Nearsurface pattern in the California Current: coupling between physical and biological structure

The results of a four-year program of continuous nearsurface mapping and a 12-year time series of nearsurface chlorophyll measurements, both made by t he CalCOFI program, are interpreted in the context of the CalCOFI hydrograp hic time series. There are consistent regional differences in the mechanism s affecting nutrient input to the upper layers, and these result in differe nt spatial and temporal patterns of chlorophyll concentration. We define th ree regimes in which nearsurface ecosystem structure appears to be regulate d differently. A sharp physical and biological front at the inner edge of t he low-salinity California Current jet separates offshore and inshore regio ns. The inshore area is further divided into northern and southern regions based upon the intensity of isopycnal shoaling, which alters the relationsh ip between physical structure and chlorophyll concentration. These observat ions indicate that even on the scale of the CalCOFI area a regional approac h to developing models and interpreting mesoscale structure will improve ou r understanding of important physical-biological interactions. (C) Elsevier Science Ltd. All rights reserved.