The Danger of Melting Permafrost

THIS ARTICLE tells of the dangers of permafrost melting - release of methane. It is based on THIS ACADEMIC PAPER. (The article has less than 650 words, the paper has over 14,000 so the paper is more nuanced than the article.) 

It seems that permafrost acts as a "cap rock" for methane. The research was done in Svalbard where there has been a long history of hydrocarbon exploration. 

The methane has two sources - biogenic - recent sources - and thermogenic - geologic timescales - and both sorts have been sealed from the atmosphere by permafrost.

With global warming permafrost is becoming less permanent and methane is likely to escape into the atmosphere where it is a potent greenhouse gas. The amounts involved are unknown. 

Something else to worry about.