Snow Cover Climate Sensitivity and Glacier Indicators in the Tupalang River Basin from 2001 to 2025
Keywords:
Tupalang River Basin; seasonal snow; climate sensitivity; glacier inventory; MODIS; Sentinel-2; uncertaintyAbstract
Reliable cryosphere information is limited in many mountain catchments of Central Asia. This paper develops a basin-scale evidence base for the Tupalang River Basin by combining MODIS snow observations, climate reanalysis, gridded water-balance products, a glacier inventory, and a 2025 Sentinel-2 snow and ice classification. Daily MODIS records for 2001 to 2025 were summarized as annual, winter, spring, and persistent-snow areas. Trend magnitude was estimated with the Sen slope, statistical significance was assessed with the Mann-Kendall test, and climate controls were examined through correlation analysis. Mean annual snow area was 1397.85 km2, whereas winter and spring means were 2182.48 and 1434.75 km2. The four snow indicators declined in slope terms, but none passed the 0.05 significance threshold. Annual mean air temperature increased by 0.041 degrees C per year and was the only significant monotonic climate trend reported in the study. Warmer conditions coincided with smaller snow areas in the annual, winter, and spring series. The GLIMS layer contained 618 mapped glacier polygons covering 78.61 km2. A Sentinel-2 classification for 2025 identified 526.35 km2 of snow and ice, of which 23.16 km2 intersected the mapped glacier layer. Tests with MODIS NDSI thresholds of 20, 30, and 40 produced different area totals but similar negative trend estimates. Comparisons with Landsat and Sentinel-2 showed that seasonal aggregation, image date, cloud screening, and spatial resolution materially affect area estimates. The results define a transparent monitoring baseline, while observed discharge and station measurements remain necessary for hydrological attribution.
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