Observational constraints on glacier sliding laws

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Glaciers are an important seasonal source of freshwater in many places around the world, including the Canadian West. Continental-scale ice sheets such as those in Greenland and Antarctica play an important role in regulating global sea levels. Both types of ice masses are sensitive to their ambient climate through snowfall and melting, and their response to a change in climate depends crucially on how the ice in them flows. Sliding of ice over bedrock or sediments is often a major component in the overall flow of a glacier or ice sheet, and sliding speeds can vary dramatically according to the input of lubricating meltwater to the bed. Computer simulations of glacier and ice sheet dynamics therefore require an accurate representation of sliding. However, due to the inaccessibility of most glacier beds, direct studies of glacier sliding have been limited and many simulations rely on purely theoretical models of sliding. The proposed research aims to provide better observational constraints on models of sliding. Specifically, I will use Global Positioning System and satellite-based radar technology to measure spatial and temporal variations in the sliding speed of a glacier in the Yukon Territory. Using a mathematical tool known as an inverse model, friction at the bed will be calculated from these measurements, and will be correlated to direct measurements of water pressure at the base of the glacier obtained through in-situ instrumentation. The aim of the research is to establish quantitative links between friction at the glacier bed, sliding velocity and the pressure of lubricating basal water.