On the characteristics of cosmogenic in situ C-14 in some GISP2 Holocene and late glacial ice samples

In previous studies, we have shown that information on ice accumulation pro cesses is recorded by the in situ production of C-14, from nuclear interact ions of cosmic rays with oxygen in ice (Lal et al., 1997). In this report, we discuss a study of a number of Holocene and several glacial ice samples from the GISP2 core whose accumulation rates are known and which should be little affected by uncertainties in ice flow models (Cuffey et al., 1997), to determine trapping efficiencies of in situ C-14. We present new results along with discussion of the earlier results of Lal et al. (1997), which in clude results on partitioning of in situ C-14 among the CO and CO2 phases t hrough time in ice. The usefulness of the in situ C-14 data to measurements of ice accumulation rates and ages are discussed. (C) 2000 Elsevier Scienc e B.V. All rights reserved.