TRACKING HOLOCENE HYDROLOGY IN HIGH SIERRA NEVADA, CALIFORNIA

Sediments from the Baboon Lakes, Sierra Nevada, California, offer insight into the hydrology of the American West over the last 12,000 years. Some paleoclimate literature has associated periods of past abrupt climate change in this region with shifts in the position and intensity of the Northern Hemisphere Westerlies (NHW). This is due to their control on regional temperature and precipitation. However, few records have documented past shifts in wind patterns independently from precipitation amount proxies. The Sierra Nevada are key, as the mountains steer incoming storms either north or south of the range, depending on location of the westerlies. This region is not only a potential contributing factor to the spatial pattern of droughts in the American West, but also is ideal for precipitation-source tracking, as the difference in storm-track position, and thus isotopic values of precipitation, between north and south-shifted positions of the wind belt is large. An understanding of the influence of the wind belt on regional precipitation patterns, as well as the mechanisms behind NHW shifts, will help inform models used to predict precipitation patterns and the snowpack levels of the Sierra Nevada and Great Basin region more accurately.

Here, we present a modern calibration of surface waters and local vegetation plant waxes, as well as a 12,000-yr-long plant-wax isotope paleoclimate record from the Baboon Lakes (3,400 m asl) of the high Sierra Nevada Plant wax biomarkers, specifically n-alkanes, can provide independent information on plant community composition and productivity, relative evapotranspiration rates, precipitation sourcing, and water availability for a specific basin. We pair these isotopic analyses with pollen assemblage and charcoal data from the same sediments to assess any associated variations in plant communities and fire history. Together, these proxies will afford information on precipitation changes and the relative position of the NHW compared to our field site. Preliminary results suggest that hydrologic shifts are paired with coeval changes in plant community and overall fire activity. Further comparison to published records across the Great Basin will facilitate a regional scope on the past impacts of the NHW.