AGS-PRF: Seasonal-resolution Examination of Asian Monsoon Dynamics as Recorded in Chinese Speleothems

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This Postdoctoral Research Fellowship (PRF) teams a recent Ph.D. from the University of Wisconsin with expereinced paleoclimate researchers to study the Asian monsoon system using Chinese cave deposits. Orland's graduate research documented the potential for using ion microprobe measurements of oxygen isotopes in speleothems to develop extremely high-resolution paleoclimate records. He plans to apply this technique to the collection of cave deposits from China that in the last decade have proven to be among the most influential paleoclimate records of orbital and millennial scale climate changes during the late Quaternary. Orland will test three competing hypotheses about the causes of the isotopic changes in the Chinese speleothem records: 1) the degree to which the ratio of summer and winter monsoon precipitation affects the average annual isotopic composition, 2) whether changes in summer rainfall and winter temperatures are controlling the isotopic composition of the rainfall, or 3) whether an overall stronger monsoon system increases the isotopic composition but does not alter the ratio of summer and winter rains. By resolving annual variability in oxygen isotopic composition--which is only possible using methods developed by the PI--he will be able to choose among these three different hypotheses and isolate the causes of the long term changes observed in the speleothem stable isotope records.The broader impacts of this project include strong postdoctoral training and mentoring. In addition the scientific results should provide better understanding of monsoon dynamics under different climate boundary conditions.