With brutal blizzards, dry air, and some of the coldest temperatures on earth, the Antarctic is inhospitable to the best of us. But not, apparently, to the 21,000 billion metric tons of organic carbon that could be producing up to four billion metric tons of methane – a potent greenhouse gas – beneath the continent.
In a new study, scientists have discovered that sedimentary basins beneath the Antarctic Ice Sheet contain huge quantities of organic carbon that work in concert with microbes to produce methane. The microbes metabolize the organic carbon to carbon dioxide and methane gas. Coupled with the lack of oxygen under ice sheets, these conditions are “the perfect ingredients for methanogenesis,” University of Bristol professor of glaciology Jemma Wadham said. Their findings were published in the August 30 issue of Nature.
“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,” University of California-Santa Cruz earth and planetary sciences professor Slawek Tulaczyk said in a statement. Sedimentary basins in the Antarctic may have contained over ten times more organic carbon than parts of the Arctic, according to the study. “Our modeling shows that over millions of years, microbes may have turned this old organic carbon into methane.”
The researchers used an established numerical model to simulate how much methane might accumulate below the sea floor. The model demonstrated that most of the organic carbon eventually turns into methane hydrate – an ice-like solid structure in which water molecules surround methane – because of the Antarctic’s low temperature, high pressure conditions. The rest becomes free methane gas. Because the methane hydrate inventories are likely to be located at shallow depths, ice-sheet melting could cause the gas to come out of hiding and enter the atmosphere, the scientists said. They noted, however, that this is still speculation – there’s a lot of uncertainty left about how much methane could be lurking down there. For the moment, the study simply raises questions about the possibility.
“It’s always difficult to talk about risk, especially risk that has to do with natural processes,” Tulaczyk said.
Wadham noted that their findings might even have a positive spin to them if the Antarctic methane hydrate could one day become another energy source. Natural gas is, after all, mostly made up of methane. But that’s far off until there is an economically viable way to get that methane out – the lack of an airport or harbor and any other infrastructure with which to do this undercuts the possibility for now, not to mention the Antarctic Treaty’s prohibition of mineral mining on the continent. For now, the spotlight is on how, for all its remoteness, Antarctica may be a far larger player in the climate game than we’ve appreciated in the past, and one we’d be smart not to ignore.