Effect of an orientation-dependent non-linear grain fluidity on bulk directional enhancement factors

Abstract Bulk directional enhancement factors are determined for axisymmetric (girdle and single-maximum) orientation fabrics using a transversely isotropic grain rheology with an orientation-dependent non-linear fluidity. Compared to fluidities that simplified as independent, we find bulk strain-rate enhancements intermediate-to-strong can be up factor of ten larger, assuming stress homogenization over the polycrystal scale. Our work thus extends previous results based on simple basal slip (Schmid) rheologies rheology, which has implications large-scale anisotropic ice-flow modelling relies rheology. In order derive arbitrary evolving fabrics, expand c-axis distribution in terms spherical harmonic series, allows rheology-required structure tensors through eight easily calculated provides alternative current structure-tensor-based modelling.