Unexpectedly a team of Russian scientists researching Siberian methane emissions discovered that methane is already venting from the sea floor of the East Siberian Arctic Shelf (ESAS) to the atmosphere. They estimate that 90% of potential Arctic subsea methane is located below the ESAS. This received widespread attention when published by the National Science Foundation in 2010,
N Shakhova 2009 Environmental Problems The Contribution of the East Siberian Shelf to the Modern Methane Cycle N. E. Shakhova, provides the background
The East Siberian shelf is the largest continental shelf on Earth.
Their research to date shows that methane hydrate was destabilized starting thousands of years ago after the last ice age, and it suggests the amount of methane released is increasing.
There are three sources of ESAS methane (see cross section) 1) permafrost cap 2) methane hydrate 3) deep free methane gas.
The results of this research were the subject of a special NSF publication in 2010, Methane Releases from Arctic Shelf May Be Much Larger and Faster than Anticipated.
The methane hydrate chapter of the WWF Arctic feedback report was written by the Russian scientists Igor Similetov and Natalia Shakhova who researched the ESAS.
EAST SIBERIAN ARCTIC SHELF
The Russian team, after more than five years of onsite research, considered that one plausible explanation for this methane venting could be warming of the permafrost and hydrates from above by increased warmed water flowing onto the shelf from thawed permafrost (on land).
Their modeling research has shown the potential for methane to traverse permafrost from below to reach through to the sea water (Modeling sub-sea permafrost in the East Siberian Arctic Shelf: The Dmitry Laptev Strait).
Here is an account (click button) of the research in Northeastern Siberia by Dr. Natalia Shakhova. Shakhova’s research results show that the East Siberian Arctic Shelf is already a significant methane source, releasing 7 teragrams of methane yearly, which is as much as is emitted from the rest of the ocean. (A teragram is equal to about 1.1 million tons.)
At the 2011 AGU meeting in San Francisco, Semiletov presented the results of drilling a bore hole into the floor of the Laptev Sea. No permafrost cap was found down to 53 metres. "Preliminary data indicate that the seabed at this site functions as a pathway by which volatile gas components are able to migrate upward. The numerical modeling also demonstrated that in areas affected by the inflow of warm water (such as the Lena River plume), the permafrost can significantly degrade from the top down in addition to the 'geothermal' down-top thawing; this may explain both our drilling result, finding no subsea permafrost at a depth >>53 m."
The Russian research estimates that methane venting to the atmosphere from the ESAS "is on par with previous estimates of methane venting from the entire World Ocean." There is potentially an enormous amount of methane below the ESAS. "Remobilization to the atmosphere of only a small fraction of the methane held in East Siberian Arctic Shelf (ESAS) sediments could trigger abrupt climate warming."
Natalia Shakhova (et al) has published convincing evidence of methane venting from the Arctic continental shelf off northeastern Siberia (Laptev and East Siberian Sea), based on painstaking repeated surveys since 2003. In this region, the relatively shallow continental shelf extends up to 1000 kilometres north of the coastline. The seabed consists of relict permafrost from the last glaciation, when sea levels were considerably lower than today. The permafrost layer is assumed to contain substantial amounts of organic carbon; it also traps methane seeping up from underneath. In the permafrost, the methane forms relatively stable methane hydrates, but warming of the seawater will destabilize the hydrates, releasing methane into the sea waters.
The Russian team has found large areas with surface waters highly super saturated in methane; in some places, methane concentrations are more than 100 times higher than expected in equilibrium with the ambient atmosphere. Based on their extensive data set, team members estimate an annual outgassing to the atmosphere of ~8 × 10 grams of carbon (8 Tg C) as methane from the ESAS waters. Consistent with this, concurrent atmospheric concentration measurements on the ship and with a helicopter documented methane levels up to four times higher than recorded elsewhere in the Arctic basin.
Dr. Shakhova feels that a very small disturbance of gas hydrates could cause catastrophic consequences within a few decades. Shallow bottom sediment and underlying permafrost have warmed approximately 15°C since the time they originated. The implications of this trend are that shallow off-shore gas hydrate deposits could become vulnerable (Fig.2). She also notes that methane plumes found in the East-Siberian Sea (ESS) during the 1 st and 2nd Russian-U.S. joint cruises during September of 2003 and 2004 may indicate decaying gas hydrates in thawing undersea permafrost.
Aug 2014 SWERUS-C3: First observations of methane release from Arctic Ocean hydrates
2014 poster pres US national labs Arctic methane hydrate
2012 US national labs Review mitigation of rapid methane release from Arctic
24 Nov 2013 Ebullition &storm-induced methane release East Siberian Arctic Shelf. Twice as much methane is being vented as the research team estimated in their 2010 paper.
October 1019 Scientists find methane bubbling to the surface in the East Siberian Sea