Late Pleistocene Paleoclimate Studies in Tibetan Plateau and Adjacent Areas

9614585 Ku晚第四纪古环境记录包含地球过去环境和气候的自然变率信息。这些数据对于理解过去和现在气候变化的机制以及评估气候变化预测的有效性是有价值的。要获得对气候变化过程的全球理解，需要收集和整合区域和多学科证据。值得特别关注的一个重要地区是青藏高原及其邻近地区。青藏高原是地球上海拔最高的大型高原，地质历史较晚，自早第三纪至第四纪以来经历了显著的隆升。它位于中纬度地区，对全球气候有着深远的影响，因为它就像“第三极”，使急流西风带偏转，影响西伯利亚-蒙古高压的位置以及印度和东亚季风的内陆渗透。近年来，中国科学家在青藏高原及邻近地区获得的钻孔沉积物岩心为研究该地区的古环境记录提供了难得的机会。作为一个中美合作项目，本研究旨在提取两个岩心记录的干湿和冷暖条件的古气候信息，一个岩心位于青藏高原西南部海拔4836m的天水海湖(35(20′n, 79(30′e))，另一个岩心位于内蒙古西北角海拔900m的聚盐海湖(42（10′n, 100(05′e)）。这些岩心将使用放射性碳和铀系列同位素进行年龄测定，以确定其晚更新世的年代学，直至大约230ka。采用多代理方法对两个地区的湖泊水位和气候历史以及中国北方黄土高原的古气候记录进行破译。收集到的信息将有助于了解中纬度大陆晚更新世气候变化及其与极地冰芯观测到的快速气候振荡（Dansgaard-Oeschger事件）的可能联系，以及大气环流（包括冬季和夏季季风和西风带）对中国西部古气候的影响。

9614585 Ku Late Quaternary paleoenvironmental records contain information on the natural variability of Earth's past environments and climate. These data are valuable for understanding mechanisms of past and present climate changes and for assessing the validity of climate-change predictions. To gain a global understanding of the climate change process requires assembly and integration of regional and multidisciplinary evidence. One important region deserves special attention is Tibetan Plateau and its adjacent areas. Being the highest large plateau on Earth, Tibetan Plateau has a relatively recent geological history and has undergone significant uplift since the early Tertiary and into the Quaternary. Located at mid-latitudes, it has a profound influence on global climates in that it acts like a "third pole", deflecting the Jet Stream Westerlies and influencing the position of the Siberian-Mongolian Highs and the inland penetration of the Indian and East Asian monsoons. Drilled sediment cores obtained in recent years from the Plateau and adjacent regions by Chinese scientists provide a rare opportunity for studying the paleoenvironmental records in that part of the world. As a U.S.-China collaborative project, the proposed research aims at extracting paleoclimate information in terms of wet/dry and warm/cold conditions recorded by two of the drill cores, one from Lake Tianshuihai (35(20'N, 79(30'E) located in the southwestern Tibetan Plateau at an elevation of 4836m, and the other core from Lake Juyanhai (42(10N, 100(05'E) near the northwest corner of Inner Mongolia at an altitude of 900m. The cores will be age-dated using radiocarbon and uranium-series isotopes to establish their late Pleistocene chronologies up to about 230ka. A multi-proxy approach will be carried out to decipher the lake-level and climate histories of the two regions, as well as with the paleoclimate record of the Loess Plateau in northern China. The information gathered will contribute to the understanding of the late Pleistocene climatic variations in mid-latitude continents and their possible link to the rapid climatic oscillations (Dansgaard-Oeschger events) observed in polar ice-cores, and of the influence of atmospheric circulation (involving winter and summer monsoons and westerlies) on paleoclimates of the western China.