Antarctic ice sheet a 'sleeping giant': expert

Melbourne: The East Antarctic ice sheet is a 'sleeping giant' and the world is on track for massive sea level rises resulting from its melting due to the rising carbon dioxide levels, scientists warn.

Research showed that if carbon dioxide levels in the atmosphere continue increasing as predicted, the giant East Antarctic ice sheet will 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," said lead author Tim Naish, Director o Victoria University's Antarctic Research Centre in Australia.

"If the Antarctic ice sheet completely melted, global sea level would rise about 60 metres. It's a sleeping giant," Naish said.

The research documents the growth of the first continent-wide ice sheet on Antarctica 34 million years ago. Led by Professor Simone Galeotti from the University of Urbino, the research is based on geological drill cores taken from the Ross Sea near New Zealand's Scott Base 16 years ago.

"The drill cores show that the first Antarctic ice sheet was quite dynamic. It advanced and retreated many times between 34 to 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," said Naish.

With carbon dioxide levels already at 400 parts per million and predicted to go higher, this study provides valuable insights into the potential future stability of the Antarctic ice sheet.

"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," said Naish.

"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," he said.

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.

The researchers cored through 1,500 metres of sedimentary strata beneath the seafloor between October 1997 and December 1999, capturing Antarctic ice margin history from 35 to 17 million years ago.

The study was published in the journal Science.