Incorporating Glacial Blisters into Models of Subglacial Drainage

Glaciers are currently undergoing major changes in their structure due to climate change; new features are appearing which are not well understood for which better models are needed. As the global climate has warmed, so has the prevalence of meltwater lakes on the surfaces of glaciers during warmer seasonal fluctuations. Such 'supraglacial' lakes can drain rapidly (on the order of hours) through fractures in the ice with the meltwater then collecting in 'subglacial' lakes. These, in turn, force a gap between the ice and bedrock causing the glacier to rise locally with the water stored below in a pool under pressure - such features are known as 'glacial blisters' due to their structure.
These sudden drainage events can flood a pre-existing subglacial drainage system with an overwhelming influx of water. Near the glacier terminus large channels in the drainage system are able to carry water away quickly, reducing the effects of such events. However, further inland such expansive channels don't usually exist. Thus, inland blisters can drain on the order of days, at a much slower pace than they are initially formed.
It is recognised that the quantity of water flowing through a subglacial drainage system can significantly affect the ice sheet motion due to lubrication at the base of a glacier. However, how to incorporate blister drainage into glacial hydrology models remains an open area and any potential link between this and increased ice velocity has not yet been established through mathematical models.
The aim of this project is to extend current subglacial drainage system models to incorporate the effects of lakes driven by supraglacial drainage. In extending the models we can then attempt to observe if there are any significant changes on the overall glacier behaviour. For example, during drainage, one might see that larger channels are formed further inland to enable water to drain form blisters more quickly. Alternatively one might observe that longer term drainage leads to greater lubrication at the base of the glacier hence resulting in faster motion at the surface.
On the length scale of a blister, the ice can be modelled under an elastic deformation but on the scale of the glacier a more sensible choice would be to treat the ice as viscous. Marrying these two models, or indeed using a more complex visco-elastic setup, will form a major part of this project.
This project falls within the EPSRC Continuum Mechanics research area, specifically in relation to modelling fluid and solid mechanics. It will involve fundamental aspects of fluid flow and deformations within a porous medium. It has the potential to better our understanding of what causes an increase in glacier velocity and thus overall glacier melting and calving rates that lead to global sea level rise. Given the rapidly changing climate has increased the occurrence of glacier ponding, modelling the effects of drainage (and hence refining our models) will enable us to better predict the effects the warming atmosphere will have on the reduction of global glacier coverage.