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News July 2012

A mechanism for abrupt release of methane clathrates from shallow waters

on Friday, July 26, 2013

This is a little speculative on my part.

I noted a commentator pointing out that methane clathrate is buoyant in water (lighter than the water) and would therefore tend to float.

It seems possible to me that this is enough to provide a mechanism for abrupt and large releases without the need to invoke tectonic activity or submarine landslides or other external mechanical rupturing of containment. It should be noted that free methane gas is also trapped with the clathrate - made very clear in the Semiletov/Shakhova paper titled "The Degradation of Submarine Permafrost and the Destruction of Hydrates on the Shelf of East Arctic Seas as a Potential Cause of the "Methane Catastrophe": Some Results of Integrated Studies in 2011".

Therefore the mechanism I suggest could work like this:

  1. Warming and destabilisation of the upper portion of a concentrated large clathrate deposit, accompanied by thawing where containment was done by frozen permafrost.
  2. Methane gas under pressure is able to escape, forcing open migration pathways
  3. The escaping gas erode and enlarges the migration pathways, carrying away sediment (or other mass pinning down the main deposit)
  4. With pinning mass removed, the main portion of the clathrate deposit is free to float up, leaving a large crater on the seabed
  5. Result - large and abrupt release of methane to the atmosphere, without an external event forcing matters (eg submarine landslide or tectonic activity)
I realise there are a few details to increase credibility, that I don't know offhand - for example I don't know how concentrated the clathrate deposits are and to what extend they would have overall buoyancy in large volumes. Still - this would seem to be a route to accelerating release and to getting deeper into the clathrate layer (200m thick in the case of ESAS) than just relying on wind driven mixing and warmer water run off.

Thanks to Professor Peter Wadhams of Cambridge (an Arctic expert, with a long standing and illustrious career specialising in this field) the issue of methane clathrate in the ESAS has recently gained more of the attention it deserves.