The scavenging of atmospheric sulfate by arctic snow

Scavenging ratios for sulfate on the south-central Greenland Ice Sheet at Dye 3 have been computed for 1982-1984. The ratios are based on measured concentrations in snow and estimated concentrations in air. The snow data have been obtained from snowpit samples which were dated by comparing δ¹⁸O values with meteorological records. The airborne concentrations have been estimated from data collected at coastal Greenland sites. Scavenging ratios resulting from this process are found to be in the range ~ 100-200 in winter and ~ 200-400 in summer. The greater summer values are attributed to increased riming, resulting in scavenging of sulfate as condensation nuclei and possible oxidation of SO₂ in cloudwater droplets. Using the airborne and snowpit concentrations with assumed dry deposition velocities of 0.02-0.05 cms^-, it is estimated that dry deposition is responsible for roughly 10-30% of the total sulfate deposition on a year-round basis at Dye 3. During portions of the Arctic winter, however, when the snow is unrimed and when there is less precipitation, dry deposition may be dominant.