Evidence for two intervals of enhanced ¹⁰Be deposition in Antarctic ice during the last glacial period

Abstract

We have previously reported concentration profiles of cosmic ray produced (cosmogenic) ¹⁰Be in deep ice cores from Dome C and Vostok, Antarctica^1,2. In both these cores we found a concentration of ¹⁰Be approximately two times larger in ice from the late glacial period than in the Holocene ice. We interpreted this as probably resulting from a lower precipitation rate on the Antarctic plateau during glacial periods, compared to interglacial periods. In the Vostok profile there was one sample, corresponding to ∼60,000 yr BP, which gave an unusually large ¹⁰Be concentration, not correlated with any obvious climatic event. We suggested that this sample might be reflecting increased ¹⁰Be production, as for example during a period of reduced solar modulation². We have now measured a much more detailed concentration profile for ¹⁰Be in the Vostok core. The results confirm a ¹⁰Be 'peak', lasting ∼1,000–2,000 years, at ∼60,000 yr BP, and show another similar peak at ∼35,000 yr BP. We have also observed the latter peak in the Dome C core. We discuss possible sources for these peaks, and their potential as stratigraphic markers.