The detailed physical processes involved in slowing glacier ablation by material cover remain poorly understood so far. In the present study, using the snow cover model SNOWPACK, the effect of geotextile cover on the energy and mass balance at the tongue of the Urumqi Glacier No. 1 (Chinese Tien Shan) was simulated between July 12, 2022 and August 31, 2022. The mass changes and the energy fluxes with and without material cover were compared. The results indicated that the geotextile covering reduced glacier ablation by approximately 68% compared to the ablation in the uncovered regions. The high solar reflectivity of the geotextile reduced the net short-wave radiation energy available for the melt by 45%. Thermal insulation of the geotextile reduced the sensible heat flux by 15%. In addition, the wet geotextile exerted a cooling effect through long-wave radiation and negative latent heat flux. This cooling effect reduced the energy available for ablation by 20%. Consequently, only 37% of the energy was used for melting compared to that used in the uncovered regions (67%). Sensitivity experiments revealed that the geotextile cover used at a thickness range of 0.045-0.090 m reduced the ice loss by approximately 68%-72%, and a further increase in the thickness of the geotextile cover led to little improvements. A higher temperature and greater wind speed increased glacier ablation, although their effects were small. When the precipitation was set to zero, it led to a significantly increased melt. Overall, the geotextile effectively protected the glacier tongue from rapid melting, and the observed results have provided inspiration for developing an effective and sustainable approach to protect the glaciers using geotextile cover.

Despite projections of extreme reduction in glacier volume in the Qilian Mountains by the end of the century, comprehensive studies of regional glacier-wide mass and energy balance characteristics remain lacking. This study undertook a comparative analysis of the surface energy and mass balance characteristics of Laohugou glacier No. 12 (LHG glacier) in the Shule River Basin (western Qilian Mountains) and Bailanghe glacier No. 21 (BLH glacier) in the Heihe River Basin (middle Qilian Mountains) based on in situ measurements from September 2020 to August 2021. During the cold season (September-April), precipitation was greater on the BLH glacier than on the LHG glacier. This resulted in a more positive mass balance on the BLH glacier during the cold season, and less melting in May-June owing to the higher incoming shortwave radiation. During the ablation season (May-August), snowfall was greater on the LHG glacier owing to its higher elevation, while melting was also greater owing to the anomalously low cloud fraction during summer 2021. The annual mass balance was notably more negative on the LHG glacier than on the BLH glacier at the same elevation below 5000 m, whereas the annual glacier-wide mass balance was just slightly more negative on the LHG glacier than on the BLH glacier because most of the area in the LHG glacier is at higher elevation. The equilibrium line altitude varied between 4900 and 5100 on the glaciers of Qilian Mountains during recent two decades, which signified that only 5.8-25.5% of the total glacier area is within the accumulation zone in the Heihe River Basin; thus, further global warming will place the regional glaciers in a very vulnerable position.