Global ChangeIntersection of Nature and Culture

East Siberian Arctic Ocean discovered to be venting a lot of methane

Thursday, March 4th, 2010

Methane (CH₄) release from ocean sediments has long intrigued scientists.  There is an event that happened 54 million years ago called the Paleocene-Eocene Thermal Maximum (PETM), when 3,000-4,500 gigatons of carbon were released from the oceans, possibly as large methane burps caused by underwater landslides.

That’s a lot of carbon—more than 10 times the total amount we have burned as fossil fuels since the Industrial Revolution began.   Researchers think that it could have caused ocean temperatures to rise by as much as 5 degrees C and the atmosphere to warm by 5-9 degrees C. And when all of that methane carbon in the atmosphere oxidized to CO₂, it dissolved back into the ocean and it reacted with water to form a weak acid

H₂O + CO₂ –> H₂CO₃ (carbonic acid)

which caused the ocean to acidify, melting the calcium carbonate shells of marine organisms and leading to one of the largest known marine extinction events of all time.

A new study by Natalia Shakhova and colleagues¹ in this week’s issue of Science indicates that the coastal marine shelf in eastern Siberia may now be venting as much methane as was previously thought for all of Earth’s oceans combined.

In their words:

These findings do change our view of the vulnerability of the large sub-sea permafrost carbon reservoir on the [East Siberian Arctic Shelf] ESAS; the permafrost “lid” is clearly perforated, and sedimentary CH₄ is escaping to the atmosphere.

For a cool visual of what methane release from ocean sediments looks like, check out the images in this article at Science Daily.

Whether or not the thawing of sub-sea permafrost will release enough methane to cause another PETM-type warming/extinction event is an active area of investigation.  Nobody knows for sure yet.  There is a lot of uncertainty in determining the size of the frozen methane pool in global marine sediments (possibly 500 – 2,500 gigatons of carbon), and the potential rate of release with warming is poorly known.  Clearly, there’s more work to do.

Even if the methane release is not as catastrophic as a PETM-type event, accelerated release will likely lead to a positive feedback on current warming, meaning that all associated impacts will happen faster than originally expected.  As I’ve said before, that becomes a nightmare scenario for policy makers.

¹Shakhova, N., Semiletov, I., Salyuk, A., Yusupov, V., Kosmach, D., & Gustafsson, O. (2010). Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf Science, 327 (5970), 1246-1250 DOI: 10.1126/science.1182221

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Photo credit:  http://www.flickr.com/photos/artic/ / CC BY-SA 2.0