Ice sheet collapse disaster scenarios ‘exaggerated’

DISASTER-MOVIE scenarios resulting from a collapse of the West Antarctic Ice Sheet (WAIS) have been greatly exaggerated, say climate scientists.

But even a sea-level rise half as much as previously estimated would have a devastating impact on major coastal cities such as New York.

The massive ice sheet, which covers an area as big as Texas, extends 2,000 metres below sea level.

Scientists believe it is inherently unstable and could collapse rapidly if grounded ice around its edges melts away. Frightening forecasts have predicted that if that were to happen, global sea level could rise five or six metres, or up to 17 feet.

The new estimate suggests a rise of 3.3 metres – but this would still be enough to swamp many low-lying coastal regions.

US cities such as New York, Washington DC and San Francisco are especially vulnerable because sea levels around North America are expected to rise 25% more than the global average.

Professor Jonathan Bamber, from the University of Bristol, who led the research in the journal Science, said: “There’s a vast body of research that’s looked at the likelihood of a WAIS collapse and what implications such a catastrophic event would have for the globe.

“But all of these studies have assumed a five metre to six metre contribution to sea level rise. Our calculations show those estimates are much too large, even on a thousand-year timescale.”

Prof Bamber, who carried out the work as a visiting academic at the University of Colorado in the US, made the forecast on the basis that not all of the ice sheet is equally unstable.

His team assumed that ice on bedrock sloping upwards inland, or lying above sea level, would survive.

But he said that sea level rises would vary regionally, largely as a result of ice from the vast Antarctic continent melting into the oceans.

With less mass at the South Pole, the Earth’s gravity would strengthen in the northern hemisphere. This would cause water to pile up in the northern oceans.