A 485 year record of atmospheric chloride, nitrate and sulfate: results of chemical analysis of ice cores from Dyer Plateau, Antarctic Peninsula

Detailed ionic analyses of Dyer Plateau snow show that major soluble impurities in snow consist of sodium (Na + ), chloride (Cl − ), nitrate (NO 3 − ), sulfate (SO 4 2− ), and acidity (H + ). The ratios of Na + to Cl − concentrations are close to that of sea water, indicating little or no fractionation of sea-salt aerosols. The analyses of core sections from three sites along a 10 km transect show that local spatial variation of snow chemistry in this area is minimal and that temporal (decadal, inter-annual and sub-annual) variations in snow chemistry are very well preserved. Anion analyses of the upper 181 m section of two 235 m ice cores yield a data set of 485 years (1505-1989) of annual snow accumulation and fluxes of Cl − , NO 3 − , and non-sea-salt (nss) SO 4 2− . No significant long-term trends are observed in any of the anion fluxes. This is consistent with other Antarctic ice-core records showing no significant anthropogenic atmospheric pollution in the high southern latitudes. Linear regression analysis shows that Cl − flux is independent of snow-accumulation rate. Significant positive correlations are found between accumulation rate and both NO 3 − flux and background nss-SO 4 2− flux. These results suggest that dry deposition is primarily responsible for air-to-ground Cl − flux while wet deposition dominates the NO 3 − and nss-SO 4 2− flux (≥90% and ≥75%, respectively). The nss-S0 4 2− fluxes provide a chronology of explosive volcanic emissions reaching the Antarctic region for the past 485 years.