Changes in Larsen B ice shelf dynamics prior to breakup: satellite borne observations and modelling outcomes

The pattern of the final break-up of the northern Larsen B ice shelf in March 2002 was comparable to the collapse of Larsen A in January 1995, although the retreat of Larsen A previous to the collapse was more gradual, extending over a multi-year period. This can be attributed to the different geometry of the confining bay, where Lindenberg Island acted as pinning point delaying the disintegration. For both ice shelf sections, the presence of abundant melt water during summers as a consequence of climate warming is regarded as one of the key factors which increased the vulnerability of the ice shelf. The rapidity of the final disintegration event was fostered by pre-existing rifts along major parts of the grounding zone, along the boundaries to the stagnant ice shelf section at Seal Nunataks, and on major parts of the ice shelf (Rack and Rott, in press). Remote sensing analysis based on ERS and Envisat SAR as well as optical imagery is used to set up boundary conditions for a numerical ice shelf model. This finite-difference model (Sandhager, 2000; in press) solves the usual continuum-mechanical equations of ice shelf motion, but also considers large-scale influences of fractures on the flow regime.