A 2009 study by ecologists estimated that Arctic lands and oceans are responsible for up to A 2009 study by ecologists estimated that Arctic lands and oceans are responsible for up to 25 percent of the global net sink of atmospheric carbon dioxide. Under current predictions of global warming, this Arctic sink could be reversed, accelerating predicted rates of climate change.
The vast amount of carbon stored in the Arctic and boreal regions of the world is more than double that previously estimated. The new estimate is over 1.5 trillion tons of frozen carbon, about twice as much carbon as contained in the atmosphere (Global Carbon Project 2009).
The doubled amount of permafrost carbon is mostly potential methane as it thaws, creating a wet environment. (If permafrost is dry when it thaws, it emits CO2.) Also recently, it has been found that cryroturbation of thawing permafrost emits a burst of extra methane when it refreezes and also a large amount of nitrous oxide, another potent greenhouse gas.
A 2009 review of Arctic carbon and its response to warming is Sensitivity of the carbon cycle in the Arctic to climate change by S.Macguire. The Arctic is a substantial source of CH4 to the atmosphere (between 32 and 112 TgCH4/yr), primarily because of the large area of wetlands throughout the region.
The most authoritative assessment of Arctic methane was published 2010 Possible role of wetlands, permafrost, and methane hydrates in the methane cycle under future climate change: A review.
... significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out.
We have reviewed the available scientific literature on how natural sources and the atmospheric fate of methane may be affected by future climate change.
We discuss how processes governing methane wetland emissions, permafrost thawing, and destabilization of marine hydrates may affect the climate system.
It is likely that methane wetland emissions will increase over the next century.
Uncertainties arise from the temperature dependence of emissions and changes in the geographical distribution of wetland areas.
Another major concern is the possible degradation or thaw of terrestrial permafrost due to climate change. The amount of carbon stored in permafrost, the rate at which it will thaw, and the ratio of methane to carbon dioxide emissions upon decomposition form the main uncertainties.
Large amounts of methane are also stored in marine hydrates, and they could be responsible for large emissions in the future. The time scales for destabilization of marine hydrates are not well understood and are likely to be very long for hydrates found in deep sediments but much shorter for hydrates below shallow waters, such as in the Arctic Ocean.
Uncertainties are dominated by the sizes and locations of the methane hydrate inventories, the time scales associated with heat penetration in the ocean and sediments, and the fate of methane released in the seawater.
Overall, uncertainties are large, and it is difficult to be conclusive about the time scales and magnitudes of methane feedbacks, but significant increases in methane emissions are likely, and catastrophic emissions cannot be ruled out.
A 2011 Nature paper by E. Schuur and B. Abbott Northern soils will release huge amounts of carbon in a warmer world, say Edward A. G. Schuur, Benjamin Abbott and the Permafrost Carbon Network.- estimates the amount of carbon vulnerable for release by 2100 is 1.7–5.2 times larger than those reported in previous modelling studies.
The estimated carbon release from this degradation is 30 billion to 63 billion tonnes of carbon by 2040, reaching 232 billion to 380 billion tonnes by 2100 and 549 billion to 865 billion tonnes by 2300. These values, expressed in CO2equivalents, combine the effect of carbon released as both CO2 and as CH4.
Scientists estimate from latest research that 40 percent of total terrestrial organic carbon is locked away in Arctic soil.
Global warming projections to not include extra carbon emissions from permafrost
The IPCC 2007 and 2014 assessments do not include feedback additional warming from Arctic carbon. UNEP December 2012. Though this from UNEP refers to permafrost, all Arctic carbon is being omitted by the IPCC models projecting future global warming.
Estimate of vulnerable carbon increased - AGU 2012
Arctic land based carbon is contained in permafrost, wetlands (peat), and the Boreal forerst.
In large part they erxist together. Wetlands and tundra can exist above permafrost, and trees can grow above permafrost in tundra. A lot of the permafrost region thaws to some extent and freezes seasonally.
11 Feb 2016 Alaska New study suggests northern tundra shifting from carbon sink to carbon source.
2015 Expert Survey Permafrost Zone Carbon Balance Survey.