A 10,000 YEAR RECORD OF PACIFIC DECADAL OSCILLATION (PDO)-RELATED HYDROLOGIC VARIABILITY IN SOUTHERN CALIFORNIA (LAKE ELSINORE, CA)

High-resolution, complete terrestrial records of Holocene climate from Southern California are scarce. Moreover, there are no records of Pacific Decadal Oscillation (PDO) variability – a major driver of decadal-to-multi-decadal climate variability for the region - older than 1000 years. Recent research on Lake Elsinore, however, has shown that the lake's sediments hold excellent potential for paleoenvironmental analysis and reconstruction. New 1cm contiguous grain size data reveal a more complex Holocene climate history for Southern California than previously recognized at the site. A modern comparison between the 20th century PDO index, lake level change, San Jacinto River discharge, and percent sand suggests that sand content is a robust, qualitative proxy for PDO-related, hydrologic variability at both multi-decadal-to-centennial as well as at event (i.e., storm) timescales. A depositional model is also proposed to explain the sand-climate proxy. The sand-hydrologic proxy data reveal nine intervals of wet (+PDO) and dry (-PDO) climate throughout the Holocene. Percent total sand values >1.5 standard deviation above the 150-9800 cal yr BP average are frequent between 9800 and 3300 cal yr BP (n=41), but they are rare from 3300 to 150 cal yr BP (n=6); this disparity is interpreted as a change in the frequency of exceptionally wet (high discharge) years and/or changes in large storm activity. A comparison to other regional hydrologic proxies (10 sites) shows occasional similarities across the region (i.e., 6 of 9 Elsinore wet intervals are present at >50% of the comparison sites). Only the Little Ice Age interval is interpreted consistently across the region as uniformly wet (8 of 10 sites). A comparison to ENSO reconstructions indicates little, if any, correlation to the Elsinore data suggesting that ENSO variability is not the predominant forcing of Holocene climate in Southern California.