The Arctic occupies a special place in the climate system and affects the occurring global changes. The temperature of the troposphere of the Earth continues to increase and, thus, globally influences the planet, causing negative consequences. It leads to an increase in global sea level due to various factors, including the melting of polar glaciers that creates a threat to coastal areas. Melting of permafrost is a potential source of methane and hence, brings the greenhouse effect on a global scale. At the same time the polar oceans absorb carbon dioxide, thereby reduce the rate of accumulation of greenhouse gases in the atmosphere. At high latitudes, there are driving forces of the global thermohaline circulation, which affect the regional climate change outside of the Polar Regions (McBean, 2005).
Today Arctic climate undergoes significant changes, such as increases in temperature, the reduction in thickness and area of ice. Climatologists have called several reasons causing the Arctic to heat. The first and the main cause of abundant melting of Arctic ice is considered the gradient of temperature change, which is associated with height. Experts believe that the Arctic is warming relatively faster than other parts of the world, since the temperature rises much faster there. The air temperature decreases by 0,65?C on average every 100 meters (AMAP, 2015).
The second reason for the increase in temperature is a process that is related to Planck’s law. Its essence lies in the fact that the colder the temperature of the radiating surface, the greater the increase in temperature is necessary in order to balance the process. Experts note that in the Arctic and the hotter regions, the radiation emissions coming from the planet are different. In the Arctic, temperature and humidity are low. Therefore, in the upper atmosphere the air is not mixed with lighter air and simply remains in high concentration on the surface, which in turn, causes the melting of the ice (AMAP, 2015).
And the third reason is the albedo. Albedo is a value that characterizes the reflectivity of the surface of the body. When in the Arctic ice melts, it releases a dark surface, which is either water or soil. These surfaces are able to absorb even greater amount of heat than snow or ice. The reflectance of the surface causes the Arctic to become extremely hot and snow and ice to melt (AMAP, 2015).
The Arctic is called the “weather kitchen”. In fact, the region plays a major role in climate change and the formation of the planet. Here fresh water that subsequently comes the North Atlantic is formed. These waters have an impact on the circulation of the water masses on the planet. In addition, the local ice cools the climate of the whole earth, and the Arctic Ocean plays the role of the most important natural heat exchanger.
Arctic Basin is a very specific object for mathematical modeling of the general circulation due to the number of important differences between the basin and the rest of the world’s oceans. Firstly, it is covered with ice almost universally and permanently. At the same time, a flow of heat, moisture, and momentum from the atmosphere to the ocean is largely determined by the state of sea ice, including its thickness, cohesion, etc. Secondly, a water density distribution in the Arctic Ocean is influenced by the distribution of its salinity, and not temperature as in other oceans. Third, a significant share of the ocean accounts for shallow marginal seas and high underwater ridges ident the bottom of its deep part (Church, 2013).
A multi-layer hybrid model of the general circulation of the ocean was developed. Calculations were carried out at the nodes of the grid in increments of 2 ° in latitude, that is, about 220 km. Water column in the ocean was divided vertically into 6 layers. The salinity of the adjacent layers differs by approximately 0.8%. The bottom relief was set in very general terms but retained all the basic features of nature. Run-off of the main rivers flowing into the ocean was taken into account. The additional continental run-off was distributed evenly throughout the border region.
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The results of calculation revealed the response of the ocean to the greenhouse effect. The weighted average warming throughout the depth of the ocean was about 1,5 ° C, which is less than in the whole northern hemisphere. It is caused by the fact that the top layer of the ocean turned out to be greatly desalinated due to the melting of ice and increase in river flow. Warmer, fresh, and, therefore, less dense water, accumulating in the upper layer prevents the penetration of heat into the lower layers. The melting of sea ice due to warming has been so strong that the area is reduced by 80% in the summer months (Church, 2013).
Violation of the vertical convection of ocean waters (the greatest warming in the upper layer) causes the restructure of the entire ocean circulation. More specifically, both the increased rate of wind flow and lowered depth of ice result in the expansion of the ridge concentrate. Such changes of the climate will inevitably have consequences not only on the water area, but also on coastal areas. Thus, the rise in sea level due to warming will be from 0.1 to 0.2 m, which could flood large rivers, especially in Siberia (Church, 2013).
The area of Arctic sea ice which was gradually decreasing since the beginning of satellite observations in 1979 reached the absolute minimum in 2005 ( Danilov et al. 2004). Fast (fixed) ice takes about 29% of the areas of the Arctic seas in winter. During the observation period from 1930, the change in the total area of fast ice in the Arctic seas occurred by 470-800 thousand km2. The minimum area of fast ice was observed in 1995. On average, over the last 20 years the total area of fast ice in comparison with the same previous period decreased by 20 thousand km2, which is only 3% of the average area ( Danilov et al. 2004). In general, inter-annual fluctuations in the area of fast ice distribution and its thickness do not show significant decreases, confirming the lower sensitivity of the winter ice growth to changes in air temperature.
The indicators of the approaching summer outflow of the sea ice from the Artic seas by the middle of XXI century are the fact that during the last five years there has been a speedy reduction of summer ice areas and the calculations made by the global climate models. Moreover, the previously mentioned calculations indicate that by the end of the century during the summer season the ice will completely disappear (Danilov et al., 2004).
Much less information is available about the thickness of the drifting ice. An analysis of the distribution of rainfall in the Arctic basin collected by submarines of the US and the UK, showed, in particular, a reduction of the average thickness of ice by about 42% (from 3.1 to 1.8 m) from 1958-76 for 1993-99(Yu, Maykut, and Rothrock). The total volume of ice has decreased by almost 32%. (Yu, Maykut, and Rothrock). However, these estimates were obtained from incomplete measurement of the coverage of Arctic basin. Thus, there are doubts in their representation due to the possible movement of multiyear ice outside the field observations.
Permafrost reacts to climate change, and this is due to the penetration of air temperature fluctuations into the rocks. The depth of this penetration is directly dependent on the length and amplitude of the oscillation period. Thus, 5 to 8 thousand years ago warming of climatic optimum changed the temperature field of powerful permafrost that existed around 20 – 18 thousand years ago, to a depth of approximately 400 meters (The UNEP). In the northern regions of Western Siberia, the North of Europe and the south of the Arctic Circle, the warming led to the thawing of permafrost on top by 100 – 200 meters (The UNEP). Although permafrost is preserved from below, the temperature rose almost to zero degrees. The impact of the smaller cycles of temperature was not significant, since their periods were shorter and amplitude was smaller. Thus, cooling, which occurred between 2 and 4 thousand years ago, penetrated to a depth of only 130 – 150 meters (The UNEP).
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In Western Siberia, at the latitude of the Arctic Circle, there is a two-layer frozen ground, the upper layer of which starts from the ground and responds to the current climate. The lower layer, which is separated from the upper one by the hundred-meter layer of rock, is the residue of the ancient permafrost; it is the so-called relict permafrost. Thus, in the natural course of evolution, the temperature field of permafrost was completely rebuilt, mainly in accordance with the large 35-40-millennial cycles of fluctuations in air temperature (The UNEP). Permafrost after cooling increases into the depth and as well the area of distribution.
During the past 19 years, the sea level near the coast raised by the extra 2 cm compared to the average around the world. The reason for this is fresh water formed from the melting of glaciers. The rapid rise in sea level was discovered by studying satellite imagery, giving information about the territory of more than one million square kilometers (Church, et al, 2013). The melting of the Antarctic ice sheet and the thinning of the continental shelf, that is floating glaciers contributed to the release of about 350 gigatons of fresh water, which led to a decrease in the salinity of the surrounding oceans. Fresh water is less dense than salt water; therefore, in regions where fresh water has increased, the local sea-level rise can be expected. A particular concern of the ecologists is the so-called enhancing effect of reducing snow and ice sheets in the Arctic. The surface of the soil and the polar oceans, opening due to the melting of ice, absorbs more solar heat that, in turn, could further accelerate the pace of climate change.
In addition, experts indicate that thawing of permafrost can lead to the release of ancient greenhouse gases stored in them. The upper part of permafrost in northern and arctic ecosystems contains about 70 billion tones of organic carbon (McBean, 2005). This is ten times more than the amount of CO2 that is emitted into the atmosphere each year because of human activities. In addition, the researchers studied the effect of underwater permafrost degradation on climate. As a result, researchers have found that at a depth of 60-100 meters in the ice lay about 500 anomalous fields of methane emissions. Melting glaciers release gas into the atmosphere. The underwater permafrost has been in contact with the bottom warm water for approximately 9-10 thousands of years. This is enough to ensure that it thawed. In the worst scenario, up to 5% glacial gases can release into the atmosphere, leading to an abrupt increase in the concentration of methane in the air (McBean, 2005). This in turn will lead to catastrophic consequences.
Besides, abrupt changes in the Arctic climate have an impact on the existence of the polar animals. Arctic ice is a habitat for many marine mammals. Ringed seals, polar bears and other polar animals, which go into hibernation for winter, experience the critical period in the spring. Malnutrition, in recent years, has a negative effect on the health of polar bears, especially pregnant females and calves who have deteriorated markedly. The level of fertility has fallen; the number of cubs younger than one year has reduced, and their average weight became 15% smaller (Allsopp, Santillo & Johnston, 2012). Moreover, the other major species of marine mammals suffer from the shift of the ice edge from the shore. The main food for walrus is bottom mollusks, and due to the increasing distance of the ice floes from the coast, the depth for walruses to get food increases as well (Allsopp, Santillo & Johnston, 2012).
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Global climate models, which consider the increase of greenhouse gas emissions, have estimated the changes of climate in the Arctic. They predict that by the middle of XXI century a notable increase of air temperature will lead to a continuous warming during the wintertime. The observed warming of the Arctic and particularly its possible increase in the future leads to the degradation of glaciers and permafrost in the arctic land. In general, it can be said that the climate of the Arctic Basin will be warmer and more humid, storm winds will intensify, and the area of ice in the ocean will reduce almost to zero in summer. Permafrost is highly sensitive to climate change. Melting may lead to the uncontrolled release of methane and carbon dioxide. The consequences of this process are unpredictable. Today this area is continuously experiencing different studies. However, the topic is still unexplored.