HR: 0800h
AN: C11A-0091    [Abstracts]
TI: Modeled Increase of ice Drainage of Jacobshavn Isbrae due to ice bed Uncoupling
AU: * Hofstede, C M
EM: coen.hofstede@maine.edu
AF: Coen Hofstede, Department of Earth Sciences Climate Change Institute BGSC University of Maine, Orono, ME 04469,
AB: Increased ice drainage of major ice sheets will lead to a rise in sea level. The Greenland Ice Sheet seems to react faster to global warming than originally was thought. Three major outlet glaciers in Southern Greenland, increased their ice drainage significantly since 1997. Most of the draining takes place through fast moving calving glaciers called ice streams. A not well understood condition for ice streams to occur is the presence of basal water. We present a possible mechanism for the dynamics of ice streams by splitting up each column of ice along a flow line into a floating part and a grounded part. The floating part of the ice column is balanced by a tensile force and the grounded part is balanced by basal drag. Using this model, the center flow line of Jacobshavn Isbrae in West Greenland is monitored from 1985 to 2003. A gradual uncoupling of ice from it's bed is observed from 1993 to 2003. One observation is that the small ice shelf of Jacobshavn Isbrae was simply pushed forward by the increasingly uncoupled ice before the shelf collapsed. The uncoupling pinches off some sixty kilometers upstream from the grounding line. This uncoupling is then quantified as a force perturbation that is used in a time dependent model of ice surface lowering. The initial reaction to the perturbation is a strong increase in ice draining velocity that dies out after several years until a new steady state is accomplished.
DE: 0730 Ice streams
DE: 0774 Dynamics
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 0798 Modeling
SC: Cryosphere [C]
MN: 2007 Fall Meeting