The main rift in Antarctica that was discovered late in 2016 is spreading and now the rift in the Larsen C ice shelf has a second branch moving toward the ice front.

After reviewing satellite data, researchers from Swansea University in the U.K. claim that the main rift—likely leading to one of the largest icebergs ever recorded—is 180 km long and the new branch of the rift is 15 km long. They found that there is just 20 km of ice keeping a 5,000 square km piece from floating away and becoming an iceberg.

“While the previous rift tip has not advanced, a new branch of the rift has been initiated,” Adrian Luckman, a professor at Swansea University College of Science and head of Project Midas, said in a statement. “Although the rift length has been static for several months, it has been steadily widening, at rates in excess of a meter per day.

“This is the first significant change to the rift since February of this year,” he added.  “Although the rift length has been static for several months, it has been steadily widening, at rates in excess of a meter per day.”

However, Luckman said there are challenges in gathering information about the rift.

“It is currently winter in Antarctica, therefore direct visual observations are rare and low resolution,” he said. “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.”

The discovery builds on research from the U.K.’s Project Midas, led by Swansea University, that revealed that the rift was growing fast.

According to the researchers, if the 5,000 sq. km piece does in fact break off it will leave the entire shelf vulnerable to future break-ups of Larsen C—which is approximately 350 meters thick and floats on the seas at the edge of West Antarctica. The ice shelf is important because it holds back the flow of glaciers that feed into it.

“When it calves, the Larsen C Ice Shelf will lose more than 10 percent 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 neighbor Larsen B, which disintegrated in 2002 following a similar rift-induced calving event.”

R&D Magazine covered the last update on the rift in February.