Equilibrium Structure and Dynamics of
the California Current System
Patrick Marchesiello, James C. McWilliams,
and Alexander F. Shchepetkin
Institute of Geophysics and Planetary Physics
University of California at Los Angeles, USA.
We have examined the structure and dynamical mechanisms of regional
and meso-scale physical variability in the Northeast Pacific Ocean
using ROMS. It is configured in subtropical, west-coastal domains that
span the California Current System (CCS), with meso-scale resolution
that currently is as fine as 3.5 km. Its forcing is by the mean
seasonal cycle for atmospheric fluxes at the surface and adaptive
nudging to gyre-scale fields at the open-water boundaries. Its
equilibrium solutions show realistic mean and seasonal states and
meso-scale eddies, fronts, and filaments. We find that the amount of
eddy kinetic energy produced in the model is comparable to drifter and
altimeter estimations in solutions with sufficiently fine resolution,
from which we conclude that the dominant mesoscale variability in the
CCS is intrinsic rather than forced. The dominant eddy generation is
by baroclinic instability of the upwelling, along-shore currents.
There is progressive movement of eddy energy off-shore and downwards
into the oceanic interior in an annually recurrent cycle. The
associated eddy heat fluxes provide the principal balance against the
near-shore cooling by mean Ekman-transport and upwelling. The currents
are highly non-uniform along the coast, with capes and ridges having
very important influences in both maintaining mean standing eddies and
launching off-shore transient filaments and fronts.