Knight, P.G. and Knight, D.A. (2004) Conference paper. "Field observations and laboratory simulations of basal ice formed by freezing of supercooled subglacial water." Invited contribution to AMICS (Antarctic ice-sheet dynamics and climatic change: Modelling and Ice Composition Studies) workshop Dynamic Interaction between the Antarctic Ice Sheet and the Subglacial Environment, Vrije Universiteit Brussel, Brussels, April 2004. Sponsored by the Belgian Federal Science Policy Office (BELSPO).

It has been suggested that supercooling of meltwater in overdeepened subglacial basins can freeze large quantities of ice and debris to the glacier bed. This process has been invoked to explain high sediment flux from the Laurentide ice sheet, and in a modern glacial context it has been suggested, for example, that all of the basal ice at some Icelandic glaciers can be attributed to subglacial supercooling. To test this hypothesis we compared basal ice facies at supercooling sites in Iceland with ice facies created experimentally by supercooling in the laboratory. We found that specific, distinctive, basal ice facies appear to be created directly by freezing of supercooled water, but that these facies account for a only small proportion of the total basal ice sequence. We are now designing experiments to test whether the remaining basal ice could be created by a multi-stage process with supercooling as the primary entrainment mechanism, or whether mechanisms such as regelation and flow diagenesis, not requiring supercooling, remain tenable. At issue is the question of whether basal ice characteristics in modern glaciers, and sediment flux signatures from former glaciers, can be used as evidence of glaciohydraulic supercooling in the way that has recently been proposed.