Lay summary
LeadA new radiocarbon dating method for glacier ice will be developed to provide complementary age information for the time period 15'000-500 years before present. IntroductionHigh-alpine ice cores from mid- and low-latitude glaciers and ice caps provide regional climate signals. To interpret the information contained in natural climate archives requires a precise chronology. For high-alpine ice cores there is a lack of an appropriate dating tool for the lowermost section since counting of annual layers is in the best case limited to a couple of centuries and is not suitable for the oldest and deepest ice. For these timescales, radiocarbon analysis can provide an absolute date. Recently a novel radiocarbon method has been developed by our group, using carbonaceous aerosols contained in the ice for radiocarbon dating. Carbonaceous particles are a major component of naturally occurring aerosols that are emitted ubiquitously or formed in the atmosphere and transported to potential ice core sites. The method is operational and may in principle be valuable for any ice body, that accumulated enough contemporary carbonaceous particles in the past and that remained undisturbed since then.Aims of the projectIn order to improve the skill of the radiocarbon dating method for broader application, we want to test the prospect of using total organic carbon (TOC) or water-soluble organic carbon (WSOC). TOC or WSOC represent the majority of carbon-containing compounds in ice and are therefore the most obvious carbon fraction for dating purposes. Using these major carbon fractions will increase the sensitivity and precision and will thus allow wider application to ice samples with generally lower carbon content, for example from polar regions, or to smaller sized samples. To achieve this goal a technique for extracting 14CO2 from the TOC or WSOC fraction of snow and ice will be developed and validated through analysis of well dated ice from existing ice cores.ImplicationsThis innovative radiocarbon method is thought to have major implications for dating non-polar and polar ice cores in the future, as it provides complementary age information for the time period 15'000-500 years BP which is not accessible with common dating techniques.