T1-3 Chemical exchanges between snow, ice, atmosphere and ocean in polar regions

Until recently, it was generally assumed that the main biogeochemical role of ice was that it restricted exchanges between the more active ocean and land surfaces and the atmosphere. However, a number of field programs, principally in the Arctic and Antarctic, have revealed many unexpected and interesting phenomena, and shown that the chemistry of the ice may control aspects of boundary layer chemistry over large regions of the world, rather than the other way round. In addition, for some species the exchanges between snow and the atmosphere, and the postdepositional processing have adecisive impact on the famous palaeoclimatic signal that is retrieved from ice cores. This session welcomes studies on all aspects of the chemistry of the polar lower troposphere, especially those involving exchanges with the surface. Of particular interest are phenomena associated with halogen, VOC and NOx releases and associated effects on ozone and mercury, and processes of snow photochemistry. The session should include observations from IPY field studies, laboratory studies providing underpinning data, and modeling studies that aim to understand the field data. Assessments of the effects on these processes of a changing climate and cryosphere are also welcome.