State of the California Current, Spring 2008-2009: cold conditions drive regional differences in coastal production

Abstract

This report describes the state of the California Surrent system (CCS) between the springs of 2008 and 2009 based on observations taken along the west coast of North America. the dominant forcing on the CCS during this time period were La Nina type conditions that prevailed from the summer of 2007 through early 2009, transitioning to neutral El Nino-Southern Oscillation conditions in the spring of 2009. The Pacific Decadal Oscillation index was negative during this time period and its values had not returned to normal by the spring of 2009. The general effects on the California Current system were stronger than normal southward winds and upselling as well as generally colder that normal SST and shallow nitraclines; however, there were regional differences. Off Baja California sea surface temperatures did not respond to the La Nina conditions; however, concentrations of chorophyll a (Chl a) were significantly above normal, probably due to the anomolously high upwelling off Baja during most of the year. Off southern California there was no clear evidence of increased promary or secondary production, despite observations that previous La Nina conditions affected mixed layer depth, temperatures, nutrients, and nitracline depths. In both central and northern California and Oregon, stronger than normal upwelling increased primary production and prevented potential spawning of sardine north of San Francisco. In central California the midwater fish community resembled that of recent cool years, and cover by kelp was much reduced along the coast. Off Oregon there was evidence of increased abundance of boreal copepods, although the neritic boreal species did not appear to extend as far south as central California. Current predictions are for cooler conditions to change to El Nino conditions by the end of 2009; these are expected to last through the Northern Hemisphere winter of 2009-10.