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Project Title

Modelling the dynamic evolution and sensitivities of two palaeo ice-masses: the Welsh Ice Cap and the Icelandic Ice Sheet

Thesis Abstract

Geological data and numerical modelling are used in combination to further understand the dynamic evolution and sensitivity of two contrasting ice sheets during the last glaciation – the Welsh Ice Cap and the Icelandic Ice Sheet. Through this approach, data derived at different scales, both spatially and temporally, are compared and applied holistically to provide an empirically constrained reconstruction.

Dynamics of the Welsh Ice Cap – a peripheral ice accumulation centre of the British-Irish Ice Sheet during the Late Devensian – have remained relatively poorly understood, in part due to the lack of glacial modification observed throughout the interior of the domain. High-resolution numerical modelling experiments reveal a thick ice mass dominated by strong flow partitioning, with the majority of the high terrain overlain by cold-based, non-erosive ice driven by internal deformation. The timing and dynamics of the topographically constrained outlet glaciers that drain the interior of the ice cap become modulated by, and respond rapidly to, oscillations within the forcing climate. New bathymetric data from Tremadog Bay reveal an asynchrony and asymmetry in the style and timing of retreat during Welsh deglaciation in response to climatic fluctuations.

Previous reconstructions of the Late Weichselian Icelandic Ice Sheet are revisited in light of new offshore landform mapping revealing an extensive glacial ‘footprint’ across the entire continental shelf. Modelling experiments determine that the levels and distribution of precipitation during the Last Glacial Maximum are crucial in driving the ice sheet to the continental shelf break in all sectors. Deglaciation occurs rapidly, triggered by widespread surface melting and exacerbated by rising sea-levels enhancing calving losses. Younger Dryas glaciation is characterised by strong aridity, likely a result of extensive sea-ice cover in the North Atlantic shifting cyclone tracks southwards. Sensitivity tests of the reference experiment reveal the geothermal flux to be a considerable control on the dynamic behaviour of the Icelandic Ice Sheet, influencing its effective mobility via isostatic loading on the crust and mantle. The modelled large-scale instabilities of this geothermally influenced, marine-terminating ice sheet reveal potentially alarming implications for a direct present-day analogue: the West Antarctic ice sheet.

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So far, research from the project has been published in the following papers:

  • Patton, H., Hubbard, A., Bradwell, T., Glasser, N. F., Hambrey, M. J., and Clark, C. D., 2013. Rapid marine deglaciation: asynchronous retreat dynamics between the Irish Sea Ice Stream and terrestrial outlet glaciers, Earth Surface Dynamics Discussions 1, 277-309, doi:10.5194/esurfd-1-277-2013, 2013. Link
  • Patton, H., Hubbard, A., Glasser, N.F., Bradwell, T., Golledge, N.R., 2013. The last Welsh Ice Cap: Part 2 – Dynamics of a topographically controlled ice cap. Boreas 42(3), 491-510. Link
  • Patton, H., Hubbard, A., Glasser, N.F., Bradwell, T., Golledge, N.R., 2013. The last Welsh Ice Cap: Part 1 – Modelling its evolution, sensitivity and associated climate. Boreas 42(3) 471-490. Link

Timeslices of a modelled Welsh Ice Cap


Dr. Alun Hubbard and Prof. Neil Glasser – Aberystwyth University
Dr. Tom Bradwell – British Geological Survey
Dr. Nick Golledge – Victoria University, Wellington