Investigating emerging boulder impacts on snowpack ablation

The impact of emergent boulders within a thinning and melting snowpack remains poorly understood. Our research examines how boulders, exposed by melting snowpack influence the spatial and temporal patterns of snow ablation in the Shár Shaw Tagà Valley, Yukon, Canada. A multimethod approach, combining thermal infrared time-lapse imaging, drone-based photogrammetry, and terrestrial laser scanning, was used to monitor snow surface temperature, elevation changes, and melt variability. This approach underscores the importance of comprehensive techniques in assessing the spatial and temporal variability of snow surface temperature and topography. Results indicate that boulders accelerate snowmelt in their vicinity during the ablation season, with snow surface thermal characteristics shaped by local terrain and meteorological conditions. The fastest rates of ablation occur during periods of mild weather with no precipitation. These findings highlight the role of boulders as micro-scale heat sources that can modify energy fluxes and influence broader melt patterns in subarctic alpine environments. Understanding these processes is essential for improving snowmelt modelling and predicting hydrological changes in mountain regions affected by climate change. Profiles of snow in the vicinity of a boulder in a subarctic mountain catchment in the St. Elias Mountains, Yukon, Canada. In mountain regions, boulders emerge from the snowpack as the surrounding snow melts, potentially enhancing the rate of snowmelt in their immediate vicinity. We evaluate this effect by using high spatial and temporal measurement techniques to measure snow elevations around an emerging boulder and compare these profiles to a model of what should be expected. The Figure shows the snow profile at the beginning (blue line) and at the end (light blue line) of the nine-day observation period. The blue shaded area delineates the difference in snowmelt between what we observed and what would be expected, demonstrating the boulder feedback on snowmelt. • Emergent boulders accelerate snowmelt by modifying local energy fluxes. • This study uses a multi-method approach, integrating thermal imaging, LiDAR, and photogrammetry. • Snow ablation near boulders peaks under mild, clear weather conditions. • Boulders store and release heat, enhancing melt beyond radiative effects.