Abstract for "Studies of the California Current and Undercurrent"

Like the Benguela off Southern Africa, the California Current is an eastern boundary current which exhibits strong mesoscale variability. Two recently completed, large-area, high-resolution surveys of the California Current using ADCP and SeaSoar show that a substantial portion of the equatorward transport in the California Current is provided by a concentrated alongshore current jet, meandering but continuous over hundreds of kilometers, which traces the edge of the front between coastally upwelled water and offshore waters.

Inshore of this front, numerous eddies are observed in AVHRR and in-situ data; one cyclonic eddy was sampled in-situ four times as it traveled WSW at about 0.05 m/s from its point of origin off Point Arena. During June, eddies inshore of the front were 40-70 km across, with intensities of f/3, while in August, eddies were larger (70-90 km) and the circulations somewhat intensified (to f/2). Eddy circulations extended below 200m, with anticyclones tending to be more prominent at depth than the cyclones.

As part of the same study, the variability in the California Undercurrent during 1992-1994 was measured with a coherent array of five current meter moorings deployed over the continental slope. The Undercurrent was highly polarized along the bathymetry and strongly trapped to the inner slope; maximum poleward flow was seen at the 150m instrument. Empirical orthogonal function analysis shows that the strongest mode of variability in the subsurface currents was a fluctuation in the alongshore current, with a strong spectral peak at a period of about 60 days. ADCP measurements from a survey of closely-space cross-slope transects covering a large latitude range (35-47N) show a nearly ubiquitous poleward undercurrent, with core velocity averaging 0.24 m/s.

Move up one level.