Measurements of Airborne Ice Nucleating Particles in the Arctic

The Arctic is facing unprecedented warming, exceeding that of lower latitudes. The thawing of permafrost and melting of terrestrial- and sea-ice caps under a warming climate may lead to greater sources of aerosols, some which may serve as ice nucleating particles (INPs) that influence cloud evolution and lifetime. Arctic mixed-phase clouds (MPCs), containing both liquid and ice below 0 ºC remain poorly represented in numerical models, leading to large uncertainties in their simulated evolution, lifetime, and radiative effects. While significant efforts in recent years have been dedicated to quantifying and characterizing the potential sources and annual cycle of INPs in the Arctic, predominantly from surface sites, there remains gaps in our understanding of how these potential sources may reach and subsequently interact with MPCs. In this study, we will present airborne observations of INPs that were collected during two aircraft campaigns: the Cold Air Outbreak Experiment in the Sub-Arctic Region (CAESAR) campaign over the Norwegian Sea, and the Arctic Radiation Cloud-Aerosol Surface Interaction Experiment (ARCSIX) spanning areas north of Greenland and the Canadian Archipelago. These studies cover a broad geographical range of the Arctic, and collected observations of airborne INPs in the boundary layer, free troposphere and in clouds, enabling a more complete picture of the INPs concentrations that reach these complex clouds. CAESAR provided unique measurements of airborne INPs during several winter cold-air outbreaks, while ARCSIX focused on measurements during the pre- and post-melt periods. Comparisons between airborne INP measurements from these two campaigns with previously reported surface INP measurements may offer new insights into the sources of INPs in Arctic MPCs.