Conceptual Framework for Interpretation of Exchange Processes

Polar firn and ice contain the most detailed, long-term, complete record of past climatic conditions on the Earth. Gas enclosed in bubbles and released from ice when it is brought to atmospheric pressure are samples of ancient atmospheres. Impurities in the ice matrix are related to atmospheric composition at or shortly after the time the snow that forms the ice was deposited. Climate reconstruction from polar ice cores offers the only possible indication of historical concentrations for many atmospheric chemical species that are critical to understanding how the Earth’s atmosphere responds to changes in emissions of the various carbon, nitrogen and sulfur species. These historical records provide the data against which to evaluate chemical/climate models that are designed to simulate how the Earth’s atmosphere will respond to changing patterns of anthropogenic emissions.