Summary
Break-up of ice shelves has been regarded as an indicator of climate change1. Observations around the Antarctic Peninsula have shown a pattern of gradual retreat, associated with a regional atmospheric warming and increased summer melt and fracturing processes2-9. Collapse of the northernmost section of Larsen Ice Shelf within a few days in January 1995 implies that, after retreat beyond a critical limit, ice shelves may disintegrate rapidly. We have examined the break-up history of the two northern sections of Larsen Ice Shelf (Larsen A and Larsen B)2 between 1986 and 1997 to establish stability criteria for ice shelves, using a finite element numerical model that treats ice as a continuum without fracture10. Analysis of various ice shelf configurations reveals characteristic patterns in the strain-rates near the ice front which we use to describe the stability of the ice shelf. On Larsen A, only the initial and final ice front configurations show a stable pattern. Larsen B presently exhibits a stable pattern, but if the ice front were to retreat by a further few kilometres, it too is likely to enter an irreversible retreat phase.