The California Current system off Monterey, California: physical and biological coupling

Abstract

Repeated hydrobiological surveys over the period 1988-2002 perpendicular to the central California coast indicate strong coupling between physical circulation and biological production. An equatorward-flowing jet about 100-200 km from shore marked the inshore edge of the California Current. This "CC Jet" had its highest valocities during late winter and spring. The jet divided inshore, biologically productive waters from offshore, low-production waters. Mean flow in the inshore waters is poleward. However, this flow is interrupted in late spring and summer by a surface-enhanced, equatorward-flowing, coastal upwelling jet. The upwelling jet coincides with maxima of nutrients, chlorophyll-a and primary production. Annual variability in the inshore zone is related to (1) vertical pycnocline movements associated with geostrophic adjustments to accelerations of the California Current system, and (2) coastal upwelling. In offshore waters, the annual cycle accounted for a small fraction of the variability, indicating the dominance of eddies and meanders in this zone (J. Geophys. Res. 92 (1987) 12947). The offshore regime was mesotrophic to ogliotrophic, with a subsurface chlorophyll-a maximum above the nutricline. Considerable subduction may occur under the California Current jet and be an important process in the export of biogenic material to the deep sea.