Collaborative Research: P2C2--East African Monsoon Hydroclimate over the Last 11,500 Years

该项目旨在建立洞穴沉积物稳定同位素的代用记录，以辨别东非水文气候的十年至百年尺度变化。该研究地点对全球大气环流的大尺度特征（厄尔尼诺南方涛动、步行者环流、季风系统）敏感，新的水文气候记录将提高对这一关键地区及以外地区十年至千年水文气候变化驱动因素的理解。具体而言，研究人员将：1）使用广泛的铀-钍（U-Th）测年法建立高分辨率的多洞穴地质年代学，以确定东非水文气候变化的持续时间和幅度。这些高分辨率的日期将允许确定活跃的生长间隔与干燥间隔，如整个洞穴网络所示; 2）描述不同过程的作用（例如大尺度大气环流和对流过程、局部陆地-大气过程（如再蒸发等）和岩溶水文过程（如混合，通过监测洞穴现代水文学、分析仪器气候数据和同位素启用气候模型输出，对现代雨水和滴水氧稳定同位素进行监测; 3）对通过U-Th定年靶向确定的几个石笋共享的相对较短的时间间隔（约9000年）进行高分辨率重建。潜在的更广泛影响包括详细了解过去11，500年来东非气候和环境变化的性质、时间和地方/区域范围以及与全球大气环流大规模特征的联系。该项目将为本科生和研究生提供培训，并将有助于培训下一代气候科学家，特别是来自代表性不足群体的气候科学家。重点将放在分析技术，数据分析和建模的交叉培训。该奖项反映了NSF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 build proxy records of speleothem stable isotopes to discern decadal to centennial scale variability in eastern African hydroclimate. The study site is sensitive to large- scale features of the global atmospheric circulation (El nino Southern Oscillation, Walker circulation, monsoon system) and new hydroclimate records will improve the understanding of the drivers of decadal to millennial hydroclimate change in this key region and beyond. Specifically, the researchers will: 1) Establish a high–resolution multi-cave geochronology using extensive Uranium-Thorium (U-Th) dating to determine the duration and magnitude of hydroclimate changes in East Africa. These high-resolution dates will allow identification of active growth intervals vs dry intervals as expressed across the network of caves; 2) Characterize the role of different processes (e.g. large-scale atmospheric circulations and convective processes, local land-atmospheric processes such as re-evaporation etc, and karst hydrological processes such as mixing, recharge) on modern rainwater and dripwater oxygen stable isotopes via the monitoring of cave modern hydrology, analysis of instrumental climate data, and isotope-enabled climate model output; 3) Carry out high-resolution reconstructions of relatively short intervals at ~ 9000 years that are shared across several stalagmites as identified through the U-Th dating targeting. The potential Broader Impacts include generating a detailed knowledge of the nature, timing, and local/regional extent of climatic and environmental changes in Eastern Africa over the last 11,500 years and links to large- scale features of the global atmospheric circulation. The project will provide training for undergraduate and graduate students and will contribute to training of next generation climate scientists particularly from underrepresented groups. Focus will be on cross training in analytical techniques, data analysis, and modeling. This project will facilitate knowledge-based international cooperation with Ethiopian universities.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.