Firn Accumulation Processes in Taylor Dome, Vostok and Siple Dome Ice Using Cosmogenic 14 C and 10Be as Tracers

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9909484LalThis award is for support for three years of funding to develop a history of snow accumulation and physical processes occurring in the upper layers of ice deposited at several sites in Antarctica, using cosmogenic in-situ Carbon-14 (14C) and cosmogenic Beryllium-10 (10Be) as radiotracers. The proposed research emerges from recent studies of cosmogenic in-situ 14C in GISP2 Holocene and several Antarctic ice samples, which revealed marked differences in the 14C concentrations in the samples, compared to the theoretically expected values. The GISP2 samples have about the expected amount of 14C but the Antarctic samples are deficient by 30-50% or more. These results suggest that in slowly accumulating ice samples (such as occur in Antarctica), the cosmic ray implanted 14C is somehow partially lost, but quantitatively preserved in samples from areas of high accumulation. These results suggest that after deposition of the cosmogenic 14C, its concentration is decreased in firn due to processes such as recrystallization, sublimation/evaporation and redeposition. In order to quantify these processes, the atmospheric cosmogenic 10Be in ice samples will also be measured. Since 10Be and 14C have different responses to the firnification processes, their simultaneous study can help to elucidate the nature and importance of these processes. Samples from Taylor Dome, Vostok and Siple Dome will all be studied.