Interannual forcing mechanisms of California Current transports I: Meridional Currents

In agreement with previous studies, coastally trapped waves dominate large-scale interannual CCS sea surface height variability. In contrast, we find that large-scale alongshore currents (v) are driven predominantly by local wind stress curl variability rather than coastally trapped waves. A simple wind-driven diagnostic model of the time-dependent large-scale geostrophic meridional transport captures ~50% (R=0.7) of the total variance. The local wind-stress curl gradient that controls the largest fraction of meridional transport is not independent of the modulations in atmospheric circulation that drive the Pacific Decadal Oscillation (PDO), and a significant fraction of the monthly transport variability in the model ensembles is correlated to the PDO (R=0.4).