9614384 Zielinski 9615167 Dunbar This award supports a project to characterize the volcanic material in the Siple Dome and Taylor Dome ice cores. The time series of volcanic aerosol and tephra deposition available in high-resolution, bi-polar ice cores is the most reliable means of developing continuous and lengthy records of past volcanic activity and assessing the climatic and environmental impact of global volcanism. The volcanic records from the Siple Dome ice core, initial ice core in the West Antarctica Ice Core Program (WAISCORES), and the Taylor Dome core, recently collected from the Transantarctic Mountains, will provide the Southern Hemisphere component of this record. These results will complement the lengthy GISP2 volcanic record from Greenland. Annual resolution should be available in the Siple Dome core for the Holocene resulting in the longest volcanic record with such resolution from Antarctica. Total length of record thought to be available from the Siple Dome core is 80,000 years whereas that for the Taylor Dome core is probably over 100,000 years. Although temporal resolution will be much coarser in the glacial portion of the Siple Dome core and in much of the Taylor Dome core, correlations and comparisons of the volcanic records from those cores with those from the GISP2 core are still possible. Evaluation of the timing of the volcanic signals in relationship to the record of changing climatic conditions available in these ice cores provides critical information on the climate forcing capabilities of global volcanism on decadal to century time scales through the Holocene. The key to developing a reliable chronology of past volcanism from the Siple Dome core is the simultaneous and continuous measurement of SO42-, a direct measure of the volcanic H2SO4 produced from the eruption, and the search for tephra in the same subsamples over the entire length of the core. The glaciochemical record will be available through other investigator s in the Siple Dome project. The glaciochemical record for the Taylor Dome core is presently available. Locating tephra and identifying the source of the volcanic glass through both optical microscope and microbeam (both electron and ion microprobes) analyses will verify the source of the chemical signal and help differentiate between equatorial and local eruptions. Comparisons with the GISP2 volcanic record will assist in achieving this goal. This multiparameter approach to deciphering the volcanic record will improve on our understanding of the influence of volcanism on climate both interhemispherically and intrahemispherically. The correlation of tephra found in these cores with that found in marine sediments and in the terrestrial record will expand on the chronology of global volcanism and improve the correlation among ice core, marine, and terrestrial proxy climatic records. Visible tephra layers that should exist in the Siple Dome core and do exist in the Taylor Dome core will provide additional absolute time lines for possible correlations between the two cores, among previously collected Antarctica ice cores and with tephra studies in blue ice areas of Western Antarctica and the Transantarctic Mountains.
