D.: The role of crystal fabric in flow near an ice divide

• Main Authors: Erin C. Pettit, Throstur Thorsteinsson, H. Paul Jacobson, Edwin D. Waddington
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Siple; Siple Dome; West Antarctica; Antarc*; Antarctica; Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.634.8843; http://www.igsoc.org/journal/53/181/j05j053.pdf

ABSTRACT. Polycrystalline ice near an ice divide typically shows a crystal fabric (crystal preferred orientation) with c axes clustered vertically. We explore the effect of this fabric on the large-scale flow pattern near an ice divide. We incorporate an analytical formulation for anisotropy into a non-linear flow law within a finite-element ice-sheet flow model. With four different depth profiles of crystal fabric, we find that the effect of fabric is significant only when a profile has a minimum cone angle of less than 258. For a steady-state divide, the shape and size of the isochrone arch can depend as much on the crystal fabric as it does on the non-linearity of ice flow. A vertically oriented fabric tends to increase the size of the isochrone arch, never to reduce it. Also, non-random fabric has little effect on the ice-divide-flow pattern when ice is modeled as a linear (Newtonian) fluid. Finally, when we use a crystal-fabric profile that closely approximates the measured profile for Siple Dome, West Antarctica, the model predicts concentrated bed-parallel shearing 300m above the bed.