What is permafrost, its characteristics and where is it?

Frozen soil is known as permafrost . It is difficult to classify it since it can have different characteristics and shapes, since it can be composed of solid rock, sediments or sandy and rocky soils as well as rich organic ones. All possible types of soils that are considered permafrost must be frozen, which implies that they must have been below the freezing point of water of 0 ºC or 32 F for at least two consecutive years. The water concentration is not decisive either, as long as they have a slight percentage of frozen water it is enough.

Next, we highlight the most relevant permafrost characteristics to begin to understand this type of soil well.

• About 20% of the Earth’s surface is recognized as permafrost, which was formed during the last Ice Age .
• It is part of both the cryosphere when it is frozen, and therefore the hydrosphere , as well as the geosphere when it contains rocks and soil.
• It has an active layer, more superficial, and another inactive, deeper. The active layer stands out for having a depth of between 30 to 200 cm. It melts in the summer season and refreezes in winter. In it, plant life develops depending on how far its roots can penetrate and be supplied with water. For this reason, vegetative landscapes can vary from tundra regions to boreal forests or taigas . The inactive layer is the one that remains frozen and can go up to 1,500 m deep.
• The aforementioned effect can generate, over thousands of years, polygonal patterns on the surface of the earth, associated with the contraction and expansion of the soil due to temperature differences.
• The ice that it has acts as cement, making the components of the soil stay together, so its melting can generate landslides or landslides. It also acts as an insulator, so some lakes and wetlands can disappear when they infiltrate the ground due to the loss of ice.
• If the hotspot is very deep, it cannot be refrozen in the winter season, causing the permafrost to recede.

After knowing what it is and its main characteristics, it is convenient to clarify where the permafrost is . It is found in cold climates, in high latitudes and in high mountain areas with high altitude. It is found in the circumpolar areas of Russia, Canada, Alaska, China, Greenland, Scandinavia and Antarctica, as well as high mountain areas such as the Pyrenees, the Alps or Tibet, among others.

Due to the increase in temperature of the Earth , the cryosphere melts. Regarding this increase in temperatures, a point of no return is being reached and the active permafrost surface is getting deeper and deeper.

It is one of the great carbon sinks on the planet, so it is expected that the carbon retained in it is four times higher than that found in the atmosphere. Its release would imply a very drastic increase in the greenhouse effect, motivating a feedback loop.

Since the last Ice Age, organic matter has been accumulating in it, from dead plants and animals. This organic matter has been preserved by freezing in permafrost for millions of years. When the permafrost melts , this organic matter is exposed to decomposing microorganisms that, when found in anaerobic environments (with a lack of O2), emit CO2 and CH4 in higher concentration, due to the process of methanogenesis or biomethanization. Unfortunately, methane from permafrost , and other sources, has a power 25 times greater than CO2 on the greenhouse effect .

In addition, the methane gas hydrates that were retained in the permafrost are also gradually released and rise as it thaws.

The gradual thawing of permafrost is an irreversible factor that generates major problems such as those related to the loss of soil structure. The main associated consequences of permafrost thaw are:

• Damage to infrastructures, due to the loss of cohesion of the soil.
• Coastal erosion.
• Landslide due to the instability of the slope.
• Increase in the greenhouse effect due to the escape of GHG (Greenhouse Gases) that were retained (CO2 and CH4).
• Damage and loss of biodiversity and the ecosystem.
• Sea level rise and related catastrophes.
• Appearance of pathogenic microorganisms that were in a latent state with reduced metabolism, such as viruses.
• Migration of people due to the instability of the area.
• Associated economic problems.

An example of the consequence of the thawing of permafrost related to the appearance of pathogenic microorganisms that were latent is that it is estimated that, in 2016, the anthrax outbreak that occurred in the Yamal Peninsula was due to this environmental problem. The reindeer must have ingested the virus in the permafrost and later transmitted it to humans, when they ingested their meat.