Photo: NASA

An Antarctic ice shelf that’s been cracking up for years is now very close to giving birth to an iceberg roughly 30 times the size of Manhattan. With a long-term scientific research station right in the neighborhood, the far-flung event is being watched closely, and with some trepidation.

On Wednesday, NASA released a new image of the Brunt Ice Shelf captured via satellite on January 23. It reveals that a series of cracks, which have been growing in the ice along a roughly east-west and north-south axis, have advanced considerably of late. Soon, the north-south oriented crack, portentously dubbed “chasm 1,” will reach the far end of the shelf, plopping an approximately 660-square mile iceberg into the sea.

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In standard American English, that’s two New York Cities, 30 Manhattans, or about 1.4 million Olympic swimming pools.

“It’s hard to make a projection when it will happen exactly but it will happen,” TU Delft satellite remote sensing expert Stef Lhermitte, who has been closely monitoring the crack’s progression, told Earther. He estimates the chasm has about 2.5 miles to go before it makes a clean break, something that could occur within “days but it can also take a year.”

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Two cracks, the Halloween crack (top) and chasm-1 (center) have been accelerating along the Brunt Ice Shelf in recent months.
Image: NASA

Spectacular as it sounds, so-called iceberg calving events like this are nothing new for the frozen continent, which has spat out a series of considerably larger ‘bergs over recent history. As NASA’s Earth Observatory notes, this ice hunk likely won’t even register in the top 20. But two facts conspire to make the event both significant and worrisome.

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For one, as Lhermitte noted, the Brunt Ice Shelf is currently at its largest extent in on record. After the iceberg goes, it’ll be at its smallest since Ernest Shackleton mapped the coastline in 1915. That raises questions about the long-term fate of the shelf and whether it’s poised for an even more significant breakup. As a paper published earlier this month in the Cryosphere notes, the structural integrity of the remaining ice could hinge on whether the break occurs upstream or downstream of a key pinning point known as the McDonald Ice Rumples. Right now, it’s tough to say.

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What’s more, the impending break is already having a direct impact on human activities on the frozen continent.

For decades, the Brunt Ice Shelf has played host to the Halley research station, an Earth, atmospheric, and space science station managed by the British Antarctic Survey (BAS). The BAS has been watching the cracks in its icy real estate closely, and has recently been forced to cancel wintertime field seasons due to the “complex and unpredictable glaciological situation.” The survey even went so far as to tow its current station, Halley VI, 14 miles inland in late 2016 to ensure it wasn’t on the “wrong side of the crack” should the ice shelf go.

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That turned out to be a good move.

Map of the Brunt Ice Shelf showing the former location of Halley VI, on the seaward side of chasm one, and its new site upstream.
Image: British Antarctic Survey

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This year’s summertime field season—which runs through the end of February—hasn’t been affected by the nearby ice action, BAS communications manager Layla Batchellier told Earther in an email. The survey is, however, once again preparing to close Halley down for winter.

“The station will operate as a summer-only station until it can be established that the Brunt Ice, on which it sits, is once again safe for year-round operation and occupation,” Batchellier said. She added that if the ice shelf fractured while staff was still at the station, they would be swiftly transported out “using ships and aircraft.”

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To gauge the likelihood of a sudden seismic shift in the ice, science teams deployed a suite of monitoring instruments across the shelf last November, Batchellier said. “Our teams on the ice and in Cambridge use these to check for any changes in the ice that might impact the station. No such changes have been seen,” she continued.

Hopefully, that’ll remain the case for as long as people are in the area. But if recent Antarctic happenings have taught us one thing, it’s that nature is a powerful and unpredictable beast.

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[NASA Earth Observatory]