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| Titel |
Stable isotope ratios of atmospheric CO2 and CH4 over Siberia
measured at ZOTTO |
| VerfasserIn |
Anastasiya Timokhina, Anatily Prokushkin, Jost Lavric, Martin Heimann |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250130848
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| Publikation (Nr.) |
 EGU/EGU2016-11167.pdf |
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| Zusammenfassung |
| The boreal and arctic zones of Siberia housing the large amounts of carbon stored in the
living biomass of forests and wetlands, as well as in soils and specifically permafrost, play a
crucial role in earth’s global carbon cycle. The long-term studies of greenhouse gases (GHG)
concentrations are important instruments to analyze the response of these systems to climate
warming. In parallel to GHG observations, the measurements of their stable isotopic
composition can provide useful information for distinguishing contribution of individual
GHG source to their atmospheric variations, since each source has its own isotopic signature.
In this study we report first results of laboratory analyses of the CO2 and CH4 concentrations,
the stable isotope ratio of δ13C-CO2, δ18O-CO2, δ13C-CH4, δD-CH4 measured in
one-liter glass flasks which were obtained from 301 height of ZOTTO (Zotino Tall
Tower Observatory, near 60˚ N, 90˚ E, about 20 km west of the Yenisei River)
during 2008 – 2013 and 2010 – 2013 for stable isotope composition of CO2 and
CH4.
The magnitudes of δ13C-CO2 and δ18O-CO2 in a seasonal cycle are -1.4±0.1‰ (-7.6 –
-9.0‰ ) and -2.2±0.2‰ (-0.1 – -2.3‰ ), respectively. The δ13C-CO2 seasonal pattern
opposes the CO2 concentrations, with a gradual enrichment in heavy isotope occurring during
May – July, reflecting its discrimination in photosynthesis, and further depletion in August –
September as photosynthetic activity decreases comparatively to ecosystem respiration.
Relationship between the CO2 concentrations and respective δ13C-CO2 (Keeling plot) reveals
isotopic source signature for growing season (May – September) -27.3±1.4‰ and
-30.4±2.5‰ for winter (January – March). The behavior of δ18O-CO2 associated with both
high photosynthetic rate in the June (enrichment of atmospheric CO2 by 18O as consequence
of CO2 equilibrium with “heavy” leaf water) and respiratory activity of forest floor in June –
October (depletion of respired CO2 by 18O because of the use of “light” soil water by
microorganisms).
There is large temporal variation of δ13C-CH4 (-50.0 – -46.1 ‰ ) with clear minimum in
the late summer (August) that corresponds to CH4 concentration maximum and reflects
biogenic sources of methane in the surrounding peatbogs. The δD-CH4 varies from -77.4 to
-110.2 ‰ and showed no seasonal cycle with many irregular spikes throughout a year.
Keeling plot analysis between the CH4 concentration and isotopic composition
revealed that isotopic signature of source in the winter (December – February) is
-61.3±2.2‰ and -247.5±17.7‰ for δ13C-CH4 and δD-CH4, respectively. For growing
season (June –September) the corresponding values for δ13C-CH4 and δD-CH4 are
-76.4±2.6‰ and -342.2±14.8‰Ṫhe strong depletion of methane in heavy isotopes
throughout a year is the indication of continuous CH4 emissions from biogenic
sources.
The study has been supported by cooperation agreement between SIF SB RAS and
MPI-BGC and RSF grant (14-24-00113). |
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