Ice Stream B Margin Revisited

• Main Authors: Martin Truffer, Keith Echelmeyer
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ice Sheet; Ice Stream B
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.524.5189; http://www2.gi.alaska.edu/~truffer/WAIS_poster.pdf

Ice stream margins are some of the most interesting natural ice dynamics laboratories. Large temperature differences between the base and the surface of the ice stream cause large variations in the ice flow parameter. Ice traversing the margins is exposed to large strains. This is expected to lead to an alignment of c-axis and a consequent softening of the ice in lateral shear. Echelmeyer and others (1994) used a finite element model to show that the very steep velocity gradients across the ice stream margin could only be reproduced if the ice in the margins is up to ten times softer than the adjacent ice sheet ice. We repeated this modeling effort using a more accurate ice stream geometry, and adjusting the ice flow parameters for ice temperatures that have been measured in the mean time. Reproducing the measured surface velocity profiles still requires enhancement factors of about ten. Since the temperature effects have been accounted for we conclude that these enhancement factors are due to fabric changes in the marginal ice. Method A commercial Finite Element package (FEMLAB(R)) was adapted to solve the non-linear ice flow equations. The method solves for all three velocity components and their gradients in a plane. It does not account for out-of-plane velocity gradients, however. It is possible to specify velocities or stresses at the model boundaries.