Permafrost - and permafrost - is frozen at a certain depth throughout the year. By definition, permafrost " soil, sediment or rock, which has in varying thickness and depth below the surface at least two consecutive years in temperatures below freezing ." As glaciers permafrost subject of research in glaciology.
Permafrost soils form where the annual average temperature -1 ° C and the annual precipitation does not exceed 1000 mm. Thus there are the large permafrost areas of the Earth in the polar regions to the Arctic and Antarctic tundra, large parts of the boreal forest areas, but also in all the areas that meet the conditions for permafrost, such as high mountains. As permafrost zone is called " the circumpolar region of eternal Gefrornis that includes the tundra of northern continents, the large forest areas and offshore areas of the seabed ."
Geographically, there are large parts of northern Canada, Alaska, Greenland and eastern Siberia. 20 to 25 % of the land areas of the earth are permafrost, with 99% of Greenland, Alaska to 80%, Russia 50%, Canada up to 20% are 40 to 50%, and China from permafrost soils. To the south, a few rich permafrost areas to Mongolia. Permafrost penetrates to different depths in the ground: In Siberia the permafrost reaches depths of up to 1500 meters, in Scandinavia there are only about 20 meters. Reasons for this are the large Kontinentalvergletscherung the last ice age ( Weichsel glaciation ). While Siberia was never glaciated to a greater extent, and the ground permanently was thus the cold air exposed, so that he could freeze up in very deep layers, Scandinavia was more or less isolated by the mighty ice sheets in the underground, which the permafrost does not penetrate as deeply could.
Permafrost areas is also available in high mountain regions such as the Alps. They are formed during the last ice age ( Würm glacial period ) as the ground froze in places up to several 1000 meters depth. In addition to these fossil permafrost areas in the Alps will be held today - even if only to a very limited extent - recent permafrost formation instead ( for example, by the retreat of an insulating effect glacier or rock glacier, so the soil is directly exposed to the cold air and permafrost can form new, provided that the conditions are met ).
In addition, there are also submarine permafrost, so permafrost at the bottom of the seas. Due to the density anomaly of water actually physically impossible to explain this as follows: by the eustatic sea level fluctuation of the last Ice Age were many continental shelves that are now under water again, above sea level, making the soils up to several 100 meters depth were able to form permafrost. The sea water that flooded the shelf in the subsequent warm phase again was to cold to thaw the submarine permafrost then again can. The famous submarine permafrost areas are in the Laptev Sea in the Arctic Ocean.
Permafrost can thaw the surface in summer; the Auftauboden ( in the literature often referred to as "active layer") is usually between 30 centimeters and 2 meters deep. The soil underneath remains frozen. Due to the Auftauboden held numerous periglacial Denudationsprozesse. The outside of the Periglazialgebiete formed periodically frozen upper layer of soil is called winter frozen ground; this is not one of the permafrost (for example, the frozen topsoil in Central Europe in winter).
Future forecasts due to the warming climate of a decline in the world's permafrost to 25-44 % for an increase in the global temperature by 2 K from.
Outline of the permafrost
Vertical layout ( top to bottom )
A non- frozen area within the permafrost is called Talik. In this case, open and closed Taliki be distinguished, the latter have no contact with the Auftauboden.
In permafrost voreiszeitliche the fauna and flora was excellently preserved. The found biological material is permanently frozen. This also DNA analysis of the finds are possible, which is otherwise not possible with fossils. Thus, a well-preserved woolly mammoth was 1997 ( the Jarkov mammoth ) on the Taimyr Peninsula in northern Siberia found by the Dolgans Gennady Jarkov which has been extensively studied.
The Leinkrautart Silene stenophylla could stay in the Siberian permafrost over 30,000 years. 2012 scientists from the Russian Academy of Sciences, grow plants from frozen remains.
Decline of permafrost
In the course of global warming a Northward migration of permafrost in North America and to a lesser extent was also observed in Eurasia in the last few decades. The consequences are damage to roads and houses that now stand where the permafrost thaws only on mud. In the long term a thawing in still much higher proportion is feared because the climate models predict an above-average warming in the Arctic. Some scholars assume that there could be a positive feedback, as in the permanently frozen soils is present as biomass carbon compounds in a large amount of the greenhouse gas carbon dioxide would be emitted as to the atmosphere during defrosting and degradation of biomass.
In addition, escape in this case in the permafrost bound in large amounts of methane into the atmosphere. This process would be a strengthening of the warming since the global warming potential of methane is about 25 times as large as that of CO2. According to a study from 2009, this factor is even 33 when interactions are taken into account with atmospheric aerosols. The economic costs alone of the release of methane gas during defrosting of the permafrost under the East Siberian Sea (Arctic) during the warming is estimated to be the world 60 trillion dollars.
According to Scientific Reports melt along the coasts of Antarctica itself been stable permafrost mainly because of a more intense sunlight faster than previously expected.
The thawing of permafrost provides short-term and locally already for significant and threatening changes in the topography. Especially in northern Russia sink large flat areas in a short time suddenly when the frozen water thaws and loses volume, trapped gas escapes, and collapses the perforated soil in the sequence under its own weight in itself. This leaves vast expanses of a crater landscape with crooked and uprooted trees and lakes, filled with condensation. Also the lying below the sea ( " submarine " ) permafrost before the Russian coast begins by the inflow of warm water to thaw reinforced.
The superficial thawing of the soil, many problems in the construction of buildings. Were Building Built in winter on the frozen ground, it can happen that they fall down at his thawing. In areas with permafrost why buildings are built primarily on piles that reach down into the permanently frozen regions of the soil and thus stand on firm ground. Also air may flow around the bottom floor of the house and carry away the radiated heat from the building, so as not to leave the underlying floor thawed.
The thawing of permafrost in the Alps, however, is whole mountainsides in motion. On Bliggferner in the Alps currently slipping about four million cubic meters of rock and ice in the valley. This mountain mass travels daily 20 centimeters, pulls the glacier growing up, and makes a sudden slipping more and more likely. Slipping into the Gepatsch reservoir could be occur over the dam of the lake and thus trigger similar to the case of the Vajont dam in the Italian Alps a tidal wave.
Even in mountainous areas of Norway shows a similar picture: With 0 to -3 ° C, the local permafrost is warmer than most people realize. Therefore, massive landslides are also there likely with continued global warming, because the frozen water as a binder loose rock, sand and the like together. As a result of debris flows could occur in the narrow fjord gorges up to 45 meter high tsunami.
It is believed that the once abundant water on Mars today is at least partly as ice in the soil. Thus, it would also be there frozen soils.
A geothermal heat pump heating -use can lead to an artificial permafrost, if the extracted heat energy can no longer be adequately replenished by the environment. In this case forms around the heat exchanger coils in the ground a block of frozen ground, which significantly reduces the heat output.