I was watching an episode of Nature on PBS about sea turtles, and at one point the narrator mentioned vast deposits of methane at the bottom of the ocean in solid form. Then he gave some vague warning that the warming oceans may unleash all this methane into the atmosphere. What’s the straight dope on methane lurking beneath the sea? Will it give us an energy-independent utopia or burn us all to a crisp? –Ndevir, via e-mail
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What we’re talking about are the strange crystals called methane hydrates, in which molecules of methane (the main component of natural gas) are trapped inside tiny cages of ice. The result is an icelike substance that contains up to 15 percent methane by volume. First observed in the 1800s, methane hydrates were initially regarded mainly as a nuisance that formed in cold natural-gas pipelines. In 1964, however, a Siberian gas rig discovered a large methane hydrate deposit underground, spurring research on whether such deposits could be a good source of natural gas. Deep-sea exploration turned up even greater deposits in the oceans, and with the rise of natural-gas prices and the push to reduce carbon dioxide emissions, methane hydrates are now getting serious attention in the energy industry.
Just a couple problems. The first is that no one has figured out how to extract hydrated methane economically, although several countries have research efforts under way. The second is that while methane hydrate is stable as long as it’s kept cold and under pressure, vast amounts of methane could be suddenly released into the atmosphere under certain circumstances–for example, if a rise in sea temperature due to, say, global warming caused shallow deposits of methane hydrate to melt. We don’t want that to happen, because methane is a potent greenhouse gas. Some believe a methane hydrate release 251 million years ago contributed to the Permian extinction, the largest mass die-off in earth’s history, when perhaps 95 percent of all species on the planet were wiped out. And the Late Paleocene Thermal Maximum–a severe temperature spike, possibly triggered by a Caribbean volcanic eruption or even a comet impact, that coincided with another mass extinction 55 million years ago–may have been compounded by a similar release of undersea methane.
