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Melting Antarctic Ice Sheet Is a “Sleeping Giant”

Victoria University of Wellington scientists have warned of massive sea level rises if carbon dioxide levels in the atmosphere continue increasing, as predicted, causing the giant East Antarctic ice sheet to melt.

“Our study shows that this ice sheet becomes unstable and melts if carbon dioxide levels in the atmosphere reach 600 parts per million – levels which may be reached by the end of the century if emissions reductions targets agreed to recently in Paris are not met,” says Prof Tim Naish. “If the Antarctic ice sheet completely melted, global sea level would rise about 60 metres. It’s a sleeping giant.”

The research, published in Science (www.tinyurl.com/ha69e5g), is based on geological drill cores taken from the Ross Sea near New Zealand’s Scott Base. “The drill cores show that the first Antarctic ice sheet was quite dynamic. It advanced and retreated many times between 34–35 million years ago before finally stabilising at its largest extent when atmospheric carbon dioxide levels dropped below a threshold of 600 parts per million,” Nash says.

Carbon dioxide levels are currently 400 parts per million and are predicted to increase. Last year alone they rose by more than 3 ppm.

“We know that parts of the ice sheet sitting below sea-level in West Antarctica are already melting in response to current global warming, but the much larger East Antarctic ice sheet, which sits mostly on rock above sea level, was thought to be more stable,” Naish says. “We found it is vulnerable, and was much smaller the last time atmospheric carbon dioxide levels matched those predicted before the end of the century.”

The research also provides the first direct evidence that ice expanded all the way to the coast and out into the ocean, causing erosion of the seabed.