Methane & Warming Oceans (extracts)

Methane (CH4) is a very potent greenhouse gas, 20-30 times more powerful than carbon dioxide (CO2) on a century timescale. Fortunately, it only occurs in very low concentrations in the atmosphere – about 0.3 to 0.4 parts per million during ice ages and 0.6 to 0.7ppm during warmer periods………

……The description of Stage 2: Very rapid and massive release of carbon with low ∂13C does put one in mind of the Methane Gun hypothesis. This hypothesis states that rising temperature and/or lower sea level causes clathrate at shallow depth to begin melting which in turn causes warming to increase, melting even larger and deeper clathrate deposits. The result: the relatively sudden, massive and catastrophic release of methane into the atmosphere – the firing of the Methane Gun. The recent discovery by Davy et al (2010) of kilometer-wide (ten 8-11 kilometer and about 1,000 1-kilometer-wide features) eruption craters on the Chatham Rise seafloor off New Zealand adds further ammunition to the Methane Gun hypothesis……

……..However, measurements by Shakhova indicate that emissions of methane from the ESA may be as high as 3.5 billion tonnes per annum (if verified, this amount is enough to trigger abrupt climate change), or about 3 times the total mankind artificially adds into the carbon cycle yearly. This methane release is likely coming from sediments previously covered by thin and now melting permafrost at the sea bed as well as melting clathrate, or some combination of both. Even more troubling, the ESA is estimated to hold 1,000 billion tonnes of methane in the form of clathrates alone…

Continued..(long article)

via Wakening the Kraken: Methane & Warming Oceans : TreeHugger.