Developing a Network of n-Alkane Hydrogen Isotope Records to Identify Drivers and Impacts of Holocene Droughts

该项目将探讨以往干旱的模式和驱动因素及其对人类和生物圈的影响。研究人员将分析湖泊沉积物岩心，以记录与影响更广泛的环加勒比地区（包括美国墨西哥湾沿岸）的大气环流主要驱动因素过去变化相关的降水变化。降水记录将与湖泊流域过去人类活动和生物质燃烧的证据进行比较，以探索大气驱动因素区域变化的当地后果。这项工作将为扩大整个区域的降水重建网络奠定基础，这将使人们能够在更大的空间尺度上检查过程和其他驱动因素。该项目将为四名教师和十名或更多的研究生和本科生提供多实验室合作研究的经验。项目活动的成果将在出版物和专题介绍中广泛传播。研究人员将与田纳西州和北卡罗来纳州的K-12学生和教师分享过去环境变化的科学知识，通过包括实践活动和真实研究的外展项目。研究人员将利用化合物特有的氢同位素分析，对横跨气候和生态系统区域的两个断面上的沿着五个湖泊的沉积物芯中的脂质中的正构烷烃进行分析，从而建立降水记录。沉积物岩心中脂类的氢同位素分析是生物碳酸盐氧同位素分析的替代方法，可应用于各种湖泊，从而有可能使用相同的降水代用品开发一个站点网络。氢同位素记录将从哥斯达黎加湖泊的现有岩心中产生，并将作为研究人员计划通过更广泛的环加勒比地区（包括美国海湾沿海平原）开发的更大降水记录网络的西部锚。氢同位素分析将记录在终端经典干旱（~1200-850 cal yr BP），小冰期（~500-100 cal yr BP）和其他时间的数十年干旱的地理，并揭示这些是例外还是异常干旱的全新世作为一个整体。 与当地古环境和考古证据的比较将显示过去的干旱如何影响植被，火灾制度和史前农业。

This project will address patterns and drivers of past droughts and their effects on humans and the biosphere. The researchers will analyze lake-sediment cores to develop records of precipitation variability associated with past shifts in major drivers of atmospheric circulation that influenced the broader circum-Caribbean region, including the U.S. Gulf Coast. The precipitation records will be compared to evidence of past human activity and biomass burning in lake watersheds, to explore local consequences of regional shifts in atmospheric drivers. The work will form the foundation for an expanded network of precipitation reconstructions across the region that will allow examination of processes at a larger spatial scale and of additional drivers. The project will provide experience in multi-laboratory collaborative research to four faculty and ten or more graduate and undergraduate students. Results from project activities will be broadly disseminated in publications and presentations. The researchers will share scientific knowledge of past environmental change with K-12 students and teachers in Tennessee and North Carolina through outreach projects that will include hands-on activities and authentic research. The researchers will develop precipitation records using compound-specific hydrogen isotope analyses of n-alkanes in lipids in sediment cores from five lakes along two transects that cross climate and ecosystem regions. Hydrogen isotope analysis of lipids in sediment cores is an alternative to oxygen isotope analysis of biogenic carbonates that can be applied in a wide variety of lakes, making possible the development of a network of sites using the same precipitation proxy. The hydrogen isotope records will be produced from existing cores from lakes in Costa Rica, and will serve as the western anchor in a larger network of precipitation records that the researchers plan to develop through the broader circum-Caribbean region, including the U.S. Gulf Coastal Plain. The hydrogen isotope analyses will document the geography of multi-decadal drought during the Terminal Classic Drought (~1200-850 cal yr BP), the Little Ice Age (~500-100 cal yr BP), and at other times, and reveal whether these were exceptional or outlier droughts for the Holocene as a whole. Comparison with local paleoenvironmental and archaeological evidence will show how past droughts affected vegetation, fire regimes, and prehistoric agriculture.