A new study from the University of California has revealed that a vast reservoir of methane underneath the Antarctic ice sheet could be unleashed into the atmosphere if the ice melts. The report, which was published in the August 30 issue of Nature by an international team of scientists, noted that the Antarctic ice sheet is an overlooked but important source of methane, which is one of the planet’s most potent greenhouse gases.

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It is believed that old organic matter trapped in sedimentary basins located beneath the Antarctic ice sheet have been converted to methane by micro-organisms living under oxygen-deprived conditions. If the ice sheet shrinks, these sedimentary basins would be exposed and the methane would be released into the atmosphere.

In a statement, report co-author Slawek Tulaczyk and professor of Earth and planetary sciences at UC Santa Cruz, said “It is easy to forget that before 35 million years ago, when the current period of Antarctic glaciations started, this continent was teeming with life.”

“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 modeling shows that over millions of years, microbes may have turned this old organic carbon into methane.”

It is estimated that approximately 50% of the West Antarctic ice sheet (1 million square kilometers) and 25% of the East Antarctic ice sheet (2.5 million square kilometers) lie over the basins, which potentially contain about 21,000 billion metric tons of organic carbon. This is approximately 4 billion metric tonnes of methane.

“This is an immense amount of organic carbon, more than ten times the size of carbon stocks in northern permafrost regions,” Wadham said. “Our laboratory experiments tell us that these sub-ice environments are also biologically active, meaning that this organic carbon is probably being metabolized to carbon dioxide and methane gas by microbes.”

Any methane released during episodes of ice-sheet collapse would act as a positive feedback on global climate change during past and future ice-sheet retreat.

“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,” Tulaczyk said.

+ University of California

via The Guardian

Images:  NASA Goddard Photo and Video