Modelling mineral dust emissions from proglacial valleys of the St. Elias Mountains, Canada

Abstract

Abstract. Proglacial valleys of western Canada and Alaska demonstrate extensive historical and contemporary records of mineral dust emissions. These contributions remain unresolved by current dust emission modelling and unaccounted for in global emission estimates. We developed and evaluated a sub-km implementation of the Weather Research and Forecasting model with Chemistry (WRF-Chem) capable of simulating dust emissions from proglacial valleys of the St. Elias Mountains, Canada. Modelling these dust sources required precise treatment of surface characteristics and wind dynamics to accurately resolve surface erodibility, emission rates and aerosol dispersion within this mountainous terrain. Land-surface inputs were overhauled, with explicit treatment of glaciofluvial deposit heterogeneity and inundation conditions. Simulations covering 5–19 d periods across 2019–2022 were evaluated against in situ meteorological and dust emission measurements, camera stations and surface-based Doppler LiDAR data. A total emission rate of 1.0×104 kg km−2 d−1 was estimated from erodible deposits across 47 d of simulation, providing a first-order estimate of emissions from these valleys during dusty periods. Seasonal-dependent skill in reproducing surface meteorology and in-valley vertical dispersion is demonstrated, modifying dust dispersion. Emission dynamics from a variety of glaciofluvial deposits were successfully reproduced, however the sensitivity of the emission scheme to soil texture is discussed in light of glaciofluvial deposit heterogeneity and dataset scarcity. The successful model implementation under extreme topographic conditions and arguably the most severely constrained deposits (channel width: 0.1–3 km; sidewalls up to +1.7 km) supports the potential of this approach to simulate dust emissions from currently unaccounted for proglacial valleys across northwest North America and other regions.