On modeling the anisotropic failure and flow of flawed sea ice

The failure and flow of sea ice on scales small and large is characterized by the propagation of oriented leads and cracks. In this paper a theory for the dynamical treatment of anisotropic oriented flaws in sea ice is developed and used to examine the interaction of these oriented flaws under idealized stress forcing. The essential idea of the theory is to take one or more oriented weak leads imbedded in thick ice. A constitutive law for both the thin and thick ice is taken to be similar to laboratory observations, which are consistent with Mohr Coulomb-like failure. Application of normal continuum mechanics boundary conditions leads to anisotropic flow and failure characteristics of this anisotropic composite under both near- and far-field forcing. The local failure characteristics show that there is a preferred orientation for failure with the intersection between leads increasing as confinement increases. For spatially separated interacting flaws the theory predicts a preference for the weakening of flaws in a narrow range of angles of similar to 10 degrees-20 degrees relative to the principal far-field stress. Imbedding isolated flaws leads to simulated damage directions consistent with local failure characteristics. In the case where the ice is considered to have available flaws in all directions, fracture propagation is found to proceed by picking out oriented flaws alternating in direction along large-scale damage strikes with individual flaw alignments of similar to 20 degrees relative to far-field principal stresses. The mechanisms responsible for these results and how this anisotropic sea ice rheology might be implemented in current dynamic/thermodynamic sea ice models are discussed.