An Ice Shelf Twice The Size Of New York City Is About To Break Off Antarctica

Two cracks on Antarctica's Brunt Ice Shelf will meet any day now, breaking away a chunk of ice more twice the size of New York City.

Two massive cracks in the shelf are now mere kilometres from reaching one another. If they meet, a chunk of ice spanning about 1700 square kilometres will break off -- the largest berg to break from the Brunt Ice Shelf since observations began in 1915.

The first chasm -- which was stable for approximately 35 years -- began accelerating its growth in 2012. The second chasm first appeared in October 2016, earning itself the nickname 'Halloween crack'.

The process of ice shelves breaking from the continent is known as "calving", but NASA's Earth Observatory notes the recent changes to the ice are "unfamiliar in this area" and may not be part of Antarctica's natural ice cycle.

Cracks growing in the Brunt Ice Shelf, Antarctica. Source: Earth Observatory NASA

The first chasm is creeping towards Halloween crack at a rate of 200 metres per month. While scientists cannot predict the exact date that the cracks will meet, the detaching of the shelf seems imminent.

The Brunt Ice Shelf has been a particular focus of research attention in recent years because it's the site of the British Halley Research Station. The almost certain calving of the shelf has caused concerns for the researchers based in the area who are conducting Earth, atmospheric, and space science research.

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At the end of 2016, Halley researchers were forced to move the station and its equipment to a safer location on the shelf due to the growing chasms. The new research station is located just south of the Halloween crack on a subsection that will not break away when the chasms meet.

While is not "terribly large by Antarctic standards", according to NASA, it is still of concern.

"The near-term future of Brunt Ice Shelf likely depends on where the existing rifts merge relative to the McDonald Ice Rumples,” NASA glaciologist Joe MacGregor said.

“If they merge upstream (south) of the McDonald Ice Rumples, then it’s possible that the ice shelf will be destabilised.”

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