In situ cosmogenic ³H, ¹⁴C, and ¹⁰Be for determining the net accumulation and ablation rates of ice sheets

Abstract

We explore the usefulness of the in situ cosmogenic 3 H, 14 C, and 10 Be produced by spallation of oxygen nuclei in ice, as tracers to determine net accumulation/ablation rates of ice sheets. The application of the in situ 3 H and 10 Be is severely constrained because at deposition, ice contains appreciable amounts of these isotopes from the atmosphere. The case is much more favorable for 14 C, which is not carried with wet precipitations; atmospheric 14 C gets mechanically trapped in the ice during deposition. We point out that cosmogenic 14 C would probably exist as 14 CO in ice. This seems to be supported by the published results of Fireman and Norris. Considering their inherent amounts in the ice and the expected in situ production rates, we discuss conditions under which these isotopes can be used to study net accumulation and ablation rates. We also discuss available data on 14 C and 10 Be on polar ice from accumulation and ablation zones. We conclude that 3 H and 14 C should find wide applications in studying ice dynamics and 10 Be in very special circumstances.