The only remaining intact section of a massive ice shelf in Antarctica is weakening, and the complete shelf will probably disappear in a matter of a few years, researchers say.
The final collapse of the Larsen B Ice Shelf, one of dozens of glacier-fed floating platforms of ice that hang off the edge of the frozen continent, will likely increase the rate of sea level rise around the world, they say.
The Larsen shelf has existed for at least 10,000 years, but after a partial collapse in 2002, what was left was a 625 square-mile section, around half the size of the state of Rhode Island.
Now, that remnant is showing signs of increasing fragmentation, with large cracks becoming visible, a study by NASA researchers reported.
"These are warning signs that the remnant is disintegrating," said study leader Ala Khazendar of the space agency's Jet Propulsion Laboratory in Pasadena, California. "Although it's fascinating scientifically to have a front-row seat to watch the ice shelf becoming unstable and breaking up, it's bad news for our planet."
The Larsen ice shelf is one of two areas in Antarctica where researchers have been closely documenting thinning ice formations.
The researchers predict that a large fissure at the base of the ice shelf at the continent's edge could crack all the way through by 2020, resulting in the entire ice shelf breaking up into hundreds of icebergs floating away into the ocean.
The accelerating pace of ice shelf melting can be attributed to global warming, which is increasing faster at the planet's poles than anywhere else, the researchers pointed out.
Antarctica has warmed 4.4 degrees Fahrenheit in the past 50 years, three times the average warming rate seen in the rest of the world, they say.
When the Larsen ice shelf—acting as a gatekeeper, holding glaciers in place on the continent—is gone, there will be nothing holding back three glaciers that have been feeding it, and they themselves will advance into the ocean at a faster rate, with a resulting impact on global sea levels.
The United Nations has projected that by 2100 the world may experience sea level rises of as high as 3 feet, but the NASA researchers emphasize those projections have not included the potential significant ice loss now being seen in Antarctica.
"What is really surprising about Larsen B is how quickly the changes are taking place," said Khazendar. "This ice shelf has existed for at least 10,000 years, and soon it will be gone."
