The Hydrology of Subglacial Overdeepenings

Abstract:

Subglacial overdeepenings are common features beneath contemporary ice masses and in formerly glaciated regions that raise management issues related to the disposal of radioactive waste in deep geological repositories. Their formation mechanisms are still unclear but subglacial hydrology likely plays a key role. Subglacial water flow is strongly influenced by the bed topography through the dependence of the melting point of ice on pressure. This means that water descending into an overdeepening has more energy available to melt channels and conversely water ascending out has less or even no energy available for melt. The latter process leads to a reduced drainage capacity and, consequently, to increased water pressures.

I investigate the effects of an overdeepening on subglacial hydrology using the GlaDS model, which simulates distributed and channelized drainage in 2D. Of primary interest are the extent and location of distributed and channelised flow, and magnitude and distribution of effective pressure. I present results for different bed topographies as well as for a range of model parameters and forcings. I interpret the results using GlaDS coupled to models of erosion based on plucking, and sediment transport capacity in suspension and as bed-load.