Tipping Points

On March 4th, the National Academy of Sciences announced that a section of the Arctic Ocean seafloor holding vast stores of frozen methane is showing signs of instability and widespread venting of the powerful greenhouse gas. According to a press release, research conducted by University of Alaska scientists, and published in the journal Science, indicates that the permafrost layer under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is starting to leak large amounts of the gas into the atmosphere.

"Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming," warned the Academy.

As a greenhouse gas, methane is more than thirty times more potent than carbon dioxide (CO2), though it doesn't linger in the atmosphere as long. On land, most methane comes from wetlands (natural and artificial) and agricultural zones associated with livestock and rice production. In frozen soils, it reaches the atmosphere when organic material stored in permafrost begins to thaw and decompose, gradually releasing methane. Under the sea floor, however, when frozen methane hydrates begin to thaw they can be released abruptly.

The East Siberian Arctic Shelf encompasses more than two million square kilometers of seafloor, and research shows it is already releasing the equivalent of 1 million tons of methane a year. One reason for alarm is the shallow nature of the Shelf. In deep water, methane gas oxidizes into CO2 before it reaches the surface (which can be absorbed by the ocean). In shallow water, it