Repeated ice streaming on the northwest Greenland continental shelf since the onset of the Middle Pleistocene Transition

Abstract

Ice streams provide a fundamental control on ice sheet discharge and depositional patterns along glaciated margins. This paper investigates ancient ice streams by presenting the first 3D seismic geomorphological analysis of a major glacigenic succession offshore Greenland. In Melville Bugt, northwest Greenland, six sets of landforms (five buried and one on the seafloor) have been interpreted as mega-scale glacial lineations (MSGLs) that provide evidence for extensive ice streams on outer palaeo-shelves. A gradual change in mean MSGL orientation and associated depocentres through time suggests that the palaeo-ice flow and sediment transport pathways migrated in response to the evolving submarine topography through each glacial-interglacial cycle. The stratigraphy and available chronology show that the MSGLs are confined to separate stratigraphic units and were most likely formed after the onset of the Middle Pleistocene Transition at 1:3 Ma. The MSGL record in Melville Bugt suggests that since 1:3 Ma, ice streams have regularly advanced across the continental shelf during glacial stages. High-resolution buried 3D landform records such as these have not been previously observed anywhere on the Greenland continental shelf margin and provide a crucial benchmark for testing how accurately numerical models are able to recreate past configurations of the Greenland Ice Sheet.