Why is there an eddy gap in the Northern California Current System?

Delphine Hypolite1, James C McWilliams2, Pierre Damien1, Faycal Kessouri3 and Lionel Renault4, (1)University of California, Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, United States, (2)University of California in Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, United States, (3)University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, (4)University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, United States
Abstract:
The California Current System (CCS) is an eastern boundary upwelling
regime on the United States West Coast (USWC). It has abundant
year-round mesoscale eddy activity generated primarily by baroclinic
instability of the alongshore current, and these eddies in turn
modulate the overturning circulation and primary productivity by
eddy-induced buoyancy advection and burial of partially consumed
nutrients. In a realistic 10-year reanalysis simulation at high
horizontal resolution (dx = 1 km) of the USWC, there is a noticeable
collapse of the offshore eddy field north of Cape Blanco (43 N)
in clear contrast to the CCS eddy field to the south. This behavior
is explained in relation to the seasonal reversal of the alongshore wind,
separation of the alongshore current from Cape Blanco headland,
and other instability characteristics of the 3D seasonal mean currents.