ON EXTRACTING PALEOCLIMATE PROXY FROM LAKE RECORDS IN SOUTHWESTERN GREAT BASIN

Quantitative paleoclimate information is necessary for the realistic estimation of groundwater recharge and prediction of future climate change. A physically based catchment-lake model was developed to extract quantitative paleoclimate information over the past 18,000 years from lake records in the Owens River System, California, a hydrologically closed basin including Owens Lake, China Lake, Panamint Lake, and Death Valley Lake. Since the lake serves as an integrator that reflects climatic and hydrologic conditions for the entire catchment, it is sensitive to regional as well as local climatic fluctuations. Shoreline terraces, beach deposits, lake sediments, and fossil data in this chain of lakes document several cycles of pluvial events in the late Quaternary. Studies have shown that these pluvial events were triggered by the global climate change. We used our catchment-lake model to reconstruct the observed paleolake levels for Owens Lake and Searles Lake at key times in the past (18,000, 12,000, 9,000, 6,000, and 3,000 years before present). The initial model inputs were prepared based on regional modern spatial and temporal climate data, boundary conditions from the General Circulation Model, and fossil proxy data. The inputs subsequently were systematically varied in order to produce the observed lake levels. In this way, a large number of possible paleoclimatic combinations can quickly narrow the possible range of paleoclimatic combinations that could have produced the paleolake level and extension. Finally, a quantitative time-series of paleoclimate information for those key times can be obtained.