A
300-foot-wide, 70-mile-long rift in Antarctica’s Larsen C Ice
Shelf, as seen in November 2016.
John
Sonntag/IceBridge/NASA Goddard Space Flight
Center
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.
Diti
Torterat/Wikipedia (CC BY 2.0)
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.)
The
Larsen C Ice Shelf rift snaking into the distance, as seen from
an IceBridge flight.
John
Sonntag/IceBridge/NASA Goddard Space Flight
Center
“[R]ifting of this magnitude doesn’t happen so often, [so] we
don’t often get a chance to study it up close,” Joe
MacGregor, a glaciologist and geophysicist at NASA’s Goddard
Space Flight Center, told Business Insider in an email.
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.
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