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

这个博士后研究奖学金（PRF）将威斯康星大学最近的博士与经验丰富的古气候研究人员联合起来，利用中国的洞穴沉积物研究亚洲季风系统。Orland的研究生研究记录了使用离子探针测量洞穴中氧同位素的潜力，以开发极高分辨率的古气候记录。他计划将这项技术应用到中国洞穴沉积物的收集中，这些洞穴沉积物在过去十年中已被证明是第四纪晚期轨道和千年尺度气候变化的最具影响力的古气候记录之一。Orland将测试关于中国洞穴记录中同位素变化原因的三个相互竞争的假设：1)夏季和冬季季风降水的比例对年平均同位素组成的影响程度，2)夏季降雨和冬季气温的变化是否控制了降雨的同位素组成，或3)一个整体更强的季风系统是否增加了同位素组成，但没有改变夏季和冬季降雨的比例。通过解决氧同位素组成的年度变化——这只能通过PI开发的方法实现——他将能够在这三种不同的假设中进行选择，并分离出在洞穴稳定同位素记录中观察到的长期变化的原因。该项目更广泛的影响包括强大的博士后培训和指导。此外，科学研究结果还有助于更好地理解不同气候边界条件下的季风动力学。

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.