Glacier area changes in the Nujiang-Salween River Basin over the past 45 years

Automated image classification and visual interpretation of Landsat imagery were used to extract the glacier boundary in the Nujiang-Salween River Basin (NSRB) around the years 1975, 2000, and 2020. The spatiotemporal characteristics of glacier area changes in the NSRB were determined and the reasons for the spatial heterogeneity in glacier area changes were discussed, based on comparative analyses of temperature and precipitation data from meteorological stations around the NSRB. The results indicate that 1) the total glacier area in the NSRB decreased by 477.78 km² (28.17%) at a rate of -0.62%/a in 1975-2020. Most shrinkage occurred at low and mid altitudes, with the most severe occurring at 5290-5540 m, accounting for 40% of the total shrinkage. Considering other river basins in China, the relative glacier area change rate in the NSRB was similar to that for typical inland river basins in northwest China but lower than that for other transboundary river basins in the southeastern Tibetan Plateau. 2) These areal changes in the NSRB presented obvious regional differences. The glaciers in the Hengduan Mountains retreated significantly, followed by those in the Nyainqentanglha Mountains, with relatively low shrinkage observed in the Tanggula Mountains. The number of cold and hot spots indicating areal changes increased after 2000, along with their spatial heterogeneity. 3) The glacier shrinkage rate over different time intervals was positively correlated with temperature. Thus, spatial heterogeneity of climate change effects could elucidate differences in the glacier area change rate in different regions of the NSRB. The temperature rise was determined as the primary reason for the significant glacial retreat over the past 45 years. As the significant warming trend continues, the glacier area in the NSRB is likely to shrink further.