In-Situ Radiocarbon Production by Neutrons and Muons in an Antarctic Blue Ice Field at Scharffenbergbotnen: A Status Report

Abstract

In the radiocarbon accelerator mass spectrometry (14C AMS) analysis of gases obtained in a dry extraction from a 52–m Antarctic ice core, we observed 14CO2 and 14CO concentrations decreasing with depth. The concentrations are explained in terms of in-situ production by neutrons and captured muons in ablating ice. The ratio of the 14CO2 concentration to that of 14CO has been found to be constant at 1.9 ± 0.3. The ablation rates obtained of 42 ± 18 cm.yr−1 and 40 ± 13 cm.yr−1 for the neutron and muon components, respectively, are about three times higher than observed from stake readings. The discrepancy may point to an incomplete extraction of the dry extraction method. Using the constant ratio in 14CO2 and 14CO concentrations we correct for the in-situ component in the trapped 14CO2 and deduce an age of 10,300 ± 900 BP for the ice core.