Fracture and back stress along the Byrd Glacier flowband on the Ross Ice Shelf

Abstract

East Antarctic ice discharged by Byrd Glacier continues as a flowband to the calving front of the Ross Ice Shelf. Flow across the grounding line changes from compressive to extensive as it leaves the fjord through the Transantarctic Mountains occupied by Byrd Glacier. Magnitudes of the longitudinal compressive stress that suppress opening of transverse tensile cracks are calculated for the flowband. As compressive back stresses diminish, initial depths and subsequent growth of these cracks, and their spacing, are calculated using theories of elastic and ductile fracture mechanics. Cracks are initially about one millimeter wide, with approximately 30 m depths and 20 m spacings for a back stress of 83 kPa at a distance of 50 km beyond the fjord, where floating ice is 600 m thick. When these crevasses penetrate the whole ice thickness, they release tabular icebergs 20 km to 100 km wide, spaced parallel to the calving front of the Ross Ice Shelf.