CHARACTERISTIC PATTERNS OF THE CIRCULATION IN THE SANTA-BARBARA CHANNEL

The subtidal near-surface circulation in the Santa Barbara Channel (SE C) and on the shelf north of Point Conception is described based on ob servations obtained during the 3-year period from 1993 to 1995. Near-s urface currents in the channel are a superposition of a larger-than-SB C scale flow and a cyclonic circulation of variable intensity located inside the channel. On seasonal timescales the larger-than-SEC scale f low near the surface is equatorward in spring and poleward from summer through winter. The increase in equatorward flow in spring occurs con currently with the increase in equatorward wind stress and the decreas e in near-surface temperatures and synthetic subsurface pressures (SSP s). The flow reverses in late spring, simultaneously with the increase in the along-channel SSP difference and months before wind stress has reached its peak. The period during which the cyclonic circulation wi thin the SEC is strongest coincides with the period of strongest polew ard flow through the eastern entrance. A synoptic description of the c irculation in the SEC is presented in terms of six characteristic patt erns, labeled Upwelling, Relaxation, Cyclonic, Propagating Cyclones, F lood East, and Flood West. An analysis of the 5- and 45-m currents int o empirical orthogonal functions (EOFs) isolates 50% (53%) of the 5-m (45-m) low-frequency current variance into three (two) modes. Combinin g these modes with the mean current fields, the modes have spatial pat terns that correspond to the characteristic flow patterns subjectively deduced from inspection of daily averages of the near-surface current s. From late spring through fall the two largest 5-m current modes pro duce a repeating pattern of circulation in which the sequence of four states (namely, Upwelling, Cyclonic, Relaxation, and Quiescent) is tra versed roughly every 16 days. In addition to the large-scale cyclonici ty in the central SEC, smaller cyclonic eddies form frequently in the eastern channel and travel toward the west with an average speed of 0. 06 m s(-1). The patterns described here develop in response to the win d stress and the along-channel SSP gradient.