Arctic seafloor methane could hasten global warming

Data from the World Factbook. Graphic by Tom Hewitt.

By Kelsey Gobroski
Sun Star Contributor

Methane gas escaping into the atmosphere from melting arctic undersea permafrost may contribute more to global warming and climate change than carbon dioxide, say two Russian scientists who have been studying the effect. The two discussed their findings at a press conference at the International Arctic Research Center (IARC) on March 4 attended by local and national press.

Natalia Shakhova and Igor Semiletov summarized data from eight expeditions to an isolated ocean shelf above Siberia from 2003 to 2008. The result of their research was published in the journal Science on March 5, 2010. Semiletov studies the carbon cycle, and Shakhova leads the methane study in their team. The scientists are visiting from the Pacific Oceanological Institute in Vladivostok, Russia. Both hold joint research appointments at UAF

Methane gas, also known as natural gas, is a product of microbial metabolism, which usually results from biomass decomposition. It is produced at the bottom of all the world’s oceans and diffuses up through the water column into the atmosphere where it, along with carbon dioxide, helps to trap the suns heat… the “greenhouse effect”. Despite carbon dioxide’s notoriety, methane is at least 25 times more potent a greenhouse gas. One paper last year indicated that it could be up to 40 times more potent.

The shallow underwater Eastern Siberian Arctic Shelf, north of Russia, has never been considered to be a source of atmospheric methane because its deposits are trapped by a permafrost “cap”. However, the team of Russian scientists found that the permafrost cap might be destabilizing and becoming perforated. Holes appear to be developing in the continuous layer of underwater frozen ground. The results indicate that this shelf may contribute as much methane to the atmosphere as the combined quantity from the rest of the world’s oceans.
Normally, methane generation and release is a very gradual process. However, this methane has been trapped under permafrost, Shakhova explained. Methane is lighter than air, and is highly pressurized under the permafrost. When seawater warms enough for the permafrost to perforate, the methane escapes in bursts of bubbles. According to Semiletov, his team found a 200-mile-long cloud of these bubbles.
“It’s the shallowest and broadest shelf in the world’s ocean which contains 90% of arctic subsea permafrost … which is in a transition phase.” Semiletov said.
If the shelf were deeper, much of the methane would transform into carbon dioxide as it bubbled up through the water, but most of the shelf is less than 50 meters deep, so most of the methane escapes directly into the atmosphere, Shakhova said.

According to Shakhova, the Eastern Siberian Arctic Shelf naturally goes through many changes in each climate cycle. In the colder part of the cycle when sea level is lower, the shelf is exposed to air and becomes a coastal plain. The world is now in a warmer period, which raises sea level and submerges the shelf. Seawater is only slightly below freezing point so small increases in seawater temperature can melt permafrost.
Semiletov said the Earth entered the highest point of this warming cycle a few thousand years ago, and has been cooling — but man-made sources have brought the temperature up to what appears to be an unnatural second peak. The politics surrounding this new peak aren’t the point of his paper, Semiletov said, and he wouldn’t call his findings alarming until he does more research.

Shakhova said freshwater runoff is beginning to accelerate this process. She said critical areas to study are those with a combination of warming from freshwater and warming from fault lines.

Right now, global methane atmospheric concentration is nearly three times the historical average, with highest concentrations in the Arctic. Shakhova found areas on the shelf with over four times the global average. According to her, this is the highest the total worldwide atmospheric concentration has been in 400,000 years. No one knows how long this new rise has been occurring, Semiletov said.
Many lakes in arctic Russia and Alaska also produce and hold methane. However, most of these lakes are less than two meters in depth. Studies show that lakes are completely frozen at this depth, and do not contribute to methane emissions, Semiletov said. He studied two regions in Siberia and found that the further north he went, the fewer methane emissions there were. However, once he reached the coasts, atmospheric methane concentrations spiked. This prompted the research that led to this study. At this point, very few questions can be answered without international collaboration on a large scale.

The paper has already raised interest in methane research, Semiletov said. Last November, before the paper was published, John Calder, director of Arctic research at NOAA, helped broker an agreement in Moscow between U.S. and Russian agencies to collaborate on methane studies. There will be a strategic workshop of experts in Moscow this summer.

Semiletov said there is another expedition planned for April 2011, underwritten by the National Science Foundation. Researchers will drill holes in the permafrost at key locations to “evaluate the potential of methane to be released for different climate scenarios,” Semiletov said. He said there is increased interest to join him on expeditions, but without new sources of funding, he cannot upgrade the scope of the study. “Every summer, we have a cruise,” he said, “but the scale of the cruise depends on funds.”

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