Variations in glacier peak water timing and its influencing factors in High-Mountain Asia

High Mountain Asia (HMA) has the largest volume of glaciers outside the polar region and protects approximately 800 million people in the downstream basins against water stress. HMA is facing rapid glacier melting and substantial glacier mass loss, reaching the peak of runoff ('peak water') in the following decades. In the present study, the timing of glacier peak water was calculated using a projected glacier runoff dataset forced by twelve General Circulation Models under the Shared Socioeconomic Pathway (SSP) scenarios. The dominant factors that influence the timing of peak water, such as glacial area, elevation, aspect, slope, latitude and debris thickness, were investigated using partial correlation and stratified analysis. Our results demonstrated that, for the entire HMA, glacier peak water was predicted to occur in 2028, 2052, 2057, and 2059 under SSP126, SSP260, SSP370, and SSP585, respectively. For each subregion, Hengduan Shan is projected to reach the earliest peak water in HMA in 2024, 2025, 2021, and 2024 under SSP126, SSP260, SSP370, and SSP585, respectively. In West Tianshan, glacier peak water is projected to occur in 2027, 2036, 2050, and 2050 under SSP126, SSP260, SSP370, and SSP585, respectively. In the West Kunlun, glacier peak water will occur in 2070 under SSP126 and 2080 under SSP245 but will not appear until 2100 under SSP370 and SSP585. Glacier elevation and latitude are highly correlated with peak water timing for the entire HMA, with the partial correlation coefficients being 0.48 and 0.47, respectively (P < 0.01). Additionally, earlier glacier peak water normally occurs in glaciers with a small area or steeper slope. Debris can also influence the timing of glacier peak water with a thinner debris cover (< 5 cm) leading to delayed peak water. Our findings indicated that glacier elevation and latitude are highly correlated with glacier peak water timing for the entire HMA.