Experimental and theoretical fracture mechanics applied to Antarctic ice fracture and surface crevassing

• Main Authors: Rist, MA, Sammonds, PR, Murrell, SAF, Meredith, PG, Doake, CSM, Oerter, H, Matsuki, K
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: AMER GEOPHYSICAL UNION 1999
• Subjects: FRESH-WATER ICE; BOTTOM CREVASSES; TOUGHNESS; SHELF; DISINTEGRATION; RESISTANCE; SPECIMENS; SHEETS; STRAIN; Antarctic; Antarctic Peninsula; Rho; Ronne Ice Shelf; The Antarctic; Antarc*; Filchner Ronne Ice Shelf; Filchner-Ronne Ice Shelf; ice core; Ice Shelf; Ice Shelves
• Online Access: http://discovery.ucl.ac.uk/125317/

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, K-init, for which crack growth commences. The tests cover a full range of nearsurface densities, rho = 560-871 kg m(-3) (10.9-75.7 m depth). Results indicate an apparently linear dependence of fracture toughness on porosity such that K-int = 0.257 rho-80.7, predicting a zero-porosity toughness of K-o = 155 kPa m(1/2). 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 K-init, 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.