New evidence has emerged that a large plate of floating ice shelf attached to Antarctica is breaking up, in a troubling sign of global warming, the European Space Agency says.
Images taken by its Envisat remote-sensing satellite show that Wilkins Ice Shelf is "hanging by its last thread" to Charcot Island, one of the plate's key anchors to the Antarctic peninsula.
"Since the connection to the island helps stabilise the ice shelf, it is likely the breakup of the bridge will put the remainder of the ice shelf at risk," it said.
Wilkins Ice Shelf had been stable for most of the last century, covering around 16,000 square kilometres before it began to retreat in the 1990s.
Since then several large areas have broken away, and two big breakoffs this year left only a narrow ice bridge about 2.7km wide to connect the shelf to Charcot and nearby Latady Island.
The latest images, taken by Envisat's radar, say fractures have now opened up in this bridge and adjacent areas of the plate are disintegrating, creating large icebergs.
The Antarctic peninsula - the tongue of land that juts northward from the white continent towards South America - has had one of the highest rates of warming anywhere in the world in recent decades.
However, this latest stage of the breakup occurred during the Southern Hemisphere's winter, when atmospheric temperatures are at their lowest.
One idea is that warmer water from the Southern Ocean may be reaching the underside of the ice shelf and thinning it rapidly from underneath.
"Current events are showing that we were being too conservative, when we made the prediction in the early 1990s that Wilkins Ice Shelf would be lost within 30 years. The truth is, it is going more quickly than we guessed, " says researcher David Vaughan of the British Antarctic Survey.
In the past three decades, six Antarctic ice shelves have collapsed completely - Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B, Wordie, Muller and the Jones Ice Shelf.
