What is permafrost?

There is a terrestrial part of the planet that is always in the form of ice. It is permafrost , also known as permafrost or permafrost, an underground layer of ice that cannot be seen with the naked eye. We often associate it with distant landscapes such as Siberia or the Arctic, but we can find permafrost in many cold regions of the planet, even in high mountains such as the Catalan Pyrenees.

However, the state of permafrost worries us. Due to global warming , its melting is accelerating , which is releasing large amounts of greenhouse gases that had been trapped for centuries . For this reason and many others that we will now explain, the state of permafrost is a key indicator for understanding and studying the effects of climate change. For this reason, we must pay attention to what is happening to it.

In the strict sense of the word, permafrost means “permanent ice”. It refers to layers of soil, rock or sediment that remain completely frozen at temperatures equal to or below 0 °C. This is for long periods of time of at least two consecutive years.

The areas where it is most common to find this soil permanently are in the cold regions of the planet, such as high mountain areas and, above all, at higher latitudes, those close to the North and South Poles.

Permafrost is made up of a system of layers. The most superficial one is called the active layer , and it is the one that thaws during the summer and freezes again in the winter. Below this, there is the permafrost , which remains frozen continuously throughout the years.

The thickness of these layers can vary greatly, from a few meters to hundreds, depending on the geographical area where it is located, the climate, latitude, altitude and terrain characteristics. Thus, permafrost is classified into the following types:

• Continuous permafrost: between 90 and 100% of the ground frozen
• Discontinuous permafrost: between 50 and 90%
• Sporadic permafrost: between 10 and 50%
• Isolated permafrost: less than 10%

If you want to discover firsthand what lies beneath the permafrost, a unique experience awaits you in Alaska. The Permafrost Tunnel Research Facility (PTRF) is a tunnel located in Fox, Alaska, excavated between 1963 and 1969 to test mining, construction, and tunneling techniques in permafrost soil.

Today, the tunnel is managed by the Cold Regions Research and Engineering Laboratory (CRREL) and functions as a center for research, education, and outreach about permafrost. Inside, you can see natural features and fossils up to 40,000 years old, such as giant ice wedges, preserved grass thousands of years old, and animal bones trapped in the ice. You can take a virtual tour through their website!

Carbon storage

Permafrost is a large natural store of carbon. It is estimated to contain 1.7 trillion tons of carbon, more than twice the amount in the atmosphere. Inside it accumulates a lot of frozen organic matter formed by the remains of plants and other organisms.

Gives stability to the ground

Permafrost also stabilizes the soil and landscape , especially in mountainous and high-latitude regions. By keeping the ground frozen, the ice acts as a “cement” that holds rocks and sediments together.

Maintains surface and groundwater flows

Permafrost plays a key role in the hydrology of cold regions. The active layer of soil, which thaws in the summer, keeps the ground moist, an ideal condition for plants typical of cold areas such as mosses , lichens and shrubs.

The basis of “cold” ecosystems

Permafrost also shapes the type of ecosystems and biodiversity found in cold regions. The type of vegetation that grows above the active layer, such as mosses and lichens, allows other species typical of arctic and alpine ecosystems to live there.

Permafrost is mainly located in cold areas of the planet , either by latitude or altitude, but where it is most abundant is in the Northern Hemisphere . There, it occupies 24% of the land with an area of about 10.5 million km². The main regions with permafrost are the Arctic, in areas such as Alaska, northern Canada, Greenland and Siberia. It is also found in Central Asia, Mongolia, Tibet and northern China, but it is also found in alpine areas, for example in large mountain systems such as the Alps and the Himalayas.

Permafrost in the Southern Hemisphere is very scarce , occupying only 0.05% to 0.08% of the exposed land surface, a very small portion compared to the Northern Hemisphere. It is mainly concentrated in high mountain areas and polar regions. It is found mainly in the Andes, but also on Kilimanjaro, the Southern Alps of New Zealand, and some subantarctic islands.

Although it may come as a surprise, permafrost also exists in the Iberian Peninsula , but in the form of very localized alpine permafrost . It is found in some high mountain areas of the Pyrenees, especially on shady slopes and at high altitudes, where average annual temperatures are quite low.

In Catalonia, permafrost is found in the highest areas of the Pyrenees , at over 2,800 metres above sea level, especially on the northern slopes and in rocky areas such as screes. In these places, the frozen ground forms rocky glaciers that slowly move downhill when the ice melts. This, in turn, serves to detect hidden permafrost. In fact, a Catalan research team with the participation of CREAF is studying permafrost in the Sotllo massif and also in the Catalan Pyrenees, Andorra, Occitania and Aragon.

The tundra is one of the ecosystems most closely linked to permafrost. It is a cold, treeless landscape where mosses , lichens, grasses and small shrubs live. As a curiosity, permafrost prevents water from seeping into the ground and causes the tundra soils to be saturated with water in the summer. This poor drainage capacity means that the vegetation that lives in these areas has very shallow roots.

Some studies by CREAF warn that Arctic vegetation is changing . With climate change, species native to boreal forests and the transition zones between boreal and tundra, such as grasses and shrubs, are expanding into the Arctic. These are plants that colonize the land easily and establish themselves better when climate conditions are warm and humid. This movement of plants can have consequences because it can harm the native vegetation of the tundra, and at the same time, unbalance entire ecosystems.

Climate change is accelerating the melting of permafrost around the world. Some climate projections suggest that a global increase of 2°C could lead to the loss of up to 40% of current permafrost , and by the end of the century only 10% could remain.

The consequences of permafrost thawing are multiple:

Greenhouse gas release

While the ground remains frozen, carbon is “sequestered” in the permafrost. But when it thaws, microorganisms reactivate the decomposition of organic matter and large quantities of carbon dioxide (CO₂) and methane (CH₄) are released into the atmosphere, two very powerful greenhouse gases . This process generates a positive feedback loop or amplification : more warming causes more melting, and more melting accelerates global warming even further.

Another factor that could release more greenhouse gases is the increasing number of fires in Arctic regions. A CREAF study stated that the fires of 2019 and 2020 damaged the permafrost and consequently released more greenhouse gases than were previously contained.

Geological and infrastructure risks

As ground ice melts, the ground loses its cohesion and stability. This can lead to landslides and ground subsidence, as well as serious damage to roads, buildings, pipelines and airports. In addition, the loss of stability increases the risk of landslides , rock falls and sediment movement, as well as the likelihood of flash floods associated with glacial lakes. In fact, an international study estimates that 70% of Arctic infrastructure could be at risk by 2050.

Transformation of ecosystems

The thawing of permafrost also alters the functioning of ecosystems. When thawed, water can drain more easily, changing hydrological cycles , river courses and the transport of sediments and dissolved substances. These changes can modify vegetation, habitats and affect biodiversity . If permafrost degrades significantly, many of the species closely linked to the conditions of the tundra and permanently frozen soil may disappear. CREAF has been able to verify these effects in Alaska and the Tibetan Plateau .

From CREAF we recommend visiting this interactive web portal of the REUTERS agency where you can find a lot of information about permafrost.