A Holocene record of Pacific Decadal Oscillation (PDO)-related hydrologic variability in Southern California (Lake Elsinore,CA) |
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Authors: | M E Kirby S P Lund W P Patterson M A Anderson B W Bird L Ivanovici P Monarrez S Nielsen |
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Institution: | (1) Department of Geological Sciences, California State University, Fullerton, Fullerton, CA 92834, USA;(2) Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA;(3) Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada;(4) Department of Environmental Sciences, University of California, Riverside, Riverside, CA 92521, USA;(5) Byrd Polar Research Center, The Ohio State University, Columbus, OH 43210, USA |
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Abstract: | High-resolution 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 1,000 years. Recent research on Lake Elsinore, however, has shown that the lake’s sediments hold excellent potential
for paleoenvironmental analysis and reconstruction. New 1-cm 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 twentieth century
PDO index, lake level change, San Jacinto River discharge, and percent sand suggests that sand content is a reasonable, qualitative
proxy for PDO-related, hydrologic variability at both multi-decadal-to-centennial as well as event (i.e. storm) timescales.
A depositional model is proposed to explain the sand-hydrologic proxy. The sand-hydrologic proxy data reveal nine centennial-scale
intervals of wet and dry climate throughout the Holocene. Percent total sand values >1.5 standard deviation above the 150–9,700 cal year
BP average are frequent between 9,700 and 3,200 cal year BP (n = 41), but they are rare from 3,200 to 150 cal year 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 more then occasional similarities
across the region (i.e. 6 of 9 Elsinore wet intervals are present at >50% of the comparison sites). Only the early Holocene
and the Little Ice Age intervals, however, are interpreted consistently across the region as uniformly wet (≥80% of the comparison
sites). A comparison to two 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. |
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