Tensile failure is insufficient for glacier retreat in a Nye zero stress calving model including crevasse advection

Abstract:

Glacier calving remains one of the largest sources of uncertainty in future projections of mass loss and sea level rise from the world’s ice sheets. To reduce this uncertainty, it is necessary to develop calving laws based on testable physical principles. One such simple calving rule, the Nye zero stress criteria, has been used in the past to model the calving behavior of marine terminating glaciers under tensile failure. In this study, we generalize the Nye zero stress model so that crevasse depths are not solely a function of the instantaneous stress field. Instead, we track the formation and advection of crevasses as they form upstream from the calving cliff. We examine the influence of crevasse advection in a sequence of idealized cases. As expected, the inclusion of crevasse history increases calving flux in all parameter sets tested. Including crevasse history also reduces the stability of floating ice tongues and discourages the formation of an ice tongue if one is not present. However, we find that in all tests, including varying the sliding coefficient, ice temperature, and bed slope, our model does not produce sustained glacier retreat due to calving. For a marine ice cliff instability scenario to be allowed, we hypothesize that additional modes of failure, such as shear failure, are necessary to trigger retreat.