Failure Propagation Effects in an Anisotropic Sea Ice Dynamics Model

Abstract

Formation of oriented failure patterns is a phenomenon common to geophysical scale pack ice and to the biaxial failure of laboratory ice. Moreover, examination of the fine structure of these failure patterns shows them to be highly irregular with sets of smaller oriented features occurring coincidentally along the failure zones. These observations suggest oriented anisotropic weaknesses are critical aspects in both the failure of laboratory samples and in the formation of oriented failure features in large scale pack ice. To investigate this problem numerically, a series of numerical experiments are carried out to examine how collections of anisotropic oriented flaws (Hibler and Schulson, 2000) may lead to oriented and intersecting failure patterns. Numerical experiments are carried out in both an idealized laboratory mode and, to a more limited extent, on the basin scale with fixed wind forcing. In both these experiments weakening effects are included in a simple form by weakening oriented flaws that open. These numerical experiments show that the presence of these ‘flaws’ leads to larger scale intersecting damage patterns. Moreover, in the case that multiple flaws, initially of equal strength, are allowed in each grid cell, the failure strike tends to be composed of alternating oriented flaws. These general features are also present in a basin scale simulation, except that in the basin case failure patterns tend to be formed in response to wind field patterns together with particular boundaries. Overall, these results demonstrate that oriented weaknesses tend to lead to intersecting failure patterns qualitatively similar to linear deformation features seen in sequential SAR imagery of pack ice.