Rapid increase of lakes in Tibetan Plateau

The Tibetan Plateau, covered with a huge area of snow, glaciers and lakes, feeds several large rivers, incluidng Yangtze River, Yellow River, Yarlung Tsangpo River and Lancang River. Climate change can cause lakes to expand and bring floods and mudflows, and the response of lakes in this plateau to global climate change is very crucial. Using time-series Landsats clear-sky images in summer from the late 1980s to 2015, we established a new finer-resolution (30m) database of lakes in the plateau among five stages (1980s, 1995, 2000, 2005 and 2015), analyzed lake changes in the past three decades, and explored the possible driving forces. Results and discussions(1) Changes in lakes > 1km2 between 1980s and 2015The changes of lake numbers and surface areas were investigated between 1980s and 2015. The lakes were identified by visual interpretation and classified to several different sizes: small (1-10km2), medium (10-50km2), large (50-100km2) and huge (>100km2) lakes. A total of 1375 lakes (>1km2) were detected in 2015, in which the small, medium, large and huge lakes respectively account for 97, 74, 262 and 942 (Fig.1 and Table 1). The numbers of lakes (> 1km2 ) has increased by 384 from 991 in 1980s (Fig.2 a, b). Meanwhile, a rapid increase of lake surface area also occurred: increased by 28.2% from 37711.0km2 in 1980s to 48335.2km2 in 2015 (Fig.2c and Table 1). (2) Temporal changes in lakes > 10km2 between 1980s and 2015Temporal variation in all lakes > 10km2 were investigated at the five stages. Most lakes have expanded (Fig.3). The water surface area of large and huge lakes increased by 13.7% from a total area of 32056.7km2 in 1980s to 36437.0km2 in 2015. For example, Siling Co, which is the largest lake in Tibet region and second largest lake in Tibetan Plateau, has increased by 702.1 km2 (41.0%) to 2416.08 km2 since 1980s with an rate about 28 km2 /a. Some new lakes or water bodies appeared due to melting glaciers or anthropogenic intervention. A few of small lakes were dried up. (3) Effects analysis on Lake changesWe used annual average temperature (AVT), annual precipitation (AP), snow cover (SC) and glacier cover (GC) in spring, and lake salt mining (LSM). The preliminary results shows that the AVT anomaly and GC are the possible drivers for most lake changes, while some lakes are affected by LSM. More details are still on investigation.