Study suggests large methane reservoirs beneath Antarctic ice sheet

Terra Daily via SPX: The Antarctic Ice Sheet could be an overlooked but important source of methane, a potent greenhouse gas, according to a report in the August 30 issue of Nature by an international team of scientists. The new study demonstrates 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 methane could be released to the atmosphere if the ice sheet shrinks and exposes these old sedimentary basins.

Coauthor Slawek Tulaczyk, a professor of Earth and planetary sciences at UC Santa Cruz, said the project got its start five years ago in discussions with first author Jemma Wadham at the University of Bristol School of Geographical Sciences, where Tulaczyk was on sabbatical.

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

The science team estimated that 50 percent of the West Antarctic Ice Sheet (1 million square kilometers) and 25 percent of the East Antarctic Ice Sheet (2.5 million square kilometers) 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," 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."...

Antarctic mountains, pack ice and ice floes, shot by Jason Auch, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license