The tipping point in action: twice as much methane released due to seabed permafrost melting

Report doubles estimates of methane released from an important oceanic source which may be "leaking" the potent global warming gas as warming melts the permafrost.
© Courtesy of Natalia Shakhova

A study under the auspices of University of Alaska Fairbanks doubles estimates of methane released from an important oceanic source which may be "leaking" the potent global warming gas as permafrost melts.

The accelerated release of methane is one of the so-called "tipping point" concerns related to climate change. On land, increased warming melts the permafrost, making previously frozen organic matter available for decomposition which releases methane. Melting of the arctic tundra has long been on scientists' radars as one of the largest potential sources of methane in the northern hemisphere. In the ocean, the methane lies ready for release in larger amounts, trapped by the permafrost.

This report on methane releases from the seafloor puts the East Siberian Arctic Shelf (ESAS) on par with the tundra in potential methane releases. Previous estimates predicted 8 teragrams of methane per year released into the atmosphere from ESAS. Doubling that to 16 teragrams approaches the 17 teragrams of methane per year that scientists reckon the arctic tundra contributes. A teragram equals 1 million tons.

From the press release: "During field expeditions, the research team used a variety of techniques—including sonar and visual images of methane bubbles in the water, air and water sampling, seafloor drilling and temperature readings—to determine the conditions of the water and permafrost, as well as the amount of methane being released."

Scientist Natalia Shakhova, one of the paper’s lead authors, says:

We believe that the release of methane from the Arctic, and in particular this part of the Arctic, could impact the entire globe. We are trying to understand the actual contribution of the ESAS to the global methane budget and how that will change over time.

What do these numbers really mean? In Bill McKibben's Rolling Stone article on Global warming's terrifying new math, McKibben notes that we can emit no more than 565 gigatons of CO2 into the atmosphere by 2050 if warming is to be kept within the 2 degrees margin which represents an upper border to what our ecosystems can adapt to without disruptive change.

Remember, methane's greenhouse effect potential is significantly worse than carbon dioxide. You may have seen statements that methane is 20 times or 30 times more powerful than carbon dioxide at warming our planet (20ish was adjusted up to 30ish by the 2013 IPCC report). But both of these numbers represents a 100-year term, adjusting for the speed of decomposition of the chemicals in the atmosphere and other interactions.

In a 20 year time span, methane is 86 times more potent than carbon dioxide. Using that multiplier, the ESAS methane release between now and 2050 represents over 8% of McKibben's magic number. Now, keep in mind that the 565 gigatons represents what humans can release, while the methane releases are natural. But the 565 tons was calculated before the knowledge that the natural releases from ESAS are much higher than predicted. Clearly, these methane contributions make a significant contribution that must be accounted for as we plan to manage climate change.

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