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article imageChunk of Larsen C ice shelf now hanging on by a thread

By Karen Graham     Jan 6, 2017 in Environment
An iceberg, expected to be one of the 10 biggest ever recorded, is ready to break off from the Larsen C ice shelf at any moment, MIDAS project scientists say.
The British Antarctic Survey (BAS), as part of the MIDAS Project, has been monitoring the ever-widening rift in Antarctica's Larsen C ice shelf in the northwestern part of the Weddell Sea for some time.
On December 16, according to Digital Journal, new NASA images, taken by researchers on November 10 showed the crack was getting wider, longer and much deeper. Scientists measured and determined the fracture was about 70 miles long, more than 300 feet wide and about a third of a mile deep.
The news of the new NASA photos came just a week after the BAS had made the decision to relocate the Halley VI research station because a giant chasm in the Brunt ice shelf in East Antarctica is threatening to break off.
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Project MIDAS
But according to MIDAS, the rift suddenly grew an additional 18 kilometers (11.2 miles) during the second half of December 2016, and now, there is only a thread, 20 kilometers (12.4 miles) long holding the huge chunk of ice to the shelf.
Depending on which side of the Atlantic Ocean you live on, the resulting chunk of ice will be the size of the state of Delaware or one-fourth the size of Wales. Either way, the Larsen C Ice Shelf will lose more than 10 percent of its area, leaving the ice front at its most retreated position ever recorded.
The break will leave the Larsen C ice shelf very vulnerable to future break-offs. Larsen C is about 350 meters (1.148 feet) thick and floats on the sea, acting as a barrier holding back the flow of the glaciers that feed it. "If it doesn't go in the next few months, I'll be amazed," project leader Prof Adrian Luckman, from Swansea University, told BBC News.
"There haven't been enough cloud-free Landsat images but we've managed to combine a pair of ESA Sentinel-1 radar images to notice this extension, and it's so close to calving that I think it's inevitable."
Larsen B ice shelf on January 31  2002. By April 13  2002  the ice shelf had collapsed.
Larsen B ice shelf on January 31, 2002. By April 13, 2002, the ice shelf had collapsed.
NASA Earth Observatory
Researchers point out that the eventual calving of the iceberg should be considered a geographical and not a climate event. They say the rift has been present for decades and has chosen this particular time to break-off. Scientists do say that climate change may have hastened the separation of the iceberg, but they have no direct evidence to support this.
But there is concern over the consequences of a break-off and how it will impact the remaining ice shelf. In 2002, Larsen B had a spectacular calving event that caused the shelf to disintegrate. "We are convinced, although others are not, that the remaining ice shelf will be less stable than the present one," said Prof Luckman.
More about Larsen C ice shelf, Delawaresized, British Antarctic Survey, MIDAS, hanging by a thread
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