Glacier-level and gridded mass change in the source rivers in the eastern Tibetan Plateau (ETPR) from 1970s to 2000

Abstract. The highly glacierised eastern part of the Tibetan Plateau is the key source region of the five major rivers Yangtze, Yellow, Lancang-Mekong, Nu-Salween and Brahmaputra rivers. These exotic rivers are vital freshwater resources for more than one billion people downstream for their daily life, irrigation, industrial use, and hydropower. However, the glaciers have been receding during the last decades and are projected to further decline which will profoundly impact the water availability of these larger river systems. Although few studies have investigated glacier mass changes in these river basins since the 1970s, they are site and temporal specific and limited by data availability. Hence, knowledge of glacier mass changes is especially lacking for years prior to 2000. We therefore applied digital elevation models (DEMs) derived from large scale topographic maps based on aerial photogrammetry from the 1970s and 1980s and compared them to the SRTM DEM to provide a complete picture of mass change of glaciers in the region. The mass changes are presented on individual glacier bases with a resolution of 30 m and the grided (0.1° and 0.5°). Our database consists of 17444 glaciers with a total area of 17426 ± 523 km2. The annual mean mass loss of glaciers is -0.28 ± 0.15 m w.e. in the whole region. This is larger than the previous site-specific findings, the surface thinning increases on average from west to east along the Himalayas-Hengduan mountains with the largest thinning in the Salween basin. Comparisons between the topographic map-based DEMs and DEMs generated based on Hexagon KH-9 metric camera data for parts in the Himalayas demonstrate that our dataset provides a robust estimation of glacier mass changes. However, the uncertainty is high in high altitudes due to the saturation of aerial photos over low contrast areas like snow surface on a steep terrain. The dataset is well suited for supporting more detailed climatical and hydrological analyses and are available at https://doi.org/10.11888/Cryos.tpdc.272884 (Liu et al., 2022).