Future glacier mass loss in the Tien Shan strongly impacts summer water availability

Glaciers in the Tien Shan act as natural reservoirs, storing freshwater in the form of snow and ice and releasing it during dry periods. This water source serves various purposes and is particularly crucial during dry periods, where it serves agriculture, hydropower, industry, and human consumption. Here, we use GloGEMflow to simulate the future evolution of all glaciers in the Tien Shan under CMIP6 SSP climate scenarios. In all climate scenarios, our results reveal an exceptionally pronounced retreat of the glaciers, surpassing the projected glacier loss for most regions of the world. By 2040, we project a loss of 30% of the glacier mass from 2020, which increases to 60% by 2100 under low emission scenarios (SSP1-1.9, SSP1-2.6) up to 90% under moderate to high emission scenarios (SSP3-7.0 and SSP5-8.5). This drastic retreat is driven by the unique climate of the Tien Shan, with most precipitation occurring during spring and early summer. Rising temperatures not only accelerate glacier melt but also reduce snow accumulation. Regardless of the scenario, we project that peak water from the glacier runoff will occur before 2050. By 2100, total annual glacier runoff decreases by 35% compared to the 2015-2020 mean level. The annual glacier runoff peak shifts from summer, when water demand is highest, to spring, presenting challenges for both agricultural and industrial sectors. We also examine and combine the simulated glacial runoff with information on water availability and demand from the ISIMIP framework. This helps to grasp and evaluate how important glacial meltwater is in the Tien Shan region. Our research provides essential insights for creating adaptive policies to handle water resources effectively at both local and regional level.