Collaborative Research: Indian Summer Monsoon Variability Reconstructed from Tibetan Lake Sediments

印度夏季季风直接影响着10亿多人，但人们对它的变化知之甚少-每年降雨量的大幅增加或减少是否正常。这项研究将调查季风的变化采样底部沉积物从四湖高在青藏高原东南部，这被认为是一个记录可以追溯到6000多年前。了解变率的范围将有助于改进气候模型，这些模型用于模拟该地区对温度、风循环模式和水分来源的一系列突然和长期变化的反应。此外，了解该地区过去的气候条件将有助于更好地了解该地区的植物和动物种群及其相互作用，以及该地区人类文化的变化。这项工作将加强美国和中国科学机构、科学家和学生之间的国际科学关系。将为两名早期职业科学家提供支持，一名博士。学生和本科生。该研究小组将与印第安纳州的地球与环境科学中心合作，为4至9年级的学生开发一个新的外展模块，以提高印第安纳州印第安纳波利斯当地水资源问题的认识。本研究将利用四个高山湖泊的年代际沉积物记录来研究全新世期间印度夏季风的变化位于青藏高原东南部。拟议的研究建立在以前NSF支持的念青唐古拉山的工作基础上，念青唐古拉山是夏季季风系统的主要活动中心，也是水分进入青藏高原的主要门户。从以前的工作结果表明，该地区的湖泊含有全新世长度的沉积物档案，可以与放射性技术的日期。这些湖泊也有十年的沉积速率，并包含各种各样的气候代理，捕捉当地和天气季风的变化。该小组将利用物理沉积学和地球化学重建当地季风的变化，并利用对陆地叶蜡的氢同位素测量重建天气变化。研究结果将与青藏高原及周边地区的古气候记录以及全球气候系统关键区域（如热带太平洋和北大西洋）的记录进行综合，以解决三个核心问题：（i）全新世期间印度夏季风降雨量如何在十年时间尺度上变化？(ii)在距今5300年前的全新世中期，印度夏季风对全球气候边界条件变化的响应是否有证据？(iii)中世纪气候异常和小冰期对印度夏季风降水的影响是合理的吗？

The Indian Summer Monsoon directly impacts over one billion people, but very little is known about how variable it can be -- whether large increases or decreases in the amount of rainfall from year to year are normal or not. This research will investigate the variability of the monsoon by sampling bottom sediments from four lakes high in the southeastern Tibetan Plateau, which are believed to hold a record stretching back well over 6000 years into the past. Understanding the range of variability will help to improve climate models that are used to simulate the region's response to a range of abrupt and long term changes in temperature, wind circulation patterns, and moisture sources. In addition, understanding the past climate conditions of the region will allow a better understanding of the regional plant and animal populations and interactions, as well as changes in the human cultures of the area. This work will strengthen international scientific relationships between U.S. and Chinese scientific institutions, scientists, and students. Support will be provided for two earlier career scientists, a Ph.D. student and undergraduate students. The research team will collaborate with the Center for Earth and Environmental Sciences in Indiana to develop a new outreach module for 4th to 9th graders that will raise the awareness of issues surrounding water resources locally in Indianapolis, IN, and the United States as well as in the monsoon region.This research will investigate Indian summer monsoon variability during the Holocene with decadally resolved sediment records from four alpine lakes on the southeastern Tibetan Plateau. The proposed research builds on previous NSF-supported work in the Nyainqentanglha Mountains, which are a major center of action in the summer monsoon system and a primary gateway for moisture entering the Tibetan Plateau. Results from previous work demonstrate that lakes in the region contain Holocene-length sediment archives which can be dated with radiometric techniques. These lakes also have decadal sedimentation rates and contain a diverse range of climate proxies that capture both local and synoptic monsoon variability. The team will reconstruct local monsoon variability with physical sedimentology and geochemistry, and synoptic variability with hydrogen isotope measurements on terrestrial leaf waxes. The results will be synthesized with paleoclimate records from the Tibetan Plateau and surrounding region, as well as with records from key regions in the global climate system, like the tropical Pacific and the North Atlantic, to address three central questions: (i) How did Indian Summer Monsoon rainfall vary on decadal timescales during the Holocene? (ii) Is there evidence for an Indian Summer Monsoon response to changing global climate boundary conditions during the middle Holocene at ~5300 years before present? (iii) Did the Medieval Climate Anomaly and Little Ice Age discernibly influence Indian Summer Monsoon precipitation?