Snow of Tomorrow | Permafrost in Climate Change

Invisible climate indicator

The retreating glacier tongues are clear signs, visible to the naked eye, that the climate in the Alps is warming far too quickly - more than +2 °C since the end of the 19th century. Another significant climate indicator is (alpine) permafrost: it hides inconspicuously beneath the earth's surface in soils, debris or rock faces - but its significance and, above all, the effects when it thaws are anything but inconspicuous.

If soil or rock material remains permanently below 0 °C for at least two years in a row, it is referred to as permafrost - i.e. permanently frozen material, regardless of whether ice is present or not. The top layer of soil thaws every summer to a certain depth, the so-called thaw layer, but below this layer the soil or rock temperature never exceeds the freezing point - and this has been the case for more than 10,000 years since the end of the last ice age.

Glue of the Alps is becoming brittle

In the high mountains, the stability of entire mountain flanks, scree and moraine slopes and even rock faces can be directly dependent on permafrost. The colder the mixture of rock and ice, the more stable the whole thing is: cold permafrost is the glue in the Alps. And it doesn't even matter whether the permafrost actually goes beyond the 0-degree limit and disappears permanently: simply warming the material to between -2 and -4 °C is enough to make the mass soften and creep. The deeper the heat penetrates into the mountain and the thicker the thawing layer becomes, the more material can be mobilized and the higher the probability that stabilizing ice will thaw in the frozen fissures and crevices in the rock. In combination with the steepness of the Alps, the consequences are obvious: slopes can creep downhill, rockfall from rock faces increases and previously stable hut and cable car foundations collapse. Thawing permafrost can even be increasingly identified as the main culprit for triggering large rockfalls and landslides.

Mountain sports facing changing conditions

In short, the dangers in the high mountains are changing, increasing in area and presenting us mountain sports enthusiasts with new challenges. For decades, stable cold permafrost kept alpine dangers, especially rockfall and rock avalanches, halfway at bay along many classic normal routes or on north faces in the high mountains of the Alps; the risk was more calculable. Today, the windows of opportunity for safe ascents are getting shorter and shorter and some routes are even inaccessible.

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From practice 1: The small permafrost lens between Tyrol and Bavaria

You don't have to travel to the Arctic to find permafrost: in the Eastern Alps there is widespread permafrost along the main Alpine ridge, but permafrost can also occur in the lower foothills of the Alps, such as in the Karwendel or the Berchtesgaden Alps. Measurements along a tunnel within the Zugspitze have revealed a small permafrost zone between Bavaria and Tyrol. If the current warming trend in air and ground temperatures continues as it is at present, the Bavarian-Tyrolean permafrost lens will probably have disappeared by 2040.

From the field 2: A hut falls into disrepair

For more than 120 years, the DAV's Hochwildehaus at 2,883 m altitude stood stably on the edge of the Gurgler Ferner in the Ötztal Alps. For decades, small ice lenses were stored under the hut, permanently frozen in the supposedly eternal permafrost. The ice lenses have now thawed and the floor has sunk together with the hut, making it dilapidated. The mountain station of the cable car to the Gemsstock at around 3,000 m near Andermatt also has to contend with this and now has to be secured at great technical expense. These examples will not remain isolated cases: many huts, cable car foundations or mountain stations in the Alps are still standing on permafrost, but are precisely in the altitude range where the lower limit of the permafrost is currently shifting upwards and thus the greatest changes are occurring.

Global excursion: thawing permafrost as a climate time bomb

Permafrost exists on around a quarter of the land surface of the northern hemisphere. While permafrost in the Alps is relevant for the stability of our mountains, Arctic permafrost still fulfills a central function as a carbon store and is a ticking climate time bomb.

Organic material (e.g. plants) and therefore large amounts of carbon have been stored in permafrost over thousands of years and stored permanently. Specifically, this amounts to around 1,500 gigatons (1 gigaton = 1 billion tons) of carbon, about twice as much as is currently in the atmosphere. At the same time, the Arctic is warming twice as much as the global average and permafrost soils are thawing over large areas. This creates swamp-like landscapes and lakes in which the organic material is broken down and released into the atmosphere as methane. Methane is a greenhouse gas four times more potent than CO₂. Due to warming, permafrost will therefore change from a carbon sink (carbon is removed from the atmosphere and stored) to a carbon source (permafrost releases more carbon into the atmosphere than can be stored).

Is this "tipping point" (there was also an issue of Snow of Tomorrow) is reached, permafrost will accelerate global warming to a still uncertain but alarming extent and become one of the largest sources of greenhouse gases.

Further information and maps on permafrost in the Alps:

• Permafrost maps Bavarian Alps

• Interactive permafrost map of Switzerland

• Permafrost map for the entire Alps to download as a .kmz file for Google Earth

Dr. Tobias Hipp is a physical geographer and completed his doctorate in Norway at the University of Oslo on the effects of climate change on alpine permafrost in the mountains of Norway. His main job is at the German Alpine Association in the nature conservation and cartography department.