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CEFAC Project

Chemical Exchange and Feedbacks between the Atmosphere and the Cryosphere (CEFAC) is a component project of the Climate and Chemistry: forcings, feedbacks and phasings in the Earth System (CACHE) research programme, part of the British Antarctic Survey research strategy Global Science in an Antarctic Context (GSAC) 2005–2009


Project Leader: Anna Jones

The Challenge

To determine the chemical exchanges that take place between ice and the atmosphere, and to estimate how the size of the cryosphere would affect atmospheric chemistry in the present day, under past glacial conditions, and in a future warmer world with reduced snow cover.


  • To determine the year-round oxidative capacity at Halley for the present day;
  • To quantify variables (eg. light intensity, wavelength, chemical precursors) that determine photochemical emissions from snow;
  • To determine the spatial and temporal scale of Antarctic tropospheric ozone depletion events, and assess their cause and impact;
  • To determine the factors that control sea salt aerosol production;
  • To propose simple parameterisations that could be used in polar regions to generate sea salt aerosol in models;
  • To use numerical models to assess the importance of air-snow interactions for atmospheric composition under different climate conditions

What we will do

We will conduct year-round atmospheric chemistry measurements at Halley of key oxidants (OH, HO2, NO, O3, CO, Js), to study the role of the snowpack in determining the oxidant system. This will be in collaboration with Dr Greg Huey (http://www.eas.gatech.edu/people/faculty/huey.htm) from Georgia Institute of Technology. The Antarctic work will be carried out in the Clean Air sector Laboratory (CASLab)at Halley.

Controlled laboratory experiments will be carried out at BAS HQ, using both natural and artificial snow, to study emissions triggered by light and how they vary with snow impurity content and mix. We will set up a network of surface ozone sensors in an area around the Antarctic coast, to measure the spatial extent of surface ozone depletion events; this will be done as part of the International Polar Year and include collaborators from other countries.

Results from daily aerosol sampling at Halley will be combined with back trajectory analyses to assess the dominant source of sea salt aerosol to coastal Antarctica. Similar high resolution sampling will be carried out at an inland site. The results from these sampling programs will be used to generate parameterisations for sea salt that can be used in global models, while numerical models will also be used to explore the global implications of the emissions from, and losses over, snow and ice.

More information about CACHE-CEFAC