Arctic Ocean leaking methane at alarming rate –‘What we’re observing right now is much faster than what we anticipated and much faster than what was modeled’

By WESTON MORROW
29 November 2013   FAIRBANKS, Alaska (Fairbanks Daily News-Miner) – Ounce for ounce, methane has an effect on global warming more than 30 times more potent than carbon dioxide, and it’s leaking from the Arctic Ocean at an alarming rate, according to new research by scientists at the University of Alaska Fairbanks. Their article, which appeared Sunday in the peer-reviewed journal Nature Geoscience, states that the Arctic Ocean is releasing methane at a rate more than twice what scientific models had previously anticipated. Natalia Shakhova and Igor Semiletov at the university’s International Arctic Research Center have spent more than a decade researching the Arctic’s greenhouse-gas emissions, along with scientists from Russia, Europe and the Lower 48. Shakhova, the lead author of the most recent report, said the methane release rate likely is even greater than their paper describes. “We decided to be as conservative as possible,” Shakhova said. “We’re actually talking the top of the iceberg.” The researchers worked along the continental shelf off the northern coast of eastern Russia — the East Siberian Arctic Shelf, which is underlain by sub-sea permafrost. Much like the now-submerged Beringia, the land bridge that once connected Alaska to Russia, the East Siberian Arctic Shelf was dry land until around 7,000 to 15,000 years ago, when it flooded and became part of the Arctic Ocean. During its time as dry land, the shelf developed a layer of permafrost that is now in danger of melting away and releasing vast amounts of greenhouse gases. Past studies in Alaska and other circumpolar regions have found that the boreal forests covering much of the world’s Arctic and sub-Arctic dry land contain more than 30 percent of the world’s stored carbon. This carbon is protected from atmospheric release in large part by the permafrost layer. The submerged East Siberian Arctic Shelf contains much the same stored carbon as the dry-land tundra just to its south, but it also contains at least 17 teragrams of methane, the study states. A teragram is equal to 1 million tons. Those carbon stores are similarly protected by the layer of sub-sea permafrost, but that permafrost is on the brink of disappearing. Core samples taken of the sub-sea permafrost by Shakhova and her peers showed temperatures near the freezing mark, around 30 to 32 degrees. Top and lower layers of sediment had already thawed. Some climate modelers had previously suggested the sub-sea permafrost would not thaw for 5,000 to 7,000 years, but according to Shakhova’s team, data gathered from the actual shelf show the process is happening on a much more rapid time scale. “What we’re observing right now is much faster than what we anticipated and much faster than what was modeled,” Shakhova said. This revelation should be a cause for alarm, Shakhova said. “Absolutely. We think so,” she said. “We should not only just worry. We should study.” [more]

Arctic Ocean leaking methane at alarming rate, researchers say

ABSTRACT: Vast quantities of carbon are stored in shallow Arctic reservoirs, such as submarine and terrestrial permafrost. Submarine permafrost on the East Siberian Arctic Shelf started warming in the early Holocene, several thousand years ago. However, the present state of the permafrost in this region is uncertain. Here, we present data on the temperature of submarine permafrost on the East Siberian Arctic Shelf using measurements collected from a sediment core, together with sonar-derived observations of bubble flux and measurements of seawater methane levels taken from the same region. The temperature of the sediment core ranged from −1.8 to 0 °C. Although the surface layer exhibited the lowest temperatures, it was entirely unfrozen, owing to significant concentrations of salt. On the basis of the sonar data, we estimate that bubbles escaping the partially thawed permafrost inject 100–630 mg methane m−2 d−1 into the overlying water column. We further show that water-column methane levels had dropped significantly following the passage of two storms. We suggest that significant quantities of methane are escaping the East Siberian Shelf as a result of the degradation of submarine permafrost over thousands of years. We suggest that bubbles and storms facilitate the flux of this methane to the overlying ocean and atmosphere, respectively.

Ebullition and storm-induced methane release from the East Siberian Arctic Shelf