Meltwater as a Local Source of Ice Nucleating Particles in the Central Arctic Summer

Identifying sources of ice nucleating particles (INPs) in the Central Arctic is important for understanding controls on the phase of Arctic mixed-phase clouds (AMPCs). We show meltwater samples collected from the Arctic pack ice in July 2020 contain biological INPs active at relatively warm temperatures (T ≥ -10 °C). We attribute the meltwater INPs to organisms and processes unique to a meltwater habitat. Concentrations of biological INPs active at T ≥ -10 °C on filters deployed downwind of meltwater sites showed an enhancement associated with surface proximity and no apparent relationship with residence time of the airmass over open ocean. We hypothesize that time over the pack ice drove the INPs on the aerosol filters and suggest the melt covered surface emits biological INPs. More work to resolve emission mechanisms from melt ponds is necessary for understanding the extent of this potential source as melt seasons extend spatiotemporally.