Description: A subglacial drainage network underneath the paleo-ice sheet off West Greenland is revealed by a new compilation of high-resolution bathymetry data from Melville Bay, northeast Baffin Bay. This drainage network is an indicator for ice streaming and subglacial meltwater flow toward the outer shelf. Repeated ice sheet advances and retreats across the crystalline basement together with subglacial meltwater drainage had their impact in eroding overdeepened troughs along ice stream pathways. These overdeepenings indicate the location of a former ice sheet margin. The troughs inherit characteristics of glacial and subglacial meltwater erosion. Most of the troughs follow tectonic weakness zones such as faults and fractures in the crystalline bedrock. Many of these tectonic features correspond with the orientations of major fault axes in the Baffin Bay region. The troughs extend from the present (sub) glacial fjord systems at the Greenland coast and parallel modern outlet-glacier pathways. The fast flowing paleo-ice streams were likely accelerated from the meltwater flow as indicated by glacial landforms within and along the troughs. The ice streams flowed along narrow tributary troughs and merged to form large paleo-ice streams bedded in the major cross-shelf troughs of Melville Bay. Apart from the troughs, a rough seabed topography characterises the bedrock, and we see a sharp geomorphic transition where ice flowed onto sedimentary rock and deposits.

Description: High-resolution bathymetric data from close to the northwest Greenland coast in northern Melville Bay, northeast Baffin Bay, reveal a range of glacial and nonglacial landforms. The glacial landforms include crag-and-tails, mega-scale glacial lineations (MSGL), rock drumlins, and roche moutonnées that indicate paleo-ice sheet dynamics. The nonglacial landforms include steep ridges that are interpreted as volcanic dykes (Neoproterozoic Thule dyke swarms and Paleoproterozoic Melville Bugt dyke swarms). These dykes are glacially overprinted and may have channeled ice and subglacial meltwater flow through narrow subglacial cavities. Some of the glacial landforms eroded into bedrock indicate a southward paleo-ice stream orientation; while other glacial landforms, including the sedimentary depositional landforms, indicate a westward paleo-ice stream orientation. The glacial landforms were likely produced during at least two epochs and under changing thickness of the ice streams. The glacial landforms eroded into the bedrock are likely older than the sedimentary glacial landforms and were likely produced by a thin south/southeastward ice stream that allowed cavity formation. The westward-oriented glacial landforms were likely produced by a thick ice stream that was probably active during the Last Glacial Maximum (LGM). The different orientations of the glacial landforms indicate a reorganization of the ice streams that may have occurred during retreat and subsequent readvance. This reorganization likely coincided with a migration of the ice divide from south to north.