Pardon the pun, but one of the more hotly debated ideas about mass extinctions is whether or not giant methane "burps" in Earth's past have been responsible for causing runaway global warming and wiping out huge chunks of life.
Argentinian geologist Rodolfo del Valle has found a similar belch going on right now in Antarctica, albeit on a smaller scale. Gases bubbling up from the seafloor are turning parts of the waters off the Antarctic Peninsula into a noxious Alka-Seltzer, potentially worsening global warming and even killing local wildlife.
The tricky thing is, no one really knows how dangerous the frozen methane ice is. We know there's a lot of it, probably trillions of tons, locked in near-freezing temperatures of continental shelves around the world. If it all burst into the atmosphere at once, the effects on climate would be catastrophic.
What we don't know is just how unstable the "clathrate" deposits are. How much warming of the deep ocean will it take to set off this carbon bomb? Are they already starting to explode?
That's what del Valle plans to find out. He and a team of researchers will spend the next three years investigating what's going on with methane in the waters off Antarctica, and what it may mean for global climate.
In a recent interview with Nature, del Valle expressed his concern that the bubbling he's seeing could be the start of a vicious cycle: as the planet warms, it triggers the release of methane. The gas is 25 times better at trapping heat than carbon dioxide, so even a little could enhance global warming, which would trigger the release of still more methane, and so on.
The methane seep could also be having an impact on local wildlife. Says del Valle:
...findings from the mid-1950s showed unusual numbers of crabeater seals dying in this area. [...] One theory is that methane accumulates under the marine ice and escapes through cracks during low tides. The methane deposits located below the ice then expand. These emissions would be responsible for the massive death of seals: methane is usually accompanied by hydrogen sulphide, a toxic metabolite of methanogenic bacteria at the seabed.
One of the main reasons to worry about methane as a driver of global climate change is that it has likely happened before. The classic case is the Paleocene-Eocene Thermal Maximum (PETM), a time 55 million years ago when global temperatures suddenly shot up between 5 and 11 degrees Fahrenheit - about what is expected under the worst-case scenarios for global warming by the end of this century.
No one knows for sure how the PETM happened. But the leading idea suggests that trillions of tons of methane frozen in the sea floor suddenly became unstable and erupted into the atmosphere. The change wrought across the globe was immense.
Del Valle and his team's work could go a long way toward explaining how the PETM worked, and whether another, similar episode may be in the offing.
Image: Christian Revival Network on Flickr