(Chart Reference: http://arctic-news.blogspot.de/2013/11/horrific-amounts-of-methane-over-laptev-sea.html)
An uncomfortably high proportion of current estimated arctic methane releases come from a source which is very poorly understood, and that could conceivably change considerably in the very near future. Both the HIPPO program and researchers at the Wegener Institute have estimated emissions from an unexpected source -- the ocean surface itself -- which demands far more scrutiny in predicting near-term evolution of arctic conditions. This is the opposite of discussing the drama of methane hydrate -- it is a very mild source of methane emission, and is very diffuse. However, it is deeply dependent upon sea surface conditions, which are rapidly changing with changes in summer sea ice cover, and thus has a potential for very large changes in its emissions rate in the very near future. The estimates of current emissions make this source currently about the same as the total combined emissions from subsea permafrost, free gas and some hydrate which have, cumulatively, been widely discussed in the media, stemming from the research of Natalia Shakhova, Igor Semiletov and others, and usually attributed in the media to methane hydrates. The hypothesized but somewhat mysterious biochemistry of this surface production is based on the assumption that shifts in the N:P (nitrogen to phosphorous) ratio (one of the so-called Redfield ratios), make aerobic methanogenesis possible in arctic surface waters, and the estimates are that this is probably releasing about 8Tg methane annually now. Could these emissions suddenly increase? If losses of sea ice induce further emissions from this source, then increases could be very considerable. (Reference: http://1250now.org/near-future-arctic-methane/)
A 2014 paper has found strong evidence for a bacterial source of the carbon-cycle disruption: the methanogenic archaeal genus Methanosarcina. Three lines of chronology converge at 250 mya, supporting a scenario in which a single-gene transfer created a metabolic pathway for efficient methane production in these archaea, nourished by volcanic nickel. According to the theory, the resultant super-exponential bacterial bloom suddenly freed carbon from ocean-bottom organic sediments into the water and air [contributing the Permian Mass Extinction]. (Reference: http://www.pnas.org/content/111/15/5462)
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