HR: 0800h
AN: C51B-0296    [Abstracts]
TI: The Conditions Necessary for Glaciohydraulic Supercooling
AU: * Creyts, T T
EM: tcreyts@eos.ubc.ca
AF: Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4 Canada
AU: Clarke, G K
EM: clarke@eos.ubc.ca
AF: Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC V6T 1Z4 Canada
AB: Beneath many glaciers and ice sheets, hydrology influences various basal processes. One phenomenon that occurs within the hydraulic system is supercooling. Water supercools when it flows from a an area of higher pressure (lower ambient temperature) to an area of lower pressure (higher ambient temperature) without equilibrating its internal energy. As a result of this movement, the temperature of the water is below the ambient temperature and may begin to freeze. The process is governed by the Clausius-Clapeyron equation and is geometrically dependent on water ascending a subglacial adverse slope. Ice that forms can then be accreted to the base of the glacier or be advected in the flowing water. Alluvial sediment transported in the flow may be accreted with the ice to the base of the glacier. Much recent work has been devoted to analysis of data from several glaciers to discern the controlling parameters. In this study, we use a numerical model that couples hydrology and erosion to investigate the possible and probable conditions associated with glaciohydraulic supercooling. We modify the usual channel geometry to allow for high velocity water sheets. Several flavors of the water-flow model are then joined to an englacial aquifer and a subglacial sediment erosion model. One of the principal governing parameters is the heat transfer coefficient; and we show how different parameterizations affect the the rate and along-flow occurrence of supercooling. In addition, spatial lags in heat transfer associated with the curvature of the flow path are also critical to the accretion rate as shown in our simulations of examples from Sweden, Iceland, and Alaska. We also corral the effects of water loss to an englacial flow system. The rate of water loss to an englacial system relative to the subglacial discharge can limit subglacial supercooling. Finally, we show how sediment transport affects the supercooling process via changes in the balance equations. We conclude by discussing supercooling during the collapse of the late Pleistocene ice sheets.
DE: 0720 Glaciers
DE: 0766 Thermodynamics (1011, 3611, 8411)
DE: 1824 Geomorphology: general (1625)
DE: 1862 Sediment transport (4558)
DE: 4926 Glacial
SC: Cryosphere [C]
MN: Fall Meeting 2005