Residual heights from Geostat (11/86-10/88, Figure 1b), TOPEX (12/92-12/96) and ERS-1 (10/92-12/93) (Figure 1c) are added to a climatological mean dynamic height relative to 500 m (Figure 1a) and gridded to form 2-month and 3-month mean pictures of seasonal changes in circulation. Tide gauge heights increase coverage next yo the coast.

A 29-year (1967-1996) mean annual cycle of daily Bakun indices (Figure 2a, positive for equatorward wind stress) is subtracted from a similar mean annual cycle formed over the 6 altimeter years (Figure 2b). The difference (Figure 2c) shows that summer wind stress was slightly weaker and winter forcing was stronger than the long-term mean. Some of the difference may come from changes in the FNOC atmospheric model between 1967 and 1987-1996.

The altimeter height fields (Figure 3) show the poleward Davidson Current in winter and the equatorward California Current (CC) jet that begins near the coastt in spring and moves steadily offshore until fall. Shading shows that water from the west wind drift only affects the region offshore of the CC jet core during most of the year, except in the Southern California Bight. The region inshore of the core of the CC jet is colder and richer due to coastal and offshore upwelling, as shown by overlaying 3-month seasonal means of altimeter data on AVHRR SST (Figure 4) and CZCS surface pigment concentrations (Figure 5). Both poleward and equatorward jets connect to the subarctic Alaska Gyre along the boundary off Vancouver Island. We hypothesize that interannual variability in water properties off central California comes more from the upstream boundary currents than from the interior west wind drift (WWD).

Continues in PART 2...

---

PART 1 PART 2 PART 3

---

Any Questions? e-mail me.