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Tuesday, February 17, 2009

Burp of Arctic laughing gas is no joke

by Angela Self

The arctic tundra, shown here looking to the Ural Mountains, periodically releases nitrous oxide (Photo courtesy Pertti Martikainen)

The arctic tundra, shown here looking to the Ural Mountains, periodically releases nitrous oxide (Photo courtesy Pertti Martikainen)


It seems the Arctic is belching out nitrous oxide – commonly known as laughing gas. Unfortunately, the punchline is that it is a powerful greenhouse gas.

Previously, emissions of N2O were thought to enter the atmosphere mainly from tropical forests and intensively managed farmland, with only a negligible amount from northerly environments.

Maija Repo and colleagues from the University of Kuopio, Finland, measured emissions from peat circles in northern Russia. These sit on peatland plateaux, which are widespread throughout the Arctic, covering 20% of the total land surface. The bare surfaces of peat circles develop because cycles of freezing and thawing churn up the peat, preventing plant growth.

During the snow-free season, they found the peat circles emitted 1.2 grams/m2 of N2O, which is just as much as tropical forests release in a year. The team reckons that a lack of plants decreases competition for the mineral nitrogen. This allows nitrate to accumulate in the soil which is then metabolised by bacteria to produce N2O.

Although this means N2O remains a small contributor to the greenhouse effect, compared with methane and carbon dioxide, the gas persists unaltered in the atmosphere for over 110 years, compared with around 10 years for methane – which is also periodically released by the tundra.

Unfortunately, global warming may promote churning, and expand bare areas. Since the flow of the gas from the peat circles is so high, even a small increase in bare surfaces would cause significant changes in N2O emissions, says Repo.

Original here

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