Rift in Antarctic ice shelf sprouts new branch

A big crack on Antarctica's most watched Larsen C ice shelf has developed a second branch which has been steadily widening, satellite data has unveiled.
The main rift in Larsen C, which is likely to lead to one of the largest icebergs ever recorded, is currently 180 kilometres (km) long.
The new branch of the rift is 15 km long, researchers from Swansea University in the UK have found.
Last year, the rift was growing fast. Now, just 20km of ice is keeping the 5,000 square km piece from floating away, they said.
"While the previous rift tip has not advanced, a new branch of the rift has been initiated. This is approximately 10km behind the previous tip, heading towards the ice-front," said Adrian Luckman, professor at Swansea University.

Although the rift length has been static for several months, it has been steadily widening, at rates in excess of a metre per day, researchers said.

"It is currently winter in Antarctica, therefore direct visual observations are rare and low resolution. Our observations of the rift are based on synthetic aperture radar (SAR) interferometry from ESA's Sentinel-1 satellites.
"Satellite radar interferometry allows a very precise monitoring of the rift development," they said.
Researchers said the loss of a piece a quarter of the size of Wales will leave the whole shelf vulnerable to future break-up.
Larsen C is about 350 metres thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.

"When it calves, the Larsen C Ice Shelf will lose more than 10 per cent of its area to leave the ice front at its most retreated position ever recorded, this event will fundamentally change the landscape of the Antarctic Peninsula," Luckman said.
"We have previously shown that the new configuration will be less stable than it was prior to the rift, and that Larsen C may eventually follow the example of its neighbour Larsen B, which disintegrated in 2002 following a similar rift-induced calving event," researchers said.