Is The Permafrost Melting In Siberia?
Most of Siberia has been frozen solid since the last Ice Age. Now, there are concerns that after a period of 40,000 years of freezing, an area the size of France and Germany is showing clear evidence of melting.
This might not seem particularly worrying, perhaps a little less ice could even be good news and, after all, Siberia is is the middle of nowhere. It's not as if the melting is happening in an area full of cities, or used for agriculture or industry. Instead, it's remote areas changing from snow covered wilderness into a mass of shallow lakes and exposed mud.
The geographical processes behind the change in the landscape will be familiar to most geography students. Firstly, the rising air temperatures create "frost-heave", which turns the flat permafrost into a landscape of hollows and hummocks. These are known as salsas. As the permafrost begins to melt, water collects on the surface and forms small lakes or ponds that cannot drain away because the ground below them is still frozen. These ponds coalesce, or merge together, forming ever larger lakes. Eventually, when all the permafrost melts, the lakes will drain away underground leaving a much drier surface. In fact, this cycle is already completing in eastern Siberia where the permafrost began melting long ago. The eastern area has been losing lakes during the last 30 years as the last remains of the deep permafrost thaw.
A change in the surface landscape will have major implications for wildlife, plants etc, but its what happens to gasses trapped in the soil that is worrying scientists.
Siberia has a secret buried in its permanently frozen ground. Before the Ice Age Siberia was a massive peat bog, covering a million square miles. Peat bogs contain mud, water and peat ( decayed vegetation) and when vegetation decomposes it produces methane gas. The frozen ground is believed to hold somewhere near to 70 billions of tonnes of methane, (a quarter of the world's reserve of methane stored in the ground) and methane is a greenhouse gas twenty times more damaging than carbon dioxide. The fear is that if the permafrost thaws, all the trapped methane will be released into the atmosphere, triggering an increase in global warming. The increased temperatures will cause more melting, expose more muddy ground and new lakes, which in turn will warm up faster than the previous covering of snow and ice and the cycle continues onwards.
Some scientists () have predicted that releasing all this gas would double the quantity of methane in the atmosphere, and lead to a 10% to 25% increase in global warming.
Scientists can't give exact details of how the release of Siberian methane will alter global warming because it's a complicated process, and we can't predict how much of the released gas may be re-absorbed by plants and the oceans, how quickly it will be released, or whether the sudden increase in methane will trigger an, as yet, un-predicted event.
Other scientists are more concerned about the amount of carbon dioxide that will be released. Professor Schurr, from the University of Florida in Gainesville, collected samples of permafrost and analysed them in his laboratory. As he thawed out the samples microbes attacked the carbon content of the soils and produced carbon dioxide gas. From his research it is estimated that a Siberian thaw could push 500 billion tonnes of carbon dioxide gas into the atmosphere.
The U.N.-sponsored Panel on Climate Change has published it's estimate for global warming over the next one hundred years, producing a rise of between 3 and 11 degrees F. The addition of Siberian gas releases could change these predictions to 5 to 15 degrees F.
 |
 |
 |
