Permafrost Loss est
Estimates of permafrost loss... consequences
November 30, 2015
http://www.usgs.gov/newsroom/article.asp?ID=4400
Using statistically modeled maps drawn from satellite data and other sources, U.S. Geological Survey scientists have projected that the near-surface permafrost that presently underlies 38 percent of boreal and arctic Alaska would be reduced by 16 to 24 percent by the end of the 21st century under widely accepted climate scenarios. Permafrost declines are more likely in central Alaska than northern Alaska.
Northern latitude tundra and boreal forests are experiencing an accelerated warming trend that is greater than in other parts of the world. This warming trend degrades permafrost, defined as ground that stays below freezing for at least two consecutive years. Some of the adverse impacts of melting permafrost are changing pathways of ground and surface water, interruptions of regional transportation, and the release to the atmosphere of previously stored carbon.
“A warming climate is affecting the Arctic in the most complex ways,” said Virginia Burkett, USGS Associate Director for Climate and Land Use Change. “Understanding the current distribution of permafrost and estimating where it is likely to disappear are key factors in predicting the future responses of northern ecosystems to climate change.”
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https://en.wikipedia.org/wiki/Permafrost
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https://en.wikipedia.org/wiki/Tundra
A severe threat to tundra is global warming, which causes permafrost to melt. The melting of the permafrost in a given area on human time scales (decades or centuries) could radically change which species can survive there.
Another concern is that about one third of the world's soil-bound carbon is in taiga and tundra areas. When the permafrost melts, it releases carbon in the form of carbon dioxide and methane, both of which are greenhouse gases. The effect has been observed in Alaska. In the 1970s the tundra was a carbon sink, but today, it is a carbon source. Methane is produced when vegetation decays in lakes and wetlands.
The amount of greenhouse gases which will be released under projected scenarios for global warming have not been reliably quantified by scientific studies, although a few studies were reported to be underway in 2011. It is uncertain whether the impact of increased greenhouse gases from this source will be minimal or massive.
https://en.wikipedia.org/wiki/Methanogenesis
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A self-reinforcing positive feedback loop is akin to a "vicious circle": It accelerates the impacts of anthropogenic climate disruption (ACD). An example would be methane releases in the Arctic. Massive amounts of methane are currently locked in the permafrost, which is now melting rapidly. As the permafrost melts, methane - a greenhouse gas 100 times more potent than carbon dioxide on a short timescale - is released into the atmosphere, warming it further, which in turn causes more permafrost to melt, and so on...
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Predicted rate of temperature change in Arctic
Arctic temperatures are expected to increase at roughly twice the global rate. The Intergovernmental Panel on Climate Change (IPCC) will in their fifth report establish scenarios for the future, where the temperature in the Arctic will rise between 1.5 and 2.5°C by 2040 and with 2 to 7.5°C by 2100. Estimates vary on how many tons of greenhouse gases are emitted from thawed permafrost soils. One estimate suggests that 110-231 billion tons of CO2 equivalents (about half from carbon dioxide and the other half from methane) will be emitted by 2040, and 850-1400 billion tons by 2100. This corresponds to an average annual emission rate of 4-8 billion tons of CO2 equivalents in the period 2011-2040 and annually 10-16 billion tons of CO2 equivalents in the period 2011-2100 as a result of thawing permafrost. For comparison, the anthropogenic emission of all greenhouse gases in 2010 is approximately 48 billion tons of CO2 equivalents. Release of greenhouse gases from thawed permafrost to the atmosphere may increase global warming.
https://en.wikipedia.org/wiki/Permafrost#Carbon_cycle_in_permafrost
