Analysis of snowline changes during snowmelt period in the source region of the Yangtze and Yellow Rivers based on MODIS snow cover product

Climate change has exacerbated the melting of glacier and snow in the source region of the Yangtze and Yellow Rivers (SRYY) over the past few decades, with the snowline consistently rising. However, the scarcity and uneven distribution of observation stations, as well as the dispersed glacial regions, there has been a lack of long-term continuous monitoring of snowline changes in the SRYY. In this study, we developed a dynamic FSC threshold classification method to analyze the historical normal and extreme values of the snowline elevation (SLE) in the major glacial regions. We compared the impact of climate factors on SLE using the snowfall temperature threshold method, and estimated future SLE changes using CMIP6 data. The results indicated that in the past few decades, the SLE change rate varied greatly among different glacial regions (ranging from 0.9 m/10 yr to 22.3 m/10 yr), and rising temperatures were the main cause, whereas the decrease in snowfall had less impact. In the future, the SLE in the SRYY will continue its upward trend. From 2020 to 2040, the SLE in Anyemaqen is expected to rise by around 75 ± 4 m, while the G_T3 zone of Tanggula is projected to experience an increase of approximately 20 ± 4 m. By the end of the 21st century, the SLE in Anyemaqen is forecasted to rise by a minimum of 151 m and a maximum of 303 m; for the G_T3, the estimated minimum increase is 45 m, and the maximum is 96 m. The sustained increase in temperature is the dominant factor behind these changes, and the augmentation of liquid precipitation will accelerate the melting of glaciers and snowpack.