A RECONSTRUCTION OF COASTAL TEMPERATURES AND UPWELLING INTENSITY ALONG THE CENTRAL CALIFORNIA COAST OVER THE PAST 4000 YEARS

Several studies have documented regional changes in climate during the Holocene (11,000 years ago to present) along the Pacific coast. Very little is known about the climate history of central California. Previous studies have shown that the geochemical composition of mollusk shells records the environmental conditions under which they live. We are measuring the d¹⁸O, d¹³C, Mg/Ca, and Sr/Ca composition of Mytilus californianus (California mussel) shells from Native American middens (shell mounds) at two sites along the central California coast, and from modern sites at several latitudes in the Eastern Pacific. Geochemical data from archeological specimens are compared to data from modern specimens, and used to determine past changes in coastal temperatures and upwelling intensity. These data are used to reconstruct the natural climate variability over the past 4000 years. Preliminary results indicate significant temporal variability in coastal climates.