P2C2: Evaluating Mean Annual Precipitation in the Southwestern United States (US) during the Pliocene-Pleistocene Transition Using Nitrate D17O Anomalies

本项目旨在建立上新世-更新世过渡时期（1-3百万年）美国西南部降水新记录。研究人员建议使用一种新的降水同位素示踪剂：土壤硝酸盐17O异常。分析将在加利福尼亚死亡谷的信心山古湖沉积物中进行。这种类型的干旱环境适合硝酸盐沉积。主要目标是利用土壤硝酸盐17O异常来评估年平均降水量的定量变化，并将其与沉积环境变化等气候变化的定性标志联系起来。新数据将作为上新世-更新世降水变化模型模拟的试验台。潜在的更广泛的影响包括开发一个长期的定量降水记录，测试和应用一种新的同位素示踪剂，用于陆地沉积物的降水重建，并在深度时间尺度（1-3百万年）上提供关键的数据输入，以测试上新世-更新世气候模型。该项目将指导两名本科生和一名研究生（将从部落本科院校招收博士生）。美国本土K-12学生实地考察被纳入到该项目中，并将由来自普渡大学的两名美国本土学生领导。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project aims to develop a new precipitation record in Southwestern US during the Pliocene-Pleistocene transition (1-3 Million years). The researchers suggest to use a new isotopic tracer of precipitation: soil nitrate 17O anomalies. The analyses will be carried out on sediment samples collected from the Confidence Hills paleo- lake deposits in Death Valley, CA. This type of arid environment is suitable for nitrates deposition. The main objective is to assess quantitative changes in mean annual precipitation using soil nitrate 17O anomalies and link it to qualitative markers of climate variations such as shifts in depositional environments. The new data will serve as a test bed for model simulations of Pliocene-Pleistocene changes in precipitation.The potential Broader Impacts include developing a long quantitative precipitation record, testing and applying a new isotopic tracer for precipitation reconstruction from terrestrial sediments, and providing a critical data input at deep time-scales (1-3 Million years) to test Pliocene-Pleistocene climate models. Two undergraduate and one graduate student (PhD student to be recruited from tribal undergraduate colleges) will be mentored through the project. A Native American K-12 student field trip is incorporated in to the project and will be led by two native American students from Purdue University.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.