Cross-shelf phytoplankton pigment variability in the California Current

A. Thomas et Pt. Strub, Cross-shelf phytoplankton pigment variability in the California Current, CONT SHELF, 21(11-12), 2001, pp. 1157-1190
Citations number
Categorie Soggetti
Aquatic Sciences
Journal title
ISSN journal
0278-4343 → ACNP
Year of publication
1157 - 1190
SICI code
Five years (1979-83) of satellite ocean color data from the coastal zone co lor scanner (CZCS) data are used to calculate cross-shelf transects of phyt oplankton pigment concentrations in the California Current and quantify the ir seasonal and interannual variability. Alongshore means over six regions. , Washington-northern Oregon (48.4-42.8 degreesN), Cape Blanco to Cape Mend ocino (42.8-40.4 degreesN), northern California (40.4-37.8 degreesN), centr al California (37.8-34.5 degreesN), northern Baja (32.5-29.4 degreesN) and southern Baja (27.9-22.9 degreesN) are used to contrast latitudinal differe nces. The general seasonal cycle shows minimum cross-shelf pigment extensio ns in March (2.0 mg m(-3) isoline within 80 kin of shore). expansion of pig ment concentrations offshore in April and May often to the annual maximum ( 2.0 mg m-(3) isoline up to 200 km offshore), a mid-summer (July-August) red uction in cross-shelf extension followed by a late summer (September) expan sion and a fall collapse back towards the coast by late October. Amplitude of this seasonal pattern is minimum along the northern Baja coast and stron gest off central California. Strong interannual variability is evident in b oth the timing and strength of these seasonal features. The most latitudina lly consistent pattern of interannual variability is of negative anomalies and reduced concentrations during the 1983 El Nino. Time series of cross-sh elf pigment distribution are compared quantitatively with concurrent alongs hore wind stress and wind mixing (U*(3)) from each region. Maximum correlat ions occur when pigment lags wind forcing by 1 or 2 ten-day periods. Strong est correlations are in the region from Cape Blanco to Cape Mendocino. Corr elations are weaker both in the Pacific Northwest and off Baja. Correlation s which excluded the anomalous conditions of 1983 are stronger in the three regions from Cape Blanco south to Point Conception suggesting that connect ions to wind forcing are stronger during non-El Nino years in these regions . Lastly, preliminary comparisons of the CZCS seasonal cycles are made to t hose evident in the first 19 months of SeaWiFS chlorophyll data which inclu de the strong 1997-98 El Nino. (C) 2001 Elsevier Science Ltd. All rights re served.