A high-resolution 1200-year lacustrine record of glacier and climate fluctuations in Lofoten, northern Norway

Abstract

Here we present the first high-resolution late-Holocene glacier record from the Lofoten archipelago in northern Norway. The study is based on analyses of lacustrine sediments from the distal glacier-fed lake Kveitvikvatnet (30.1 m a.s.l.), as well as glacial-geomorphological mapping of the ~4.2-km2 surrounding catchment. The lake sediment cores have been examined for input of glacial-derived sediments by using physical, geochemical and magnetic sediment properties, including x-ray fluorescence (XRF), magnetic susceptibility (MS), grain size analyses, dry bulk density (DBD) and loss-on-ignition (LOI). Former glacier extent has been reconstructed using aerial photography and glacial-geomorphological mapping. Lichenometric dating has been used to construct a moraine chronology covering the recent fluctuations of the largest glacier (back to AD ~1740). AMS radiocarbon dating reveals that the lake sediment record covers the last 1200 years, thereby including both the ‘Little Ice Age’ (LIA) and the ‘Medieval Climate Anomaly’ (MCA). By linking continuously deposited lake sediment proxies of glacier fluctuation to known glacier frontal positions and an independent temperature reconstruction, former fluctuations in the equilibrium-line altitude (ELA) and winter precipitation have been reconstructed. Reconstructed winter precipitation estimates have also been correlated to instrumental data from the region back to AD 1895 and show a remarkable correlation, which further strengthens our approach. We found that both MCA and LIA were periods of substantial glacier variations with respect to the present, with a maximum lowering of the ELA of ~75 and ~85 m, respectively. Increased precipitation during these intervals, associated with more frequent and/or intense winter storms, is suggested to be the major driving force of glacier fluctuations in Lofoten.