Sea salt from blizzards above sea ice - magnitude and climate impacts of a new particle source in a warming world

Brief summary:

This project investigates relationships between atmospheric sea salt particles from a new source associated with blowing snow and the changing sea ice environment, and then quantifies polar-region wide impacts on background aerosol, clouds and climate.

Importance of the area of research concerned:

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. Sea salt aerosol (SSA) is a major component of the global natural background aerosol and originates mainly from the open ocean. Recent in situ observations confirmed that blowing salty snow above sea ice, which undergoes sublimation, releases SSA rivalling the open ocean source per surface area. Furthermore, a fraction of SSA from blowing snow may consist of cloud condensation nuclei (CCN) or ice nucleating particles (INPs), which can significantly influence occurrence and phase of low-level clouds. Thus, in order to make a step-change in improving climate models it is paramount to quantify magnitude and climate sensitivity of the new aerosol source.

Project summary:

The project main objectives are a) to quantify the magnitude of sea salt aerosol (SSA) production in the polar regions from blowing snow above sea ice, and b) assess the potential contribution of SSA from blowing snow to cloud forming particles and impact on clouds. A first step is to refine the parameterisation of SSA production from blowing snow taking into account the spatial variability of physical and chemical sea ice properties. To do this existing in-situ and satellite measurements as well as novel laboratory experiments at BAS or in the UEA sea ice chamber will be used. In a second step, a parameterisation of a CCN/INP sea ice source will be developed based on existing/ new observations associated with storms. And finally, the sensitivity of SSA and CCN/INP production from blowing snow and impacts on polar climate will be estimated under modern climate change scenarios.

What will the student do?:

First, you will develop a new parameterisation of SSA production from blowing snow for use in global models that takes into account spatial and temporal variability of sea ice surface properties. To do this you will map existing sea ice data and analyse them together with in situ observations available at BAS; back trajectory modelling will constrain air mass origin and the contribution of SSA from local sources. And you will carry out novel laboratory experiments e.g. in the UEA sea ice chamber to constrain relevant parameters under environmental conditions. You will use the new parameterisation together with sea ice maps and blowing snow detection by satellite-based lidar to upscale the SSA blowing snow source to the polar regions. Second, you will analyse available measurements of CCN/INP from a recent Arctic cruise, and develop a new parameterisation of a potential snow source associated with blowing snow. This will be aided by further sample analysis in the laboratory. And finally, you will estimate the sensitivity of SSA and CCN/INP production from blowing snow at high latitudes and associated impacts on climate and air quality under two modern climate change scenarios.