An international team of researchers has discovered the oldest permafrost soil in Siberia.

The 50-meter layer of soil has been frozen for around 650,000 years, as the Alfred Wegener Institute (AWI) announced in Bremerhaven on Tuesday.

This means that this permafrost layer has already survived several cold and warm periods.

According to the experts at the Helmholtz Center for Polar and Marine Research, this is important because it shows that permafrost soils do not have to completely thaw, even in warmer times.

The examined permafrost soil evidently survived particularly warm phases around 130,000 years ago, when it was around four to five degrees Celsius warmer in the Arctic in summer than it is today.

Irreparable damage

On the other hand, the find near the East Siberian community of Batagai also shows how sensitive the permafrost soil reacts to human disturbance.

The 650,000 year old permafrost is actually located on a mountain slope at a depth of around 50 meters, where there is a constant temperature of around minus ten degrees Celsius.

However, a part of the slope was partially deforested between the 1940s and 1960s and driven over with heavy track vehicles from a nearby mine.

As a result, the protective and insulating plant cover was lost.

As a result, the younger permafrost thawed on the surface in summer until the ground finally began to slide and exposed the old permafrost.

The damage is irreparable because the exposed permafrost soil continues to thaw every summer.

In the past 50 years, the landslide has expanded to a width of around 900 meters, explained AWI researcher Thomas Opel.

Permafrost consists of soils and rocks that are permanently frozen, sometimes up to several hundred meters deep.

They occur mainly in North America and Siberia, but also in high mountains and, like a gigantic freezer, conserve huge amounts of dead biomass, especially plant remains, but also remains of animals from the last Ice Age such as mammoths and woolly rhinos.

When the permafrost thaws, bacteria become active, which break down the ancient biomass and, through their metabolism, release the greenhouse gases carbon dioxide and methane.

Because of climate change, experts fear that it will exacerbate the greenhouse effect.