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 latest research from the Russian team, conducted by drilling deep into the sea floor on the Laptev Sea (ESAS), found lots of methane rising up but no permafrost cap, suggesting the venting methane is the result of bottom to top warming rather than top to bottom (in other words, slow warming of the Earth's crust since the last ice age). This is just one location, so we could be facing both sources of warming. Only more drilling will tell that, but stabilizing Arctic sea ice to prevent planetary catastrophe cannot wait on more ESAS research.
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.)
Some model research suggests that the venting of ESAS methane by warming from above is not plausible and so Siberian shelf methane emissions not tied to modern warming.
Professor Igor Semiletov wrote a convincing response to this to Andrew Revkin's New YorkTimes blog, explaining "the mechanism of (ESAS) subsea permafrost destabilization as a result of inundation with seawater thousands of years ago," and that "the rate at which the subsea permafrost is currently degrading largely depends on what state it was in when recent climate change appeared."
The 2007 record Arctic summer sea ice brought record sea surface warming of the exposed water as high as 5C increase. The largest warming was right over the shallow ESAS methane hydrate location.
In conclusion, the amount of carbon on the ESAS is estimated to be double all the carbon in the atmosphere. If global warming is allowed to progress or if other Arctic methane carbon feedback sources (wetlands and land permafrost) are not stabilized, methane hydrates will emit methane in catastrophic amounts and no one knows when that could happen.
The other Arctic location where large numbers of methane plumes have been found rising from the sea floor is off the Norwegian island of Svalbard.
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.
2012 Laptev sea bottom warmed >3C 2007 (subsea floor methane hydrate location )