Modelling the propagation of subglacial floods

Subglacial flooding, in which large volumes of water are suddenly released beneath a glacier, is a process which has the potential to significantly modify the dynamics of the overlying ice. The routing of the water beneath the glacier and the extent of its incorporation into existing drainage networks determines the response of the ice. As a result, modelling of subglacial flooding is both necessary for understanding the detailed dynamics of glaciers responding to meltwater and also a useful test case for investigating the properties of the contact between glacial ice and the bed on which it sits. A number of studies have looked at the initial axisymmetric spreading of subglacial floodwater by considering the coupling between the flow of the water and the elastic deformation of the ice. Other studies have examined the movement of the water downstream, but without modelling the detailed, potentially elasticity-controlled dynamics at the flood front. In this thesis I combine these two approaches in order to model the processes which determine the propagation speeds of subglacial floods and their impact on the overlying ice. In chapter 1 I discuss subglacial flooding in the broader context of subglacial drainage systems and review previous modelling approaches. In chapter 2 develop a model for flood propagation beneath glaciers by considering the behaviour of a blister of water trapped between a rigid sloping base and an elastic sheet. I use an asymptotic analysis to show that, by removing a jump in curvature otherwise present at the upslope edge, the presence of a sloping base results in a new, nearly-translating regime in which the body of the blister moves at an approximately constant speed, leaving behind a thin layer of fluid. In chapter 3 I compare this model to GPS observations of six different subglacial flooding events. The observed uplifts are compared to those predicted by the model and processes at the front of the blister which could regulate flood propagation speeds are discussed. Linking observations of ice acceleration to the hydraulic jacking of the ice caused by subglacial floods requires combining both viscous and elastic deformation, so in chapter 4 I investigate the impacts of viscoelasticity on ice dynamics. To explore potential effects, I investigate the impact of viscoelastic bending on the movement of grounding lines. I then develop a model for viscoelastic bending and stretching of ice which I discuss in the context of subglacial flooding. In chapter 5 I conclude and discuss future directions for this work.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Tobin, Sophie

Advisor dc:contributor.advisor

• Neufeld, Jerome

• Fluid dynamics
• Ice sheets

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/bf54c946-08a5-4f95-b8cb-62b11fa4b845/download
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.108451

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/368138