Summertime ice-nucleating particle concentrations over the Eurasian-Arctic Seas

Ice nucleating particles (INPs) catalyze primary ice formation in Arctic low-level mixed-phase clouds, influencing their persistence and radiative properties. Knowledge of the abundance, sources, and nature of INPs over the remote Arctic Ocean is scarce, particularly in the Eurasian Arctic. In this work, we present summertime measurements of INP concentrations ( N INP ) in immersion mode from the ship-based Arctic Century Expedition exploring the Barents, Kara, and Laptev Seas and the adjacent high Arctic islands and archipelagos during August to September 2021. Atmospheric N INP were found to be lower than in continental high-latitude sites, particularly at temperatures below −15 °C, suggesting a lower abundance of mineral dust INPs. The geographical N INP variability in the Eurasian Arctic shows that the highest N INP are observed when the ship was in the ice-free ocean, marginal ice zones (MIZ), and in the vicinity of land. Very low N INP were measured within the ice pack. The peak N INP was observed north of Novaya Zemlya where backward trajectories indicate air parcels arriving from the western Siberian coast. Overall, we find that INP sources are local to regional, with little evidence for long-range transport to the investigated area of the Eurasian Arctic in summer months.