SO42− minimum in summer snow layer at Dome Fuji, Antarctica, and the probable mechanism

[1] By chemically analyzing snow samples at Dome Fuji, Antarctica, we found that the snowdrift deposited just after snowfall and the snow layer down to 3.4 m have summer minima in the non-sea-salt (nss)-SO42− and Na+ concentrations and summer maxima of Cl−/Na+. Such a summer nss-SO42− minimum in either snowdrift or the snow layer has not been reported at any other site in Antarctica and arises in spite of the known maximum in the nss-SO42− concentration in aerosol at Dome Fuji in summer. We then did laboratory experiments to better understand the phenomenon. The results supported the following mechanism for the summer nss-SO42− minimum in the snowdrift and snow layer. In summer, water vapor sublimates from within the snow in the daytime and condenses on the surface as frost in the nighttime, resulting in a dilution of the nss-SO42− concentration. This sublimation-condensation process likely occurs at other cold inland regions. In addition, the results might be useful for obtaining a high-resolution dating method for Dome Fuji deep ice cores by counting the number of layers with low nss-SO42− concentration.