Biogenic ice-nucleating particles (INPs) can significantly impact mixed-phase clouds by enhancing precipitation and reducing albedo. As Arctic sea ice diminishes, the exposure of open ocean may increase aerosolization rates of marine bioaerosols and INPs. We investigated INP concentrations and microbial communities in ambient marine air, sea bulk water (SBW), and sea surface microlayer (SML) along a transect from the Davis Strait to Baffin Bay. INP concentrations in SBW increased with latitude, regardless of the extent of terrestrial freshwater input. We further identified correlations between INP levels and abundances of specific microbial taxa, including Formosa, Lewinella, Micromonas, and Dino-Group-I-Clade-5, suggesting potential ice nucleation activity of these taxa. Air samples exhibited distinct microbiomes compared to seawater, indicating terrestrial contributions, but at the highest observed wind speeds (7-8 m/s), substantial contributions of the seawater microbiome were detected in the air. Elevated atmospheric INP concentrations at higher latitudes correlated with seawater INP levels, which was supported by laboratory sea spray experiments showing that INPs in SBW influenced aerosol INP levels. Our findings highlight the Arctic Ocean as a significant source of biogenic atmospheric INPs and enhance our understanding of marine microbes as contributors to biogenic INPs. By identification of potential ice nucleation active microbial taxa and examination of aerosolization processes, this study provides a framework for future research on Arctic marine-derived INPs and their atmospheric impact.
Castenschiold et al. (Wed,) studied this question.