This giant chunk of ice could break off Antarctica any day

Two cracks on the Brunt Ice Shelf are creeping closer to each other. When they intersect, an iceberg twice the size of Manhattan will slide into the ocean.

BY ALEJANDRA BORUNDA - 

NATIONAL GEOGRAPHIC - 

PHOTO: THE GUARDIAN

A CHUNK OF ice more than twice the size of New York’s Manhattan could break off from Antarctica’s Brunt Ice shelf essentially at any moment. Two large cracks in the shelf have been inching further open over the past few years. When they finally intersect, a berg about 660 square miles wide and almost 500 feet thick will be released into the ocean—where it will eventually melt, joining its brethren in adding more water to the world’s oceans and pushing global sea levels a tiny bit higher.

It’s no surprise that the giant berg would eventually break off: The Brunt Ice Shelf is one of the most carefully monitored ice tongues in the world, because it’s the site of the Halley Research Station, a major center for the British Antarctic Survey’s research activities in the region. But no one knows exactly when the berg will dislodge.

Nor is the berg the biggest to break off Antarctic ice sheets in recent years. That prize goes to a Delaware-sized chunk (something like 2,240 square miles) that peeled off the nearby Larsen-C ice sheet in 2017. But this hunk is nothing to sneeze at.

Πηγή: NATIONAL GEOGRAPHIC

Unlike the dramatic ice break-ups observed over the past few years on the Antarctic peninsula, though, this calving event is not likely driven by warming air or seas.

“The Brunt ice shelf is relatively far south compared to the ice shelves that have calved dramatically on the Antarctic Peninsula,” says Oliver Marsh, a glaciologist at the British Antarctic Survey in Cambridge, England, and the extra-warm air temperatures that have toasted that region haven’t had such a dramatic effect at Brunt yet. 

“This calving event is just part of a natural cycle.”

The first fault line on the Brunt Ice Shelf, called Chasm 1, has been in place for over 35 years (glaciologists call breaks in the ice sheet that extend all the way from surface to the ocean below “chasms,” while shallower faults are called “cracks” or “crevasses”). It remained relatively stable until 2012, when surveyors noticed that it starting to grow again, creeping across the wide tongue of ice that protruded out over the ocean. Now, it’s extending outward in fits and starts, growing by a few hundred meters each week, on average.

Source: NATIONAL GEOGRAPHIC