Atmospheric aerosols represent the largest source of uncertainty in global climate predictions. Aerosols influence radiative forcing and thus climate because they alter the planetary albedo both directly by absorbing and scattering sunlight and indirectly by modifying the reflectivity, lifetime, and extent of clouds. Sunlit aerosols can also release reactive chemical trace gases, which alter significantly the concentration of atmospheric pollutants such as tropospheric ozone and gaseous mercury. Sea salt aerosol (SSA) is a major component of the global natural background aerosol and originates mainly from the open ocean. Recently, sea ice has been discovered to be a significant source of SSA especially during winter and spring, rivalling that of the open ocean per surface area. In situ observations confirm that blowing salty snow, which undergoes sublimation, is the dominant SSA source above sea ice in the Antarctic. Linking SSA production via the blowing snow mechanism to snow and sea ice properties is urgently needed to estimate the magnitude of a so far neglected aerosol source and to significantly reduce the uncertainty in model predictions of polar climate and air quality.
The project main objective is to quantify variability and magnitude of sea salt aerosol (SSA) production in polar regions from a new source associated with blowing snow above sea ice. A first step is to parameterise SSA production from blowing snow based on physical and chemical properties of snow and sea ice surfaces. To do this existing observations from sea ice cruises and satellite data will be used as well as novel lab experiments in the UEA sea ice chamber. In a second step, the blowing snow detection by satellite-based lidar will be validated and used together with sea ice maps and the new parameterisation to upscale SSA production to the Arctic and Antarctic regions. And finally, the sensitivity of SSA production from blowing snow and associated impacts on polar climate and air quality will be estimated under modern climate change scenarios.
In a first step, you will develop a new parameterisation of SSA production from blowing snow for use in global climate models that takes into account spatial and temporal variability of sea ice surface properties. To do this you will i) compile existing data of sea ice surface properties (e.g. salinity, snow depth, density) and analyse them together with in situ observations of SSA during blowing snow events available at BAS; back trajectory modelling will aid to determine air mass origin and constrain the contribution of SSA from local sea ice sources in particular from blowing snow. And ii) you will carry out novel lab experiments at the UEA sea ice chamber to further constrain relevant parameters under environmental conditions. In a second step, you will i) validate the blowing snow detection by satellite-based lidar and then ii) used it together with the new parameterisation and detailed sea ice maps for upscaling of the SSA blowing snow source to the Arctic and Antarctic regions. And finally, you will estimate the sensitivity of SSA production from blowing snow at high latitudes and associated impacts on climate and air quality under two modern climate change scenarios.
Frey, M. M., Norris, S. J., Brooks, I. M., Anderson, P. S., Nishimura, K., Yang, X., Jones, A. E., Nerentorp Mastromonaco, M. G., Jones, D. H., & Wolff, E. W. 2019. First direct observation of sea salt aerosol production from blowing snow above sea ice, Atmos. Chem. Phys. Disc., 2019, 1–53, doi: 10.5194/acp-2019-259.
Yang, X., Frey, M. M., Rhodes, R. H., Norris, S. J., Brooks, I. M., Anderson, P. S., Nishimura, K., Jones, A. E., & Wolff, E. W. 2019. Sea salt aerosol production via sublimating wind-blown saline snow particles over sea ice: parameterizations and relevant microphysical mechanisms, Atmos. Chem. Phys., 19, 8407–8424, doi:10.5194/acp-19-8407-2019.
Palm, S. P., Kayetha, V., Yang, Y., & Pauly, R. 2017. Blowing snow sublimation and transport over Antarctica from 11 years of CALIPSO observations, The Cryosphere, 11, 2555--2569, doi:10.5194/tc-11-2555-2017.