Controls upon the Last Glacial Maximum deglaciation of the northern Uummannaq Ice Stream System, West Greenland

Abstract

Citation for published item:vneD FF nd oertsD hFrF nd eD fFF nd ¡ y gofighD gF nd ieliD eF nd od¡ esD eF @PHIRA 9gontrols upon the vst qlil wximum deglition of the northern ummnnq se trem ystemD est qreenlndF9D uternry siene reviewsFD WP F ppF QPREQRRF Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe Uummannaq ice stream system (UISS) was a convergent cross-shelf ice stream system that operated in West Greenland during the Last Glacial Maximum (LGM). This paper presents new evidence constraining the geometry and evolution of the northern sector of the UISS and considers the factors controlling its dynamic behaviour. Geomorphological mapping, 21 new terrestrial cosmogenic nuclide (TCN) exposure ages, and radiocarbon dating constrain LGM warm-based ice stream activity in the north of the system up to 1400 m a.s.l. Intervening plateaux areas either remained ice free, or were covered by cold-based icefields. Beyond the inner fjords, topography and bathymetry forced ice flow southwards into the Uummannaq Trough, where it coalesced with ice from the south, and formed the trunk zone of the UISS.Deglaciation of the UISS began at 14.9 cal. kyr BP. Rapid retreat from the LGM limit was forced by an increase in air temperatures and rising sea level, enhanced by the bathymetric over- Greenland, which suggest ice had retreated beyond its present margin by 9-7 kyr. This demonstrates the potential importance of topographic control on calving margin stability, and its ability to override climatic forcing.

The Greenland Ice Sheet during the last glacial cycle: Current ice loss and contribution to sea-level rise from a palaeoclimatic perspective

“…Kelly, 1985;Roberts et al, 2009), however, from recent studies (e.g. Corbett et al, 2013;Roberts et al, 2013;Lane et al, 2014;Winsor, 2014;Winsor et al, 2015) it seems likely that most trimlines in Greenland reflect an englacial thermal boundary rather than the LGM ice surface, i.e. that they mark a transition from warm-based ice (below the trimline) to cold-based, non-erosive ice (above the trimline).…”

The glacial history of the southern Svartenhuk Halvø, West Greenland

“…Sugden [84] classified southern and western Svartenhuk Halvø as displaying little or no glacial erosion, with the north and east classified as landscapes of cirque glaciers and plateau remnants. Recent mapping has reclassified a larger proportion of the peninsula as areas of mountain valley and cirque glaciers [54]. Sedimentological studies in Svartenhuk Halvø reported the presence of deltaic deposits with in situ marine molluscs (thought to be glacioisostatically uplifted), widespread shell-bearing littoral gravel and sublittoral muds, and a single exposure of diamicton [13].…”

“…The present ice-free landscape of Greenland is dominated by landscapes resulting from ice sheet activity (e.g. areal scour and selective linear erosion) and those formed through the action of independent valley and mountain glacier systems [54,84]. During full glacial conditions, the majority of land surrounding Greenland was inundated and covered by thick, ice stream and interstream ice as it moved offshore [35].…”

“…These areas would have potentially developed due to the intense focusing of ice flow which occurs in ice streams, starving peripheral, interstream areas of warm-based ice. This would leave them ice-free, or more likely stranded as fields of cold-based ice [53,54]. It is also possible that the existence of persistent, cold-based ice helped to preserve the sedimentary deposits throughout such regions.…”

Seafloor geomorphology and glacimarine sedimentation associated with fast-flowing ice sheet outlet glaciers in Disko Bay, West Greenland

“…e.g. Alley et al, 2005;Bamber et al, 2007;Nick et al, 2009;Ó Cofaigh 10 et al, 2013;Dowdeswell et al, 2014;Lane et al, 2014;Joughin et al, 2014;11 2 Hogan et al, 2016;Sheldon et al, 2016). Jakobshavn Isbrae, in central West and the overall interaction of the glaciers with the marine environment since the…”