澳门金沙网页版开户注册:Giant mass of Antarctic ice 'set for collapse'
By Anil Ananthaswamy A mass of Antarctic ice larger in area than Connecticut is in “imminent” danger of breaking up, according to scientists from the European Space Agency. The ESA reported that an ice bridge between two islands protecting the Wilkins Ice Shelf from the open ocean has now collapsed, leaving in its wake a channel full of icebergs, and exposing the northern front of the ice shelf. “We expect in the next few days and weeks, that the northern ice front will lose between 800 and 3700 square kilometres of ice,” says Angelika Humbert of Münster University, Germany, who has been using ESA’s Envisat probe to monitor the events. Last year, the 13,000-square-kilometre Wilkins Ice Shelf experienced three break-ups, during which massive chunks of ice totalling nearly 1800 square kilometres separated and floated away as icebergs. These events left behind a narrow ice bridge just a few kilometres wide, as the only connection between the northern front of the Wilkins Ice Shelf and the ice surrounding Charcot and Latady islands. The exposure of the shelf will inevitably lead to its break up, but the break-up of the Wilkins Ice Shelf will not lead to sea-level rise as it is already floating on water. Neither will it cause the acceleration of glaciers towards the sea, since there are no big ice-streams and glaciers feeding it. However, the events serve as a dire warning. “It shows us that ice shelves have the potential to become unstable on very short timescales,” says Humbert. If other ice shelves around West Antarctica start breaking up, then the ice-streams and glaciers that feed them could drain more speedily into the ocean, leading to sea-level rise. Meanwhile, the scientists are carefully monitoring the Wilkins Ice Shelf. In January, David Vaughan of the British Antarctic Survey and colleagues from the Netherlands placed a GPS unit on the bridge between Charcot and Latady islands. Data is transmitted from the GPS station once every six days and the next transmission is expected soon. “If we are really lucky it is on one of those icebergs which have not capsized,” says Humbert. More on these topics: