A MASSIVE ICEBERG IS POISED TO FRACTURE IN ANTARCTICA
A widening rift leaves the fourth-largest ice shelf on the continent at risk
BY ALEXANDRA MALLOY | JAN 12 2017
NASA photograph by John Sonntag
Within the past two decades, the Larsen ice shelf along the Antarctic Peninsula has undergone drastic geographical changes to the coastline. In 1995 and 2002, the Larsen A and B shelves splintered off. Now, a rift gradually splitting the section of Larsen C has expanded rapidly and once again poses a dramatic change to the landscape.
When pictured by NASA’s IceBridge mission on November 10, 2016, the fissure measured roughly 70 miles. Within the last month, it has expanded by 11 miles, with only a 12-mile sliver holding Larsen C to the main ice shelf. Once it calves, it will take on new life as an iceberg the size of the state of Delaware.
The rapid expansion of the cavernous fracture, which is more than 300 feet wide and a third of a mile deep, has been closely studied by Project MIDAS, a United Kingdom–based Antarctic research group with Swansea and Aberystwyth Universities in Wales, and the British Antarctic Survey. The team began monitoring the fissure two years ago, but noticed in August 2016 that the rift was starting to expand faster.
Erin Pettit, associate professor of geophysics with a specialty in glaciology at the University of Alaska Fairbanks, says that warmer temperatures in the past decades have led to the collapse of the Larsen A and Larsen B ice shelves and to this new rift.
“It's not necessarily that unexpected in the overall trend over the last few decades due to climate change,” Pettit said, speaking by phone from the McMurdo Station on the continent. “We’ve seen a very strong trend in the destabilization of all these ice shelves in the last couple of decades, and this spring and summer has been much warmer than average.”
Antarctica itself is one of the fastest-warming regions in the world, with temperatures rising by 36.5 degrees Fahrenheit in the last 50 years.
“The atmosphere really has the power to destabilize these ice shelves,” Pettit said.
Larsen C is already floating in icy waters, so the calving will not affect sea level rise in the short term. However, the loss of the ice shelf leaves open space for the glacier to push ice into the sea. “Ice shelves act like a dam, and if you take out the dam, the river flushes everything,” Pettit said. With the loss of the shelf, there is no barrier to hold back glacial ice from moving into the sea and melting.
In a statement to the Washington Post, Paul Holland, a member of the British Antarctic Survey, estimates that the ice that will fill the gap left by Larsen C and melt into the Weddell Sea could cause sea level to rise by roughly 10 centimeters (3.9 inches). The collapse of Larsen C could also affect the nearby marine ecosystem and ocean circulation as well as destabilize the remainder of the Larsen ice shelf.
As to when the ice shelf will break off is up for debate, with some scientist predicting months and others years.
“As long as there is a balance between the chunks that calve off and the ice that comes in off the mountains, it’s a normal part of the process,” Pettit said. “This one is very large and will put the whole system into the negative. And that’s why it’s particularly interesting to us.”