STEADY-STATE THREE-DIMENSIONAL ICE FLOW OVER AN UNDULATING BASE: FIRST-ORDER THEORY WITH

• Main Author: Linear Ice Rheology
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.429.9252; http://www.igsoc.org/journal/33/114/igs_journal_vol33_issue114_pg177-185.pdf

ABSTRACT. The problem of ice flow over threedimensional basal irregularities is studied by considering the steady motion of a fluid with a linear constitutive equation over sine-shaped basal undulations. The undisturbed flow is simple shear flow with constant depth. Using the ratio of the amplitude of the basal undulations to the ice thickness as perturbation parameter, equations to the first order for the velocity and pressure perturbations are set up and solved. The study shows that when the widths of the basal undulations are larger than 2-3 times their lengths, the finite width of the undulations has only a minor influence on the flow, which to a good approximation may be considered two-dimensional. However, as the ratio between the longitudinal and the transverse wavelength L / W increases, the three-dimensional flow effects becomes substantial. If, for example, the ratio of L to W exceeds 3, surface amplitudes are reduced by more than one order of magnitude as compared to the two-dimensional case. The L / W ratio also influences the depth variation of the amplitudes of internal layers and the depth vanatlOn of perturbation velocities and strain-rates. With increasing L / W ratio, the changes of these quantities are concentrated in a near-bottom layer of decreasing thickness. Furthermore, it is shown, that the azimuth of the velocity vector may change by up to 100 between the surface and the base of the ice sheet, and that significant transverse flow may occur at depth without manifesting itself at the surface to any significant degree.