Abstract
Ice sheets and glaciers have been accumulating snow, and atmospheric gases and aerosols since they built up. It has been recognized that ice-core chemical records provide invaluable information on past climate and atmosphere. However, due to a lack of understanding of air to snow transfer and post-depositional processes of chemical substances, interpretation of ice-core chemical records could be misleading. Large amounts of chemical data have not been properly interpreted. It is essential to understand those processes to avoid the misinterpretation, and to obtain the maximum information from ice-core chemical records. Ice-core chemical records are affected by many processes: (1) large-scale transport of chemical constituents from tropical and mid-latitude (as well as high latitude) sources to polar regions; (2) cloud scavenging processes; (3) wet and dry deposition processes and their relative contributions; (4) post-depositional processes such as re-emission of chemical constituents from the snow, sublimation/ evaporation, redistribution by winds, melting and re-freezing, diffusion and chemical reactions within the snow, firn and ice . This paper reviews evidence of post-depositional changes found in polar snow, firn and ice, such as changes due to wind scouring, nitrate losses, movement of methane sulfonic acid (MSA), etc.
