There's a 70-mile-long crack in Antarctica and it's growing bigger every day
A slab of ice nearly twice the size of Rhode Island state is cracking off of an Antarctic glacier, and the rift between it and the southern continent is growing longer and wider every day.
The 2,300-square-mile ice block is part of the Larsen C Ice Shelf, which is the leading edge of one of the world's largest glacier systems.
It's called an ice shelf because it's floating on the ocean. It's normal for ice shelves to calve big icebergs, since snow accumulation gradually pushes old glacier ice out to sea.
But this 1,000-foot-thick piece of floating ice is colossal, and it's quickly fracturing off of Antarctica's prominent peninsula, likely due to rapid human-caused global warming.
Satellite images suggest the crack began opening up around 2011 and lengthened more than 18 miles by 2015. By March 2016 it had grown nearly 14 miles longer.
Now a team of scientists, who flew over the region in November as part of NASA's Operation IceBridge survey, have confirmed the rift is at least 70 miles long, 300 feet wide, and one-third of a mile deep. (Other estimates peg it at 80 miles long.)
So how long until the epic ice block chips off?
"Maybe a month, maybe a year," MacGregor said. "The more we study these rifts, the better we'll be able to predict their evolution and influence upon the ice sheets and oceans at large."
When the block does break off, it will be the third-largest in recorded history. MacGregor said it'd "drift out into the Weddell Sea and then the Southern Ocean and be caught up in the broader clockwise [...] ocean circulation and then melt, which will take at least several months, given its size."
Computer modeling by some researchers suggests the calving of Larsen C's big ice block might destabilize the entire ice shelf itself, which is about 19,300 square miles (or nearly two times larger than Massachusetts), via a kind of ripple effect.
MacGregor downplayed this possibility, noting that other "computer models predict that the eventual calving of this iceberg won't affect the overall stability of the ice shelf."
However, a rapid ice shelf collapse would not be unprecedented.
In 2002, a large piece of the nearby Larsen B Ice Shelf snapped off, but within a month - and quite unexpectedly - an even larger swath of the 10,000-year-old feature behind it rapidly disintegrated. The rest of Larsen B may splinter off by 2020.
If there's any good news about the rift in Larsen C, it's that the ice shelf "is already floating in the ocean, so it has already displaced an equivalent water mass and minutely raised sea level as a result," MacGregor said. "Melting of the resulting iceberg won't change that contribution."
The bad news is that if Larsen C collapses, all the ice it holds back might add another 4 inches to sea levels, and it's just one of many major ice systems around the world affected by climate change.