Sulfur isotopic signals in two shallow ice cores from Dronning Maud Land, Antarctica

Sulfate deposited onto the Antarctic ice sheet originates from a mixture of sulfur sources. Two 100 m long ice cores from Dronning Maud Land have been studied by means of sulfur isotopic analysis and detailed ion analysis to reveal temporal and spatial differences in the influencing sulfur source. The two ice cores represent the coastal area and the polar plateau, respectively. The isotopic signals were similar within each ice core, indicating no temporal change of influencing sources during the last 1100 yr. The mean values at the two different sites were also similar: 14.6 +/- 0.3 parts per thousand and 14.7 +/- 0.3 parts per thousand, respectively. The similarity remains between calculated non-sea-salt values when a sulfate-depleted sea-salt aerosol is assumed in the costal core. When the influence of sporadic explosive volcanic eruptions is subtracted from the signal, the isotopic value from the polar plateau (15.4 +/- 0.6 parts per thousand) is significantly lower than prescribed values for marine biogenic sulfur. This suggests that one or more additional sources contribute to the sulfate budget. Several possible contributors are discussed in the context of former sulfur isotopic signals presented from Antarctica.