Developing a Novel Temperature Proxy to Test Hypotheses about Atmospheric Circulation in Western North America during the Last Deglaciation

Kowler Andrew, Tucson AZ

Investigators

Abstract

Dr. Andrew Kowler has been awarded an NSF Earth Sciences postdoctoral fellowship to implement a research and broadening participation plan at the University of California - Los Angeles, in collaboration with Northern Arizona University. The research project will answer fundamental questions about controls on water balance in western North America through refinement of clumped isotope paleothermometry, which will allow utilization of gastropod shells for reconstructions of ancient air temperatures. This project will make a valuable contribution to the understanding of the driving forces behind this region's long-term hydroclimatic sensitivity. Exportation of this work will enable similar evaluations to be conducted for wet intervals that occurred in other arid regions, leaving climate models better equipped to examine possible regional responses to anthropogenic perturbations of the global climate system. Moreover, the economic and cultural well-being of traditionally underrepresented Native American populations depends upon the availability and sustainability of hydrologic resources in both urban and rural areas. The proposed broadening participation activities address this through establishment of a direct link between existing educational and conservation initiatives. The PI will partner with established organizations that work with Native Americans (like Spring Stewardship Institute, Northern Arizona Univeristy Tribal Environmental Professionals, GLOBE, UCLA's American Indian Program, and USDA Extension offices) to map and characterize springs, develop curriculum on hydrological survey methods for high school students, provide field experiences, and share data with local communities. This study addresses a fundamental question in climate dynamics by quantifying air temperature changes associated with wet intervals in the now-arid southeastern Basin and Range, during and after the Last Glacial Maximum (LGM: ~24-19 Ka). Specifically, clumped isotope geochemistry will be used to test the core assertion of the "Monsoon" hypothesis that LGM age lakes and wetlands in the southern Basin and Range primarily resulted from a reduction in summertime evaporation, in contrast to H1 highstands which occurred in response to warmer, wetter summers, 17.5-14.5 Ka. Results from this study would shed much needed light on the climatic significance of speleothem- and lake core-based proxy records, now the staple of climate model validation efforts. This, in turn, will markedly improve meso-scale climate simulations of short-lived intervals of atypical, yet poorly understood modes of atmospheric circulation that led to wetter conditions in the past. Improved models will also inform current understandings of the relationship between temperature and long-term drought, a topic of intense interest to the Southwestern paleoclimatological community.