HR: 0830h
AN: C11C-0824    [PDF]
TI: Reversal of ice-stream surface slope: constraints from a simple model.
AU: * Dupont, T K
EM: dupont@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences and EMS Environment Institute, 532 Deike Building, University Park, PA 16802 United States
AU: Alley, R B
EM: ralley@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences and EMS Environment Institute, 532 Deike Building, University Park, PA 16802 United States
AB: Here we use a simple model to examine the conditions for which an ice shelf, once grounded on a sill, will develop an ice-air surface slope reversal. Such reversals are of interest because subglacial water flow is sensitive to the potential gradient from the ice-air surface slope and so is strongly affected by the slope reversal. We use a non-dimensional, 1-d model of the coupled mass and momentum balance of ice flowing over a transition from a subglacial lake to a flat bedrock sill and then to an ice shelf. The model produces slope reversals for reasonable parameter values. Two key paramters are dimensionless numbers which measure the importance to ice flow of thickness gradients and basal drag, respectively; the prescribed boundary conditions are also of import. Strong positive feedbacks are suggested by these results. For potential subglacial lakes, ice-sheet thinning or cooling favor development of surface-slope reversals that contribute to lake trapping. Similarly sticky spots may produce surface-slope reversal, water diversion and increased flow resistance. Conversely ice-stream thickening or warming favor loss of surface-slope reversals, throughflow of basal meltwater with both lubricating and warming effects, and loss of subglacial lakes and sticky spots.
DE: 1863 Snow and ice (1827)
DE: 4540 Ice mechanics and air/sea/ice exchange processes
SC: Cryosphere [C]
MN: 2003 Fall Meeting