New geophysical evidence for a revised maximum position of part of the NE sector of the Greenland ice sheet during the last glacial maximum

• Published in: arktos
• Main Authors: Laberg, Jan Sverre, Forwick, Matthias, Husum, Katrine
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Verlag 2017
• Subjects: VDP::Matematikk og Naturvitenskap: 400::Geofag: 450::Kvartærgeologi; glasiologi: 465; VDP::Mathematics and natural science: 400::Geosciences: 450::Quaternary geology; glaciology: 465; Greenland ice sheet; Last glacial maximum; Subglacial landforms; Recessional moraines; Greenland; Store Koldewey; Ice Sheet; Store koldewey
• Online Access: https://hdl.handle.net/10037/13367; https://doi.org/10.1007/s41063-017-0029-4

Accepted manuscript version. Published version available at https://doi.org/10.1007/s41063-017-0029-4 The extent and dynamics of the north-eastern sector of the Greenland ice sheet (GIS) during the last glacial still remain very uncertain, and maximum ice extents to inner-shelf, mid-shelf and outer-shelf positions have been suggested. Here we argue that the margin of the GIS reached the shelf break along part of its NE sector during the last glacial maximum. Swath-bathymetry and sub-bottom profiler data from the outermost part of the Store Koldewey glacial trough reveal the first documentation of moraine ridges/grounding-zone wedges in this area, supporting ice expansion to the shelf break at ~76°N. A complex pattern of retreat moraines in the outer trough reflects a stepwise early deglaciation. It is suggested that this behavior is not in line with a deglaciation triggered by an abrupt sea level rise. According to established glacial geomorphological models this should have resulted in ice lift-off and a sea floor dominated by landforms formed during full-glacial conditions (streamlined bedforms) and ice disintegrations (iceberg plough marks). Instead, formation of the recessional moraines must have involved other mechanisms resulting in a step-wise ice retreat. This could possibly be related to melting of the grounded ice controlled by a temperature increase of the ocean as inferred for other parts of the Greenland ice sheet. An ice front position at the shelf break instead of at the inner or mid-shelf also implies a larger ice volume for this sector of the GIS during the LGM. It also implies a larger contribution of meltwater from GIS during the deglaciation.