Late Holocene High Discharge and Erosion Events Inferred from Sediment Proxies and Catchment Geomorphology, Lake Vuoksjávrátje, NW Sweden

Tuesday, 16 December 2014
Annika Berntsson1,2, Krister N Jansson1, Malin E Kylander1,2, François De Vleeschouwer3 and Sebastien Bertrand4, (1)Stockholm University, Stockholm, Sweden, (2)The Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden, (3)EcoLab, Auzeville Tolosane, France, (4)Ghent University, Ghent, Belgium
Alpine lakes in NW Sweden are highly sensitive to variations in catchment erosion and in precipitation. Previous studies aimed at reconstructing past summer temperatures have suggested that this sensitivity may influence chironomid species composition enough to cause bias in quantitative temperature reconstructions. In this study we have analysed lake sediments covering the last 5100 years from Lake Vuoksjávrátje in NW Sweden and catchment geomorphology with the aim to separate between different erosional regimes in the lake and its catchment and to identify sediment sources and processes behind sediment deposition in the lake basin. Methods include XRF core scanning, grain size analysis, chironomid analysis, TOC and C/N analysis and detailed mapping of geomorphology.

From the integrated results we identify time intervals with increased catchment erosion, inferred to result from intense precipitation. Based on the combined proxy data it was concluded that a major flood event took place at the Vindelfjällen site c. 2800 cal BP, unique for the 5100-year long record. The chironomid species composition shows stronger influence from wetland surface erosion at c. 2800 cal BP and during the last c. 1000 years. By combining multi-proxy lake sediment analysis with study of catchment geomorphology it is possible to improve the understanding of Late Holocene hydro-climatic change and how it may influence Arctic alpine lakes.