View of Dry Lake from Mt. San Gorgonio

Mt. San Gorgonio

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A 9000-year Record of Long-Term Climate Change and Abrupt climate events from Dry Lake, Southern California

Dry Lake is located in the San Bernardino Mountains of Southern California near Big Bear Lake. The lake is usually dry during recent times except during unusually wet years with heavy winter snows. Geophysical and sedimentological studies of the lake reveal that the basin contains at least a 9000-year record of climate variability. High lake levels between 9000 and ~6400 cal yr B.P. show that the early Holocene was generally wetter than the present. A relatively short lived cool and dry event occurred between ~8400 and ~8100 cal yr B.P. at Dry Lake. We suggest that this early Holocene event is contemporaneous with the 8.2 ka event, which was first observed in the Greenland ice cores. After ~6400 cal yr B.P., Dry Lake shows an overall drying trend with diminishing lake levels. The late Holocene from ~4500 cal yr B.P. to present is similar to the modern, with persistently low lake levels. The observed lake level changes at Dry Lake correlate well with orbital changes in solar insolation. We suggest that changes in summer insolation over the course of the Holocene influenced sedimentation dynamics at Dry Lake through moderation of the North American Monsoon.