Exploring surface snow ions in the Arctic
Lead supervisor: Dr Xin Yang
Location: Atmosphere, Ice and Climate, British Antarctic Survey, Cambridge
Duration: 8 weeks
Suitable undergraduate degrees: Chemistry, Physics, Earth Science, Maths
Not only has the Arctic sea ice coverage reduced dramatically in recent decades, but the type of sea ice has also changed. For example, the amount of older, perennial sea ice in the Arctic ocean has declined, and is being replaced by younger saltier sea ice. This has important implications for air-sea interactions and the circulation of chemicals within the atmosphere, including reactive bromine and reactive bromine.
The field data for this project is from from the hotspot of polar sea-ice chemistry. For instance, sea ice has the largest emission flux of reactive bromine on Earth, which not only rapidly destroys ozone, but also oxidises elemental mercury – making Arctic sea ice one of the centres of polar atmospheric chemistry and global climate research. Since sea ice is mostly covered by snow, the actual air-sea interaction is mainly through snow pack, particularly the top (a few cm) layer of snow. This is because the amount of chemicals within this thin layer is greatly influenced by the air above (e.g. through depositions of chemical compounds) and can be easily modified by meteorology such as precipitation, evaporation/sublimation and surface winds. The surface snow salt level or salinity has been found to play a key role in determining the production of sea salt aerosol (through blowing snow events). Inland coastal (tundra) snow pack also contain salts due to the transport of saline particles. Therefore, the amount of surface snow salts changing with time is critical in terms of understanding polar boundary layer chemistry and atmospheric oxidising capacity. However, we are lacking key information about the ion concentrations in the top layer of snow – particularly their temporal variation on a daily time scale and spatial variation from sea ice to inland. This information gap prevents us from using numerical global chemistry models to make robust predictions of polar environment. Therefore, a systematic surface snow ionic dataset is necessary.
In Feb-March 2018 and 2019, supported by two UK-Canada bursary programmes, more than a thousand snow samples were collected from a Canadian high Arctic site (Eureka, Canada, 80.1N, 86.4W) on a daily basis from six different sampling locations: off-shore and on-shore sites at near sea level and ~600 m above it (a few km inland). We have done ionic analysis for most of the snow samples.
The major aim of this project is to
(i) conduct a statistical analysis for those samples with focuses on major ions, including Na+, Cl-, Br-, and NO3-, and then explore the differences of the ions among the land types, e.g. between the off-shore and on-shore locations, as well as between the inland location at sea level and 600 m above sea level; and
(ii) explore the daily variation of surface snow ions and the possible physical and chemical processes involved in determining it.