Antarctic ice shelf faces threat from warm waters

Scientists have punched holes in Antarctic's viability by refuting the prevalent assumption that its Weddell Sea ice shelves would remain impervious to global warming due to the sea's peripheral location.

Filchner-Ronne Ice Shelf, fringing the Weddel Sea, may start to melt rapidly this century and no longer act as a barrier for ice streams draining the Antarctic Ice Sheet.

"The Weddell Sea was not really on the screen because we all thought that unlike the Amundsen Sea its warm waters would not be able to reach the ice shelves," said Hartmut Hellmer, oceanographer at the Alfred Wegener Institute for Polar and Marine Research, Germany, who led the study, the journal Nature reported.

"But we found a mechanism which drives warm water towards the coast with an enormous impact on the Filchner-Ronne Ice Shelf in the coming decades," added Hellmer, according to a Alfred Wegener statement.

Using different calculations, Hellmer and colleagues Frank Kauker, Ralph Timmermann and Jurgen Determann, besides Jamie Rae from Met Office, Hadley Centre, Britain, demonstrate that large ice masses could presumably slide into the ocean within the next six decades, thanks to a chain reaction.

This chain reaction is triggered by rising air temperatures above the southeastern Weddell Sea. "Our models show that the warmer air will lead to the currently solid sea ice in the southern Weddell Sea becoming thinner and therefore more fragile and mobile in a few decades," said Kauker.

If this happens, fundamental transport processes will change. "This will mean that a hydrographic front in the southern Weddell Sea will disappear which has so far prevented warm water from getting under the ice shelf. According to our calculations, this protective barrier will disintegrate by the end of this century," explained Hellmer.

An inflow of warmer water beneath the Filchner-Ronne Ice Shelf will melt the ice from below. "We expect the greatest melting rates near the so-called grounding line, the zone in which the ice shelf settles on the sea floor at the transition to the glacier," said Determann.

"At this point the Filchner-Ronne Ice Shelf is melting today at a rate of around five metres per year. By the turn of the next century the melt rates will rise to up to 50 metres per year," added Determann.