Reconstruction of the paleocenaography west of Lofoten during the Last Glacial Maximum

Abstract

<p>A 513 cm long sediment core from the Lofoten Contourite Drift at the continental slope west of the Lofoten Islands has been investigated. The aim was to reconstruct the paleoceanography during the Last Glacial Maximum (LGM). The Lofoten Contourite drift was relatively protected by the Lofoten Islands from the ice streams of the Scandinavian Ice Sheet during LGM. <p>An age model was constructed based on four ¹⁴C dates from the core and correlations to nearby cores described in Vorren et al. (2015) and Weinelt et al. (2003). The core dates range throughout most of the LGM from at least 17,000 to 24,500 years BP. <p>The results are based on multiproxy analysis of the sediment core. Lithology log, x-ray, physical properties, grain size analysis, sortable silt analysis and IRD analysis was used to reveal the sedimentary processes, glaciation, and current speeds. The foraminifera analysis, Mg/Ca analysis and stable oxygen – and carbon isotope provides information about bioproductivity, ventilation, bottom environment, surface freshening and bottom water temperature. The core holds unique data. There are Mg/Ca samples for almost every ~100 years on average for the LGM record (~23-18.5cal. ka BP), so it is possible to resolve centennial changes, which is new for the LGM in the Nordic Seas. <p>The Mg/Ca showed a consistently cold Bottom Water Temperature (BWT) throughout the record. The bottom water temperature is colder than expected for the North Atlantic Intermediate Water during the LGM. The minima in the BWT correlate with low δ¹³C, low abundance of planktic and benthic foraminifera and reduction of the current strength. This may indicate intermediate water formation and interruption of the warm North Atlantic Intermediate Water. There is also a cold period between 20 and 19.8 cal. ka BP with high bioproductivity which is believed to a be a period with polynyas and mixed water masses.