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.
