From pre-bomb levels to industrial times: A complete tritium record from an alpine ice core and its relevance for environmental studies

An ice core recovered from a cold glacier in the Swiss Alps (Fiescherhorn Plateau, 4000 m a.s.l.) provides a high resolution climatic and environmental proxy data for the last four decades. The stable isotope record indicates that the seasonal variation of the stored precipitation is not remarkably altered by post-depositional processes. By combining it with a tritium record of equally spaced resolution, a much better control of time and seasonality is obtained. This control allows a more quantitative reconstruction of the ice core proxies by comparing them with nearby contemporary instrumental data sets. The times series on tritium in precipitation, which started in 1961 for Middle Europe (IAEA/WMO network station in Vienna) and in 1971 for Switzerland, could be extended back to 1946. A comparison with Swiss isotope network stations indicates that the tritium concentrations in the ice core are less influenced by locally emitted industrial tritium. The reconstructed pre-bomb values are somewhat higher than those obtained from single wine samples and show an increase towards 1946. Regarding the evolution of environmental tritium in precipitation, the full data set is suitable as a reference, at least for Middle Europe. (author)