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A damage mechanics assessment of the Larsen B ice shelf prior to collapse: Toward a physically-based calving law

  • Author(s): Borstad, CP
  • Khazendar, A
  • Larour, E
  • Morlighem, M
  • Rignot, E
  • Schodlok, MP
  • Seroussi, H
  • et al.
Abstract

Calving is a primary process of mass ablation for glaciers and ice sheets, though it still eludes a general physical law. Here, we propose a calving framework based on continuum damage mechanics coupled with the equations of viscous deformation of glacier ice. We introduce a scalar damage variable that quantifies the loss of load-bearing surface area due to fractures and that feeds back with ice viscosity to represent fracture-induced softening. The calving law is a standard failure criterion for viscous damaging materials and represents a macroscopic brittle instability quantified by a critical or threshold damage. We constrain this threshold using the Ice Sheet System Model (ISSM) by inverting for damage on the Larsen B ice shelf prior to its 2002 collapse. By analyzing the damage distribution in areas that subsequently calved, we conclude that calving occurs after fractures have reduced the load-bearing capacity of the ice by 60 ± 10%. © 2012. American Geophysical Union. All Rights Reserved.

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