Sack Lunch Seminar (SLS)

SLS: Ian Hewitt - UBC
Date Time Location
April 6th, 2011 12:10pm-1:00pm 54-915
Subglacial drainage and its impact on ice dynamics


Melting land-ice is contributing at an increasing rate to rising sea levels and could cause up to 1 meter of rise by the end of the century. One of the major uncertainties in our current predictions lies in the feedback that increased melting has on ice dynamics; meltwater from the surface is routed through crevasses and moulins to the glacier bed, where it can lubricate the contact between ice and the underlying rock or till. The overall impact of increased melt water quantities on the ice flow is not well understood, however, and observations are inconclusive. Current large-scale ice sheet models typically involve little or no description of the hydrology.

In this talk I will describe models for how water flows at the base of the ice, and discuss how these may be used to improve ice sheet forecasting. In the simplest description, water flows through a sequence of connected cavities formed as the ice slides over small-scale bumps in the bed. The water flow generates heat, however, causing the surrounding ice `roof' to melt. This can lead to a positive feedback with the formation of narrow water channels, thermally eroded into the ice in much the same way as sub-aerial rivers erode into sediments. Channels are very efficient at evacuating water and their presence may mitigate the lubricating effects of increased melt water. This talk will therefore focus on modelling where, when and how such channels form.