UC Berkeley

Sediments from the crater lake on Isla Isabela, in the southern Gulf of California, were used to investigate precipitation and evaporation changes in this region over the past 6,000 years. Stable isotopes of oxygen and carbon provided a proxy record of Pacific climate variability on timescales ranging from decadal to millennial. Strength in the dominant periodicities of the Pacific Decadal Oscillation appears to have been intermittent over the past two millennia, suggesting changes in Pacific forcing not previously recognized. In addition, productivity in the lake varies on timescales that suggests a link between increased productivity and solar maxima. Although the precise role of solar activity on climate variations remains unclear, this data represents a convergence of model output with empirical evidence over the past millennium. Over the late Holocene, it appears that there have been a number of pronounced dry periods that generally coincide with cold sea surface temperatures in the eastern Pacific, and generally dry conditions across western North America.