Environmental disequilibrium, fire, and erosion in response to abrupt climate change and climate teleconnections during the Holocene in the Sierra Nevada, California

There is concern that additional global warming could trigger destructive changes in the Earth's climates. There is also scientific disagreement concerning the global extent of abrupt climate change events during the Holocene. This study investigated the environmental effects of abrupt climate change over the past 8,500 yrs. I tested the hypothesis that Coburn Lake charcoal peaks represent stand-replacing fires in the Coburn Lake watershed in response to climate change. I compared the timing of Coburn Lake charcoal peaks with high-resolution precipitation and temperature chronologies from the Sierra Nevada and Greenland. Coburn Lake charcoal peaks were associated with inputs of organic detritus and inorganic sediments into the lake. Coburn Lake charcoal peaks were deposited at the beginning of droughts in the northern Sierra Nevada, usually during overall moister climate intervals, over the past 8,500 yrs. For at least the last 2,000 yrs, the beginnings of these droughts also coincided with extreme cold temperatures or abrupt temperature change. These results suggest an hypothesis that abrupt climate change during the late Holocene caused vegetation and mountain slopes around Coburn Lake to be seriously out of balance with changing climates; resulting in forest die-off, stand-replacing fires, and severe soil erosion. Coburn Lake charcoal peaks also coincided with peak drought conditions in Greenland over the last 8,500 yrs, including during the 8,200 yr event. These results suggest climate teleconnections between the Sierra Nevada and Greenland over the last 8,500 yrs. The out-of-phase character of the relationship between Sierra Nevada and Greenland droughts, wet in the Sierra Nevada while peak drought conditions prevailed in Greenland, suggests north-south migration of polar fronts during periods of abrupt climate change during the Holocene. Finally, the results support the appropriate use of individual charcoal peaks as evidence of past abrupt climate change.