Studying primary biological aerosol particles in the Arctic is crucial to understanding their role in cloud formation and climate regulation at high latitudes. During the Arctic Ocean 2018 expedition, fluorescent primary biological aerosol particles (fPBAPs) were observed, using a multiparameter bioaerosol spectrometer, near the North Pole during the transition from summer to early fall. The fPBAPs showed a strong correlation with the occurrence of ice nucleating particles (INPs) and had similar concentration levels during the first half of the expedition. This relationship highlights the potential importance of biological sources of INPs in the formation of mixed-phase clouds during the central Arctic’s summer and early fall seasons.

Our analysis shows that the observed fPBAPs were independent of local wind speed and the co-occurrence of other coarse mode particles, suggesting sources other than local sea spray from leads, melt ponds, re-suspension of particles from the surface, or other wind-driven processes within the pack ice. In contrast, other fluorescent particles were correlated with wind speed and coarse mode particle concentration.

A multi-day event of high concentrations of fPBAPs was observed at the North Pole, during which the contribution of fPBAPs to the total concentration of coarse mode aerosol increased dramatically from less than 0.1% up to 55%. Analysis of chemical composition and particle size suggested a marine origin for these fPBAPs, a hypothesis further supported by additional evidence. Air parcel trajectory analysis coupled with ocean productivity reanalysis data, as well as analysis of large-scale meteorological conditions, all linked the high concentrations of fPBAPs to biologically active, ice-free areas of the Arctic Ocean.