Variability on the California shelf forced by local and remote winds during the Coastal Ocean Dynamics Experiment

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Abstract
The coastal response to local and remote wind forcing is examined using observations from the Coastal Dynamics Experiment (CODE) which took place on the northern California coast during 1981 and 1982. The responses to local and remote forcing are determined from multivariate statistical cross‐spectral analysis covering periods from 12 to 2.5 days. Remote forcing is deduced from coastal sea level. This analysis leads to discovery of a mode of sea level variability, apparently a barotropic Kelvin wave, with much greater alongshore and across‐shelf scales than those of coastally trapped waves; there is no measurable response to this mode in coastal temperature or velocity. Coastally trapped waves are also evident and have responses over the shelf much as predicted by theories which account for bottom friction. The local response to wind differs markedly from coastally trapped waves, showing the across‐shelf flow responsible for upwelling, surface‐intensified temperature fluctuations caused by advection and mixing and even the alongshore pressure gradient partly responsible for the across‐shelf return flow which, on the largest scale, balances Ekman transport. Unfortunately, even the extensive CODE observations are inadequate to diagnose the dynamics of the across‐shelf flow or accurately determine the cross‐shelf heat flux supported by eddies and the fluctuating responses to local wind forcing.