Late Pleistocene glacial history of Jameson Land, central East Greenland, derived from cosmogenic¹⁰Be and²⁶Al exposure dating

Abstract

Previous work has presented contrasting views of the last glaciation on Jameson Land, central East Greenland, and still there is debate about whether the area was: (i) ice‐free, (ii) covered with a local non‐erosive ice cap(s), or (iii) overridden by the Greenland Ice Sheet during the Last Glacial Maximum (LGM). Here, we use cosmogenic exposure ages from erratics to reconcile these contrasting views. A total of 43 erratics resting on weathered sandstone and on sediment‐covered surfaces were sampled from four areas on interior Jameson Land; they give 10Be ages between 10.9 and 269.1 kyr. Eight erratics on weathered sandstone and till‐covered surfaces cluster around ∼70 kyr, whereas 10Be ages from erratics on glaciofluvial landforms are substantially younger and range between 10.9 and 47.2 kyr. Deflation is thought to be an important process on the sediment‐covered surfaces and the youngest exposure ages are suggested to result from exhumation. The older (>70 kyr) samples have discordant 26Al and 10Be data and are interpreted to have been deposited by the Greenland Ice Sheet several glacial cycles ago. The younger exposure ages (≤70 kyr) are interpreted to represent deposition by the ice sheet during the Late Saalian and by an advance from the local Liverpool Land ice cap in the Early Weichselian. The exposure ages younger than Saalian are explained by periods of shielding by non‐erosive ice during the Weichselian glaciation. Our work supports previous studies in that the Saalian Ice Sheet advance was the last to deposit thick sediment sequences and western erratics on interior Jameson Land. However, instead of Jameson Land being ice‐free throughout the Weichselian, we document that local ice with limited erosion potential covered and shielded large areas for substantial periods of the last glacial cycle.

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

“…4A), but they stress that this is most probably a minimum scenario, given that some of the deposits may be recessional features formed during retreat of the ice margin rather than when it was at its largest. Other authors have favoured a scenario with more extensive LGM ice cover in this area (Ó Cofaigh et al, 2004;Håkansson et al, 2007Håkansson et al, , 2009, arguing that areas previously interpreted as being ice-free based on weathering limits could rather have been covered by cold based, non-erosive ice during the LGM, an interpretation that seems likely in light of new results from west Greenland (Corbett et al, 2013;Roberts et al, 2013;Lane et al, 2014;Winsor, 2014;Winsor et al, 2015).…”

Evidence for the asynchronous retreat of large outlet glaciers in southeast Greenland at the end of the last glaciation

“…This bedrock sample is interpreted as containing 10 Be from a previous period of exposure (e.g. Briner et al, 2008;Håkansson et al, 2009) and is excluded from further analysis. A paired bedrock sample (BS1104 e 13.6 ± 0.8 ka) from the same location is also excluded on the basis that erosion was insufficient to remove pre-existing isotope content at this location.…”

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

“…New constraints upon ice stream extent, thickness, and deglacial behaviour from the LGM to present have been established since the early 2000's both onshore (Bennike and Bjorck, 2002, Håkansson et al, 2007, Håkansson et al, 2009, Roberts et al, 2008, Roberts et al, 2009, Roberts et al, 2010, Roberts et al, 2013 and offshore (Ó Cofaigh et al, 2004, Evans et al, 2009, Dowdeswell et al, 2010. These have provided evidence for the existence of large ice streams across the West, Northeast and East Greenland continental shelves during the last glacial cycle (Lykke-Andersen, 1998, Ó Cofaigh et al, 2004, Evans et al, 2009, Dowdeswell et al, 2010.…”