Marine Biogenic Source of Atmospheric Ice Nucleating Particles
The amount of ice present in clouds can affect cloud lifetime, precipitation, and radiative properties. Ice formation in clouds is facilitated by the presence of airborne ice nucleating particles. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice. Sea spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer. Researchers, including a Department of Energy scientist at Pacific Northwest National Laboratory, show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice nucleating material is likely biogenic and less than ~0.2 μm in size. The researchers found that exudates (organic material secreted by an organism) separated from cells of the marine diatom T. Pseudonana nucleate ice. The researchers propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol in combination with the study’s measurements suggest that marine organic material may be an important source of ice nucleating particles in remote marine environments such as the Southern Ocean, North Pacific, and North Atlantic. Including organic ice nuclei in models is expected to have a significant impact on their properties and their behavior under changing climate conditions.
Wilson, T. W., et al. 2015. “A Marine Biogenic Source of Atmospheric Ice Nucleating Particles,” Nature 529, 234–38. DOI: 10.1038/nature14986.