Martin Heimann1,2 (firstname.lastname@example.org, +49 151 120 35946), Mathias Goeckede1, Nikita Zimov3, Sergey Zimov3,4
1 Max-Planck-Institute for Biogeochemistry, PF 100164, D-07701 Jena, Germany.
2 Institute for Atmospheric and Earth System Research (INAR) / Physics, University of Helsinki, Finland.
3 North-East Scientific Station, Pacific Institute for Geography, Far-East Branch, Russian Academy of Sciences, Cherskii, Russian Federation.
4 Far Eastern Federal University, 8 Sukhanova St., Vladivostok 690090, Russian Federation.
The vulnerability of the large carbon reservoir locked up in Arctic permafrost soils under global warming is largely unknown. Soil properties, in particular soil wetness as well as snow cover critically control the thermal regime of the active layer of permafrost soils, and through this also the processes which govern exchanges of carbon dioxide (CO2) and emissions of methane (CH4). Here we present results from a long-term drainage experiment conducted on permafrost soils in north-eastern Siberia. Lowering of the water table through drainage changes the surface ecosystem composition and increases the summer time insulation of the underlying permafrost, hence tends to keep it cooler than in the prevailing water logged surrounding. An increase of soil degradation and fragmentation by thermokarst processes, as expected in a warming climate, may therefore lead to more dryer soil patches with reduced greenhouse gas emissions and may thus constitute a negative climate feedback process. On the other hand, higher snow depth in winter provides an important insulation which delays or even prevents the refreezing of the active surface soil layer. Higher snow depths thus lead to warmer soil temperatures and correspondingly to higher emissions of respired carbon as CO2 and CH4. Given that a future warmer Arctic most certainly implies increases in precipitation, also as snow in fall and winter, this process might represent a positive climate feedback process. Which one of these two Arctic climate feedbacks will dominate in a warming world is very much unknown. Long-term studies of in situ measurements and high-resolution remote sensing of surface structures complemented with advanced high-resolution modelling are urgently needed to robustly predict the fate of Arctic permafrost carbon within this century.
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