Scientists Find Increased Methane Levels In Arctic Ocean

ScienceDaily (Dec. 18, 2008) — A team led by International Arctic Research Center scientist Igor Semiletov has found data to suggest that the carbon pool beneath the Arctic Ocean is leaking.

The results of more than 1,000 measurements of dissolved methane in the surface water from the East Siberian Arctic Shelf this summer as part of the International Siberian Shelf Study show an increased level of methane in the area. Geophysical measurements showed methane bubbles coming out of chimneys on the seafloor.

“The concentrations of the methane were the highest ever measured in the summertime in the Arctic Ocean,” Semiletov said. “We have found methane bubble clouds above the gas-charged sediment and above the chimneys going through the sediment.”

The new data indicates the underwater permafrost is thawing and therefore releasing methane. Permafrost can affect methane release in two ways. Both underwater and on land, it contains frozen organic material such as dead plants and animals. When permafrost thaws, that organic material decomposes, releasing gases like methane and carbon dioxide. In addition, methane, either in gas form or in ice-like methane hydrates, is trapped underneath the permafrost. When the permafrost thaws, the trapped methane can seep out through the thawed soil. Methane, a greenhouse gas 20 times more powerful than carbon dioxide, is thought to be an important factor in global climate change.

The East Siberian Arctic Shelf is a relatively shallow continental shelf that stretches more than 900 miles into the Arctic Ocean from Siberia. The area is a year-round source of methane to the globe’s atmosphere. However, until recently, scientists believed that much of the area’s carbon pool was safely insulated by underwater permafrost, which is, on average, 11 degrees Celcius warmer than surface permafrost.

Semiletov said this year’s expeditions used both chemical and geophysical measurement techniques, a first in the area. He also noted that while the high-arctic ocean readings were surprisingly high, on par with those from high-arctic lakes, they are still much lower than is being found in subarctic regions.

“That means we cannot extrapolate the subarctic data to the entire Arctic,” he said.

Semiletov, as associate research professor at IARC, leads the International Siberian Shelf Study, which has launched the multiple expeditions to the Arctic Ocean to collect data on methane release of the East Siberian Arctic Shelf. The ISSS includes 30 collaborating scientists from five countries. The project, which gained momentum during the International Polar Year, established more than 1,000 oceanographic stations in the Arctic and performed a few million measurements of methane mixing ratios of the Arctic atmosphere in the last five years. It is part of UAF’s work during IPY, an international event that is focusing research efforts and public attention on the Earth’s polar regions.

Semiletov is a chemical oceanographer who has studied carbon cycling in the arctic atmosphere-land-shelf system with emphasis on carbon dioxide and dissolved methane from both terrestrial and oceanic sources since the early 1990s. He joined the International Arctic Research Center in 2001. Since 2004, he has collaborated with IARC scientist Natalia Shakhova to develop the methane study at IARC.

International Siberian Shelf Study collaborators University of Alaska Fairbanks: Igor Semiletov, Natalia Shakhova, John Kelly, Vladimir Romanovsky, Gleb Panteleev, Sergei Marchenko, Dmitry Nicolsky, Alexander Kholodov; FEBRAS: Oleg Dudarev, Anatoly Salyuk, Irina Pipko, Viktor Karnaukh, Alexander Charkin, Denis Kosmach, Nina Bel’cheva, Svetlana Pugach, Nina Savelieva, Vladimir Iosoupov, Valentin Sergienko; Stockholm University: Orjan Gustafsson, Per Andersson, Jorien Vonk, Laura Sanchez-Garcia, Christoph Humborg, Vanja Alling; Gotheburg University: Leif Anderson, Goran Björk, Anders Olsson, Sara Jutterström, Sofia Hjalmarsson, Irene Wåhlström; Swedish Museum of Natural History: Per Andersson; Utrecht University: Celia Sapart, T. Roeckmanm; Institute of Atmospheric Physics RAS: Georgiu Golytsin, Irina Repina; Moscow State University: Nicolai Romanovskii, Vladimir Tumskoy; University of Manchester: Bart van Dongen; Luleå University of Technology: Johan Ingri, Fredrik Nordblad, Johan Gelting; Oxford University: Don Porcelli.