Characteristics of glacier surface weathering crust and light-absorbing particles, and their combined impact on glacier albedo at the Potanin Glacier, Mongolia

The glacier ablation areas in the mid-latitude mountains have a dark surface due to abundant light-absorbing particles (LAPs) (mineral dust, organic matter of microbial origin, black carbon). Conversely, the development of weathering crust on the bare ice surface increases the surface albedo. During the summers of 2022 to 2024, field observations were conducted on the Potanin Glacier in Mongolia. In this study, we defined the low-density surface layer within the weathering crust as the weathering granular ice layer. Here, we clarify the relationship between broad-band albedo (BB albedo), the thickness of surface granular ice, and LAP content within the granular ice layer. In situ measurements of BB albedo showed a significant positive correlation with the thickness of the granular ice layer (log10-transformed; r =0.41, p < 0.001), and a relatively strong negative correlation with organic matter (log10-transformed; r=-0.75, p < 0.001). It was also revealed that higher concentrations of LAPs inhibited the thickening of the weathering crust layer. Furthermore, the observed variability in correlation strength across different particle concentrations, together with evidence from previous studies, suggests that mineral particles, whether exposed within the glacier or deposited onto the glacier surface from the atmosphere, support the growth of microorganisms living on the ice. The subsequent proliferation of these microorganisms and the production of humic-like substances are considered to increase surface adhesiveness, thereby facilitating the adsorption of black carbon.