Chill out: Antarctic iceberg still hanging on
Crack in Larsen C shelf could go today or in a few months
It’s the ice crack that’s captivating the world.
One of the world’s biggest icebergs ever is poised to break off from an Antarctic ice shelf, but scientists say it’s still hanging on by a 12-mile “thread.”
They also aren’t sure when the now 110-mile-long crack will finally break open the rest of the way, creating a iceberg larger than Rhode Island. “It is particularly hard to predict when it will occur,” says Adrian Luckman of Project MIDAS, a British Antarctic research project that’s keeping watch on the ever-growing crack.
“I am quite surprised as to how long it is holding on!” he said in an email to USA TODAY.
The crack in the Larsen C Ice Shelf is more than 1,000 feet wide and has grown by 50 miles since 2011, according to the British Antarctic Survey. Once the crack goes all the way across the ice shelf, the iceberg will break off.
The largest icebergs known have all broken off from ice shelves, the survey said.
Ice shelves are permanent floating sheets of ice that connect to a land mass, according to the National Snow and Ice Data Center. (Because it’s floating, when the berg breaks off, it won’t contribute to a rise in sea levels.) But ice shelves also hold back the ice behind them: When shelves collapse, the ice that had been trapped behind them plops into the ocean, where it then increases sea levels.
Most of the world’s ice shelves hug Antarctica. The Larsen C shelf is on the Antarctic Peninsula, the portion of the continent that juts toward South America. The Larsen shelf used to have three parts: A, B and C. Larsen A and Larsen B collapsed in 1995 and 2002, respectively. Now it’s C’s turn.
“The rift has continued to open, and the berg continues to drift outward,” Luckman says. But, he adds, the crack has not grown longer in the past several weeks.
There is not enough information to know whether the expected calving event on Larsen C is an effect of climate change, although there is good scientific evidence that climate change has caused thinning of the ice shelf, according to Project Midas. In the past 50 years, the Antarctic Peninsula has experienced extraordinary warming of more than 4 degrees, the European Space Agency says.
Could the colder winter temperatures that are on the way delay the calving process? (Calving is the scientific term for the process by which the berg shears off.)
No, Luckman says. “Calving is not dependent at all on air temperatures. The ice that is fracturing is buried deep in the shelf and does not feel the change in sea- sons. If anything, I would say that winter might make the calving more likely because of mechanical stresses caused by wind and waves.
Once the iceberg shears off, the 2,000-square-mile chunk should float along Antarctica, head out into the Southern Ocean and eventually break into smaller chunks that would melt into the ocean.
“But I should stress again, this is not a predictable process because we know only a little about the nature of the ice,” Luckman says. “It could go today, or it may be months.”