Was The Wet, Wetter and The Dry, Drier? Perspectives From Past Hydroclimate in Western North America

Speaker: Alexandrea Arnold
Institution: UCLA
Location: 7124A
Date: December 6, 2023
Time: 3:30 pm to 4:30 pm


As temperatures warm, understanding how the water cycle will evolve is critical for informed decision making, especially in water-stressed and drought prone regions such as the Western United States. However, in this region, future climate model projections from CMIP (Climate Model Intercomparison Project) disagree on the sign or magnitude of precipitation change. Paleoclimatic proxy data can be used as a ‘test’ case for climate model performance under different climate states, and proxy-model comparison can provide an opportunity to increase process-based understanding and reduce future uncertainty of the water cycle in climate models.

Past intervals that are targets of model intercomparison projects include the Last Glacial Maximum, roughly 21,000 years ago, and subsequent deglaciation, relative to pre-industrial conditions. In this talk, I will show a novel methodology we developed to understand the evolution of the water cycle based on a thermodynamically-based tool, carbonate clumped isotope thermometry (denoted by Δ47), as applied to sediments from lake basins within a hydrologic modeling framework, and describe application to LGM and deglacial samples for five lakes in the region, including comparison with climate model output.