Saharan dust impacts on Argentière glacier surface mass balance during the 2022 extreme melt year

Saharan dust depositions frequently color alpine glaciers in orange. Along with other light absorbing particles, dust lowers snow albedo, increases the melt rate of snow, and lowers the surface mass balance of glaciers. Since the surface mass balance drives the evolution of alpine glaciers, assessing the impact of impurities helps understanding the current and future evolution of alpine glaciers. Here, we quantify the impact of impurities on glacier surface mass balance taking into account mineral dust. To do so, we used the SURFEX/ISBA-Crocus snow model, that explicitely accounts for the evolution of impurities content within the snowpack and computes their effect on albedo with the TARTES two stream radiative transfer model.  Over the Argentière Glacier (Mont-Blanc area, France), our modeling show that considering the impact of mineral dust leads to a decrease in the glacier-wide annual surface mass balance by around 0.25 m w.e. on average for the period 2019-2021, but it reaches the double during the exceptionnal melt of 2022 (around 0.5 m w.e.) on average over the whole glacier, and up to 1.00 m w.e. locally. This highlights the importance of accounting for the impact of mineral dust when simulating the surface mass balance of mountain glaciers, and the need to understand how this contribution varies at the mountain range scale and for different periods of times.