Critical thresholds of Antarctic ice-sheet basins

The Antarctic Ice Sheet is known to be subject to several positive feedback mechanisms which, once triggered, can accelerate ice loss and lead to unstable grounding line retreat. Antarctica is therefore considered one of the tipping elements in the climate system. This suggests that the ice-sheet displays critical threshold behaviour, and that at least part of the changes caused by progressing global warming might in effect be irreversible. Using the Parallel Ice Sheet Model PISM, we here identify critical thresholds in global mean temperature, at which large-scale decline of individual Antarctic ice-sheet basins might be induced. We further compare the relative magnitude of competing surface and ice-dynamic processes which depend on the topographic structure as well as the atmospheric and oceanic conditions of each basin.