Helium trapped in historical slags: a search for temporal variation of the He isotopic composition of air

We have synchronized records of ice-rafted rock debris deposits of three sediment cores from the Norwegian Sea and the Irminger Basin during the last glacial period from 10 to 50 ka by combining the use of radiocarbon dates and adjustments of physical properties. Our synchronized records indicate that layers rich in ice-rafted debris were deposited throughout the Nordic regions at times near to synchronous with the major collapses of the Laurentide ice sheet: during the Heinrich events. There are also millennial-scale, coherent and near to synchronous deposits of ice-rafted rock debris into the Norwegian Sea related to repetitive changes of the flux of icebergs from the Fenno-Scandinavian. The correlation with the cold phases of the Dansgaard–Oeschger temperature record points to a close coupling between atmospheric temperature oscillations and variations of iceberg fluxes into the Norwegian Sea during the last glacial. Variations in atmospheric circulation patterns bringing moisture supply to high latitudes and the distribution of this moisture over the different Northern Hemisphere coastal ice sheets and ice shelves could be controlling both the timing of ice sheet advances and the flux of iceberg to the open ocean.