Abstract. The presence of a grounded Greenland Ice Sheet on the northeastern part of
the Greenland continental shelf during the Last Glacial Maximum is supported
by new swath bathymetry and high-resolution seismic data, supplemented with
multi-proxy analyses of sediment gravity cores from Store Koldewey Trough.
Subglacial till fills the trough, with an overlying drape of maximum 2.5 m
thick glacier-proximal and glacier-distal sediment. The presence of
mega-scale glacial lineations and a grounding zone wedge in the outer part
of the trough, comprising subglacial till, provides evidence of the
expansion of fast-flowing, grounded ice, probably originating from the area
presently covered with the Storstrømmen ice stream and thereby previously
flowing across Store Koldewey Island and Germania Land. Grounding zone
wedges and recessional moraines provide evidence that multiple halts and/or
readvances interrupted the deglaciation. The formation of the grounding zone
wedges is estimated to be at least 130 years, while distances between the
recessional moraines indicate that the grounding line locally retreated
between 80 and 400 m yr−1 during the deglaciation, assuming that the
moraines formed annually. The complex geomorphology in Store Koldewey Trough
is attributed to the trough shallowing and narrowing towards the coast. At a
late stage of the deglaciation, the ice stream flowed around the topography
on Store Koldewey Island and Germania Land, terminating the sediment input
from this sector of the Greenland Ice Sheet to Store Koldewey Trough.
Last glacial ice sheet dynamics offshore NE Greenland – a case study from Store Koldewey Trough
