PROGRESS IN STUDIES OF TIBETAN PLATEAU AND GLOBAL ENVIRONMENTAL CHANGE

The progresses in studies of Tibetan Plateau and global environmental change are introduced briefly, which are summarized as follows. The Tibetan Plateau was subjected to twice cycles of uplift and planation in the Tertiary. And the plateau began to uplift again in 7MaBP, and has experienced intense uplift since 3.6MaBP. The formation and evolution of the plateau monsoon have been closely connected with the uplifting process of the plateau. Consequently a low-thin system of the plateau monsoon has been transformed to a deep-thick one since 2.5MaBP, and the modern monsoon pattern came into being. The tectonic movement during 1.1～0.8Ma BP might raise the plateau up to 3000～3500m asl and led to the plateau entering the cryosphere and forming the maximum glaciation, which gave rise to a series of drastic changes, e.g., desiccation in northwest China, main desert expanding, new loess system forming in the surrounding areas of the plateau, etc. At a time scale of ice-stage / interval ice-stage, the plateau climate was characterized by warming slowly and cooling rapidly. The density of CH 4 in Dasuopu ice core record characterized by much variation is 15%～20% higher than those of the polar areas. During the period of 40～30kaBP, the most recent high lake level on Tibetan plateau appeared, which might represent an exceedingly strong warm and humid summer monsoon events over the plateau. Evidence in the Guliya ice core record indicates that the climatic change events occurred frequently. Additionally, the response to climate change in highland areas is more sensitive than that in the lowland areas. In addition, the characteristics of temperature and precipitation of the plateau over past 2000 years were disclosed based on the records of ice-cores, lacustrine sediments, tree-rings and historical documents. Research also indicates that Tibetan Plateau has experienced three abrupt changes of climate in the 20th century, and that the warming tendency of the plateau has been higher than that of Northern Hemisphere and regions at the same latitudes since the 1950s. The cryosphere of the plateau (i.e., glaciers, snow deposit and frozen ground) responses obviously to climate change and is closely correlated with global environmental changes.