PhD Project: Protecting Glaciers - Melting and flow through snowpack

Description

The melting of glacial firn occurs at very large length scales, across more than 100km inland from the margin of the Greenland ice sheet.  The resultant meltwater ultimately makes its way from the melt region to the ocean either over the glacial surface, or funnelled through moulins and crevasses to the base of the ice sheet where it significantly enhances the sliding speed particularly early in the melt season.  As the meltwater percolates through the porous firn it leads to high-permeability pathways which promote flow, and further localise melting.  This process occurs in the small pore spaces of the firn, but also at larger scales in the form of rivulets, tributaries and streams which form on the glacial surface.  The feedback between melting and flow leading to localisation may ultimately lead to meltwater carving its way through the glacier.

This project would combine laboratory experiments on the melting of idealised porous media with larger scale numerical simulations of the Greenland ice pack.  First, warm water will be rained onto a porous matrix of pre-frozen together glass beads on a slope to examine how the flow of the distributed water becomes channelised as the connections between beads opens. Subsequent experiments will utilise crushed ice to examine the flow, melting and hence focusing with initially distributed flow down a slope.  Finally, these experiments will be complemented by catchment-scale modelling of melting and flow using Basilisk, and coupled to a hybrid parameterisation of turbulent flow, dissipation and heating, and hence melting in supraglacial river networks.  The results will be used to ask how either texturing the surface of the ice, or providing obstacles to channelised flow, might limit drainage to the bed and hence limit ice motion towards the terminus and ocean.

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