Doctoral Dissertation Research: High-Resolution Time Series of Eastern Sierra California Climate Over the Late Quaternary

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Understanding the severity of past drought events and assessing the linkages of these events to conditions in the eastern Pacific is essential for long-term water resource planning in California and adjacent portions of the southwestern United States. This doctoral dissertation research project will use the remains of aquatic organisms, specifically midge fly larvae, preserved within the sediments of small, climatically sensitive Sierran lakes to reconstruct a high-resolution record of paleotemperature and paleohydrology for California during the late-Quaternary (past 13,000 years). This research is an expansion of an earlier NSF-supported project that assessed how present-day differences in air temperature and precipitation, lake water temperature, salinity, depth, and surrounding vegetation are reflected in the modern elemental chemistry and oxygen isotopic composition of lake waters, and the chironomids (midge flies), cladocera (crustaceans), diatoms (unicellular algae), pollen, and stomates found in Sierran lake sediments. Previous work had determined that the modern distribution of midges in Sierran lakes is controlled by summer surface lake-water temperature, lake depth, elevation, and iron. The relationship between midge fly distributions and surface lake-water temperature also have been characterized through the development of a transfer function (mathematical formulae that express the value of a specific environmental variable as a function of plant or animal species composition data). This dissertation research project will apply the new transfer function to the fossil midge assemblages contained within late-Quaternary lake sediment cores, thereby enabling a high-resolution reconstruction of paleotemperature for California during the late-Quaternary.Earlier paleoenvironmental research in the Sierra Nevada indicates that drought events of greater severity than those experienced during the instrumental period (past 100 years) have occurred in eastern California during the late-Holocene (last 3,000 years). Because of the fragmentary nature of the existing paleoenvironmental records, however, understandings of earlier drought periods is limited. This research project will provide a high-resolution record of the inherent variability of eastern California climate during the past 13,000 years. More specifically, this project will use the remains of midge fly larvae preserved in Sierran lake sediments to provide a sensitive and detailed history of the climatic changes that occurred in the eastern Sierra Nevada, California over the last 13,000 years. The results of this work will assist hydrologists, paleoclimatologists, oceanographers, and climate modelers in understanding the timing, magnitude, and causal mechanisms associated with high frequency climate oscillations evident in California during the late-Quaternary. The expected results should assist water resource managers as they attempt to adequately plan for future water resource needs. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.