Award Date


Degree Type


Degree Name

Master of Science (MS)



First Committee Member

Matthew Lachniet

Second Committee Member

David David Kreamer

Third Committee Member

Zhongbo Yu

Fourth Committee Member

Stanley D. Smith

Number of Pages



The goal of this study was to determine the moisture source of winter precipitation in the central Great Basin for the past 2000 years, and to elucidate the role of Pacific Ocean and North American climate variability modes in driving observed droughts of the region around the Medieval Climatic Anomaly (MCA, ~900-1300 CE). Here a high resolution (~2-4 year) precisely dated moisture source reconstruction is presented from the δ18O values of speleothem LC-1 collected from Leviathan Cave in central Nevada, which reveals significant δ18O variability. I attribute the δ18O variability to changes in winter-season moisture circulation over the past 2000 years, which were likely forced by the Pacific/North American (PNA) teleconnection and associated ocean-atmosphere phenomena. I suggest that lower (higher) δ18O values are indicative of increased (decreased) contribution northern-Pacific sourced moisture during winter months, and this was due to the presence of a more negative (positive) state of the PNA. It was found that during the MCA there was an increase in northern sourced precipitation resulting from the presence of a negative PNA state associated with droughts in the region.


Atmospheric circulation; EL Nino/Southern Oscillation ENSO; El Nino Current; Isotopes; Medieval climatic anomaly MCA; Pacific/North American PNA; Paleoclimatology; Precipitation; Speleothems; United States – Great Basin; Uranium


Atmospheric Sciences | Climate | Geology