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Permafrost: In which regions of the world does it occur and what does it consist of?

2020-11-13T16:53:39.626Z


Huge amounts of carbon are stored in permafrost soils. Thawing them can significantly exacerbate the climate crisis. Everything you need to know about permafrost.


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Photo: Andrew Burton / Getty Images

What is permafrost?

Permafrost is soil that has been completely frozen for at least two years in a row.

It occurs in areas where temperatures have remained at zero or below zero degrees Celsius for several years.

There is permafrost above all in the Arctic, but also in the high mountains and in the Antarctic.

In Germany, for example, there is only permafrost on the Zugspitze.

Much of the permafrost originates from the last ice age or was formed immediately afterwards.

Permafrost covers almost a quarter of the land area of ​​the northern hemisphere.

As in Siberia, for example, they can reach a depth of 1.5 kilometers and consist of rock, sediments, soil, dead animal and plant remains and ice - all of which holds together like cement.

Typically there is a thin "active" layer of soil over the permafrost.

This so-called thawing floor thaws in summer and freezes over again in winter.

It is 30 to 200 centimeters thick.

The depth of the active layer varies depending on how high the temperatures rise in summer.

The higher the temperatures, the more the upper soil layer thaws.

As the earth's climate warms, the thawing zone increases, which affects the balance of the frozen layer below: the permafrost is receding more and more.

The consequences for the ecosystem are serious.

The ice melts and can no longer hold the ground together, erosion occurs.

The infrastructure of inhabited areas is being damaged and coasts are collapsing.

In the mountains, thawing permafrost can trigger dangerous landslides.

Another consequence: If the impermeable frost soil melts, the lakes and wetlands above seep away.

How does the thawing of the permafrost affect climate change?

Probably the most serious consequence of thawing permafrost is an acceleration of global warming.

Researchers fear that when thawing the carbonaceous organic material from thousands of years old animal and plant remains in the soil will be broken down by microorganisms.

This decomposition process can release enormous amounts of climate-damaging carbon dioxide and methane and enter the earth's atmosphere.

Scientists estimate that all permafrost stores up to 1,500 gigatons of carbon;

that is about twice as much as is currently in the atmosphere.

This would lead to a devastating, irreversible feedback effect, the so-called permafrost carbon feedback: the more greenhouse gases that accumulate in the atmosphere, the warmer the climate, the more the soil thaws, which in turn releases further CO2 and methane.

Warming also promotes plant growth, which means that more carbon dioxide can be absorbed from the atmosphere.

However, this is nowhere near enough to offset the enormous carbon emissions from permafrost in the long term.

In climate research, the thawing of permafrost is therefore one of the classic tipping points for our climate structure, where self-reinforcing processes cause a drastic change in the climate.

Last week's climate term: coral bleaching

Source: spiegel

All tech articles on 2020-11-13

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