Experimental and theoretical fracture mechanics applied to Antarctic ice fracture and surface crevassing
Recent disintegration of ice shelves on the Antarctic Peninsula has highlighted the need for a better understanding of ice shelf fracture processes generally. In this paper we present a fracture criterion, incorporating new experimental fracture data, coupled with an ice shelf flow model to predict the spatial distribution of surface crevassing on the Filchner-Ronne Ice Shelf. We have developed experiments that have enabled us to quantify, for the first time, quasi-stable crack growth in Antarctic ice core specimens using a fracture initiation toughness, Kinit, for which crack growth commences. The tests cover a full range of near-surface densities, ρ = 560–871 kg m−3 (10.9–75.7 m depth). Results indicate an apparently linear dependence of fracture toughness on porosity such that Kinit = 0.257 ρ-80.7, predicting a zero-porosity toughness of Ko = 155 kPa m1/2. We have used this data to test the applicability to crevassing of a two-dimensional fracture mechanics criterion for the propagation of a small sharp crack in a biaxial stress field. The growth of an initial flaw into a larger crevasse, which involves a purely tensile crack opening, depends on the size of the flaw, the magnitude of Kinit and the nature of the applied stress field. By incorporating the criterion into a stress map of the Filchner-Ronne Ice Shelf derived from a depth-integrated finite element model of the strain-rate field, we have been able to predict regions of potential crevassing. These agree well with satellite imagery provided an initial flaw size is assumed in the range 5–50 cm.
Authors: Rist, M. A., Sammonds, P. R., Murrell, S. A. F., Meredith, P. G., Doake, C. S. M., Oerter, H., Matsuki, K.