Establishment of modern circulation pattern at c. 6000 cal a BP in Disko Bugt, central West Greenland: Opening of the Vaigat Strait

摘要

Variations in the Holocene circulation of the West Greenland Current (WGC) in the Disko Bugt region have been reconstructed from a suite of sediment cores. Palaeoceanographic proxies include magnetic susceptibility (MS) and X-ray fluorescence titanium counts, which document a major shift in circulation at c. 6000 cal a BP. Before this date, sediments in southern Disko Bugt were characterized by high terrigeneous and basaltic input, suggesting widespread influence of meltwater plumes. Our data show that the WGC re-circulated in the southern Disko Bugt area because a potential northern pathway, the narrow Vaigat Strait, was blocked by icebergs that calved from marine outlet glaciers in eastern Disko Bugt. Sediments in southern Disko Bugt deposited after c. 6000 cal a BP have significantly lower terrestrial and basaltic sediment input, which coincides with minimum Holocene ice sheet extent. The reduced meltwater and iceberg discharge to the embayment caused the Vaigat Strait to become free of blocking icebergs and terrigenous input was partly diverted to the outer shelf. Thus, the modern circulation pattern of the WGC was established in the Disko Bugt region through the opening of the Vaigat Strait c. 6000 cal a BP.