Will the permafrost soils in Siberia and Alaska thaw?

The climate in some regions of our planet resembles that within a freezer: Large regions of Siberia, Alaska and Canada, are comprised of "permafrost". Here the ground is frozen year-round. However, due to climate change, this soil could at least partially thaw - with serious consequences for the environment, civilization, and probably even for Earth’s future climate. The fate of permafrost as temperatures rise, is the topic  Prof. Hans Wolfgang Hubberten deals with. He heads the Research Unit Potsdam of the Alfred Wegener Institute for Polar and Marine Research.

What exactly is permafrost?

Permafrost, is soil with a temperature at or below the freezing point of water for two or more years, and is thus permanently frozen. The permafrost regions of the Earth are surprisingly large. They make up at least 25 percent of the earth's surface, which means that they underlie approximately one quarter of the land surface on our planet. Large regions, particularly in Siberia, but also in Canada and Alaska are characterized by these frozen landscapes. In Central Siberia the soil can be frozen to a depth of over 1500 meters.

Is the impact of global warming already evident today? Are more and more regions thawing during summer?

More than 600 boreholes in various permafrost areas have been equipped with thermometers. We are observing warming of the soil to a depth of some 40 meters in many regions of Alaska, Canada and Siberia. This is happening especially where the permafrost is already relatively warm- about minus one to minus two degrees. There permafrost begins to thaw in the summer and in some areas no longer freezes in winter. Massive changes in the landscape occur. Where the permafrost is rich in ice, it turns boggy and formerly dry areas change to swamp or marshland. In some regions trees begin to tilt or fall, because they lose their hold in the ground.

Climate scientists predict that we have a global warming of at least two degrees Celsius by the year 2100, possibly even five degrees. What would this mean for the permafrost regions?

On the southern fringes, where the permafrost is already relatively warm, it could disappear completely. Further north, much more soil could melt in summer - perhaps up to 80 centimetres deep instead of 50 centimetres, as it is today. In all these areas fauna and flora have to adjust. Where it was previously dry, it could be wet. Conversely, areas with many lakes can suddenly dry up, because if the thawing of the permafrost is so severe it would become permeable and the lake water would seep into the underlying ground

What are the consequences of permafrost decline on human infrastructure, railway lines or pipelines?

There are some dramatic changes. Particularly in Siberia, where some railway can no longer used, because rails have subsided. At an airport in Siberia, I saw that the runway in some places could not be used, because it had collapsed due to the thawing permafrost. In Russia, Alaska and Canada, oil pipelines have become unstable. This could lead to rupturing and the spilling of hundreds of thousands of litres of oil. In addition, the coasts are becoming eroded, and houses are falling into the sea. Thus there are many dangers that we have previously been unaware of.

Aren’t the thawing permafrost soils an opportunity for the energy industry to exploit natural resources that previously were not accessible?

Not really. In Alaska and Canada, thawing permafrost today is already damaging roads and thus preventing accessibility to oil production sites during winter. In addition, the permafrost is not thawing to depths of several hundreds meters, but only a few meters. The natural resources do not usually lie near the surface, but deeper underground, meaning that the melting of a few meters of permafrost would not be enough to reach the resources.

The frozen ground also contains methane, a greenhouse gas. Could it be a problem if this methane is released?

This is one of the great unknowns. We know that the methane comes from three different sources. First: In the summer bacteria produce methane on the melted surfaces. An increasing paludification of the landscape could speed up methane production. Second: Free methane and carbon are sequestered at depths of up to of 30 meters in the frozen soil. When the permafrost thaws, the methane could escape, and carbon could be converted to greenhouse gases by bacteria. Thirdly: There could be tremendous amounts of gas hydrates at greater depths, i.e. methane trapped in frozen water. So far, this methane has not escaped because the permafrost constitutes a mighty lid on this source. However, should the permafrost begin to thaw in the shallow marine areas, this frost cover could become porous - veritable chimneys, through which the methane can escape. We do not yet know how big this threat is. This requires further research.

If you combine these three sources, are there estimates about how much methane would be released in total, and what consequences this would have on our climate, particularly since this methane could exacerbate the greenhouse effect?

I can’t venture any predictions. So far, we lack reliable numbers, and it is still too early to project anything. Ultimately, however, I am convinced that the thawing permafrost regions represent a danger for the climate and will lead to an increase in greenhouse gas emissions. But I am not able to estimate the extent to which this increase would cause an additional temperature increase and whether this increase in temperature would continue to melt the permafrost. So far, this is pure speculation.