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

追踪亚洲季风系统晚第四纪记录：青海湖钻探工程的古气候历史

• 批准号: 0602412
• 负责人: Steven Colman
• 金额: $ 32.53万
• 依托单位: University of Minnesota Duluth
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-10-01 至 2011-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0602412&HistoricalAwards=false
• 关键词: Tracing; Late; Quaternary; Record; Asian

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.

大型内陆湖泊保存着大陆气候过去变化的详细沉积记录。这些记录与从海洋沉积物中重建的记录形成对比和补充。最近的研究强调了湖泊沉积物对于了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支配。在全球变暖的背景下，亚洲内陆旱地生态系统的持续干旱化和相关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。本区晚第四纪以来长而优质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。这样的记录足够详细，足以追踪第四纪期间轨道变化和海因里希事件规模的大陆气候波动。然而，由于积累率相对较低，黄土高原没有检索到千年尺度气候事件的长期记录，这些事件被认为是在全球范围内表达的。以前使用青藏高原冰芯、湖泊序列和树木年轮进行的有限数量的研究给出了冰川后季风系统变化的更详细的图景，但该系统的长期行为还没有得到充分的定义。2005年夏季，在国际大陆钻探计划(ICDP)和中国科学院(CAS)的支持下，在青藏高原东北缘的青海湖成功地钻出了几个长岩心。因此，对这些核心的高分辨率分析可能会打开一扇窗，了解亚洲季风系统过去的变化。这笔赠款使用了一个90米长的钻芯，在上面将对花粉、颗粒大小和沉积物的化学成分进行高分辨率的分析和测量。青海湖的一个主要优势是同时受到亚洲冬季风和夏季风的影响，其位置靠近当代夏季风的穿透界限，对变化特别敏感。其他优势包括较高的堆积速率(与黄土高原相比)和较长的沉积历史(与冰芯和以前的湖泊记录相比)。这些数据将提供一个新的视角，了解亚洲季风系统在第四纪晚期的动态。此外，与南中国海、阿拉伯海、北大西洋的海洋记录以及古里雅、敦德和格陵兰的冰芯记录进行比较，将有助于我们理解高纬度和季风区之间的气候遥相关机制。该项目将加强研究生研究和教育，作为培训一名新研究生的基础，并支持大湖观测站的一名中国博士后。钻探项目的总体负责人是中国，因此，这里提出的工作将促进中美之间重要的合作和科学交流，因为他们共同努力，产生必要的分析数据，以揭开青海湖沉积物中记录的故事。