New insights into the past glaciation of the northeast Greenland continental shelf

Abstract:

The North-East Greenland ice stream reaches about 700 km inland and drains a major part of the Greenland ice sheet via marine terminating glaciers at the western edge of the North-East Greenland Continental Shelf (NEGCS). Previous studies suggested that, during full-glacial periods, the ice sheet only extended to the inner shelf and did not reach further to the east. Based on radiocarbon dating data it was hypothesized that the Greenland Ice Sheet reached onto the middle shelf or even the shelf edge. An advance at least to the middle shelf at about 79.5 to 80.5° N was later demonstrated by two studies using new high-resolution swath bathymetric data that showed seafloor features, including mega-scale glacial lineations and retreat moraines, indicating past ice stream activity. These data, however, only provided a fragmented picture of the behaviour of this North-East sector of the Greenland ice sheet, with the majority of the NEGCS area unmapped.

Now, we have newly processed bathymetric data from R/V Polarstern that was acquired in the area of the NEGCS from 76° to 81° N throughout the last 25 years. In addition we include processed data collected by other institutions. In total, swath bathymetric data from 26 cruises has been investigated for glacigenic seafloor features. All glacigenic seafloor features have been mapped to provide a holistic overview of the area. We present the current stage of our investigation. It shows that glacial activity on the NEGCS was far more intense than previously estimated and that the ice sheet extended even further offshore.