Properties and Concentrations of Ice Nucleating Particles in the Sea-Surface Microlayer and Bulk Seawater in the Canadian Arctic during Summer 2016 and Comparison with Summer 2014

Previous research has shown that clouds in the Arctic may be especially susceptible to concentrations of ice nucleating particles (INPs) (Yun and Penner, 2013). To better understand the sources and concentrations of INPs in the Arctic, we measured concentrations of INPs in the sea-surface microlayer and bulk seawater in the Canadian Arctic during the summers of 2016, and compared the results with previous measurements during the summer of 2014. During both years, INPs were abundant in the sea-surface microlayer and bulk seawater. Although the INP concentrations were higher in 2016 than 2014, we found that the spatial patterns of INP concentrations measured in both years were similar. In addition, the ice-active material collected in 2016 had similar properties to the ice-active material collected in 2014; the material was determined to be heat-labile and between 0.2 μm and 0.02 μm in size. Finally, the strongest predictor of INPs for both years was salinity, leading us to the hypothesis that INPs are associated with sea-ice microorganisms and exudates released into the ocean upon sea ice melting.