A crack is spreading rapidly across Antarctica’s fourth-largest ice shelf, hastening the loss of a massive chunk of ice, say scientists.
Researchers from the British Antarctic Survey's Project MIDAS found that the crack has extended 14 miles since the last time a satellite imaged it, in March 2015. Soon, the team thinks, about 12 percent of the shelf – known as Larsen C – will break away, following the pattern seen in neighboring ice sheets Larsen A and Larsen B in 1995 and 2002, respectively.
The scientists were stunned by the crack's dramatic increase in speed, as it previously took four years to grow 18 miles. It is also widening quickly. Last year, it was 650 feet wide, and now it is more than 1,100 feet wide – nearly a quarter mile.
Martin O’Leary, a MIDAS team member and glaciologist at Swansea University in Wales, told The Washington Post that the shelf could lose a 6,000-square-mile piece of ice. That's the size of Delaware.
“It’s hard to tell how soon it could break – we really don’t have a good handle on the processes which control the timing of the crack propagation,” Dr. O’Leary told the Post. “It’s a lot like predicting an earthquake – exact timings are hard to come by. Probably not tomorrow, probably not more than a few years.”
That estimate is considerably sooner than that given in a May 2015 study by another team of researchers, who expected that a collapse could occur “within a century, although maybe sooner and with little warning.”
The 2015 study found two contributing factors to the instability of the Larsen C shelf: a top layer of snow was losing air and growing more compact, probably because of increased melting from a warming atmosphere; and the shelf was losing ice from below, probably due to warming ocean currents or changing ice flow.
The collapse of Larsen C, they predicted, would tack on another 50 centimeters (20 inches) to the global rise in sea levels by 2100, adding to problems for coastal cities.
"If this vast ice shelf – which is over two and a half times the size of Wales and 10 times bigger than Larsen B – was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise,” wrote the researchers, who were funded by the Britain’s Natural Environment Research Council and the United States’ National Science Foundation, among others.
In 2002, a Rhode-Island-sized piece of the Larsen B ice shelf collapsed and broke off into thousands of smaller icebergs, in what scientists then called “the largest single event in a series of retreats by ice shelves in the Antarctic Peninsula over the last 30 years.”
The engine of those retreats, as in the case of Larsen C, was the region’s particularly dramatic rate of climate change. Annual temperatures have risen at several times the global average in the Antarctic peninsula over the past fifty years, according to the 2015 study.
It could have dire effects on human habitation. In March, The Christian Science Monitor reported on a new study finding that the melting of Antarctic ice could drive sea levels up as much as 1 meter, or 39 inches, by 2100 – if atmospheric emissions continue unabated.