What drives the decrease of glacier surface albedo in High Mountain Asia in the past two decades?

Glacier surface albedo is an important factor affecting glacier ablation, and a positive feedback mechanism has been observed between the surface albedo and mass balance of glaciers. It is important to understand the driving factors and mechanisms of glacier albedo changes (GAC). Based on the MODIS (Moderate resolution imaging spectroradiometer)-derived MOD10A1 and MYD10A1 albedo products, the glacier albedo trends in each MODIS grid cell during each melt season in High-Mountains Asia (HMA) from 2000 to 2020 were calculated. Decreasing glacier albedo trends were found, with a decline rate of 0.25 × 10^-2 yr^-1; in addition, the GACs exhibited great spatial differences among the 15 subregions. The geographical detector model (GDM) is a new spatial statistical method that can quantitatively reveal the driving forces of climate factors and light-absorbing particles on GAC under single-factor and two-factor interactions. These driving forces can be measured by the corresponding q value. The results showed that on the whole, solid precipitation (snowfall) had the strongest impact on GAC, followed by the glacier surface temperature. The q values of black carbon (BC) and dust were <0.1, but BC or dust had the greatest q value in the 9 subregions. The effects of each factor differed among different elevation zones. The interaction detector indicated that the q value under the influence of two factors was greater than that under a single factor, and the strongest interaction was between snowfall and BC, followed by between snowfall and dust. In 15 subregions, most of the greatest q values in each region corresponded to an interaction with BC or dust. Here, we obtained the main driving factors of GAC in different regions and emphasized the interactions between climatic factors and light-absorbing particles; these results provide references for further studies of glacier mass balance and surface albedo.