WAIS Divide Ice Core Project
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Ice cores provide valuable information on past atmospheric composition, chemistry, and climate. Atmospheric chemistry is controlled by its "oxidation capacity", defined by OH radical concentrations. OH concentrations determine the lifetime of many atmospheric species, including climatically important species such as methane. The oxygen isotopes of sulfate and nitrate can provide the first conservative proxy for past OH concentrations, enabling us to study the link between atmospheric chemistry and climate. |
 Photo:
ICDS 2006 |
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Our longest record of the O-isotope composition of sulfate comes from the Vostok ice core in east Antarctica, extending through the past 125,000 years.This figure shows the variability in the O-isotopic composition (D17O) of sulfate, along with dDice measurements (indicative of temperature), through the last glacial-interglacial cycle from the Vostok (Antarctica) ice core [Alexander et al. 2002]. Sulfate formation through oxidation of reduced sulfur species by OH is 30-50% more important during the cold glacial period, than the surrounding interglacial periods. This change is due to changing OH concentrations and/or cloud processing efficiency. A more quantitative interpretation of this paleo record will be provided by a global model of chemistry and transport. |
The WAIS Divide project will provide the first complete record of multiple isotope ratios of nitrate and sulfate covering the last ~100,000 years, from the deep ice core planned for the central ice divide of the West Antarctic Ice Sheet (WAIS). The WAIS Divide ice core will be the highest resolution long ice core obtained from Antarctica and we can expect important complementary information to be available, including accurate knowledge of past accumulation rates, temperatures, and compounds such as H2O2, CO and CH4. These compounds play significant roles in global atmospheric chemistry and climate. Especially great potential lies in the use of multiple isotope signatures. The unique mass independent fractionation (MIF) D17O signature of ozone is observed in both nitrate and sulfate, due to the interaction of their precursors with ozone. The development of methods to measure the multiple-isotope composition of small samples of sulfate and nitrate makes continuous high resolution measurements on ice cores feasible for the first time. This project will coincide with the International Polar Year (2007-2008), and contributes to goals of the IPY, which include the fostering of interdisciplinary research toward enhanced understanding of atmospheric chemistry and climate in the polar regions. |
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| People: | |
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Eric Steig (lead P.I.), Becky Alexander (co-P.I.), Shelley
Kunasek, and Meredith Hastings, University of Washington Mark H. Thiemens (co-P.I.), University of California, San Diego | |
| Funding: | |
| NSF-OPP 0538049 | |
| References: | |
| Alexander, B., Savarino, J., Thiemens, M.H., and Delmas, R., “Climate driven changes of the oxidation pathways of atmospheric sulfur,” Geophys. Res. Lett., 29(14), 30 (2002). | |
