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Investigating the potential for catastrophic collapse of Greenland’s ‘land’-terminating glacier margins

A proglacial lake being exposed by the retreating ice margin at Leverett Glacier on the western edge of the Greenland Ice Sheet (Photo. Andrew Tedstone)

Project summary
This project will investigate the influence of proglacial lake formation on the long-term dynamic stability of outlet glaciers draining the Greenland Ice Sheet.

The greatest store of fresh water in the northern hemisphere is held within the Greenland Ice Sheet (GrIS). Over recent decades, the ice sheet’s rate of mass loss has accelerated driven by a warming climate and substantial increases both in: 1) the speed of large marine terminating glaciers draining the ice sheet; and 2) surface melt rates and melt extent1. However, a potential area of future dynamic change and mass loss, currently unaccounted for in Greenland Ice Sheet model projections, includes the influence of proglacial lake formation on the dynamic stability of outlet glaciers. It is well known that glaciers terminating in proglacial lakes flow more rapidly, in line with marine-terminating glaciers, than their land-terminating counterparts2. It is also clear that as the Greenland Ice Sheet’s margins retreat in to glacially over-deepened basins, that more glaciers will terminate in proglacial lakes with important implications for their ice dynamics and long-term stability. The availability of dramatically improved satellite derived ice motion data3 and bed topography4, in conjunction with advances in ice sheet modelling provide compelling timing for investigating this hitherto unconsidered mechanism for enhancing Greenland’s future ice loss.

Aim and research questions
This project will use a range of earth observation data to investigate the influence of proglacial lake formation on the long-term dynamic stability of outlet glaciers draining the GrIS. More specifically, the project will quantify how ice-motion around the GrIS has responded spatially and temporally to glacier termination in proglacial lakes, determine the extent to which new ice-marginal lakes will develop due to glacier retreat and predict how these ice-margins will respond in a future warming world.
The project will use a range of earth observation data plus high-resolution bed topography, in conjunction with surface mass balance and ice-sheet modelling, in order to achieve the following objectives:

O1) Determine how glacier motion and surface elevation have changed, both at the ice-margin and inland, in recent decades in response to ice termination in proglacial lakes.
O2) Determine what processes are driving the observed changes in ice motion and elevation.
O3) Determine the upglacier geometry of the subglacial bed-topography around the GrIS margin.
O4) Determine how ice-margins, susceptible to proglacial lake development, will respond dynamically to projected climate warming and with what implications for sea level rise?

Methodology and timetable
To address these objectives, the project will: O1) analyse a wealth of available satellite data to derive ice-motion (Sentinel; Landsat) and surface elevation5 (CryoSat-2; IceSat) change over recent decades; O2) determine, using the HIRHAM5 climate model6, the extent to which the observations in O1) have been driven by surface melt as opposed to ice-dynamics; O3) use innovative GIS techniques to characterise upglacier bed-topography and the prevalence of over-deepenings; and O4) use a state-of-the-art ice sheet model (STREAMICE7), to investigate how future changes in climate, sampled from a range of IPCC projections, will impact GrIS mass loss in response to the growth of ice-marginal lakes.

Training provision
You will be supervised by a team of leading glaciologists, gaining expertise in advanced techniques in remote sensing, data manipulation and modelling while being an integral part of the >25 strong world class cryosphere research group at Edinburgh.

References and further reading

1 – Enderlin E. et al, 2014, Geophys. Res. Lett., 41; 2 – Sugiyama S. et al, 2011, Nature Geoscience, 4; 3 – Hogg A. et al, 2017, Geophys. Res. Lett., 44; 4 – Morlighem M. et al., 2017, Geophys. Res. Lett., 44; 5 – McMillan M. et al, 2016, Geophys. Res. Lett., 43; 6 – Langen P. et al, 2015, J. Clim., 28; 7 – Goldberg D. & Heimbach, P., 2013, The Cryosphere, 7.