A new study out of the University of California Santa Cruz demonstrates that old organic matter in sedimentary basins located beneath the Antarctic Ice Sheet may have been converted to methane by microorganisms living under oxygen-deprived conditions.
The study was driven by methane release concerns from global warming with the idea that methane could be released to the atmosphere if the ice sheets shrink and expose the old sedimentary basins. There in lies the opportunity –
Antarctic Lake Sediments. Frozen lake sediments can be seen in this view of the ice margin of an Antarctic glacier. When ice sheets form, they overrun organic matter such as that found in lakes, tundra and ocean sediments. Photo by J. L. Wadham. Image Credit UC Santa Cruz.
The international team of scientists got its start five years ago in discussions with author Jemma Wadham from the University of Bristol School of Geographical Sciences and coauthor Slawek Tulaczyk, a professor of Earth and planetary sciences at UC Santa Cruz.
Tulaczyk 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.”
The team of scientists estimated that 50% of the West Antarctic Ice Sheet (1 million square kilometers or 386 thousand square miles) and 25% of the East Antarctic Ice Sheet (2.5 million square kilometers or 965 thousand square miles) overlies pre-glacial sedimentary basins containing about 21,000 billion metric tons of organic carbon.
Wadham explains, “This is an immense amount of organic carbon, more than ten 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 metabolized to carbon dioxide and methane gas by microbes.”
The research team numerically simulated the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model. They found that sub-ice conditions favor the accumulation of methane hydrate (that is, methane trapped within a structure of water molecules, forming a solid similar to regular ice).
Antarctic Ice Block for Methane Experiments. Researchers extracted blocks of ice containing subglacial sediments from the margins of different glaciers and ice sheets for use in long-term incubation experiments to look at subglacial methane production. Photo by G. Lis. Image Credit UC Santa Cruz.
It was 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 the Arctic’s permafrost.
The predicted shallow depth of these potential reserves also makes them more susceptible to climate forcing than other methane hydrate reserves on Earth. It also reveals that the methane reserves could be less complex to recover.
Coauthor Sandra Arndt, a NERC fellow at the University of Bristol, who conducted the numerical modeling, said, “It’s not surprising that you might expect to find significant amounts of methane hydrate trapped beneath the ice sheet. Just like in sub-seafloor sediments, it is cold and pressures are high, which are important conditions for methane hydrate formation.”
If substantial methane hydrate and natural gas are present beneath the Antarctic Ice Sheet, the political implications in store for an effort at recovery could be a Byzantine affair.
On the other hand, methane release during episodes of ice-sheet collapse could act as a “positive feedback on global climate change” during past and future ice-sheet retreats. That might motivate some action for positive resource recovery instead of an ice thawing release of the methane scenario.
Tulaczyk said, “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.”
It seems obvious that the Antarctic has influenced the climate world wide to some degree, and always has. There is plenty of reason to think that there would be recoverable reserves – and the idea the methane is just below the ice sheet seems a huge opportunity.
Still, the right to use would immediately be an international issue of considerable complexity as the continent is not one sovereignty or even several. Instead, Antarctica is a treaty zone with no government in particular, but voices in the treaty number in the dozens. It would be great to find out just what the reserve estimates are and get on with arguing out the way to get a deal underway to bring the natural gas and methane to markets.
The research program was a collaborative venture between the University of Bristol (UK), The University of California, Santa Cruz (USA), The University of Alberta, Edmonton, and the University of Utrecht (The Netherlands).
The study was funded principally by the Natural Environment Research Council (UK), the Leverhulme Trust (UK) with additional funds from the National Science Foundation (USA), the Natural Science and Engineering Research Council of Canada and the Netherlands Organization for Scientific Research (NWO).
The next step, if reason were to rule, would be to establish existence and extent of the methane reserve. Then perhaps, the world could get on with plotting a way to make use of the methane and prevent the methane release to the atmosphere.
By. Brian Westenhaus