The Pacific Decadal Oscillation and marine food webs in the northern California Current: variations in source waters which feed the California Current may be the mechanism which links climate change with ecosystem response


Thursday, June 9, 2011
Redfield Auditorium - 12:00 Noon
Bill Peterson
Northwest Fisheries Science Center, NOAA

Analysis of hydrographic and zooplankton data collected fortnightly in the coastal upwelling zone off Oregon for the past 15 years show that variations in SST, salinity, copepod biodiversity and community structure are correlated with the Pacific Decadal Oscillation.  When the PDO is negative (1999-2002 and 2008-2009), cold salty waters from the Gulf of Alaska feed the northern California Current (NCC) and transport large, lipid-rich copepods to the shelf waters of the NCC; when positive (as in 2003-2007), a greater proportion of warm fresher waters from offshore feed the NCC and transport small, oceanic lipid-poor copepods to the coast.  Thus the basin-scale variations in winds that drive the PDO result in changes in transport that in turn control local food chain structure.  These changes in food chain structure correlate with (and predict) salmon returns to the Columbia River.  Thus to imagine how the coastal upwelling ecosystem of the NCC might react to various climate change scenarios, needed will be a better understanding of how source waters which feed the NCC might change.