Researchers from University of California - Santa Cruz and the University of Bristol found that old organic matter in sedimentary basins located beneath the Antarctic Ice Sheet may have been converted to methane by micro-organisms living under oxygen-deprived conditions.
The team estimated that 50 per cent of the West Antarctic Ice Sheet (1 million square kilometres) and 25 per cent of the East Antarctic Ice Sheet (2.5 million square kilometres) overlies pre-glacial sedimentary basins containing about 21,000 billion metric tons of organic carbon.
"This is an immense amount of organic carbon, more than ten times the size of carbon stocks in northern permafrost regions," lead author Jemma Wadham, said.
They found that sub-ice conditions favour the accumulation of methane hydrate (that is, methane trapped within a structure of water molecules, forming a solid similar to regular ice).
They also calculated that the potential amount of methane hydrate and free methane gas beneath the Antarctic Ice Sheet could be up to 4 billion metric tons, a similar order of magnitude to some estimates made for Arctic permafrost.
"Our laboratory experiments tell us that these sub-ice environments are also biologically active, meaning that this organic carbon is probably being metabolised to carbon dioxide and methane gas by microbes," Wadham said in a statement.
The researchers numerically simulated the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model.
"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," co-author Slawek Tulaczyk said.
The study was published in the journal Nature.
