LATE HOLOCENE CLIMATE INFERENCES FROM A CLOSED BASIN LAKE IN THE LEE OF THE SIERRA NEVADA, USA (Invited Presentation)

Closed basin lakes record hydrologic conditions operating over annual to millennial timescales. Geomorphic indicators of hydroclimate conditions such as shorelines can serve as targets for hydrologic modeling experiments to estimate how different precipitation and temperature regimes were in the past. These experiments also help to place historical wet or dry periods into a paleoclimatic context. For example, how wet was the period coinciding with western U.S. settlement? Did the 2012-2015 California-Nevada drought show similarities to megadroughts during the Medieval Climate Anomaly? Further, using regional and global climate model output, these precipitation and temperature estimates can be used to derive analog climates whose circulations and forcing mechanisms can be explored. Using an existing Late Holocene shoreline record and a calibrated water balance and lake evaporation model of Walker Lake Basin in conjunction with atmospheric reanalysis, we will explore the hydrometeorological processes that control regional hydroclimate in the Sierra Nevada. The modeling approach can help to constrain the frequency and magnitude of occasional wet years during otherwise extreme and persistent droughts. The value of integrated water vapor transport and the importance of atmospheric rivers will be shown to better explain lake level extremes than storm track activity. Some processes controlling Sierra Nevada rain shadow intensity will be discussed. Incorporating the specific meteorological processes that drive western U.S. hydroclimate and their coupled tropical/extratropical origins into explanations of interpreted proxy-based climate variability will improve our understanding of how large-scale climate forcing manifests upon the landscape. Explanations of these processes will be particularly valuable as climate proxy records continue to increase in resolution and spatial coverage.