Old permafrost carbon released

Aug 19, 2013 by Peter Rüegg
Eurasian arctic rivers transport carbon into the Polar Sea. Analyzes show that carbon is released from the permafrost. Credit: Jorien Vonk

Using indicator molecules, a team of researchers headed by ETH Zurich demonstrates that carbon stored in the Arctic permafrost is being mobilised in Eurasian river basins.

Arctic soils store vast amounts of in the form of dead but not decomposed plant debris. Around half of the global reservoir is stored in these permanently frozen Arctic soils. Through global warming, however, the permafrost is thawing to increasing depths, which may mobilise the carbon stored within. The amount of water drainage from rivers such as the Yenisey and the Ob in Siberia or the Kalixälven in Northern Sweden, which drain vast land areas, has also changed. Due, among other things, to a changing precipitation regime, these rivers are conducting more water away into the seas than a few decades ago, also transporting the carbon from their basins towards the sea. The main concern for scientists is that the activity of microbes or other organisms that live off organic matter and exhale CO2 could cause carbon that has been stored for thousands of years to get back into the atmosphere – and in a big way.

Age of tracer molecules determined using carbon dating

Consequently, researchers from ETH Zurich and the University of Stockholm set about finding out whether "old" carbon from permafrost areas of Arctic Eurasia is being mobilised and transported through large river basins, ranging from Northern Sweden to Eastern Siberia, to the sea. They took from near the mouths of these rivers and isolated three types of carbon compounds, the sources of which could clearly be identified. These so-called tracer compounds include derived from lignin, a rigidifying in higher plants, plant waxes that form a protective coating on leaf surfaces, and a group of compounds abundant in mosses. The researchers were able to determine the age of these molecules using radiocarbon dating.

First concrete evidence of mobilisation

Based on this age diagnosis, the research team headed by Timothy Eglinton, a professor of biogeoscience at the Department of Earth Sciences, were for the first time able to assess contributions of old carbon from permafrost soils to riverine carbon. Furthermore, the scientists were able to demonstrate that permafrost soils where the frozen areas are interspersed with gaps release more old carbon than those where the permafrost is uninterrupted. This coincides with the different permafrost profiles that Eurasia exhibits from west to east. "In Far Eastern Siberia, the majority of the mobilised carbon comes from the surface layers," says Eglinton. In the European part of Eurasia and Western Siberia, however, water can penetrate the soil between the frozen permafrost areas more effectively, release the carbon previously stored for thousands of years, and carry it to the sea.

Using carbon dating, the geoscientists were able to measure age differences of up to 13,000 years between young and old terrestrial components. "The age difference between the various carbon sources is particularly great in the Arctic due to the release of old permafrost carbon," says Xiaojuan Feng, a postdoc under Eglinton and first author on the study just published in PNAS. This leads the researchers to the conclusion that lignin represents a tracer of surface carbon sources and plants waxes reflect old permafrost.

Carbon thousands of years old released

Based on documented changes in river discharge and on relationships of radiocarbon age of lignin tracer molecules with water run-off from the , the researchers calculated that the proportion of carbon from permafrost has increased by five per cent in the last twenty years. "While masked by changes in other carbon sources, mobilisation of the carbon from the once deep-frozen soils appears well underway," says Eglinton. This proportion of this carbon is still fairly modest, and how it will change in the future remains unclear. "Nevertheless, our new results go a long way towards helping us to understand and assess the links between climate warming and the behaviour of different carbon sources in the Arctic more effectively," stresses Eglinton. It will now be interesting to extend the molecule-specific carbon dating analyses to other sediment archives in order to examine the release of carbon from Arctic permafrost soils and the past climate more effectively.

Explore further: The Arctic is especially sensitive to black carbon emissions from within the region

More information: Feng X, et al. Differential mobilization of terrestrial carbon pools in Eurasian Arctic river basins. PNAS Early Edition, published online 12 August 2013. DOI: 10.1073/pnas.1307031110

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User comments : 6

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Going
2.3 / 5 (6) Aug 19, 2013
This is bad news.
tadchem
1 / 5 (6) Aug 19, 2013
The good side of this is that, like carbon from fossil fuels, the naturally occurring radioactive material carbon-14, perhaps the most mutagenic substance in the environment due to its ubiquitous presence and extreme efficiency at damaging the DNA into which it becomes incorporated, is quite depleted in 'old' permafrost carbon.
NikFromNYC
1.9 / 5 (15) Aug 19, 2013
(1) Going: Expansion of the biosphere is bad news?

(2) tadchem: The "hormesis" hypothesis is that small amounts of radioactivity have the tonic effect of safely stimulating DNA repair mechanisms in healthy organisms.
http://en.wikiped...hormesis

(3) From this paper about Siberia: "Mean monthly temperatures recorded at climatic stations in the six watersheds from 1955 to 2004 were obtained from the Global Historical Climatology Network Monthly. In total, 102 climatic stations were identified within the great Russian Arctic river (GRAR) watersheds...."

The oldest Siberian thermometer stations go back to the late 1800s and they are stubbornly refusing to notice CO₂ enough to stop hugging their boring old natural warming trendline:
http://berkeleyea...s/169900
http://berkeleyea...s/169812

Almost *all* old thermometer records merely continue their old trends, immune to the postwar CO₂ boost: http://s24.postim...nous.gif
RealityCheck
2 / 5 (11) Aug 19, 2013
Hi NikFromNYC. Re your glib but facile retort to "Going's" brief observation on that news
Quoting NikFromNYC to Going: "Expansion of the biosphere is bad news?"


Yes, Nik, especially in Transition Period, as NET result is that more and more carbon is released into the atmosphere, beyond that already being released in current biosphere and human/industrial activity. This "expansion of biosphere" local rates/maximum biota increase potential at high latitudes in no way compensates for initial/ongoing increased releases of previously permafrost-locked-up carbon reservoir.

Extreme/unsettled events/patterns; ie, NEWLY FLUCTUATING 'patterns' which affect established crop germination, growth and maturation/harvesting (too late frosts in Spring killing off flowering stage; too late rains in Autumn rotting crop) 'cycles' which we depend on for our 'food security'. Not to mention dire effects on TRANSPORTATION and INFRASTRUCTURE. Huge losses,expense and uncertainty all round! Not good.
erich_knight
1 / 5 (7) Aug 20, 2013
In a greenhouse More CO2 is good, up to 1000 PPM in fact. Our atmospheric GH is quite different.
The only way More CO2 would be good is if we had a massive program to thermally convert biomass C, (collected CO2) into pyrolytic-Carbon char to build soil carbon.

Agronomics & Renewable Energy;
Biologically structured Carbons from Biomass; Charcoal, Plant-Coal, the elemental Carbon of the basic plant cell structure is the pyrolitic Carbon which has held my interest for the past seven years. A renown Australian climate scientist, the late, Dr. Peter Read coined the term "Biochar" for charcoal used in the soil and calculated the soil carbon building potentials to drawdown CO2e. This term embraced, has made Google filtering, to follow the exponential rates of publications in the last few years, a simple task.
erich_knight
1 / 5 (6) Aug 21, 2013
Please take a look at this video by the CEO of CoolPlanet Biofuels, guided by Google's Ethos and funding, along with GE, BP and Conoco, they are now building the farm scale reactors that convert 1 ton of biomass to 75 gallons of bio–gasoline and 1/3 ton Biochar for soil carbon sequestration. The price of production, from field to tank is $1.25/gallon.
If it's good enough for Google… It's good enough for me;
http://www.youtub...VlZ9v_0o