Ice Nucleating Particles over Oceans to High Latitudes

Sea spray aerosol (SSA) is considered a unique source of ice nucleating particles (INPs); for a given aerosol number and surface area, lower numbers of INPs are detected in SSA compared to continental sources. Studies have also demonstrated that elevated ocean biological activity is associated with increases in marine INPs measured in the atmosphere. These findings suggest that characterization of marine INPs is needed to accurately represent the variability in INP populations in coastal and pristine oceanic areas. Furthermore, especially at higher latitudes, INPs may play a critical role in determining the glaciation temperatures of clouds, whose phase properties are often not well represented in global climate models.

We present data on the number concentrations of INPs collected over oceans at varied latitudes, as well as from Antarctic snow, since 2012. Included marine region data are from the Mace Head Observatory (MHO, Ireland) and six ship campaigns in the Pacific and Southern Oceans. Variations in INP numbers and inferred compositions were observed, with strong variations related to clean marine versus continental influences. Campaigns in the North and South Pacific will be discussed, elucidating latitudinal variability. The impact of organic-rich plumes originating from biologically active ocean regions on marine INPs at MHO will be discussed. Finally, collaborative efforts for investigating the relationship between biological activity and INP source strength of the Southern Ocean will be reported for the first time, where INP abundance in seawater collected from conductivity-temperature-depth bottles is determined for two mesoscale oceanic eddies with contrasting biological productivity. These data advance our understanding of the link between biological activity and marine INPs in the natural environment. Finally, atmospheric measurements are applicable to modeling studies aimed towards determining the importance of marine INPs in cloud ice formation and cloud radiative properties in these regions under a changing climate.