‘Worst-case’ disaster for Antarctic ice looks less likely, study finds

For almost a decade, climate scientists have been trying to get their heads around a particularly disastrous scenario for how West Antarctica’s gigantic ice sheet might break apart, bringing catastrophe to the world’s coasts.

It goes like this: Once enough of the ice sheet’s floating edges melt away, what remains are immense, sheer cliffs of ice facing the sea. These cliffs will be so tall and steep that they are unstable. Great chunks of ice start breaking away from them, exposing even taller, even more-unstable cliffs. Soon, these start crumbling too, and before long you have runaway collapse.

As all this ice tumbles into the ocean, and assuming that nations’ emissions of heat-trapping gases climb to extremely high levels, Antarctica could contribute more than a foot to worldwide sea-level rise before the end of the century.

This calamitous chain of events is still hypothetical, yet scientists have taken it seriously enough to include it as a “low-likelihood, high-impact” possibility in the United Nations’ latest assessment of future sea-level increase.

Now, a group of researchers has put forth evidence that the prospect may be more remote than previously thought. As humans burn fossil fuels and heat the planet, West Antarctica’s ice remains vulnerable to destruction in many forms. But this particular form, in which ice cliffs collapse one after the other, looks less likely, according to the scientists’ computer simulations.

“We’re not saying that we’re safe,” said Mathieu Morlighem, a professor of earth science at Dartmouth College who led the research, published Wednesday in the journal Science Advances. “The Antarctic ice sheet is going to disappear; this is going to happen. The question is how fast.”

The speed at which West Antarctica’s ice disintegrates matters hugely for human civilization and the environment. A slower breakdown gives seaside populations more time to mount defenses or move inland. It gives coastal ecosystems such as wetlands and mangroves more time to adapt.

Still, there’s a lot of uncertainty about how ice breaks apart under stress, Morlighem said. So it remains hard to say with high confidence how much time the world has to prepare for higher seas. “We still have a lot to do to reduce these uncertainties,” he said.

This article originally appeared in The New York Times.

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