Ice-nucleating particles in Greenlandic glacial outwash plains

Le résumé fourni par la source

High-latitude dust (HLD) represents a source of ice-nucleating particles (INPs) with potential impacts on cloud formation and radiative forcing in the Arctic. Previous studies have shown that HLD can exhibit high ice-nucleating activity at high subzero temperatures, likely linked to a biological component. Yet, comprehensive assessments of HLD ice-nucleating characteristics and sources remain limited, especially in Greenland. Here, we show that glacial dust from three outwash plains in southwestern Greenland effectively nucleates ice at temperatures relevant for mixed-phase clouds, but with lower ice-nucleating activity than other HLD regions. Ice-nucleating activity of glacial dust shows high variability and is largely driven by small amounts of organic and biological material, as indicated by sample treatments and positive correlations of ice-active site densities per mass with total organic carbon and microbial abundance. Dust from the Narsarsuaq glacial outwash plain likely acted as a localized rather than a regional INP source during summer, as indicated by higher atmospheric INP concentrations above −20 °C and similarities between atmospheric and bulk dust INP spectra at the outwash plain site compared to other sites in the region. The atmospheric INP population was generally dominated by primarily biological and other organic contributions, highlighting the importance of better constraining biogenic INP emissions in the Arctic. Overall, the ice-nucleating activity of glacial dust in southwestern Greenland lies within the lower range of reported HLD INP activity, suggesting that highly active HLD parameterizations may overestimate INP concentrations in this region. This highlights the importance of region-specific INP parameterizations for improving representation of cloud processes and climate impacts in the Arctic.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.