Correlations between concentrations of acids and oxygen isotope ratios in polar surface snow

Investigation of centimeter-scale snow surface chemistry has been carried out at two polar sites with different site characteristics–in Dronning Maud Land, Antarctica and on the Greenland ice sheet, respectively. Large variations in both impurity content and stable oxygen isotope ratios (δ18O) were found on the submeter scale. δ18O and the concentration of nitrate correlated at both sites (r = 0.81 and 0.82, respectively). At the Antarctic site, δ18O is also correlated to concentrations of methanesulphonate (r = 0.84) and sulphate (r = 0.83) while no such correlation exists at the Greenland site. Instead, a strong anticorrelation (r = –0.85) between sulphate and methanesulphonate is found among the samples from the Greenland site. The ions correlating with δ18O at the two sites were probably deposited as acids. Our tentative explanation is that local redeposition of water vapour enriching the snow surface with the lighter isotopes is associated with simultaneous enhanced scavenging of the acids. The responsible process thereby significantly alters the chemical signals of the snow surface.