GLACIAL VARVE THICKNESS AND 127 YEARS OF INSTRUMENTAL CLIMATE DATA - A COMPARISON

Annually laminated sediments (glacial varves) from Lake Silvaplauna, a High Alpine proglacial lake in the Central Swiss Alps, were compared with glacier monitoring data and instrumental climate data from 1864 t o 1990. Long-term and short-term responses to climatic change as well as anthropogenic influence can be traced separately in the varve succe ssion. Economic development in the lake catchment has resulted in high er autochthonous production in recent years. Autochthonous components contribute around 10% to the total amount of sediment accumulated annu ally since 1960 but their contribution is negligible before this date. Decadal-scale varve thickness trends correlate with glacier size-vari ations. A stepwise, running multiple regression analysis demonstrates that interannual changes in varve thickness are strongly correlated wi th changes in mean summer temperatures, but cannot be sufficiently exp lained without considering summer precipitation and the number of days with snow per year. The wide range of observed correlation coefficien ts reveals the sensitivity of the archive to temporal variability of t he climatic forcing factors and makes the development of transfer func tions ambiguous.