Bristol professor warns of Antarctic ice methane gas timebomb

A BRISTOL University professor has warned that a greenhouse gas timebomb could be hidden below the Antarctic ice sheet.

Professor Jemma Wadham, pictured, is the co-author of a new study which suggests that a vast reservoir of methane from the remains of ancient lifeforms could be released into the atmosphere if enough of the ice melts away.

Methane is a potent greenhouse gas and its release could accelerate climate change.

Scientists have already warned that methane currently frozen in Siberia could have an impact on global temperatures if the permafrost starts to melt. But the new study, published last night in the journal Nature, says the amount that may be under the Antarctic ice is far higher - perhaps as much as four billion tonnes.

Half of the West Antarctic Ice Sheet and a quarter of the East Antarctic Ice Sheet lie on pre-glacial sedimentary basins containing around 21,000 billion tonnes of carbon.

Prof Wadham said: "This is an immense amount of organic carbon, more than 10 times the size of carbon stocks in northern permafrost regions.

"Our laboratory experiments tell us that these sub-ice environments are also biologically active, meaning that this organic carbon is probably being metabolised into carbon dioxide and methane gas by microbes."

The organic material dates back to a period 35 million years ago when the Antarctic was much warmer than it is today and teeming with life.

Study co-author Professor Slawek Tulaczyk, from the University of California at Santa Barbara, said: "Some of the organic material produced by this life became trapped in sediments, which then were cut off from the rest of the world when the ice sheet grew.

"Our modelling shows that over millions of years, microbes may have turned this old organic carbon into methane.

"Our study highlights the need for continued scientific exploration of remote sub-ice environments in Antarctica because they may have far greater impact on Earth's climate system than we have appreciated in the past," The Antarctic ice sheet covers the southern continent's land-mass and not the sea around it. Methane hydrates – a combination of frozen water ice and methane - are also found at the bottom of the oceans where they form as a result of cold temperatures and high pressures.

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