**5. The melting of the permafrost**

Warmer climate and rising temperatures affect the Arctic in many aspects. Thawing permafrost is of the phenomenon that is detected in the Arctic. Measurements over long periods of time show that the permafrost temperature has rose by up to 2°C, and shallow permafrost layers in some areas have thawed completely. Consequently, the permafrost extent has shrunk by 30–80 km in Russia and up to 130 km in Canada [8]. In addition, a decrease in the snow cover creates a feedback mechanism of increasing temperatures. These phenomena lead to unstable grounds and emissions of greenhouse gases and toxicants that had been encapsulated in the frozen ground, and the permafrost is thawing in areas which were permanently frozen until recently [9]. The Arctic shores easily erode when hit by storm surges and strong waves. As a result of melted materials being washed away, the shore becomes even more susceptible to erosion [10].

The permafrost's thermal properties, conductivity, heat capacity, thermal diffusivity, latent heat, and thermal expansion, are among the key variables in determining permafrost melting and erosion rate. The thawing rate of a given soil depends

**33**

estimated.

erosion rate.

*Coastal Erosion Due to Decreased Ice Coverage, Associated Increased Wave Action…*

on the soil composition (soil particles, ice, water, and air content of the soil) and the conditions of the physical environment. By knowing the content of frozen water in

• All melted ground will wash away and erode by the impact of storm surge and

It is possible to roughly estimate the amount of ground that will erode. When trying to assess coastal erosion, many uncertainties and parameters must be taken into consideration [10]. It was also necessary to make some simplifications and

An important parameter is the Degree days, the product of temperature and number of days. The degree days for an average temperature of 3°C over a period of 7 days is, for example, 3·7 = 21°C·d. The thawing index (Ist) is the number of degree days where the temperature is above the melting temperature (for water, 0°C). To calculate Ist, the degree days of each month were calculated: a monthly average temperature was calculated and multiplied by the number of days in each month. Under the assumption that the soil melting temperature is 0°C, Ist of the soil is the

The thermal models for coastal erosion that we used are described in [11]. For thawing depth estimation, first an evaluation of the permafrost soil consistency (soil profile and water content) was made, and then we were using the Stefan's equation (see [9–11]) to estimate the thawing depth in a partly frozen soil.

Several assumptions were made for estimating the amount of eroded soil during

• Erosion occurs between May and September (the erosion process is negligible

• A big storm surge hits the shores at the end of each season (Spring, Summer, and

As the average erosion rate in Varandey area was 2.7 m/year between 2005 and 2007 [11], based on these assumptions, the amount of eroded soil could be

The assumption that all melted material is being removed by a storm surge at the end of each "season" means that a new frozen soil layer is now exposed to heat and melting processes. A melted soil layer that stays intact could create an insulation layer that prevents heat penetration and decreases the melting processes, so the overall melted and eroded soil amount would be much smaller. For example, a single storm surge that hits the shore at the end of fall would hardly influence the

An erosion rate sensitivity analysis was made to assess and better understand the effect of the number of storms in a year on the total erosion rate. Three different

between October and April, due to sea ice and frozen soil).

assumptions in order to get a model which can predict soil temperature.

summation of degree days above 0°C for a one-year period.

**6. Permafrost erosion models**

Autumn) and erodes all melted soil.

• A season would count as a 50-day period.

the one year period:

*DOI: http://dx.doi.org/10.5772/intechopen.80604*

• Ice melts at temperatures above 0°C.

• The soil's thawing temperature is 0°C.

waves.

the ground and combining it with the assumptions that:

*Coastal Erosion Due to Decreased Ice Coverage, Associated Increased Wave Action… DOI: http://dx.doi.org/10.5772/intechopen.80604*

on the soil composition (soil particles, ice, water, and air content of the soil) and the conditions of the physical environment. By knowing the content of frozen water in the ground and combining it with the assumptions that:

• Ice melts at temperatures above 0°C.

*Arctic Studies - A Proxy for Climate Change*

surface shrinkage [2].

the absence of the ice [6].

**5. The melting of the permafrost**

been made in the eastern part of the Arctic Ocean, close to Beaufort Sea, where the sea ice cover has retreated significantly. Due to this dramatic retreat, especially in September 2012, 5 m height waves were observed in the middle of the basin. These were extremely large waves compared to what has been observed previously, testifying the assumption and the prediction of wave height enhancement due to ice

Apart from experimental campaigns and measurements, other studies using prognostic models have shown significant changes in estimated wave heights. These changes are undoubtedly linked to the increase of the fetch length created by the free-ice sea area. What is worth mentioning here is that the results showed also a rise in surface winds in the Arctic area, mainly in Kara, Laptev, and East Siberian Seas. On the contrary, at the western part of the Arctic region, in the Barents Sea, a

Moreover, research supports the assumption that in areas where the ice coverage is shrinking, the wave phenomena will change. Results have shown a growth in wind speeds and an increase of the frequency of occurrence of waves of 2 m height. On the other hand, the same studies have shown that the change in extreme wave heights is marginal. The areas where the change is more significant are those of the northern parts of Barents Sea, Kara, and Chukchi Seas, whereas, in areas where the sea is already ice free during September and October, like the North Atlantic and the main part of the Barents Sea, extreme waves would be less frequently witnessed and great changes in extreme wave heights could not be expected [7]. In conclusion, the eastern Arctic regions and areas close to the north Canadian coasts will be influenced most by

It should be noted that the discussion above relates to wave heights only. To estimate the sea level during a storm surge in the case of wind in direction toward shore has been outside our scope. A storm surge that encounters a shallow shore could climb up the coast easily, causing floods and increased erosion, while a storm surge that approaches a steep shore is more likely to break early, thus, cliff or steep shore might be sufficient obstacle to prevent a storm surge from piling-up and reaching far inland. The combined storm surge and waves will cause flooding and damages far inland. An unprecedented amount of erosion could occur due to the effect of flooding and wave action, in particular, as higher temperatures cause the increased melting of permafrost along the shores, these effects will be discussed below.

Warmer climate and rising temperatures affect the Arctic in many aspects.

The permafrost's thermal properties, conductivity, heat capacity, thermal diffusivity, latent heat, and thermal expansion, are among the key variables in determining permafrost melting and erosion rate. The thawing rate of a given soil depends

Thawing permafrost is of the phenomenon that is detected in the Arctic. Measurements over long periods of time show that the permafrost temperature has rose by up to 2°C, and shallow permafrost layers in some areas have thawed completely. Consequently, the permafrost extent has shrunk by 30–80 km in Russia and up to 130 km in Canada [8]. In addition, a decrease in the snow cover creates a feedback mechanism of increasing temperatures. These phenomena lead to unstable grounds and emissions of greenhouse gases and toxicants that had been encapsulated in the frozen ground, and the permafrost is thawing in areas which were permanently frozen until recently [9]. The Arctic shores easily erode when hit by storm surges and strong waves. As a result of melted materials being washed

away, the shore becomes even more susceptible to erosion [10].

drop of the winds and consequently the wave heights were observed [6].

**32**


It is possible to roughly estimate the amount of ground that will erode. When trying to assess coastal erosion, many uncertainties and parameters must be taken into consideration [10]. It was also necessary to make some simplifications and assumptions in order to get a model which can predict soil temperature.

An important parameter is the Degree days, the product of temperature and number of days. The degree days for an average temperature of 3°C over a period of 7 days is, for example, 3·7 = 21°C·d. The thawing index (Ist) is the number of degree days where the temperature is above the melting temperature (for water, 0°C). To calculate Ist, the degree days of each month were calculated: a monthly average temperature was calculated and multiplied by the number of days in each month. Under the assumption that the soil melting temperature is 0°C, Ist of the soil is the summation of degree days above 0°C for a one-year period.

The thermal models for coastal erosion that we used are described in [11]. For thawing depth estimation, first an evaluation of the permafrost soil consistency (soil profile and water content) was made, and then we were using the Stefan's equation (see [9–11]) to estimate the thawing depth in a partly frozen soil.
