Scientific Drilling ICDP Publications

A 450-year spring/summer flood layer time series at seasonal resolution has been established from the varved sediment record of Lake Ammersee (Southern Germany) applying a novel methodological approach. The main results are (1) a precise chronology obtained by microscopic varve counting, (2) the identification of detrital layers representing flood2 triggered fluxes of catchment material into the lake, and (3) the recognition of the seasonality of these flood layers from their micro-stratigraphic position within a varve. Tracing flood layers in a proximal and a distal core and correlating them applying the precise chronology provided information on the depositional processes. Comparing the seasonal flood layer record with daily runoff data of the inflowing River Ammer for the period from 1926 to 1999 allowed defining an approximate threshold in flood magnitude above which the formation of flood layers becomes very likely. Moreover, it was for the first time possible to estimate the ‘completeness’ of the flood layer time series and to recognize that mainly floods in spring and summer representing the main flood seasons in this region are well preserved in the sediment archive. Their frequency distribution over the entire 450-year time series is not stationary, but reveals maxima for colder periods of the Little Ice Age when solar activity was reduced. The observed spring/summer flood layer frequency further shows similar trends as the occurrence of flood-prone weather regimes since AD 1881, probably suggesting a causal link between solar variability and changes in mid-latitude atmospheric circulation patterns.

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Czymzik, M.; Dulski, P.; Plessen, B.; von Grafenstein, U.; Naumann, R.; Brauer, A. (2010): A 450-year record of spring/summer flood layers in annually laminated sediments from Lake Ammersee (Southern Germany). Water Resources Research, 46, W11528.