Investigating the Heterogeneous Ice Nucleation of Sea Spray Aerosols Using Prochlorococcus as a Model Source of Marine Organic Matter

Sea spray is the largest aerosol source on Earth. Bubble bursting mechanisms at the ocean surface create smaller film burst and larger jet drop particles. This study quantified the effects of particle chemistry on the depositional ice nucleation efficiency of laboratory-generated sea spray aerosols under the cirrus-relevant conditions. Cultures of Prochlorococcus, the most abundant phytoplankton species in the global ocean, were used as a model source of organic sea spray aerosols. We showed that smaller particles generated from lysed Prochlorococcus cultures are organically enriched and nucleate more effectively than larger particles generated from the same cultures. We then quantified the ice nucleation efficiency of single component organic molecules that mimic Prochlorococcus proteins, lipids, and saccharides. Amylopectin, agarose, and aspartic acid exhibited similar critical ice saturations, fractional activations, and ice nucleation active site number densities to particles generated from Prochlorococcus cultures. These findings indicate that saccharides and proteins with numerous and well-ordered hydrophilic functional groups may determine the ice nucleation abilities of organic sea spray aerosols.