Introduction
Permafrost is a term used about any type of rock or soil whose temperature has remained below 320F or 0oC for two years and above. But there are certain instances where the ground may be subjected to seasonal freezing and thawing. This does not qualify as permafrost. Permafrost is said to be able to last for thousands of years, however, it is often close to its melting point. This period is defined within two years so as to leave out the surfaces of the overlying layers which have the habit of freezing during winter period and thawing at the onset of every summer. These types of layers are known either as seasonal or active layers. The permafrost usually is created when the temperature of the ground cools adequately during the winter period to make frozen layers that endure the whole time of the next summer. The being of the permafrost is determined by the climatic conditions of the atmosphere, but the nature in which it is spatially distributed, its temperature and the nature of its thickness are greatly influenced by the surface of the ground temperature (National Snow and Ice Data Center, 2010). It is important to note that the temperature of the ground surface is mainly determined by the climatic conditions; nonetheless, there are other important factors that play a major role in determining the ground surface temperature level. These factors include the vegetation, snow, type of soil and density, and human activities like burning of the forests, precipitation, erosion and the presence of organic materials. The temperatures of the ground are also affected by the core of the earth. The core is the hottest part of the underground layers of the earth’s inner structure. It is then important to mention that the underground temperature increases with depth. Due to this, the structure of the earth’s surface in relation to the hottest core of the earth determines the distribution of the permafrost (Davis, 2001).
Arguments have been advanced to contravene the common beliefs that snow contributes to the formation of permafrost. The argument says that snow coverage is an impediment to the creation of permafrost; that snow cover has the potential to cause the already existing permafrost to start thawing. It is said that snow cover that comes in season acts as insulator hence preventing heat loss to the atmosphere. The heat therefore is contained within the soil underground. The period of the snow determines its effects on permafrost formation or thawing. Nevertheless, the air spaces which are always found within the snow vanish hence reducing its insulation ability thereby retaining the existing or formation of new permafrost. Seasonal snow is approximated to cover about 33% of the total surface of the earth, and approximately 98% of the snow cover is found in the Northern Hemisphere. Most of the snowstorms are found outside the Antarctic and High Arctic. This is because the extremely low temperatures do not make it possible for enough moisture to form in the atmosphere and therefore there is no precipitation. This is the reason the polar areas are referred to as deserts.
There is continuous and discontinuous permafrost; permafrost can possibly form in any climatic condition so long as the air temperatures are annually below the water freezing point. However, there are some exceptions where this may not happen like in some parts of Scandinavia, parts of Russia, and Europe. In these excepted areas, snows act as insulators hence preventing the formation of permafrost despite the existing favorable conditions. In areas where the temperatures are only slightly below 32o Fahrenheit permafrost will most likely occur only in areas under shelter and away from solar radiation. Permafrost formed under this condition is referred to as discontinuous permafrost. This form of permafrost can easily thaw under at the introduction of a small amount of temperature. Again, temperatures may be very low below the water freezing point. This kind of temperature may even go down to -12o Celsius. The extremely low temperatures offer a favorable atmosphere for the formation of continuous permafrost. Continuous permafrost is able to maintain its stability when subjected to slight increase in temperature. The continuous permafrost can last for many years while maintaining its stability; it can survive substantial increases in temperature (Rumney, 1967).
Regions Of Permafrost
Permafrost is normally found in altitudes that are high usually close to the North and South poles. The North and South Pole are the areas where permafrost is most prevalent, otherwise, it is also found in regions all over the world where there are high altitudes. The regions that experience permafrost are south of the Rocky Mountains, Alaska, parts of Canada and Western parts of North America. These regions form the Northern Hemisphere. In the Southern Hemisphere permafrost is found in the Mountains of the Andes, Antarctica, and the Islands of Antarctic. It also occurs in regions where the grounds are can stagy cold enough and meet the minimum conditions for the formation of permafrost. In the Northern Hemisphere it is approximated that permafrost cover more than 20%. But there are fears that with time, though not very soon, the areas covered by permafrost will not be having the coverage of permafrost due to the increasing global warming (Stonehouse, 1990).
Permafrost is not only found on the earth’s surfaces. Other colder planets have been found to contain permafrost. One of these planets is the Mars. Scientific research reveals that there are large landforms on mars that can only be explained to have been formed by water. It is argued that there are Islands located in the middle of wide valleys, remnant beaches and prehistoric shorelines. The scientific materials available argue that all the water could not have evaporated into the atmosphere; it may be concluded that the ancient water-inundated bottoms of the seas and lakes might have retained their contents as the temperature in those areas got lower and lower. The water therefore froze with other materials to form permafrost on the surface of the mars. Other colder planets on the solar system also experience formation of permafrost on their surfaces. The processes of formation are more or less like that on both the earth and mars (1985).
Types Of Permafrost
Permafrost comes in different types depending on the climatic and environmental factors that influence its formation. These types are:
- Cold permafrost: this type of permafrost is said to be able to take a considerable amount of heat before thawing. Its temperature is always less than -1o Celsius or equivalently below 32o Fahrenheit. In some cases the temperature can be as low as either 10o F or -12o Celsius.
- Warm permafrost: this type of permafrost is volatile and remains just under 32o Fahrenheit. This type is likely to undergo thawing at the introduction of limited marginal amount of heat.
- Thaw stable permafrost: these are permafrost that is mainly found in coarse sediments which are well-drained. These sediments include but are not limited to sand, gravel mixtures of gravel and sand and outwash gravels (Lunardini, 1981). The locomotion of this type of permafrost when thawed is limited and its foundation always remains stable. This type of permafrost can survive for long and is mostly found in areas where there are extremely low temperatures (Linell et al, 1981).
- Ice-rich permafrost: just as the name suggests, this type of permafrost has a high percentage of ice which is between the ranges of 20 percent to 50 percent of the whole permafrost. This percentage of ice is visible above the ground surface. Ice-rich permafrost is likely to melt since the ice component part of it is never permanent; it melts during summer and solidifies again during winter. This makes the permafrost experience frequent intermittent changes in temperature hence making it tom thaw more often than thaw stable permafrost (Strub, 1996).
- Thaw unstable permafrost: thaw unstable type of permafrost usually has poor drainage and has fine grain soil which consists of clay and sand. In this permafrost the amount of ice is enormous. It disintegrates when subjected even to limited amount of heat. When it is in the process of defrosting, it is likely to lose its strength; the disproportionate moisture-containing soil settlement sets it to flow, too (Kimble, 2004).
Effects Of Climate Change On Permafrost
The changes in climatic conditions have great effects on the ground, both below and above the surface. It is noteworthy to realize that the temperatures at the surface take relatively long time to exert an impact on permafrost found at great depths. Geological survey of Canada, as quoted in Weather Underground (2010), indicates that for the surface temperature to have an impact on thick permafrost at great depths, it takes many years ranging from hundreds to thousands. It is therefore safe to argue that permafrost is a thermal circumstance. Note that the changes of temperature that should have substantial effects on permafrost should be short-term. This applies especially to very thick permafrost which requires long exposure to increased temperature in order to start reasonable thawing (Arenson, 2003). The formation of permafrost, its perseverance and or disappearance are directly linked to the climatic conditions. Research has shown that changes in natural environmental factors and human activities have a great influence on the regional distribution, temperature and thickness of permafrost. The ground thermal conditions are modified by the clearance of vegetative cover, fires that consume forests, diversion of river channels, erosion effects on shorelines and removal of organic cover on the surface. Permafrost is sensitive to climatic changes. Considering the global warming that takes place currently as a result of increased greenhouse gases in the atmosphere, the permafrost is likely to gradually disappear (Riley, 2003). This may take especially in the sporadic permafrost areas where the permafrost is likely melt at ground temperature of about 1o or 2o. Further studies indicate that the process of permafrost warming and thawing is continuously increasing over time. This supports the fear that permafrost is actually on the verge of extinction. Coupled with the increasing global warming the formation of permafrost has slowed down and the already existing ones have taken the trend of disappearance (Riley, 2003).
It can be argued that as much as climate changes have some effects on permafrost, the permafrost contributes to the changes in the climate like global warming. Scientists who have studied permafrost reveal that it contains a lot of carbon trapped within the frozen organic matter in the soils. As other factors cause climate changes, especially rise in temperatures, the permafrost melt and in the process release the trapped carbon into the atmosphere. This causes further climate changes and hence more impact on permafrost.
Effects of Weather Conditions and Vegetation on Permafrost
Wind is one of climatic elements that affect the existence of permafrost. Some areas of permafrost are exposed to the wind. The speed of the wind determines its effects on the existing permafrost. High-speed wind causes fast erosion of permafrost. Wind caries some soil or silt particles which are knocked against the surface of exposed part of permafrost, with time the surface gets eroded. The effect of wind on permafrost is just similar to that of waves in cases where permafrost is located at the seashore; the force with which the wind blows across bare permafrost determines the rate at which the structural formation of the permafrost is weakened. The importance of the vegetative cover is to protect the permafrost from the wind effects and other factors that lead to its degradation. The amount of vegetation cover determines the amount of heat transfer between the environment and the permafrost. Forests and other thick vegetative cover traps very much air that leads to limited transfer of heat between the permafrost and the atmosphere (Seppälä, 2004). However, in regions where permafrost lies under thin vegetation cover, it is easy to start thawing; in fact these are the areas that experience seasonal permafrost. But then it can also be argued that the vegetative cover has the tendency to reduce the velocity of wind. It is important to note that there is a relationship between wind velocity and the surface temperature. High wind velocity reduces surface temperature which may create sufficient conditions for the formation of permafrost; when wind blows it moves away from heat from an area, and the rate at which heat is removed from an area increases with increase in wind velocity. Low wind velocity does not affect the existing surface temperatures so much. So the presence of vegetative cover, especially the forest, reduces wind velocity and hence does not favor formation of permafrost. This therefore explains the reason some areas with no vegetative cover but experience high wind velocities are associated with permafrost. This means permafrost formation depends substantially on the velocity of wind on bare earth surfaces. Contrarily, it should not be assumed that the velocity of wind alone can lead to formation of permafrost; there are other vital factors that must also exist to commence the formation of permafrost (Margesin, 2008).
As much as bear regions that experience high-velocity wind is good for the formation of permafrost, vegetation greatly serves to protect the already existing permafrost. The thick overgrowth in the forest intercepts solar radiation and prevents it from reaching the ground under which may lay permafrost. This provides cooling effects on areas covered by the vegetation hence preventing the thawing of permafrost. During transpiration the plants release moisture from the atmosphere, in this process the trees release some amount of heat into the atmosphere. The heat is derived from the ground; this also produces some cooling effects (Margesin, 2008)
Topography and Permafrost
There is various nature of terrain that affects the formation and condition of the permafrost. The surface relief or geographical relief has a direct control in the formation of permafrost. Permafrost also exists in mountain areas where the mean temperatures go below -3o Celsius annually. The permafrost in mountain regions takes varied forms; these include rock glaciers, steep rocks, debris in vegetated soil and debris dropped by glaciations process. The debris deposited by glaciers always contains dynamic amount of ice. The distributions of permafrost in mountainous areas are very inconsistent. The different topography checks the amount of radiation that reaches the ground; the irregular zones with slopes facing north are the only places where permafrost can be experienced because this is the side that gets less radiation from the solar. The topography also affects the accumulation of the snowstorm and the nature of vegetative cover found in a particular region. The snowstorm and the vegetative cover sequentially determine the thickness of permafrost.
Air the flow of air from raised ground is a microclimatic feature that has an influence on the formation of permafrost. The air current blowing from the top of the mountains, especially at night, is always cold. Alongside other factors the cold air contributes to formation of permafrost. The different levels of topography have different effects on the formation of permafrost. The higher the altitude above the sea level the colder it becomes. This implies that areas with the highest altitude have the lowest temperatures. Comparing all forms of terrains, the highest mountain regions have more permafrost than the low mountain areas. The climatic conditions up a mountain become favorable to permafrost as the height increase. Going by this argument, the effect of increased heat on permafrost found on high topographies is less than that found on low topographies. One may argue that the Solar is up and hot; therefore, the closer one moves to the solar the hotter it should be. The fact is that past certain atmospheric layers, the solar radiations have less heat energy. It is until they hit the ground that they are reflected back into the atmosphere with increased heat. The effect of this heat therefore reduces with increase in altitude. This is what explains the reason high altitudes have low heat levels.
Permafrost as a Habitat
Permafrost is considered to be very cold and sometimes it can never be imagined that it can support any form of life. In most cases the regions around the North and South Pole have never supported any meaningful human activities. Research has revealed that permafrost acts as a habitat for many microscopic organisms. In fact the discovery of these organisms has called the scientist back to the drawing board to reconsider the boundaries surrounding the biosphere. The thick and big mass of permafrost that stretches down into the ground is home to many microorganisms the first information on the existence of organisms in the permafrost was released in the 19th century; that was after the discovery of mammoths. In the successive series of scientific studies, more microbes were discovered. The available literature argues that these microorganisms could not have penetrated the permafrost from the surface but is present in the permafrost naturally (Cuff and Goudie, 2008). Their ages are estimated to correspond to that of the permafrost in which they live. This can explain how they start living there. Probably, during the formation of permafrost these organisms are found within the vicinity of the permafrost formation; they later adapt to the extremely cold temperatures and become permanent inhabitants of the permafrost. The ages of cells found in permafrost are dated back to more than two million years. These organisms are able to change their physiological activities in order to adapt to their habitat.
The permafrost is a very stable environment given that its temperatures remain right below the water freezing point. It is considered by scientists to be amongst the well-balanced environments that support life. Permafrost’s stable environment makes it possible for the microscopic organism that can adapt to extreme colds environments to adjust themselves to the conditions of its existence. With the extremely low temperatures, the micro-organisms have very low metabolic rates, are adaptable to low nutritional supply and are able to survive without oxygen. Other higher animals also benefit from permafrost. Examples of these animals are squirrels and Arctic fox. These animals are also able to live in areas dominated by permafrost. For instance, the Arctic foxes are able to store their foodstuff including birds’ eggs; the eggs remain fresh for over one year. Another animal that has adapted to the permafrost environment is the Arctic hare. The Arctic hare builds its nest on high rocks; it can eat snow in cases where it falls thirsty (Cuff and Goudie, 2008).
Implications of Melting Permafrost
Permafrost has several impacts on human activities; these effects may affect structures like roads, buildings and other infrastructures. Thawing permafrost may flow onto road networks and sometimes where roads pass over permafrost areas the thawing may cut collapse some parts of the road. It is also a danger to both oil pipes under the ground and on the surface. In cases where permafrost on mountain tops starts thawing, the effects may be covering of buildings around, blocking of river channels and destruction of vegetations around. In the regions where permafrost is most common like the North and the South Pole buildings are constructed on permafrost areas (Beniston, 2001). During thawing of the permafrost these buildings always collapse with the permafrost. It is important to note that buildings exert pressure on permafrost, but the pressure is directly proportional to temperature meaning that as pressure increases so does temperature. The effect of heavy buildings on permafrost land gradually increases temperature beneath causing the permafrost to start thawing. With time the buildings sink into permafrost leading to the destruction of property and probably loss of lives. All these effects are detrimental to economic development.
Permafrost is known to hold some carbon and other greenhouse gases. In the process of thawing the gases are released into the atmosphere. The gases cause air pollution consequently leading to causes of respiratory diseases; moreover, the greenhouse gases contribute to global warming. The amount of greenhouse gases held by the permafrost is more than what is already in the atmosphere (Chapman, 2009). The increasing temperatures are causing more and more thawing of permafrost hence releasing more greenhouse gases into the atmosphere. Evidently, it can be realized that there is interplay between increasing temperatures and the thawing of permafrost (Beniston, 2001). The permafrost has the potential of increasing global warming with actually contributes to its thawing. This poses a great danger to the entire humankind. Permafrost consists mainly of water and other debris consolidated together. In the process of thawing, ice component of permafrost melts from water. The water may cause flooding in some areas or make rivers burst their banks and cause havoc. Sometimes the silt deposits may flow in lakes hence blocking them. With the chemicals contained in it the flow of thawed permafrost may pose some dangers to the aquatic life. The inhabitants of permafrost regions are ones in most danger. The increasing global temperatures are causing the permafrost grounds to be less stable. This implies that the people must navigate new travel routes to avoid the dangers of thawing permafrost (Beniston, 2001).
Conclusion
Permafrost is defined to mean any type of rock or soil whose temperature has remained below 320F or 0oC for two years and above. The period of permafrost formation is defined within two years so as to leave out the surfaces of the overlying layers which have the habit of freezing during winter period and thawing at the onset of every summer. These types of layers are known either as seasonal or active layers. The permafrost usually is created when the temperature of the ground cools adequately during the winter period to make frozen layers that endure the whole time of the next summer. The creation of the permafrost is established by the climatic conditions of the atmosphere, but the nature in which it is spatially distributed, its temperature and the nature of its thickness are greatly influenced by the surface of the ground temperature. Apart from the climatic conditions the formation of permafrost is influenced by factors like vegetation, snow, type of soil and density and human activities like burning of the forests, precipitation, erosion and the presence of organic materials.
The North and South Pole are the areas where permafrost is mostly widespread, otherwise, it is also found in regions all over the world where there are high altitudes. Regions that also experience permafrost are south of the Rocky Mountains, Alaska, parts of Canada, and Western parts of North America. These regions form the Northern Hemisphere. In the Southern Hemisphere permafrost is found in the Mountains of the Andes, Antarctica, and the Islands of Antarctic. It also occurs in regions where the grounds are can stagy cold enough and meet the minimum conditions for the formation of permafrost. In the Northern Hemisphere it is approximated that permafrost cover more than 20%. The types of permafrost are thaw stable permafrost, thaw unstable permafrost, warm permafrost, cold permafrost and ice-rich permafrost. Climatic changes have a direct effect on the formation of permafrost; the changes in climatic conditions have great effects on the ground, both below and above the surface. It is noteworthy to realize that the temperatures at the surface take relatively long time to exert an impact on permafrost found at great depths. Permafrost formation is influenced by also by wind alongside temperature. The amount of vegetation cover determines the amount of heat transfer between the environment and the permafrost. Forests and other thick vegetative cover traps very much air that leads to limited transfer of heat between the permafrost and the atmosphere. However, in regions where permafrost lies under thin vegetation cover, it is easy to start thawing; in fact these are the areas that experience seasonal permafrost. But then it can also be argued that the vegetative cover has the tendency to reduce the velocity of wind.
The distributions of permafrost in precipitous areas are very incoherent. The different landscape checks the number of rays that reach the ground; the irregular zones with slopes facing north are the only places where permafrost can be experienced because this is the side that gets less radiation from the solar. The topography also affects the accumulation of the snowstorm and the nature of vegetative cover found in a particular region. The snowstorm and the vegetative cover sequentially determine the thickness of permafrost. The permafrost has been found to act as a habitat for microorganisms and higher animals like the Arctic hare, Arctic fox and squirrel. It is considered by scientists to be amongst the well-balanced environments that support life. Permafrost stable environment makes it possible for the microscopic organism and other higher organisms that can adapt to extreme colds environment to adjust themselves to the conditions of its existence
Permafrost also has several impacts on human activities; these effects may affect structures like roads, buildings and other infrastructures which may have direct effects on any economy and especially the lives of inhabitants of North and South Pole. Again thawing of permafrost releases the greenhouse house into the atmosphere; the increasing temperatures are causing more and more thawing of permafrost hence releasing more greenhouse gases into the atmosphere which increases global warming and causes health risks.
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