Seasonal variability of mineral dust composition on an alpine snowpack in the Tateyama Mountains, Japan

 Mineral dust deposited on snow surfaces plays an important role in snow and ice melting by reducing surface albedo and modifying surface energy balance. In addition to its direct radiative effects, mineral dust can indirectly enhance snow surface darkening by supplying nutrients that stimulate snow algal activity. Despite its importance, the sources and mineralogical characteristics of dust preserved in alpine snowpacks remain insufficiently constrained, particularly with respect to seasonal changes during the melt period.

 Most previous studies have interpreted mineral dust on snow as long-range transported material originating from continental desert regions. In alpine environments, however, progressive snow retreat during the melt season exposes surrounding ground surfaces and bedrock, potentially increasing contributions from locally derived mineral particles. How these local and remote dust sources vary seasonally, and how they are recorded in the mineralogical composition of snow-surface particles, remains poorly understood. This study aims to clarify the seasonal and spatial variability of mineral dust sources on alpine snow surfaces in the central Japanese mountains.

 We analyzed mineral particles deposited on snow surfaces in the Tateyama Mountains, central Japanese Alps. Surface snow samples collected during the melt season (May–July 2017) were compared with dust-layer samples from a snow pit excavated in April 2008, representing springtime deposition. Mineralogical analyses using X-ray diffraction and optical microscopy show that dust deposited in April and during the early melt season is dominated by quartz and feldspar, consistent with long-range transported mineral dust. As the melt season progressed, the relative abundances of Fe–Mg–bearing minerals, including chlorite, biotite, and amphibole, increased systematically. Spatial variations further reveal localized feldspar enrichment at specific sites, indicating increasing inputs from locally derived mineral particles sourced from surrounding bedrock.

 These results demonstrate a pronounced seasonal shift in mineral dust provenance on alpine snow surfaces, from dominantly long-range transported dust in spring to increasing local geological contributions during the melt season. Such changes in mineralogical composition may alter snow surface albedo and melt processes, highlighting the need to consider mineral dust composition, not only dust loading, when evaluating alpine snowmelt dynamics.