Collaborative Research: Speleothem Constraints on Decadal to Orbital Scale Hydroclimate Variations in Mainland Southeast Asia

Rainfall during the Asian summer monsoon (ASM) is a critical water resource for human use, ecosystems, agriculture, energy and industry. The behavior of the ASM varies regionally, and there is a gap in understanding of the variability through time of ASM and the Asian Winter Monsoon (AWM) in mainland Southeast Asia (MSEA), where a greater proportion of rainfall is during the autumn and winter months. This project will reconstruct rainfall intensity on timescales of decades to tens of thousands of years through geochemical measurements of cave deposits from Laos and Vietnam. These measurements, along will climate model simulations, will improve understanding the mechanisms that drive variability of the ASM and AWM, and how this system responds to climate variations through time. This project will use oxygen, carbon, calcium stable isotope ratios and trace elements measured in speleothems, cave monitoring, and hydrogeochemical modeling to reconstruct ASM and autumn/winter monsoon AWM circulation and regional precipitation patterns in MSEA over the last 200 ky. These new data will be synthesized with existing data and isotope-enabled and high-resolution climate model simulations to determine drivers of MSEA hydroclimate variability on millennial to orbital timescales and characterize decadal scale hydroclimate variability and the impacts of coupled ocean-atmosphere dynamics and hydrological extremes on ASM and AWM in different climate states. The project includes support for undergraduate students and PhD students and K-12 outreach events. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.