Rapid irreversible melting of one third to two thirds of earth's permafrost, will add huge amounts of greenhouse gases to the atmosphere, accelerating warming, reports the National Ice and Snow Data Center (NSIDC). Permafrost melt lakes portend the destabilization of the Arctic's landscapes and ecosystems and emissions of greenhouse gases CO2 and CH4.
The NSIDC model study makes "conservative" assumptions, such as no methane production and no temperature feed backs that accelerate melting. These assumptions make the models tend to underestimate the actual rate of change. The model predicts a peak in melting and CO2 emissions in 100 years, but methane and feedback loops could cause the peak to come sooner. The total quantity of carbon is calculated out to the year 2200.
"The amount of carbon released is equivalent to half the amount of carbon that has been released into the atmosphere since the dawn of the industrial age,” said NSIDC scientist Kevin Schaefer. “That is a lot of carbon.”
The models predict the irreversible melting of permafrost releasing a cumulative permafrost carbon flux to the atmosphere of 190 ± 64 Gt C.
The thaw and release of carbon currently frozen in permafrost will increase atmospheric CO2 concentrations and amplify surface warming to initiate a positive permafrost carbon feedback (PCF) on climate. We use surface weather from three global climate models based on the moderate warming, A1B Intergovernmental Panel on Climate Change emissions scenario...
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We predict that the PCF will change the arctic from a carbon sink to a source after the mid-2020s and is strong enough to cancel 42–88% of the total global land sink.
Irreversible melting of permafrost is a feedback loop that can be avoided only by rapid reduction in greenhouse gas emissions. Once the melting accelerates the feedback loops may make permanent melting impossible to stop. Moreover, much of the carbon is likely to be released as methane which is produced in wet ground and lakes by bacterial degradation of carbon. Methane is 25 times as strong a greenhouse gas as CO2 over 100 years.
Enormous amounts of carbon are stored as frozen peat.
Peat is a soil type containing at least 90% organic matter. The spongy stuff forms where vegetation accumulates faster than it decomposes, particularly in acidic, anaerobic wetlands dominated by Sphagnum mosses, which are resistant to decay. Peatlands represent large accumulations of carbon in the form of plant material. Today, about 1/3 of all carbon contained within the world’s soils is stored in present and ancient peat reservoirs. Only a small percentage of peatlands are in areas with permafrost (the Seward Peninsula being one example), but, during times of rapid peatland expansion, Jones says, carbon accumulates quickly in these regions where it remains stored in permafrost until warmer climates thaw the permafrost and release the carbon back into the atmosphere. The effects of the sudden carbon release in the form of methane gas may have important consequences to an already warming climate.
Melting permafrost may cause collapse structures to form. Melted ground is unstable, posing challenges to maintaining roads, buildings and oil and gas pipelines.
Photo credits go to the Polar Field Services Newsletter blog.
Hat tip to Joe Romm at Climate Progress.