Zero balance line method: ba=a (ELA0 ELAa). Ba is the annual net balance; ELAa is the elevation of the equilibrium line for that year; A is the gradient of material equilibrium; ELA0 is the height of the zero balance line. ELA0: Based on the topographic map and the principle of Hess method, it is inferred that the height of the equilibrium line of Glacier 72 is about 4190 meters. ELAa: Using ArcGIS platform, the annual equilibrium line position is interpreted interactively based on LandSat images. a: Obtained by observing the relationship between the material balance of the observation point and its elevation, as well as the average material balance of the elevation zone and the average elevation (with an interval of 50 meters between elevation zones).

 The interpretation of ELA is the key to the zero balance line method, which mainly depends on the quality of remote sensing images and the spatiotemporal resolution of DEM. The clearer the remote sensing image, the higher the spatial resolution, and the closer it is to the end of the ablation season in time, the closer the height of the interpreted equilibrium line position is to the true result. The spatial resolution of the images used in this study is 30 meters, and the interpretation accuracy is controlled within 0.5 pixels. The timeliness and spatial resolution of DEM are also crucial for determining the height of the equilibrium line. High resolution DEM has a high cost and requires a long time to produce high-precision topographic maps, while outdated DEM cannot accurately express the ice surface terrain of that year. According to material balance observation data, the material balance gradient of Glacier 72 varies slightly from year to year. The main reason is that the current monitoring time is relatively short, and glacier monitoring is difficult. In the first year of monitoring, the phenomenon of fallen flower stems was severe, resulting in a decrease in observation samples. It was not until after 2012 that the ice observation network data tended to stabilize. Based on the calculation of all observed sample data, the mass balance gradient of Glacier No. 72 is at latitude 0 86 m w. e.·（100m）-1。 In addition, the determination of the zero equilibrium line height is very important and cannot be directly verified on Glacier 72 at present. In future monitoring work, when conditions permit, 2-3 points can be selected near the ELA0 position or geodetic measurement methods can be used for material balance monitoring to verify the theoretical value of ELA0 for Glacier 72.