Crack in Antarctic ice shelf forks off, grows by miles

May 3, 2017, 9:46 a.m.
Rift in Antarctica's Larsen C Ice Shelf
Photo: John Sonntag/NASA

Scientists on NASA's IceBridge Mission captured this mesmerizing image of an Antarctic ice shelf, which shows a growing rift that could soon create one of the largest icebergs ever recorded.

The gargantuan crack is in Larsen C, an ice shelf in the Antarctic Peninsula. Scientists previously observed the crack on Nov. 10, 2016, and found it to be about 70 miles long, more than 300 feet wide and about a cavernous third of a mile deep. It grew by 11 miles in December 2016, and now scientists say it's hanging on by a thread. As of early February, the crack was reportedly 2 miles wide in some places and more than 100 miles long, placing it just 20 miles from the other end of the ice shelf.

The Antarctic research group Project Midas reported on May 1 that the crack had forked, and a second crack about three miles long had split off from the main one.

"“The new branch is heading off more toward the ice front, so it’s more dangerous and more likely to cause this calving event to occur [than the existing branch]," glaciologist Adrian Luckman of Swansea University in Wales told ScienceNews.

"If it doesn't go in the next few months, I'll be amazed," Luckman told BBC News in January. "It's so close to calving that I think it's inevitable."

According to NASA, ice shelves are the parts of ice streams and glaciers that float, and they support the grounded ice behind them. When an ice shelf collapses, ice races toward the ocean, where it contributes to sea level rise.

When last observed, the crack in Larsen C cut completely through the ice shelf but didn't go all the way across it. Once it does, it will create an iceberg about the size of the state of Delaware, according to IceBridge. NASA's IceBridge Mission collects information on changing sea ice and polar land. When it separates, Larsen C is projected to be one of the 10 largest icebergs ever recorded.

Larsen C, the fourth-largest ice shelf, is neighbors to Larsen B, a smaller ice shelf that partially collapsed in 2002 after developing a rift similar to the one now developing in Larsen C.

Project Midas has been tracking the rift's progression since 2014. The group estimates that when an iceberg eventually breaks away, it will remove between 9 and 12 percent of the ice shelf area and may lead to Larsen C disintegrating completely.

Editor's note: This story has been updated since it was originally published in December 2016.