Remotely sensed annual glacier mass balance in the China-Pakistan Economic Corridor during 2000–2020: Widespread mass loss and regional contrasts

Study region The glacier region in the northern China-Pakistan Economic Corridor (CPEC) mainly comprises the Karakoram, Pamir, and Hindu Kush subregions. Study focus Annual mass balance (AMB) is essential for characterizing rapid changes in glacier meltwater, yet AMB data remain scarce for widely distributed glaciers in the CPEC. This study combined remote sensing albedo and differencing digital elevation model (DEM) data (Diff-DEM-ABM) to reconstruct AMB during 2000–2020 for 1849 glaciers selected according to method applicability. We further quantified correlations between AMB and climate variables and estimated excess glacier meltwater associated with net mass loss (hereafter, excess meltwater runoff) for three major river basins. New hydrological insights for the region The study glaciers in the CPEC experienced mass loss in most years during 2000–2020. Regional AMB reached its maximum in 2010, when all three subregions showed positive mass balance, followed by predominantly negative AMB during 2011–2020. AMB variability was strongly correlated with warm-season temperature (R=-0.83, P < 0.001) and annual snowfall (R = 0.74, P < 0.001), highlighting clear climatic influence at the annual scale. Mean excess meltwater runoff was highest in the Indus basin (2.63 Gt), followed by the Amu Darya (1.24 Gt) and Tarim (0.60 Gt) basins. These results provide improved insights into interannual glacier mass change, its climatic associations, and the long-term dynamics of glacier-derived water resources in the CPEC.