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

合作研究：从西藏湖泊沉积物重建印度夏季季风变化

• 批准号: 1405072
• 负责人: Broxton Bird
• 金额: $ 33.55万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1405072&HistoricalAwards=false
• 关键词: Collaborative; Research; Indian; Summer; Monsoon

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?

印度夏季风直接影响了超过10亿人，但人们对它的多变性知之甚少--降雨量每年大幅增加或减少是正常的还是不正常的。这项研究将通过对青藏高原东南部四个湖泊的海底沉积物采样来研究季风的变异性，这些湖泊被认为保持着一项可以追溯到6000多年前的记录。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、风环流模式和水汽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动植物种群和相互作用，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。将为两名较早的职业科学家、一名博士生和本科生提供支持。研究小组将与印第安纳州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扩展模块，以提高对印第安纳波利斯、印第安纳、美国以及季风地区当地水资源问题的认识。这项研究将利用青藏高原东南部四个高山湖泊的十年分辨沉积物记录，研究全新世印度夏季风的变化。这项拟议的研究建立在NSF以前在年青唐古拉山支持的工作的基础上，年青唐古拉山是夏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。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，可以用放射性技术测定其年代。这些湖泊还具有年代际沉积速率，并包含一系列气候指标，既能反映当地季风变化，也能反映天气变化。该团队将用物理沉积学和地球化学重建当地季风变异性，并用陆地树叶蜡的氢同位素测量重建天气变异性。结果将与青藏高原及其周边地区的古气候记录以及全球气候系统中关键地区(如热带太平洋和北大西洋)的记录相结合，以解决三个核心问题：(I)全新世期间印度夏季风降雨量在十年时间尺度上是如何变化的？(2)是否有证据表明印度夏季风对距今约5300年前的全新世中期全球气候边界条件的变化作出了反应？(3)中世纪气候异常和小冰期对印度夏季风降水有明显影响吗？