Past and recent ice related impacts on the seafloor offshore Northeast Greenland

In the past, the Arctic underwent numerous phases of glaciation and deglaciation. Compared to modern times where only the mainland of Greenland is covered by an ice sheet, several kilometers thick ice sheets existed all around the Arctic Ocean during glacial periods. Large ice streams drained these ice sheets across the present-day continental shelves to the oceans. In some locations, the ice sheet still had an ice thickness of more than 1 km at the termination of the ice streams. From here, huge icebergs calved into the surrounding waters. In phases of rapid deglaciation, the iceberg calving rate was increased with the possibility of building iceberg armadas after occasional ice sheet breakup events. Afterwards, the released icebergs drifted with the currents and occasionally grounded at the seafloor where it was shallower than the iceberg draft. These grounding events of icebergs as well as from ice streams left traces on the seafloor (Fig. 1). They can persist for long time periods due to the low sedimentation rates. In high resolution swath bathymetric data, we are nowadays able to see the impacts of the icebergs on the seafloor that, sometimes, have occurred several 100 000 years ago, but in shallower areas still occur today. We will give a brief overview of glacial seafloor features in the Arctic and present results from investigations of RV Polarstern swath bathymetric data that has been collected offshore Northeast Greenland during the last decades. We found evidence of very deep iceberg scouring in Fram Strait and abundant iceberg scouring on the shoals and banks of the Northeast Greenland continental shelf. Furthermore, glacial seafloor features produced under palaeo-ice streams allow us to give new minimum extents of the past Greenland ice sheet and to provide constraints to its retreating history during deglaciation