Dynamic Glacier Change Monitoring and Its Response to Climate Change in the Koshi River Basin

Abstract

With the data available now from Landsat remote sensing images and digital elevation model (DEM), we employ both the ratio threshold technique and visual interpretation approach to discern glacier boundaries within the Koshi River Basin, across the years 1990 to 2020. Meanwhile, using meteorological grid data, we investigate the glaciers' responses to climatic change. Research findings show that: (1) The Koshi River Basin's glaciers exhibited an unbroken trend of shrinking dimensions between 1990 and 2020, and the withdrawal rate is increasing. The annual area retreat percentage of debris-covered glacier was approximately 0.28%/a and the clean glacier was 0.73%/a. (2) During the last thirty years, within the investigated zone, the glacier area takes on a upward and then downward trend with increased altitude. Debris-covered glaciers are mainly distributed at an elevation range of 5000 ~ 6600 m, while the debris-free glaciers are mainly located at elevations from 5200 to 6400 m. (3) The distribution and retreat tendency appears to have distinctions between different slopes. Debris-covered glaciers were mainly distributed between 5 ~ 10°, while debris-free glaciers were greatly distributed between 10 ~ 15°. Glacier shrinkage was largely in the range of 30 ~ 35°. (4) Glaciers shrinkage shows a certain hysteresis phenomenon. This paper comprehensively analyzes the regional temperature and precipitation data with a 10-year lag period, and finds that rising temperature and decreasing precipitation are likely to be the main factors that cause glaciers to retreat. What’s more, the former plays a greater role.