Increasing Area and Decreasing Depth: Climate Change Influence on Snow Variations in the Qilian Mountains

Abstract. The Qilian Mountains serve as a critical water source for the Yellow River and various inland rivers, playing a pivotal role in regulating the regional climate. Given their significance as one of the foremost water resources in the area, the spatial and temporal dynamics of the snow are crucial for understanding potential impacts on regional hydrology and ecology. This study examines the characteristics of spatial and temporal variations in snow-covered extent (SCE), snow depth (SD), snow-covered days (SCD), snow onset date (SOD), and snow end date (SED) within the Qilian Mountains region. We investigate the hydrological and ecological implications utilizing snow area and phenology data, alongside SD data. The findings indicate that: (1) the distribution of snow across the Qilian Mountains mainly splits between the central and western areas, with the central region showing deeper snow than both the eastern and western parts; (2) the area covered by snow in the Qilian Mountains is growing, but the depth of the snow is on a decline, especially in the central area; (3) in terms of snow phenology, most of the region is witnessing an earlier start of SOD, a longer SCD, and an earlier SED. An overall increase in precipitation is identified as the key factor behind the expanded SCE in the Qilian Mountains, while rising temperatures are pinpointed as the primary cause for the reduction in SD. As global climate change intensifies, the observed alterations in the snow of the Qilian Mountains present emerging challenges for regional water security and ecological equilibrium.