Recent lake changes of the Asia Water Tower and their climate response: Progress, problems and prospects

Abstract

The Tibetan Plateau has many endorheic lakes which are an important part of the Asia Water Tower. In recent decades, the warming rate of the Tibetan Plateau is two times higher than the global average, and precipitation also has obvious increase. As the largest cryosphere system in the middle and low latitudes, the temperature and precipitation changes in the Tibetan Plateau have profound impacts on the lakes in the region. Before 1990, low temperature caused negative balance of lake water storage by suppressing melting water. In 1990-2000, increase of lake water stoage was promoted by temperature increase. After 2000, precipitation is the dominant factor causing the increase of lake water storage, but the continuous temperature rise in 2005-2013 strengthened evaporation and weakened the increase of lake water storage. Glaciers have different impacts on lake water storage. During the period of 2000-2013, glacier melting water contribution to lake water increase in the central and northwest parts of the Tibetan Plateau is up to 50% and 100%, respectively. Changes in water quantity and salinity are the results of lake water budget under climate change, which are important indicators and their temporal and spatial characteristics may reflect the influence of the westerly and Indian monsoon on land surface water cycle. The trend of the lake water storage in different parts of the Tibetan Plateau from 1970s to 2013 is consistent with that of precipitation in the westerly and Indian monsoon-controlled areas. It is found that with the increase of lake water storage, the salinity of lakes generally decreases in the Serling Co area. The physical and chemical properties of lake water are important factors affecting lake ecosystems, and their changes under different climatic conditions have profound impacts on the composition and trend of lake ecosystems. Increase in water temperature promotes the transmission efficiency of food chain, which leads to high ratio of zooplankton to phytoplankton and low ratio of phytoplankton to total phosphorus. Decrease in lake salinity increases the biodiversity and makes lake ecosystem structure relatively complex. In lakes with salinity of about 3-5 or 25-28 g/L, zooplankton species composition is the most sensitive to salinity change. Based on the analyses of the relationships among lake area, water level, water quantity, water physicochemical parameters and climate changes in the Tibetan Plateau, this paper reviews the research progress on lakes as a response to climate change in the region, and puts forward the main objectives and tasks of the lake research in the Second Tibetan Plateau Scientific Expedition Program.