Atmospheric Residence Times Influence on Tracer Concentrations in Remote Polar Areas

Records from polar ice sheets contain invaluable information about past variations in the climate and the composition of the atmosphere. Past temperatures and precipitation rates can be deduced from stable water isotope records. Soluble (ion) and insoluble (dust) compounds forming the atmospheric aerosol are scavenged by the precipitation from the air mass above the ice sheet, or dry-deposited on the ice sheet surface, and become incorporated in the ice. Concentration records of ions and dust from ice cores can reveal the past aerosol composition and concentration in the atmosphere provided that the air-snow transfer functions are known. These are, at present, poorly known and the topic of this workshop. However, the atmospheric aerosol has a high spatial variability due to short residence times in the atmosphere of most compounds forming the aerosol. This complicates any attempt to extrapolate information from polar ice cores to airborne concentrations on a global scale.