Constraining the Conditions Under Which Ice Fractures on Antarctic Ice Shelves Using Satellite Observations

Much of the mass lost from the Antarctic Ice Sheet occurs through the calving of icebergs from large ice shelves. Calving occurs due to the propagation of fractures laterally and vertically. Previous studies have estimated the stresses at which ice fractures in the laboratory and through sparse remotely sensed observations, helping to illuminate the failure envelope of ice under various conditions. However, the conditions under which these fractures initiate and propagate remain poorly understood and the failure envelope ill defined. Here, we aim to constrain the stresses under which ice fractures on Antarctic ice shelves using a combination of optical imagery and observations of strain-rates. We estimate stress states near fractures from observed strain-rates and applying a constitutive relation for ice flow. We fit various yield criteria (Mohr-Coulomb criterion, von Mises criterion, strain energy criterion, and Drucker-Prager criterion) to evaluate the applicability of these theories to our estimated stress states. We find that the Drucker-Prager criterion best fits the failure envelope in Antarctic ice shelves and provides constraints on both the tensile and compressive strengths of ice. Further, we quantify the intensification of stress leading up to active rift tips. In doing so, we provide insights into ice fracture processes and a further step towards setting more physically informed fracture criteria in ice-flow models.