Evolution of a Lateglacial mountain icecap in northern Scotland

Authors


  • Andrew Finlayson (e-mail: afin@bgs.ac.uk), British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK and Institute of Geography, University of Edinburgh, Drummond Street, Edinburgh EH8 9XP, UK; Nick Golledge (e-mail: nick.golledge@vuw.ac.nz), Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand; Tom Bradwell (e-mail: tbrad@bgs.ac.uk), British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, UK; Derek Fabel (e-mail: Derek.Fabel@ges.gla.ac.uk), Department of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK

Abstract

Finlayson, A., Golledge, N., Bradwell, T. & Fabel, D. 2011: Evolution of a Lateglacial mountain icecap in northern Scotland. Boreas, Vol. 40, pp. 536–554. 10.1111/j.1502-3885.2010.00202.x. ISSN 0300-9483.

Detailed geomorphological mapping of the Beinn Dearg massif, northern Scotland, was conducted to examine the maximum (Younger Dryas) extent, and earlier interstadial evolution, of an icecap that existed during the Lateglacial period (14.7–11.7 cal. ka BP). Landform evidence indicates a plateau icecap configuration during the Younger Dryas. The interpreted age is supported by new cosmogenic exposure ages and previously reported interstadial sediments beyond the icecap margin. The reconstructed Younger Dryas Beinn Dearg icecap covered 176 km2. Equilibrium line altitudes (ELAs) of ∼570–580 m were calculated for the icecap as a whole. The empirically reconstructed icecap is compared with recent numerical model simulations. The two methods produce an icecap with a similar configuration; however, differences are apparent in the extent of eastern and western outlets (±1–5 km), and in the spatial variation of ELAs. Results suggest that the numerical simulation overestimates the western and underestimates the eastern icecap extent. We attempt to quantify these differences in terms of icecap mass balance and assess their possible causes. Geomorphological evidence for the pre-Younger Dryas icecap configuration indicates that the Beinn Dearg massif remained an important source during earlier deglaciation. In contrast, the neighbouring Fannich mountains acted as an ‘unzipping’ zone, and were ice-free on their northern side by the Allerød (Greenland Interstadial 1c to 1a). Deglaciation continued over the western Beinn Dearg plateau, with the possibility that glaciers remained in some central and eastern catchments prior to (Younger Dryas) icecap (re)growth.

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