NASA announced on Sunday that an iceberg twice the size of New York City is about to break off of Antarctica’s Brunt Ice Shelf, making it the largest to break off the ice shelf in years.
“Cracks growing across Antarctica’s Brunt Ice Shelf are poised to release an iceberg with an area about twice the size of New York City,” NASA said in a statement. “It is not yet clear how the remaining ice shelf will respond following the break, posing an uncertain future for scientific infrastructure and a human presence on the shelf that was first established in 1955.”
Cracking across Antarctica’s Brunt Ice Shelf is set to release an iceberg w/ an area about 2x the size of NYC. The splitting could result in an uncertain future for the shelf’s scientific research & human presence. See what @NASAEarth satellites captured: https://t.co/Atppp05I5j pic.twitter.com/WrI1p3bqVC
— NASA (@NASA) February 24, 2019
“The cracks are apparent by comparing these images acquired with Landsat satellites,” NASA explained. “The Thematic Mapper (TM) on Landsat 5 obtained the first image (left) on January 30, 1986. The second image (right), from the Operational Land Imager (OLI) on Landsat 8, shows the same area on January 23, 2019.”
The crack along the top of the January 23 image—the so-called Halloween crack—first appeared in late October 2016 and continues to grow eastward from an area known as the McDonald Ice Rumples. The rumples are due to the way ice flows over an underwater formation, where the bedrock rises high enough to reach into the underside of the ice shelf. This rocky formation impedes the flow of ice and causes pressure waves, crevasses, and rifts to form at the surface.
The more immediate concern is the rift visible in the center of the image. Previously stable for about 35 years, this crack recently started accelerating northward as fast as 4 kilometers per year.
The detailed view shows this northward expanding rift coming within a few kilometers of the McDonald Ice Rumples and the Halloween crack. When it cuts all the way across, the area of ice lost from the shelf will likely be at least 1700 square kilometers (660 square miles). That’s not a terribly large iceberg by Antarctic standards—probably not even making the top 20 list. But it may be the largest berg to break from the Brunt Ice Shelf since observations began in 1915. Scientists are watching to see if the loss will trigger the shelf to further change and possibly become unstable or break up.
Joe MacGregor, a glaciologist at NASA’s Goddard Space Flight Center, said in the statement that the “near-term future” of the ice shelf “likely depends on where the existing rifts merge relative to the McDonald Ice Rumples,” another area on the ice shelf.
— NASA Earth (@NASAEarth) February 21, 2019
“If they merge upstream (south) of the McDonald Ice Rumples, then it’s possible that the ice shelf will be destabilize,” MacGregor added.