RADIALLY SYMMETRIC POLAR ICE SHEET FLOW WITH EVOLVING ANISOTROPIC FABRIC

• Main Authors: Ryszard Staroszczyk, Leslie W. Morl
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Greenland; Antarc*; Antarctica; Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.611.5474; http://fluid.ippt.gov.pl/ictam04/text/sessions/docs/FM18/10297/FM18_10297.pdf

Summary A radially symmetric, gravity-driven, steady flow of a grounded polar ice sheet with a prescribed temperature field is considered. The ice is modelled as an incompressible, non-linearly viscous and anisotropic fluid with evolving orthotropic fabric. To describe the evolution of the fabric as an initially isotropic free surface ice descends to depth in an ice sheet, a constitutive law relating the deviatoric stress to the strain-rate and strain is applied. The solution is constructed as a leading order approximation derived from asymptotic expansions in a small parameter that reflects the small ratio of stress and velocity gradients in the longitudinal direction to those in the thickness direction. Results of calculations show the effects of a bed topography on the ice sheet thickness profile and the velocity components. Additionally, the influence of the temperature field and the free surface snow accumulation rates on the flow is illustrated. EXTENDED SUMMARY Ice cores retrieved from large polar ice caps in Antarctica and Greenland reveal strong anisotropic fabrics, with individual ice grain c-axes aligned along some preferential directions (Thorsteinsson et al., 1997). These fabrics develop and evolve in the material in its response to changing stress and deformation states which ice experiences during its passage through the depth of an ice sheet. In current numerical models used to simulate the flow of polar ice sheets on geophysical scales the mechanism of evolving (induced) anisotropy is ignored and, for the sake of simplicity of the analysis, ice is treated as an isotropic material. In order to account for local changes in viscous properties of ice, resulting from its anisotropy