Refining the Parameterisation of Sea Salt Aerosol Production from Blowing Snow on Sea Ice Based on Data Collected in the Weddell Sea

The hypothesis of blowing snow lifted snow particles, via a subsequent sublimation process, as a significant sea salt aerosol (SSA) source over sea ice has recently been strongly supported by a winter cruise through the Weddell Sea during June-August 2013. The newly collected data, including both physical and chemical components, provide a unique way to test and validate the parameterisation used to date.

The observed salinity of surface and blowing snow is very low; on average more than an order in magnitude smaller than column mean value. Here we apply a low salinity of 0.27 PSU (representing an average of the top 10cm of snow plus blowing snow samples) in the p-TOMCAT model to test its effect on sea salt concentrations reaching the Antarctic. The comparison with previous model output (using column mean salinity) shows that SSA concentration in central Antarctica is insensitive to change in snow salinity, due to the compensating effect of increasing fine SSA partitioning upon reducing the salinity. We also investigate the impact of changing the number of SSA particles formed from each snow particle on SSA concentration and size distribution. Applying a ratio of 10 SSA particles per blowing snow particle, rather than one as assumed to date, greatly increases the amount of sub-micrometer SSA reaching central Antarctica. Without applying blowing snow related SSA production in the p-TOMCAT model, the observed elevated SSA in the Weddell Sea could not be reproduced.