As I said in another thread, if all the Alaskan/Canadian permafrost melts, the effect will be to destabilise the whole north American continent. Haven't got time to look up references now, but various universities including Fairbanks are on to it, and I believe that the US governmental agency dealing with climate change is also concerned about the risk. But not, so far, the politicians, none of them being elected for more than a few years at a time.