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

Abstract

Detailed ionic analyses of Dyer Plateau snow show that major soluble impurities in snow consist of sodium (Na+), chloride (Cl−), nitrate (NO3 −), sulfate (SO4 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−, NO3 −, and non-sea-salt (nss) SO4 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 NO3 − flux and background nss-SO4 2− flux. These results suggest that dry deposition is primarily responsible for air-to-ground Cl− flux while wet deposition dominates the NO3 − and nss-SO4 2− flux (≥90% and ≥75%, respectively). The nss-S04 2− fluxes provide a chronology of explosive volcanic emissions reaching the Antarctic region for the past 485 years.