School of GeoSciences

School of GeoSciences

Nicholas Golledge

Research areas: Glacial geology and palaeoglaciology

Everest, April 2000

I've been working as a Quaternary Geologist at the British Geological Survey since 1997, and started a part-time Ph.D in April 2004 aimed principally at improving our knowledge of the glacial geology and glaciology of the Younger Dryas ice cap in the western Scottish Highlands. So I've spent the last few years mapping an area south of the main ice centre on Rannoch Moor, and recently have been running a numerical ice sheet model to simulate the entire ice cap. This combined approach means that we can directly link landform genesis and stratigraphic sequences back to the palaeoglaciological and climatological conditions that prevailed between 13-11.5 ka BP.

Field area - the Western Scottish Highlands

model

Between Rannoch Moor and Loch Lomond there are some big mountains that did their best to get in the way of the Younger Dryas icecap as it flowed from the former to the latter. Early reconstructions (e.g. those of Thorp 1984,1986) proposed coalescent low aspect ratio glaciers following the glens and together forming a 'mountain icefield', although others favoured much thicker ice (Thompson, 1972; Horsfield, 1983). My mapping suggests that the Younger Dryas ice was at least 20% thicker than envisaged by Thorp, which has important ramifications for ice sheet behaviour. The abundance of preserved sediment sequences and overprinted landforms in the field area seems to suggest that the ice cap was not particularly erosive, and probably flowed largely through internal deformation.

Testing these ideas with an ice sheet model is a powerful and independent check on field based reconstructions. I'm running Alun Hubbard's three-dimensional thermomechanical finite difference model at 500m grid resolution, mainly tweaking mass balance distribution and the basal sliding factor. Systematic perturbation of model parameters towards an optimum scenario reveals that only a small parameter window exists where the simulation accurately matches empirical limits. The model highlights a significant asymmetry in the main ice cap, with thinner, warmer and faster glaciers on the west than those flowing east. Maximum glacier velocity was around 550ma-1, but most of the interior was more-or-less immobile.

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