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Permafrost
Permafrost is the frozen soil of the tundra, composed of decaying bacteria and plants. The temperature must stay below zero degrees Celsius, or 32 degrees Fahrenheit, for two consecutive years for permafrost to be considered permanent. Once permanent, permafrost can stay in that condition for long periods of time, well over a thousand years. Soil that freezes in the winter and then thaws in the summer is considered seasonal permafrost. As part of the tundra the permafrost constantly changes. Dig down in the summer through the thawed seasonal permafrost until you strike the permanent permafrost. In some years you may have to dig quite awhile, while other years the dig is short.
Composition
According to the Discovery Channel News, the permanent permafrost in the tundra contains 100 billion tons of carbon within its first meter of depth. That carbon, which represents 10 years' worth of emissions from human activity, remains locked up as long as the permafrost remains permanently frozen. That translates into nearly 40 percent of the world's soil carbon in the tundra of Canada, Alaska and Siberia. Also trapped in the permafrost of the northern tundra is methane. Over time as the temperature rises, the permafrost will thaw, releasing the carbon and methane into the atmosphere. The resulting warming effect is already occurring.
Rising Temperatures
Research continues at locations like Toolik Field Station in northern Alaska concerning the effects of rising temperatures on the tundra. The tipping point for melting permafrost remains at zero degrees Celsius. Current data suggest that the temperatures are close to that point. As temperatures rise, the character of the tundra changes. Small shrubs and boreal forests start to appear on the barren landscape, supported by the warmer temperatures. The trapped carbon and methane are released into the atmosphere. Some of the released carbon dioxide is absorbed by the shrubs and trees; the exact amount is unknown.
Thermokarst
Rising temperatures cause the permafrost to melt and the ground to collapse. Instead of hard, frozen soil there is warm, marshy soil. The end result is a thermokarst, or a hollow place in the ground.The presence of thermokarsts is a sign of rising temperatures and melting permafrost. Although they are a natural part of the changing tundra, evidence shows that they are increasing in number and size. According to Smithsonian.com, aerial photographs from the 1980s reveal that thermokarsts were much less prevalent during that decade as compared to 25 years later.