Scientists from Europe, North America and New Zealand will investigate how the presence of snow and ice affects the chemistry of air above the polar ice caps. In the Arctic and Antarctic, sunlight triggers the release of chemicals from surface snow into the lower atmosphere. Salty sea ice surfaces host some very interesting chemistry (involving bromine compounds) during the polar spring when the sun comes back. These processes affect air quality and the interpretation of past climate using ice cores. If the amount of sea ice changes the chemical content of the lowest parts of the polar atmosphere will also change.