Biogenic Ice Nucleating Particles and Bioaerosols in Arctic Marine Environments

Atmospheric ice nucleating particles (INPs) play a critical role in cloud formation, influencing both radiative and physical properties. Biogenic INPs are particularly effective in catalyzing ice formation, triggering heterogeneous freezing between -1 degrees Celsius and -15 degrees Celsius, which can impact mixed-phased clouds by enhancing precipitation and reducing albedo. Arctic waters are known to harbour highly active INPs, and the ongoing reduction of sea ice extent and the increasing exposure to open ocean may lead to elevated aerosolization rates of marine bioaerosols and INPs. In this study, we investigated INPs and microbial cells from ambient marine air and laboratory sea spray experiments, as well as from sea bulk water (SBW) and sea surface microlayer (SML) samples collected along a latitudinal transect from the Davis Strait to Baffin Bay, off the west coast of Greenland. We observed an increase in INP concentrations in SBW with increasing latitude, independent of terrestrial freshwater input. A positive correlation was found between INP concentrations in the SBW and the absolute abundance of specific bacterial and eukaryotic taxa, such as Lewinella and Dino-Group-I-Clade-5, suggesting these taxa may have ice-nucleation activity potential. We observed a clear distinction between the seawater microbiome and the above airborne microbiome. This indicates contributions from terrestrial sources through long-range transport to the collected ambient marine air samples. However, INP concentrations were elevated at higher latitudes in both air samples and sea spray experiments, correlating with INP levels in the SBW. INP concentrations in sea spray were significantly elevated compared to air samples, indicating that marine INP aerosolization is influenced by environmental factors, such as wind speed. Additionally, the taxa identified to correlate with INP concentrations in SBW showed no preference for aerosolization, suggesting a stochastic aerosolization process, as demonstrated in our sea spray experiments. This study enhances our understanding of the aerosolization process and underscores the contribution of Arctic marine-derived biogenic INPs to the atmosphere, highlighting the role of the Arctic Oceans as a major source of atmospheric biogenic INPs.