what happens when permafrost melts

[Shiraz]

Hi

came across a few references to this permafrost slump, induced by land clearing and subsequent heating in Siberia.
I hadn't really understood the depth of the permafrost or it's potential fragility, but the images (especially the close-ups further down the thread) put it into some perspective.http://googleearthcommunity.proboards.com/thread/3809/batagaika-crater-siberia

Definitely haven't posted this to start a war over global warming or anything - was just gob-smacked to see the geological reality behind the term "permafrost". If you haven't already come across it, hope you also find it interesting - thanks for looking. regards Ray

[LewisM]

My inlaws live in Siberia. They have a well, and even in high summer, the water from the well is around 6 degrees. The root cellar about 10 metres under the house is VERY cool - they store vegetables and pickled products in there all year round

[Shiraz]

thanks Lewis. I had no idea at all of how extensive permafrost is - in some parts of Siberia it goes down 1500m!! and 700m in northern Canada.

I had naively thought of it as a layer of frozen soil maybe a few metres deep - not up to a km or more..

[billdan]

At the end of last years winter in Siberia, the melting permafrost released a lot of Anthrax into the top soil, killing 100's of Reindeer. This has scientists worried about what other deadly viruses are hidden in the frozen soil.

[AussieTrooper]

Permafrost melting imho is very likely to contribute in a big way to a runaway greenhouse effect. As it melts, vast quantities of methane are released. Methane is a far worse greenhouse gas than carbon dioxide. SBS showed a documentary on melting permafrost in Alaska, and it was frightening. The melt has gotten so bad, that a pastime of some of the locals is to drill a hole in the ice on a frozen lake, and light the gas that comes out. This isn't something they were doing years ago.
It has the second effect (not really mentioned in the doco) that thawed ground doesn’t hold snow for as long, reducing average yearly albedo. Crucially, it is at the end of each season when the sunlight is more present, and at lower latitudes, where the snow disappears from first.

[AstralTraveller]

It's not only viruses that get trapped in permafrost. Ancient DNA can also be preserved. Extracting and analysing DNA from permafrost to map the past occurrence and range of animals and humans is a young field of research that has arisen over the past decade or so; even Australia has a Centre for Ancient DNA (in Adelaide).

[Shiraz]

crikey that's a worry!



Assume that the IPCC models include terms for methane releases?? edit: apparently no, they do not - it is identified as an additional threat.

It was the potential for completely reforming the land surface (as shown in the images) that amazed me. I am used to 300mm of loam over rock, not hundreds of metres of frozen mud!

[AussieTrooper]

Someone may have better info, but as far as I know, methane is a big unknown. It wasn't until recently that we were able to work out the CO2/CH3 balance of emissions from melting permafrost, and that it was surprisingly CH3 heavy.