The goal of this project is to obtain a long-term (160K yrs.) record of the atmospheric deposition of marine derived sulfur to the East Antarctic ice sheet. Measurements of methanesulfonic acid (MSA) and non-seasalt sulfate will be made on samples on Vostok and several other Antarctic ice cores. The data will allow an assessment of the levels and variability of the organosulfur signal under a variety of climatic conditions ranging from the relatively stable interglacial or glacial maximum to the glacial/interglacial transitional periods. The MSA data will provide a basis for differentiating between sulfate of biogenic origin, which was originally present in the atmosphere as fine particle size marine aerosols, and sulfate aerosols derived from abiotic sources. This information has a direct bearing on our interpretation of the ice-core record in terms of the abundance of cloud condensation nuclei in the paleoatmosphere. The flux of dimethylsulfide, and hence MSA, through the marine atmosphere is also directly related to the primary productivity of the oceans, a critical factor in the long-term control of atmospheric PC02. Thus, the global distribution of MSA in ice cores can potentially contribute to the testing of various scenarios of climate change driven by changes in oceanic productivity. Because the MSA concentration is a regional tracer, data from a number of sites are needed. Vostok core represents an important element in a larger data set needed to reconstruct the paleoatmospheric signal of marine sulfur emissions.
