Abstract:

The levels and surface areas of lakes are indicators of climate change and climate variability. The authors extracted surface extent of all lakes in the Tibetan Plateau from Landsat remote sensing images of the 1970s, of the 1990s, around 2000 and 2010 based on RS and GIS and developed the lake spatial database in combination with on the spot investigations to a few representative lakes. The results show that the total surface area of lakes, each of which has an area larger than 0.5 km2, increased by 13.42% during the period of the 1970s to the 1990s, increased by 4.86% during the period of the 1990s to around 2000, and increased by 13.04% from 2000 to around 2010. It showed that lakes in the study area keep the expanding trend in the past forty years. We found that the climate of the Tibetan Plateau changed from warm dry to warm wet gradually characterized by increasing temperature, precipitation, and dropping evaporation through the meteorological data. Meanwhile, all lakes, each of which has an area larger than 10 km2, suitable for the surface area changes analysis were selected to compare the dynamic changes one by one, and the division of these lakes into expansion area and atrophy area was made according to dynamic changes. The variations of the lakes differ from area to area in different periods, and the response to climate is strong. In practical terms, between the 1970s and the 1990s, lakes in north and middle Tibet, southern Tibet, Qinghai Qiangtang Basin and east Qinghai were shrunk whereas lakes in other places tended to expand. From the 1990s to 2000, lakes in north Qinghai were shrunk. From 2000 to 2010, most lakes in the study area except southern Tibet expanded. Different climate parameters can produce different effects in different areas: temperature mainly affects lakes which rely on glacier melt water runoff for supply, such as Siling Lake and Chibuzhang lake; precipitation mainly influences lakes recharged by precipitation and surface runoff, such as Qinghai Qiangtang Basin; evaporation brings about water loss of all lakes, which influences areas with evaporation effect caused by raising temperature surpassing the increase in precipitation and runoff, such as Yamdrok Lake. Tectonic activities play an important role in the evolvement of lakes in long time scales, controlling the big pattern. While the climate shapes lakes more directly in short time scales. Besides, The dynamic changes of the lakes also can be influenced by other factors, such as glaciers, human activities, lake basin shape, open or closed systems and catchments.

Key words: Tibetan Plateau, lake, climate change, remote sensing, Qinghai Lake