Regional glacier mass changes and meltwater evolution in the Tianshan Mountains since 2000

Understanding regional glacier mass changes is essential for addressing local water resource challenges. However, regional glacier mass changes estimate has been hampered by glacier mass balance monitoring limitations. Here, we present glacier mass balance simulations for the recent historical period (2000−2021) and future projections throughout the 21st century (2022−2100) under Shared Socioeconomic Pathways (SSPs) for six basins in the Tianshan Mountains. The evolution of glacier meltwater runoff and its contribution to total river runoff were also analyzed. We show that, during 2000–2021, the mean annual glacier mass balance was −0.42 ± 0.04 m w.e. a −1 , while glacier meltwater runoff was 36.26 ± 9.57 × 10 8 m 3 a −1 . Glacier meltwater contributed approximately 31.45% of total river runoff. By the end of the 21st century, mean annual mass balance is projected to range from −0.47 ± 0.26 m w.e. a −1 to −0.72 ± 0.24 m w.e. a −1 under SSP 1–2.6 and SSP 5–8.5, corresponding to cumulative mass balances of −37.27 ± 12.16 m w.e. and −56.54 ± 12.54 m w.e., respectively. This implies a total glacier mass loss of 53%–77% by 2100. Glacier meltwater runoff is projected to increase until approximately 2050 and then gradually decline, indicating a weakening role of glaciers in regulating water resources. Accounting for debris cover reduces simulated glacier mass loss by 5%–22%, whereas neglecting proglacial lakes leads to an underestimation of mass loss by 5%. These results improve our understanding of glacier responses to climate change and provide a scientific basis for sustainable water resource management in the Tianshan Mountains.