Sea salt aerosol and ice nucleating particles (INP) in the Central Arctic during winter/spring – a discussion of a source from blowing snow above sea ice

<p>Arctic clouds are poorly represented in climate models partly due to a lack of understanding of their source and nucleating capability of natural aerosol in the high Arctic. Recent field campaigns provided evidence of a source of sea salt aerosol (SSA) from blowing snow above sea ice, which can account for SSA winter/spring maxima observed in the polar regions. SSA emissions from sea ice sources can potentially influence regional climate via the indirect radiative effect, but contributions to cloud-forming particles, in particular, ice-nucleating particles (INP), are unknown. Here we report the first online spring-time observations of INPs in the Central Arctic. INP concentrations were on the order of a few tens [particle m^-3] activating between -38 and -15&#176;C and were often associated with high wind speeds. Initial offline droplet assay analysis of snow on sea ice indicates the presence of potential INPs in winter/spring activating at -29 to -25&#176;C. This is evidence that snow on sea ice represents a viable reservoir of INPs, which can be physically released via the blowing snow mechanism to the air above. We discuss sea ice sources of coarse SSA and INPs and their role in the lower atmosphere with a focus on blowing snow. To do this, we consider the comprehensive set of MOSAiC observations, including aerosol size and composition, airborne snow particles, and chemical and physical properties of both aerosol and snow on sea ice.</p>