California Undercurrent variability and eddy transport estimated from RAFOS float observations

RAFOS float observations collected between 1992 and 2002 were analyzed to identify the seasonal variability of circulation in four geographical boxes which extended along the central and northern California coast and were successively located farther offshore. The mean pressure of the floats was 375 dbar. Poleward flow associated with the California Undercurrent dominated the two boxes closest to shore, extending from the 400‐m isobath to a distance of 190 km offshore. For the box closest to shore, the monthly mean alongshore velocity was maximum (minimum), 5.4 cm/s (1.7 cm/s), in May–June (February), while the eddy kinetic energy (EKE) was minimum was 33 cm 2 /s 2 (21 cm 2 /s 2 ) in September (December–February). The mean EKE in the coastal region was 28 cm 2 /s 2 , increasing to 50 cm 2 /s 2 for the region farthest offshore, a distance of about 400 km. For that region farthest offshore, EKE had a broad maximum from June to November and a minimum in April. Lagrangian correlation and dispersion tensors were estimated for floats that left the coastal region. Three different dispersive regimes of float motion were identified as ballistic transport, normal diffusion, and anomalous sub‐diffusion. Westward sub‐diffusion was induced by Rossby wave‐like structures with a periodicity of 100–120 days.