## 2 Materials and Methods  
### Study Area  
This survey selected the Rongbuk Glacier termini of Mount Qomolangma (also known as Mount Everest) and the Yangbulake Glacier termini of Mount Muztag Ata. Mount Qomolangma is located in the middle section of the Himalayan Mountains in the southern part of the TP, with a total glacier area of 1600 km\({}^{2}\)[26]. The Rongbuk Glacier is the largest subcontinental glacier on the northern slope of Mount Qomolangma, with a length of approximately 18 km and an average thickness of 120 m, a maximum thickness exceeding 300 m, and a glacier coverage of 68% [26]. From 1974 to 2008, the total area of the Rongbuk Glacier decreased by 10.4%, from 144 km\({}^{2}\) to 129 km\({}^{2}\)[27]. The region has strong solar radiation, low latitude, and varying rates of ice melting. At the Rongbuk Glacier termini, there are natural glacier phenomena such as glacial erosion lakes, cirques, and angular peaks [28]. When the median height of the Rongbuk Glacier is 5498.1 m, the movement speed of the ablation zone is 4.2 cm/day, and the movement speed of the debris zone is 3.7 cm/day from June to September 2006 [29]. The debris has a significant effect on slowing down glacier movement speed and has an important impact on the mass balance gradient of the debris-covered glacier, the development of ice cliffs, ponds, and drainage systems, and the downstream runoff process. Figure 2 shows the topographic map of Rongbuke Glacier and aerial photographs taken by an Unmanned Aerial Vehicle (UAV) at the Rongbuke Glacier termini. The red arrow in the image indicates the direction of glacier movement.  
Mount Muztag Ata is located on the eastern edge of the Pamir Plateau in the western part of the TP, with a peak elevation of about 7509 m. This area is a polar continental glacier area. From 2014 to 2021, the speed variation range of the Muztag Glacier was 68.63 m/a to 330.91 m/a, with an average movement speed of 218.49 m/a [30]. In 2021, the average glacier flow rate in the region was 0.531 m/d \(\pm\) 0.007 m/d [31]. This region is characterized by some of the most dynamic glaciers and a high frequency of natural disasters. Influenced by westerly circulation patterns and orographic barriers, annual precipitation exhibits a gradual decline from west to east. According to the statistics, the average annual precipitation at the snow line of Mount Muztag Ata Glacier ranges from 450 mm to 600 mm. A large number and scale of glaciers have developed around it and on both sides of the mountain ridge, distributed radially to provide replenishment for runoff. After leaving the valley, they supply Kalakuri Lake. After leaving the lake, they enter the Gaia River through the Kangxiwa River and finally flow into the Tarim Basin [32; 33]. The Yangbulake Glacier is located on the west side of Mount Muztag Ata, flowing due west. It is developed in a faulted trough valley, with the upper limit of the glacier reaching the top of Mount Muztag Ata. It covers an area of 8.91 km\({}^{2}\) with a length of 9.4 km. The ice tongue is 6.2 km long, with an average width of 0.7 km [34]. It has alternating rows of ice towers and ice trough valleys and is a non-debris-covered glacier. Due to the lower extension of the ice tongue, the melting of the ice tongue area is very strong, making it an active glacier. The ice-covered river channels formed by glacier meltwater and distributed along glacier flow lines have deeper incisions, generally 2 m\(\sim\)3 m lower than the debris valleys at the bottom of the ice tower, and some deeper. Figure 3 shows the topographic map of Yangbulake Glacier, etc., and aerial photographs taken by a UAV at the Yangbulake Glacier termini. The red arrow in the image indicates the direction of glacier movement.  
Figure 2: Topography and Sampling Area Map of Rongbuk Glacier.