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Schlagwörter:
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Zusammenfassung:
Wetlands of northern high latitudes are ecosystems highly vulnerable to climate change. Some degradation effects
include soil hydrologic changes due to permafrost thaw,
formation of deeper active layers, and rising topsoil temperatures
that accelerate the degradation of permafrost carbon
and increase in CO2 and CH4 emissions. In this work we
present 2 years of modeled year-round CH4 emissions into
the atmosphere from a Northeast Siberian region in the Russian
Far East.We use a revisited version of the process-based
JSBACH-methane model that includes four CH4 transport
pathways: plant-mediated transport, ebullition and molecular
diffusion in the presence or absence of snow. The gas is
emitted through wetlands represented by grid cell inundated
areas simulated with a TOPMODEL approach. The magnitude
of the summertime modeled CH4 emissions is comparable
to ground-based CH4 fluxes measured with the eddy
covariance technique and flux chambers in the same area
of study, whereas wintertime modeled values are underestimated
by 1 order of magnitude. In an annual balance, the
most important mechanism for transport of methane into the
atmosphere is through plants (61 %). This is followed by
ebullition (35 %), while summertime molecular diffusion
is negligible (0.02 %) compared to the diffusion through the
snow during winter (4 %). We investigate the relationship
between temporal changes in the CH4 fluxes, soil temperature,
and soil moisture content. Our results highlight the
heterogeneity in CH4 emissions at landscape scale and suggest
that further improvements to the representation of largescale
hydrological conditions in the model will facilitate a
more process-oriented land surface scheme and better simulate
CH4 emissions under climate change. This is especially
necessary at regional scales in Arctic ecosystems influenced by permafrost thaw.
