Impacts of Arctic warming on ice nucleating particles over recent decades: Distributions and contributions of dust, marine organic aerosols, and bioaerosols

Abstract. Aerosols serve as ice nucleating particles (INPs) and play a critical role in the formation of mixed-phase clouds. These clouds are prevalent in the lower and middle troposphere of the Arctic and exert a strong influence on both regional and global climate. However, limited understanding of INP sources and their temperature-dependent behavior has hindered accurate predictions of aerosol-cloud interactions in the Arctic. In this study, we investigate the sources, spatial distributions, seasonal variations, and long-term changes of INPs in the Arctic using a global climate-aerosol model that explicitly represents INPs from three Arctic aerosol species: mineral dust, marine organic aerosols (MOA), and bioaerosols. Simulations covering the period 1981–2020 show that Arctic-sourced INPs account for more than 70 % of total INPs in the Arctic lower troposphere. Dust is the largest contributor (36 %), followed by bioaerosols (28 %) and MOA (9 %). They exhibit distinct spatial and seasonal patterns, underscoring the importance of representing multiple INP species and applying appropriate parameterizations for each when modeling INPs and mixed-phase clouds in the Arctic. Over the past four decades, Arctic warming increases local emissions of all three aerosol species by 4.7–18 % because of the retreat of snow and sea ice. Nevertheless, INP concentrations in the Arctic lower troposphere decline by 19–29 %, primarily because the INPs per unit aerosol mass decrease with increasing temperature. This indicates that the temperature-driven reduction of ice nucleating efficiency outweighs the emission-driven increase of INP abundance, except in regions with substantial local increases of emissions.