High-Resolution Climatic Variability in the Southwestern U.S. During the Last Millennium

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Abstract ATM-9615875 Ku, Teh-Lung University of Southern California Title: High-Resolution Climatic Variability in the Southwestern U.S. During the Last Millennium This award supports a research project aimed at developing an effective proxy tool which will enable the PIs to reconstruct the precipitation variability on sub-decadal (3-10 years) time scales for the past millennium in the southwestern U.S. This is a region (at least the southern part) of atmospheric teleconnection associated with the El Nino/Southern Oscillation (ENSO) events. The key approach is to employ the high-resolution oxygen isotopic measurement on dated carbonate sediments retrieved from closed- basin lakes located along a N-S transect in Oregon, California and Nevada. The basis for the approach lies in the fact that water entering a closed-basin lake via rain and runoff mostly leaves by evaporation, and the lake's isotopic composition reflects the hydrologic balance that serves to monitor the regional climate change, especially the precipitation variability, at a given time. Past variations of lake water isotopic composition are recorded by authigenic carbonate minerals of the lacustrine sediment. The feasibility of the proposed research has been tested in a recent study conducted in Mono Lake. The method will allow the PIs to assess the moisture sources (from three climatic regimes: Pacific, continental, and Gulf of Mexico) and their relative strengths and detect any shifts in storm track in the time domain. It is anticipated that the study will allow the PIs to evaluate such climatic anomalies as the Little Ice Age, Medieval Warm Period, and ENSO, and contribute to the understanding of the causes and dynamics of sub-decadal climatic variability.