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From 2003-2005, along the Northern California Current, on the West Coast of North America, went through a warming period similar to those related to ENSO, El Nino - Southern Oscillation events, however, southern waters were in an ENSO neutral state, accompanied by delayed upwelling and a lower plankton biomass (Peterson, 2006). Paleoclimatic data suggest that upwelling in the California current system is positively correlated with temperature over millennial timescales. Furthermore, upwelling along the California coast has increased over the past 30 years, and these increases are expected to continue. There is also the possibility, however, of the waters becoming increasingly stratified, which would likely result in a decrease in upwelling. It is also fairly certain that advection should increase in the California current (Harley, 2006). The upwelling could have a beneficial effect on the ecosystem if it is not too strong, but advection would likely have an adverse effect. One study links some of these changes to a decrease in the population growth rates of the northern California Chinook Salmon. The Salmon numbers were negatively effected by increases in sea surface temperature, curl, scalar-wind and pseudo-wind stress, while positively effected by increased seasonal upwelling (Wells, 2007).
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