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| Titel |
Enhanced greenhouse gas emissions from the Arctic with experimental warming |
| VerfasserIn |
Carolina Voigt, Richard E. Lamprecht, Maija E. Marushchak, Saara E. Lind, Alexander Novakovskiy, Mika Aurela, Pertti J. Martikainen, Christina Biasi |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137699
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| Publikation (Nr.) |
 EGU/EGU2017-495.pdf |
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| Zusammenfassung |
| Temperatures in the Arctic are projected to increase more rapidly than in lower latitudes.
With temperature being a key factor for regulating biogeochemical processes in ecosystems,
even a subtle temperature increase might promote the release of greenhouse gases
(GHGs) to the atmosphere. Usually, carbon dioxide (CO2) and methane (CH4)
are the GHGs dominating the climatic impact of tundra. However, bare, patterned
ground features in the Arctic have recently been identified as hot spots for nitrous
oxide (N2O). N2O is a potent greenhouse gas, which is almost 300 times more
effective in its global warming potential than CO2; but studies on arctic N2O fluxes are
rare.
In this study we examined the impact of temperature increase on the seasonal GHG
balance of all three important GHGs (CO2, CH4 and N2O) from three tundra surface types
(vegetated peat soils, unvegetated peat soils, upland mineral soils) in the Russian Arctic (67˚
03’ N 62˚ 55’ E), during the course of two growing seasons. We deployed open-top
chambers (OTCs), inducing air and soil surface warming, thus mimicking predicted warming
scenarios. We combined detailed CO2, CH4 and N2O flux studies with concentration
measurements of these gases within the soil profile down to the active layer–permafrost
interface, and complemented these GHG measurements with detailed soil nutrient (nitrate
and ammonium) and dissolved organic carbon (DOC) measurements in the soil pore water
profile.
In our study, gentle air warming (∼1.0 ˚ C) increased the seasonal GHG release of all
dominant surface types: the GHG budget of vegetated peat and mineral soils, which together
cover more than 80 % of the land area in our study region, shifted from a sink to a source of
-300 to 144 g CO2-eq m−2 and from -198 to 105 g CO2-eq m−2, respectively. While the
positive warming response was governed by CO2, we provide here the first in situ evidence
that warming increases arctic N2O emissions: Warming did not only enhance N2O emissions
from the known arctic N2O hot spots (bare peat soils; maximum seasonal release with
warming: 87 mg N2O m−2), but also from the vegetated peat surfaces, not emitting N2O
under present climate. These surfaces showed signs of a hampered plant growth, leading to
reduced soil N uptake with warming, indicating that plants are regulating arctic N2O
emissions.
The warming treatment was limited to temperature of air and upper soil surface, and did
not alter thaw depth. Nonetheless, we observed a clear increase of all three GHGs deep in the
soil profile, and attribute this to downward leaching of labile organic substances from the
surface soil and/or plants, fueling microbial activity at depth. Our study thus highlights the
tight interlinkage between the surface soil, vegetation, and deeper soil layers, which could
lead to losses of all three GHGs, including N2O, with subtle temperature increase.
We therefore emphasize that indirect effects caused by warming, such as leaching
processes, as well as arctic N2O emissions, need to be taken into account when
attempting to project feedbacks between the arctic and the global climate system. |
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