The future fate of the Antarctic ice sheet under a warming climate is dynamically tied to geometric changes of the floating ice shelves. The reason is that ice shelves transmit buttressing to upstream regions. Sources for buttressing are shearing at lateral confinements and positions where the ice shelf locally runs aground, such as at ice rises and ice rumples. As Antarctic ice shelves are known to be thinning at increasing rates, their buttressing potential is expected to reduce. Under continuous atmospheric warming over t he Antarctic Peninsula, vast ice-shelf areas have already be en lost. Before break-up, ice shelves accommodated a certain gradual recession of the ice front. During this recession, a transition of the calving front was observed from being convex to be coming concave, reaching either further or less out into the ocean between any anchor points. After break-up, the extant glacier fronts were no longer buttressed and tributary glaciers accelerated with, in places, an eightfold velocity increase. This had direct consequences for ice flowing over the boundary between grounded and floating ice—that is, the ice discharge over the grounding line. More than one decade after the major break-up events on the Antarctic Peninsula, glaciers still adjust to these past perturbations.
The safety band of Antarctic ice shelves
by Johannes Jakob Fürst, Gaël Durand, Fabien Gillet-Chaulet, Laure Tavard, Melanie Rankl, Matthias Braun and Olivier Gagliardini
http://www.nature.com/nclimate/journal/v6/n5/full/nclimate2912.html
https://www.nature.com/articles/nclimate2912.epdf?referrer_access_token=k6qS3_eTdrGp2hMPzrZkR9RgN0jAjWel9jnR3ZoTv0PSCyZr7STyVSDMsOXI9HIwEYJbNa4isYJatle68rggCOnw-2VVnHqdwv2rdhs9WVrcdAjoP1Hgc1rVqZoQr1lWXRvfWKKKwfM7hk35lOmt4OT3nJ-pUdhd-9RxkdYdLiGTvIayN-Eql6XyUP-KlEHcYTt2WwRFopq_zz5IPcfYiPEQF0tsJUNWHyz8E8sf1vmA0T5dFGbKhS1BARF3yTmVJ_sDV6sFSt-axYhE6Gy49iK9R4Ukualb04Rj9sEssUPrqBaYEMSC7zZJr-72SC3LHlXs0XN-Uxy6gHojJ6DNLw%3D%3D&tracking_referrer=www.lemonde.fr
The floating ice shelves along the seaboard of the Antarctic ice sheet restrain the outflow of upstream grounded ice. Removal of these ice shelves, as shown by past ice-shelf recession and break-up, accelerates the outflow, which adds to sea-level rise. A key question in predicting future outflow is to quantify the extent of calving that might precondition other dynamic consequences and lead to loss of ice-shelf restraint. Here we delineate frontal areas that we label as ‘passive shelf ice’ and that can be removed without major dynamic implications, with contrasting results across the continent. The ice shelves in the Amundsen and Bellingshausen seas have limited or almost no ‘passive’ portion, which implies that further retreat of current ice-shelf fronts will yield important dynamic consequences. This region is particularly vulnerable as ice shelves have been thinning at high rates for two decades and as upstream grounded ice rests on a backward sloping bed, a precondition to marine ice-sheet instability. In contrast to these ice shelves, Larsen C Ice Shelf, in the Weddell Sea, exhibits a large ‘passive’ frontal area, suggesting that the imminent calving of a vast tabular iceberg will be unlikely to instantly produce much dynamic change.