We found a mesoscale anticyclone eddy at the San Quintin Basin oxygen minimum zone. The diameter of the core of the eddy was 64 km. The core of the eddy was warm (11 °C), salty and with low-oxygen concentration (1 ml/l): water properties, which were similar to those of the California Undercurrent off northern Baja California. The eddy showed a swirl velocity of 22 cm/s, a rotational period of 11 days and a Rossby number of 0.14. A discussion about the oceanographic settings and about the generation process of the eddy is presented. Numerical modeling studies of the mesoscale dynamics of the southern region of the California Current revealed that the California Undercurrent induce anticyclone eddies at the San Quintin Basin. As well as we discuss the ecological impact of subthermocline eddies from the San Quintin oxygen minimum zone on the adjacent environment.