A few years ago the whole ‘cow farts are global climate threat’ thing seemed more than a bit overblown. (Cow and other farts being mostly methane, dontcha know.) It became difficult to mention methane in connection with global warming without raising images of bovine herds worldwide in a massive chorus of postprandial flatulence. Besides, CO2 is the real bête noir of climate. Methane would be if there was a lot more of it in the atmosphere, but its percentage is small (< 1%). It’s a more effective greenhouse gas than CO2. It can make lots of ‘interesting’ atmospheric combinations at the molecular level, and its concentration in the atmosphere can change more rapidly than CO2. That last point, rapid change in concentration, may be the parameter of concern for the new study that (revising figures from a 2005 study) indicates there may be more methane outgassing from the Siberian shelf than thought.
The East Siberian shelf is a region north of present-day Siberia (Russia) that at one time was above sea-level, and where extremely thick beds of peat once formed. However, these beds were frozen, becoming part of the permafrost and then submerged by a rising sea. In theory, the methane produced by peat beds (which can over time become lignite, brown coal) should have stopped forming, or have been trapped in the permafrost and under the sea. So when significant quantities of atmospheric methane were detected after 2003, it was assumed that something was happening to release the methane.
The speculation (hypothesizing) was that as the Arctic Sea warms due to Global Warming, especially in the summer months, the frozen beds of peat begin to unfreeze and release ever increasing amounts of methane. Then, instead of mixing with sea-water to produce CO2, the methane was making it to the surface of the sea and being released more or less raw into the atmosphere.
The new study, conducted by the University of Alaska Fairbank in conjunction with 12 other institutions, puts more data into the methane pot:
Starting in the fall of 2003, Shakhova, Semiletov and the rest of their team took the studies offshore. From 2003 through 2008, they took annual research cruises throughout the shelf and sampled seawater at various depths and the air 10 meters above the ocean. In September 2006, they flew a helicopter over the same area, taking air samples at up to 2,000 meters (6,562 feet) in the atmosphere. In April 2007, they conducted a winter expedition on the sea ice.
They found that more than 80 percent of the deep water and more than 50 percent of surface water had methane levels more than eight times that of normal seawater. In some areas, the saturation levels reached more than 250 times that of background levels in the summer and 1,400 times higher in the winter. They found corresponding results in the air directly above the ocean surface. Methane levels were elevated overall and the seascape was dotted with more than 100 hotspots. This, combined with winter expedition results that found methane gas trapped under and in the sea ice, showed the team that the methane was not only being dissolved in the water, it was bubbling out into the atmosphere.
These findings were further confirmed when Shakhova and her colleagues sampled methane levels at higher elevations. Methane levels throughout the Arctic are usually 8 to 10 percent higher than the global baseline. When they flew over the shelf, they found methane at levels another 5 to 10 percent higher than the already elevated Arctic levels.
The East Siberian Arctic Shelf, in addition to holding large stores of frozen methane, is more of a concern because it is so shallow. In deep water, methane gas oxidizes into carbon dioxide before it reaches the surface. In the shallows of the East Siberian Arctic Shelf, methane simply doesn’t have enough time to oxidize, which means more of it escapes into the atmosphere. That, combined with the sheer amount of methane in the region, could add a previously uncalculated variable to climate models.
“The release to the atmosphere of only one percent of the methane assumed to be stored in shallow hydrate deposits might alter the current atmospheric burden of methane up to 3 to 4 times,” Shakhova said. “The climatic consequences of this are hard to predict.”
Other experts point to problems with this hypothesizing. First and foremost, there is not enough data from previous years to prove the Siberian outgassing is new. Methane outgassing could have been taking place for hundreds or thousands of years; it could be a regular feature of the Arctic regions (with variations). We don’t know.
Another problem is the absolute quantity of methane. While the figures indicate that the Siberian region might produce as much methane as the rest of the world; methane from ocean sources is but a fraction of that from land – unless a catastrophic release of some kind is generated, the Siberian Margin would not, of itself, increase the methane proportion in the atmosphere that significantly. This is particularly true because methane remains in the atmosphere a relatively short time, a decade or two at most. Only a catastrophic release of methane from frozen peat (land or sea) would be significant – and there’s no evidence of such a catastrophe in the offing.
There are problems with the criticism: We will never know if this is a new phenomenon from direct data of observation. The history will have to be inferred, if reconstructed at all. What’s important is the ongoing data. Calculating the absolute amount of additional methane is also very difficult. Mostly the data shows ‘indicators’ – samples – not actual volumes. Nevertheless, the team that put together this study is currently drilling into the seafloor to attempt estimates of how much methane is stored there.
This is typical give and take for a significant scientific body of research. It’s why, in the final analysis, “More research is needed” is often the prescription.