From The Oil Drum: comments on permafrost and methane, January 11, 2011

OTOH, this is still bleeding edge science, and it is dangerous to start running around making strong claims of disaster based on it.

It's very simple science. We know sea floor clathrates are contained by pressure of the water column and pressure. We know the pressure portion is very low on the Siberian shelf because it is so shallow. We thus must conclude temperatures need to be lower to keep it contained, but at least some clathrates are now within 1C of melting, so that lack of pressure likely puts us into he melt zone.

We further know pre-industrial CH4 was about .7 ppb and are now at 1.8 ppb. You will note that is a much greater proportional change than 285 ppm to 390 ppm of CO2. Given CH4 also has a very short residence time in the atmosphere, vs. CO2's long residence time, where is it all coming from and why is it overwhelming pre-industtrial levels so?

But we also know CH4 levels above and below the water line and in the air above it, and even signifcantly above it, are many times what they should be. The additional detail in that power point should frighten you. It does me.

Permafrost (land-based) was already a problem:

http://www.arcticwarming.net/node/70

CA-CP: Experts talk of climatic thresholds – the point at which it is hard to turn back to previous conditions. How close are we to approaching climatic thresholds with regard to permafrost?

Dr. Romanovsky: When you talk about permafrost, there are some regional thresholds. It would be hard to say there is a global threshold. In terms of regions, for example, in the interior of Alaska, we are very close to this threshold. We are just a half a degree Celsius off of it and in terms of time, it all depends on how climate will warm in the future and the rate of warming. But it could be on the order of 20-50 years.

CA-CP: If you cross this climatic threshold in Alaska, what would the impacts be?

Dr. Romanovsky: What is happening now is that some permafrost is thawing already. It is really a threshold because you can’t go back easily and put all this ice that will melt out of permafrost that is water and put it back as massive ground ice. You’d need another glacial period, and in this case it’s not reversible. It’s hard to put ice back. If the threshold is crossed back to colder conditions it could develop new permafrost but not the same as it is now – generally less ice and less carbon. No return to the previous state. For Siberia and the icy permafrost there, there are two degrees to go before we cross a threshold. So, it is not as much threat yet. However, in southern regions of western Siberia there is a lot of carbon sequestered and the permafrost is actively warming there and thawing in some places. In terms of time scale, I think we could cross a threshold there in several decades. The Northern slope of Alaska is more stable. We maybe have another 70-100 years before we cross a threshold there - same for that area in Siberia. So for colder areas, this threshold is more distant and for warmer permafrost, which has ice and carbon in it, the climatic threshold is pretty close already.

http://www.arctic.noaa.gov/essay_romanovsky.html
A thicker, warmer and dryer active layer will be much friendlier for microbial activities during the summer. Significantly later freeze-up of this layer in winter and warmer winter temperatures (that means much more unfrozen water in it) will considerably enhance the microbial activities during the winter. So, the arctic and sub-arctic ecosystems could turn into a source of CO2 (especially on an annual basis) very soon. Further permafrost degradation and formation of taliks will amplify these changes because a layer that will not freeze during the entire winter (talik) will appear above the permafrost, where microbial activities will not cease during the winter. In the area of "wet thermokarst" formation, new and significant sources of CH4 will be developing.

Bear in mind the potential C held in permafrost alone is 2x that held in the atmosphere. Ten percent of that melting would be on the order almost 80 ppm, and we know that is melting with thermokarst lakes tripling in size, and increasing in number, already.

The idea that we don't know enough to be alarmed is unsupported. We know more than we need to know to take action, and by a country mile.

There are ways to reduce carbon in the atmosphere, but this is not the place to discuss them any longer.

(h/t ccpo)  permalink:  http://www.theoildrum.com/node/7264#comment-758349