Remote Sensing Monitoring of Glacier Changes in the Western Region of Tanggula Mountains in Recent 25 Years

This paper focuses on revealing the status quo and variation of glaciers in the western region of Tanggula Mountains. The ratio threshold, NIR water identification and visual interpretation were used to extract the boundary of glaciers based on Landsat data (TM/ETM+/OLI) from 1990 to 2015. In particular, the NIR water identification is a new method to extract glaciers from water, which is suitable to improve the traditional method of ratio threshold. This study used spatial interpolation method to evaluate temperature and precipitation changes. The kriging interpolation method was adapted to manipulate and to extract the appropriate data based on ten weather stations. Comparing to the variations and characteristics of glaciers and climate change from 1990 to 2015, we concluded that glacial retreat in the western region of Tanggula Mountains was serious. The glacier area reduced from 1 693.65 km² to 1 490.81 km², respectively, in 1990 and 2015, in general, approximately 202.84 km² (11.98%) of glacier area has been retreated in the last 25 years. Moreover, the rate of glacier decline after 2000 was much faster than the last decade of the 20th century. In addition, the decreased area of glaciers in the lower altitude basins below 5 000 meters occupied 94.84% of the total change area while the glacier above 5 000 meters almost had no change. The kriging interpolation of the meteorological data indicated that the southeast of the study area was damp and hot while the northwest was cold and dry. The characteristic of temperature distribution from the northwest to the southeast presented from low to high, and precipitation increased in the first of the study period and then decreased but both of them were not very significant. In short, the temperature of study area was increased more prominently since 2000, while the precipitation change was very weak. The mean annual temperature and precipitation of 1980-1989a, 1990-1999a, and 2000-2013a were -3.53 ℃, -3.20 ℃, -2.22 ℃, and 384.49 mm, 354.27 mm, 428.13 mm, respectively. The study found that the glacier change was consistent with temperature variation in spite of the adverse effects of increased precipitation. Therefore, the research concluded that the precipitation change was not more significant comparing to temperature change. In other words, the main reason of the rapid decrease of glaciers in study area was likely due to the rise of temperature.