ARCTIC NITROUS OXIDE FEEDBACK
Arctic soils store tremendous amounts of organic matter. Over millennia, cold, wet conditions have slowed the breakdown of plant material in the Arctic, and large quantities of carbon and nitrogen have built up in permanently frozen ground - permafrost.
The possibility that the warming would emit nitrous oxide (N2O) was published many years ago.
Nitrous oxide is an extremely powerful greenhouse gas.
Its global warming capacity is nearly 300 times CO2 and it lasts in atmosphere 115 years.
It is currently rising rapidly in the atmosphere.
May 2017, C.Voigt, PNAS. Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw. Vast stocks of nitrogen (>67 billion tons) in the permafrost, accumulated thousands of years ago. We report that the Arctic may become a substantial source of N2O when the permafrost thaws, and that N2O emissions could occur from surfaces covering almost one-fourth of the entire Arctic.
Nitrous oxide is now the main ozone depleting chemical.
Nature Geoscience 15 February 2009
Maija E. Repo, Sanna Susiluoto, Saara E. Lind, Simo Jokinen, Vladimir Elsakov, Christina Biasi, Tarmo Virtanen & Pertti J. Martikainen
Nitrous oxide is a potent greenhouse gas whose concentration is increasing in the atmosphere1. So far, the highest terrestrial nitrous oxide emissions have been measured in agricultural and tropical soils2, 3, and nitrous oxide emissions from northern natural soils have been considered negligible4, 5. Pristine tundra, one of the largest natural land cover types in the world, is a mosaic of different surface types including bare surfaces created by cryoturbation6, 7. Here we used a static chamber method to measure nitrous oxide emissions from the discontinuous permafrost zone in subarctic East European tundra. We show that nitrous oxide emissions from bare peat surfaces in the region, known as peat circles, range between 0.9 and 1.4 g nitrous oxide m-2 from June to October, and are equivalent to those from tropical and agricultural soils. Extrapolation of our data to the whole Arctic reveals that the emissions from these hot spots could amount to 0.1 Tg nitrous oxide yr-1, corresponding to 4% of the global warming potential of Arctic methane emissions at present. Therefore, not only carbon, but also nitrogen stored in permafrost soils, has to be considered when assessing the present and future climatic impact of tundra.
Re-wetting of previously thawed permafrost could increase nitrous oxide production by 20-fold. Soil science: Arctic thaw
Nature Geoscience 2010
Hermann F. Jungkunst
The organic matter stored in frozen Arctic soils could release significant quantities of carbon dioxide and methane on thawing. Now, laboratory experiments show that re-wetting of previously thawed permafrost could increase nitrous oxide production by 20-fold.
Nature Geoscience 26 May 2010
Bo Elberling et al
Permafrost soils contain nearly twice as much carbon as the atmosphere1. When these soils thaw, large quantities of carbon are lost, mainly in the form of methane and carbon dioxide.In contrast, thawing is thought to have little impact on nitrous oxide emissions, which remain minimal following the summer thaw4. Here, we examined the impact of thawing on nitrous oxide production in permafrost cores collected from a heath site and a wetland site in Zackenberg, Greenland. Rates of nitrous oxide production in the heath soil were minimal, regardless of the hydrological conditions. Although rates of nitrous oxide production in the wetland soil were low following thawing, averaging 1.37 μg N h−1 kg−1, they were 18 μg N h−1 kg−1 for permafrost samples following thawing, drainage and rewetting with the original meltwater. We show that 31% of the nitrous oxide produced after thawing and rewetting a 10-cm permafrost core—equivalent to 34 mg N m−2 d−1—was released to the atmosphere; this is equivalent to daily nitrous oxide emissions from tropical forests on a mean annual basis 10. Measurements of nitrous oxide production in permafrost samples from five additional wetland sites in the high Arctic indicate that the rates of nitrous oxide production observed in the Zackenberg soils may be in the low range.
Kevin Randall et al , Journal of Geophysical Research: Oceans
Nitrous oxide (N2O) contributes ∼6% of the total radiative forcing from long-lived greenhouse gases. While tropospheric concentrations have increased by 20% since the beginning of the industrial revolution, sources and sinks of N2O are still poorly quantified. In the Arctic, N2O atmospheric concentrations vary seasonally, due mainly to vertical mixing. The contributions of local natural sources to this cycle are still unknown. Here we report on N2O measurements conducted in the bottom 10 cm of the sea ice and in the underlying surface water (USW) from late March to early May 2008 in the southeastern Beaufort Sea and Amundsen Gulf. Bulk N2O concentrations in ice were low (∼6 nM) and were consistently undersaturated with respect to the USW (∼40% saturation) and the atmosphere (∼30% saturation). Loss of N2O via brine rejection during sea ice formation in fall and winter can explain these low N2O ice concentrations. An unknown fraction of this rejected N2O is likely ventilated to the atmosphere either directly from the ice or through leads during ice formation, while in spring and early summer, melting of the N2O-depleted sea ice is expected to lower the partial pressure of N2O of newly open waters which could act as a sink for atmospheric N2O. These first measurements indicate that sea ice formation and melt has the potential to generate sea-air or air-sea fluxes of N2O, respectively.