Cryosphere changes and their impacts on regional water resources in the Chinese Altai Mountains from 2000 to 202

The cryosphere has an important impact on regional water resources and ecosystems in the Chinese AltaiMountains and its piedmont zone. Using the latest remote-sensing datasets of cryosphere changes and combiningwith in-situ observation data from glacier monitoring stations and snow cover surveys, the main cryosphereelements including glaciers, snow cover, and permafrost are investigated with emphasis on their changes since2000 and the current situation. Their water resource effects are also discussed. The results indicate that althoughthe glaciers in the region have experienced continuous and intensive melting, mass loss has slowed because bothglacier area shrinkage and thickness reduction were larger during 2000–2010 than during 2010–2021. Snowcoverwater equivalent (w.e.) has increased due to obvious increases in snow depth, although snow-coverarea has decreased slightly. Permafrost has been degrading. Overall, cryosphere contributions to the regionalwater resource are approximately 40.9% since 2000, among which snow-cover melting is the largest, contributing37.1% to water resources in the Irtysh River Basin and significantly more in the mountainous sub-basinswith increased snowfall. Glacier melting contributes 2.9%~3.4%, lower than earlier estimations of 3.4%~3.6% for the late 20th century. Permafrost thaw caused by active layer thickening contributes approximately0.59%. Meteorological data shows a warming and wetting trend, but summer temperature has a much lowerincrease rate and a slowing increase trend after 2013. Moreover, snowfall frequency has increased. In the future,glacier water resource contribution will continue to decrease, but the water resource effects of snow-covermelting and permafrost degradation would increase.