科学家发现南极冰盖的新弱点

The Filchner-Ronne Ice Shelf fringing the Weddell Sea, Antarctica, may start to melt rapidly in this century and no longer act as a barrier for ice streams draining the Antarctic Ice Sheet. These predictions are made by climate researchers of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association in the journal Nature. They refute（反驳） the widespread assumption that ice shelves in the Weddell Sea would not be affected by the direct influences of global warming due to the peripheral（外围的，次要的） location of the Sea. The results of the climate modelers from the Alfred Wegener Institute will come as a surprise to the professional world with the majority of experts assuming that the consequences of global warming for Antarctica would be noticeable primarily in the Amundsen Sea and therefore in the western part of Antarctica. "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. But we found a mechanism which drives warm water towards the coast with an enormous impact on the Fichner-Ronne Ice Shelf in the coming decades," says Dr. Hartmut Hellmer, oceanographer at the Alfred Wegener Institute and lead author of the study.

Using different model calculations, he and his colleagues Dr. Frank Kauker, Dr. Ralph Timmermann and Dr. Jürgen Determann as well as Dr. Jamie Rae from Met Office Hadley Centre, U.K., demonstrate that as a result of a chain reaction large ice masses could presumably slide into the ocean within the next six decades.

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," says Frank Kauker. If this happens, fundamental transport processes will change. "This will mean that a hydrographic（水道学的） 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," explains Hartmut 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. At this point the Filchner-Ronne Ice Shelf is melting today at a rate of around 5 metres per year. By the turn of the next century the melt rates will rise to up to 50 metres per year," says Hellmer's colleague Jürgen Determann.