HOLOCENE PALEOCLIMATE RECONSTRUCTION FROM INTEGRATED GEOLOGIC, TECTONIC, GLACIAL, AND HYDROLOGIC MODELING OF THE SOUTH-EASTERN SIERRA NEVADA, GREAT BASIN

Most shoreline records include discrete periods with highstands because of a lack of evidence for lower water levels, thereby offering discontinuous estimates of paleoclimate variability associated with a given lake-level cycle. A new approach was developed to construct a continuous lake-level curve for Owens Lake during last 50,000 years by integrating lake-core data and shoreline geomorphology with wind-wave and sediment entrainment modeling of lake-core sedimentology. The elevations of stratigraphic sites, plus lake bottom and spillway positions were corrected for vertical tectonic deformation using a differential fault-block model to estimate the absolute hydrologic change of the seismically active Owens Lake basin. A coupled watershed-lake hydrologic model controlled by a continuous lake-level calibration curve, paleotemperature from local glacial evidence, and changes in paleo-solar insolation was used to reconstruct precipitation and perennial snowpack extent in the Sierra Nevada. The paleoclimate reconstruction spans 11,500 years and is summarized by precipitation ranging from ~75 to 160% of historical baseline (WY1896–2015) with temperature anomalies ranging from -1.5 to 0.31°C that supported perennial snowpack at ~55–200% of present-day extent. One of the principle findings of this research is the south-eastern Sierra Nevada was cooler and persistent droughts were not as severe during the middle to late Holocene as previously estimated from paleohydrologic modeling of other lakes in the region. The use of a physically-based water balance model that explicitly accounts for changes in solar insolation forcing, glacial ice/perennial snow accumulation, lake salinity, and runoff losses produces simulations that are representative of processes associated with a snow-dominated mountain hydrologic system. Previous paleohydrologic models in the region lacked these key hydrologic components and were controlled by either discontinuous shoreline records, tree-ring proxy data or both, and thus overestimated the severity of droughts and underestimated the intensity of pluvial periods. The new reconstruction can be used to support other paleoclimate archives in the western U.S. by providing quantitative estimates of regional hydroclimate variability during the Holocene.