New constraints on Greenland ice sheet dynamics during the last glacial cycle: evidence from the Uummannaq ice stream system

Roberts, D. H., Rea, B. R., Lane, T. P., Schnabel, C. and Rodes, A. (2013) New constraints on Greenland ice sheet dynamics during the last glacial cycle: evidence from the Uummannaq ice stream system. Journal of Geophysical Research: Earth Surface, 118(2), pp. 519-541. (doi: 10.1002/jgrf.20032)

Abstract

This paper presents the first assessment of the Uummannaq ice stream system (UISS) in West Greenland. The UISS drained ~6% of the Greenland ice sheet (GrIS) at the Last Glacial Maximum (LGM). The onset of the UISS is a function of a convergent network of fjords which feed a geologically-controlled trough system running offshore to the shelf break. Mapping, cosmogenic radiogenic nuclide (CRN) dating and model output reveal that glacially scoured surfaces up to 1266 m asl in fjord-head areas were produced by warm-based ice moving offshore during the LGM, with the elevation of warm-based ice dropping westwards to ~700 m asl as the ice stream trunk zone developed. Marginal plateaux with allochthonous blockfields suggest that warm-based ice produced till and erratics up to ~1200 m asl, but CRN ages and weathering pits suggest this was pre-LGM, with only cold-based ice operating during the LGM. Deglaciation began on the outer shelf at ~14.8 cal. kyrs BP, with Ubekendt Ejland becoming ice free at ~12.4 ka. The UISS then collapsed with over 100 km of retreat by ~11.4 ka – 10.8 cal. kyrs BP; a rapid and complex response to bathymetric deepening, trough widening and sea-level rise coinciding with rapidly increasing air temperatures and solar radiation, but which occurred prior to ocean warming at ~8.4 cal. kyrs BP. Local fjord constriction temporarily stabilised the unzipped UISS margins at the start of the Holocene before ice retreat inland of the current margin at ~8.7 ka.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Schnabel, Dr Christoph and Rodes, Dr Angel
• Authors: Roberts, D. H., Rea, B. R., Lane, T. P., Schnabel, C., and Rodes, A.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Journal of Geophysical Research: Earth Surface
• Publisher: Wiley-Blackwell
• ISSN: 2169-9003
• ISSN (Online): 2169-9011
• Published Online: 02 May 2013