6 April 2010

Permafrost soil and laughing gas

Laughing gas (N2O) is 300 times worse than carbon dioxide (CO2) in connection with the emission of greenhouse gases into the atmosphere and the depletion of the ozone layer. The nitrogen gas with the amusing name has not been preeminent in the public debate on these issues compared to the chlorine-rich CFC gases along with methane and carbon dioxide. Brand-new research, however, turns all this on its head. For the first time, research results from northwestern Greenland document that thawing permafrost can cause surprisingly high levels of laughing gas in the environment, which may potentially be released into the atmosphere. And, if laughing gas is released in combination with higher temperatures and increased precipitation in regions with permafrost, this would mean that we face a hitherto unknown and important component in relation to the issue of global warming. Professor in Environmental Geochemistry, Bo Elberling of Department of Geography and Geology (DGG), is responsible for the extraordinary research results, which are now to be published in the esteemed scientific journal, Nature Geoscience.

Not a laughing matter Drilling in greenland

The increased presence of N2O in the Arctic is not a laughing matter. New studies carried out by the research station Zackenberg in northeastern Greenland show that the thawing of the permafrost produces surprisingly large amounts of laughing gas, which can negatively impact the depletion of the ozone layer and the atmospheric content of greenhouse gases.

- "Not only Zackenberg in northeastern Greenland has produced these results, but five other localities in the Arctic region have as well. I've preserved samples from earlier studies. And it turns out that samples contain correspondingly high levels of dissolved nitrogen, and have a similar potential for producing laughing gas. Presumably, the Zackenberg locality is not in the high end of the scale. The explanation for the whole debacle is that the microorganisms capable of producing laughing gas are apparently already present in the permafrost. In addition to this, the ice content in the permafrost can be quite substantial, but at the same time contain surprising quantities of dissolved nitrogen, which, when it is broken down, in turn may be transformed into laughing gas and, in the final instance, be released into the atmosphere," Professor Bo Elberling points out.

Laughing gas in the ozone layer and plant life in the cold North

Since the year 1800, the atmospheric content of laughing gas has risen significantly. Approx. 70% of this increase has been caused by the natural process of microorganisms breaking down nitrogen in the soil, while the remaining 30% has been caused by something connected more directly with human activity, primarily the intensification of agricultural production involving more fertilizer and more animals. Laughing gas contributes significantly to the depletion of the ozone layer in the upper part of the atmosphere (the stratosphere). In the lower part of the atmosphere (the troposphere, which is at an altitude of 10 km), laughing gas is 300 times worse than carbon dioxide, CO2, in its effects as a greenhouse gas. This equation should be compared with the fact that methane gas, which has been the great culprit among the greenhouse gases, "only" is 23 times worse than CO2.

- "The new studies show that the natural production of laughing gas in the soil of Arctic regions can potentially reach levels which have hitherto only been observed in tropical areas. In other words, a hitherto unknown store of nitrogen is buried in the frozen soil of many Arctic regions, especially in marshlands. This large store can easily be transformed into laughing gas because the area of newly-thawed permafrost in the future will experience considerable variations in water content and freeze-thaw cycles year by year," says Professor Elberling.

Research results also point in the direction that this nitrogen store in newly thawed permafrost may be decisive for how Arctic plant communities respond to warmer climate conditions. This is due to the fact that nitrogen acts as a fertilizer, thereby increasing the plants' growth rate, which in turn means that plants will grow larger and thereby be able to absorb more carbon from the atmosphere than earlier presumed. In this context the story has a positive spin.

The thawing of the upper layer of permafrost is happening gradually and increases its rate by approx. 1 cm annually. The problem in connection with the natural production of laughing gas in cold, northern regions has to do with the interplay of frost and thaw periods and the drying-out of the soil during warm months followed by precipitation.


For further information, contact Professor Bo Elberling, Department for Geography and Geology, University of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K. Mobile: 23 62 84 53, e-mail: be@geo.ku.dk