36Cl/10Be as a dating tool for old ice

The ³⁶Cl/¹⁰Be ratio has the potential to be a dating tool for old ice, as it decays with a combined half-life of  years and is thought to be independent of production changes, which affect the individual radionuclide concentrations in ice cores. However, when EDC samples with various ages between the Holocene and 887 kyr BP were analysed, the ³⁶Cl/¹⁰Be ratio was found to vary significantly between samples instead of decaying smoothly over time. Due to the different physical and chemical properties of ³⁶Cl and ¹⁰Be, different sensitivities to changes in climatic parameters, such as tropopause pressure and precipitation, are potentially the cause of the observed variability. Additionally, chlorine can be lost at low accumulation sites, such as EDC, as it can turn into hydrogen chloride and gas out from the firn. We present new measurements of the ³⁶Cl/¹⁰Be ratio from the Skytrain ice core, which should be unaffected by chlorine loss, due to the higher accumulation rate at its drilling site. The measurement series extends below the dated sections of the ice core to test the decay dating and help extend the Skytrain age scale. To analyse differences in transport and deposition between radionuclides, the ³⁶Cl/¹⁰Be ratio will also be determined with annual resolution in samples from 1982 – 2013 and compared to several climate parameters of the NOAA/CIRES/DOE 20^th century reanalysis (V3) dataset. However, the data of this project are not yet available.