07 Mar 2024
 | 07 Mar 2024
Status: this preprint is open for discussion.

Ice viscosity governs hydraulic fracture causing rapid drainage of supraglacial lakes

Tim Hageman, Jessica Mejía, Ravindra Duddu, and Emilio Martínez-Pañeda

Abstract. Full thickness crevasses can transport water from the glacier surface to the bedrock where high water pressures can open kilometre-long cracks along the basal interface, which can accelerate glacier flow. We present a first computational modelling study that describes time-dependent fracture propagation in an idealised glacier causing rapid supraglacial lake drainage. A novel two-scale numerical method is developed to capture the elastic and viscoplastic deformations of ice along with crevasse propagation. The fluid-conserving thermo-hydro-mechanical model incorporates turbulent fluid flow and accounts for melting/refreezing in fractures. Applying this model to observational data from a 2008 rapid lake drainage event indicates that viscous deformation exerts a much stronger control on hydrofracture propagation compared to thermal effects. This finding contradicts the conventional assumption that elastic deformation is adequate to describe fracture propagation in glaciers over short timescales (minutes to several hours) and instead demonstrates that viscous deformation must be considered to reproduce observations of lake drainage rate and local ice surface elevation change. As supraglacial lakes continue expanding inland and as Greenland Ice Sheet temperatures become warmer than -8 °C, our results suggest rapid lake drainages are likely to occur without refreezing, which has implications for the rate of sea level rise.

Tim Hageman, Jessica Mejía, Ravindra Duddu, and Emilio Martínez-Pañeda

Status: open (until 27 Apr 2024)

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Tim Hageman, Jessica Mejía, Ravindra Duddu, and Emilio Martínez-Pañeda
Tim Hageman, Jessica Mejía, Ravindra Duddu, and Emilio Martínez-Pañeda


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Short summary
Due to surface melting, meltwater lakes seasonally form on the surface of glaciers. These lakes drive hydrofractures that rapidly transfer water to the base of ice sheets. This paper presents a computational method to capture the complicated hydrofracturing process. Our work reveals that viscous ice rheology has a great influence on the short-term propagation of fractures, enabling fast lake drainage; whereas, thermal effects (frictional heating, conduction, and freezing) have little influence.