Tracing the Late Quaternary Record of the Asian Monsoon System: Paleoclimate History from the Qinghai Lake Drilling Project

大型内陆湖泊保存着过去大陆气候变化的详细沉积记录。这些与海洋沉积物重建的记录形成对比，并补充了这些记录。最近的研究强调了湖泊沉积物对于理解过去气候变化背后的机制及其对人类的影响的重要性。亚洲内陆的气候条件在很大程度上受亚洲季风系统的控制。在全球变暖的背景下，亚洲内陆旱地生态系统正在干旱化和随之而来的退化，导致迫切需要了解亚洲季风系统的长期动态及其与全球气候模式的关系。该地区晚第四纪以来的长期、高质量的古气候记录十分罕见，以往的古气候研究主要集中在青藏高原边缘地区的黄土-土壤序列。这些记录足够详细，可以在轨道变化和海因里希事件的尺度上追踪第四纪期间的大陆气候波动。然而，千年尺度气候事件的长期记录，这已被认为是全球表达，尚未检索到黄土高原，因为相对较低的积累率。有限数量的先前研究使用冰芯，湖泊序列，树木年轮在青藏高原上提供了一个更详细的图片季风系统的冰后期变化，但系统的长期行为还没有得到充分的定义。在国际大陆钻探计划（ICDP）和中国科学院（CAS）的支持下，于2005年夏季在青藏高原东北缘青海湖成功地钻探了几个长岩心。因此，这些核心的高分辨率分析可能会打开一个窗口，亚洲季风系统的过去的变化。该项目使用了一个来自湖中心的90米长的岩芯，将对花粉、粒度和沉积物的化学成分进行高分辨率分析和测量。 青海湖的一个主要优势是，它受到亚洲冬季风和夏季风的影响，其位置接近目前夏季风的渗透极限，使其对变化特别敏感。其他优势包括更高的积累率（与黄土高原相比）和更长的沉积历史（与冰芯和以前的湖泊记录相比）。这些数据将为研究晚第四纪亚洲季风系统的动力学提供新的视角。此外，与南海、阿拉伯海、北大西洋的海洋记录以及古利亚、敦德和格陵兰的冰芯记录的对比将有助于我们理解高纬度与季风区之间气候遥相关的机制。该项目将作为培训一名新研究生和支持一名中国大湖天文台博士后的基础，加强研究生的研究和教育。钻探项目的总体领导者是中国，因此这里提出的工作将促进重要的中美合作和科学交流，因为他们共同努力产生所需的分析数据，以解开青海湖沉积物中记录的故事。

Large inland lakes hold detailed sedimentary records of past changes in continental climate. These contrast with and complement records reconstructed from marine sediments. Recent studies have emphasized the importance of lake sediments for understanding mechanisms behind past climate changes and their impact on humans. Climate conditions in the Asian interior, to a large extent, are governed by the Asian monsoon system. Within the context of global warming, the ongoing aridification and associated degradation of the dryland ecosystem in the Asian interior leads to an urgent need to understand the long-term dynamics of the Asian monsoon system and its relationship to global climate patterns. Long and high quality paleoclimate records back through the late Quaternary are rare in this area, and previous paleoclimate studies mainly focused on loess-soil sequences in the marginal areas of the Tibetan Plateau. Such records are detailed enough to trace continental climate fluctuations during the Quaternary on the scale of orbital variation and Heinrich events. However, long records of millennial-scale climate events, which have been suggested as being expressed globally, have not been retrieved from the Loess Plateau because of relatively low accumulation rates. A limited number of prior studies using ice cores, lacustrine sequences, and tree rings on the Tibetan plateau give a more detailed picture of postglacial changes in the monsoon system, but the longterm behavior of the system has not been adequately defined. Under the auspices of the International Continental Drilling Program (ICDP) and the Chinese Academy of Sciences (CAS), several long cores were drilled successfully from Qinghai Lake on the northeastern margin of the Tibetan Plateau during the summer of 2005. High resolution analyses of these cores therefore may open a window to the past changes in the Asia monsoon system. This grant uses a 90-m-long drill core from the center of the lake, on which high-resolution analyses and measurements of pollen, grain size, and the chemical composition of sediments will be carried out. A major advantage of Lake Qinghai is that it is affected by both the Asian winter and summer monsoons and its location near the limit of penetration of the present summer monsoon makes it especially sensitive to changes. Other advantages include the higher accumulation rate (compared to the Loess Plateau) and longer sedimentation history (compared to ice cores and previous lake records). The data will provide a fresh look at the dynamics of the Asian monsoon system during the late Quaternary. Furthermore, comparisons with marine records from the South China Sea, Arabian Sea, North Atlantic, as well as ice-core records from Guliya, Dunde, and Greenland will aid our understanding of the mechanism of climate teleconnection between high latitudes and monsoonal areas. This project will enhance graduate research and education by serving as the basis for training one new graduate student and supporting a Chinese postdoc at the Large Lakes Observatory. The overall lead in the drilling project is China, so the work proposed here will foster significant Chinese-American collaboration and scientific exchange as they work together to produce analytical data needed to unravel the story recorded in Lake Qinghai sediments.