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

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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.