Ice melt could raise seas by 4 feet

Melting ice in West Antarctica is a major concern for global sea levels, and a key area may already be unstable enough to unleash three meters of ocean rise, scientists said Monday.

The study follows research out last year, led by NASA glaciologist Eric Rignot, warning that ice in the Antarctic had gone into a state of irreversible retreat, that the melting was considered "unstoppable" and could raise sea level by 1.2 metres (four feet).

This time, researchers at Germany's Potsdam Institute for Climate Impact Research pointed to the long-term impacts of the crucial Amundsen Sea sector of West Antarctica, which they said "has most likely been destabilised."

While previous studies "examined the short-term future evolution of this region, here we take the next step and simulate the long-term evolution of the whole West Antarctic Ice Sheet," the authors said in the Proceedings of the National Academy of Sciences.

They used computer models to project the effects of 60 more years of melting at the current rate.

This "would drive the West Antarctic Ice sheet past a critical threshold beyond which a complete, long-term disintegration would occur."

In other words, "the entire marine ice sheet will discharge into the ocean, causing a global sea-level rise of about three meters," the authors wrote.

"If the destabilization has begun, a three-meter increase in sea level over the next several centuries to millennia may be unavoidable."

Even just a few decades of ocean warming can unleash a melting spree that lasts for hundreds to thousands of years.

"Once the ice masses get perturbed, which is what is happening today, they respond in a non-linear way: there is a relatively sudden breakdown of stability after a long period during which little change can be found," said lead author Johannes Feldmann.

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