Speaker: Dr. Ian Hewitt (University of British Columbia)
Abstract: One of the greatest uncertainties in current forecasts of ice melting and consequent sea-level rise is the role played by meltwater at the base of the ice in lubricating ice flow. Observations from many glaciers and from the ablation regions of the Greenland Ice Sheet have shown that summer meltwater penetrating from the ice surface can have a substantial effect on the rate at which the glacier slides. Faster sliding would evidently quicken the rate at which the ice moves to lower elevations and melts, but the observations to date are inconclusive about the overall effect of the meltwater: some indicate that speed-up does indeed occur, whilst others suggest quite the opposite, with more melting leading to a slow-down of the ice.

I will discuss these observations, together with current hypotheses for what is happening to the water beneath the ice. I will go on to describe the models of water flow that we are developing to investigate what the long-term effects of increased melting are likely to be. The results suggest that the subglacial drainage system may be in a constant state of flux: at times establishing an efficient network of channels eroded into the ice, but at other times squeezing closed to form nearly impermeable pockets of water. Finally, the effects on ice flow will be discussed.

Speaker's website: http://www.math.ubc.ca/~hewitt/