Large-Scale Cross-Shelf Variability in Pigment Concentrations Along the North American West Coast
The seasonal and interannual variability of cross-shelf phytoplankton pigment concentrations along the west coast of North America was analyzed using six years (1979–83, 1986) of CZCS data from the West Coast Time Series. These data were first averaged into 10-daytime periods and then divided into six large-scale (approximately 400 km of coastline) regions within which the cross-shelf pigment concentrations were meridionally averaged. Regional differences in the temporal variability of cross-shelf pigment structure in the California Current were illustrated by comparing these regions. Seasonality was most strongly developed in regions north of Point Conception and was dominated by pigment concentrations exceeding 1.5 mg m−3 extending over 400 km offshore during April–May. Strong interannual variability was evident along the entire study area, from southern Baja to northern Washington. The dominant feature of this variability is the restriction of pigment concentrations greater than 1.5 mg m−3 to within 100 km of the coast over most of the North American west coast during 1983, an El Nino year. Correlations of the cross-shelf pigment structure to along-shore wind stress and U3 in each of the regions was low, suggesting a weak relationship between wind forcing and pigment patterns on the time- and space-scales analyzed.