Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2016-212
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
25 Oct 2016
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal The Cryosphere (TC) and is expected to appear here in due course.
Shifts in permafrost ecosystem structure following a decade-long drainage increase energy transfer to the atmosphere, but reduce thaw depth
Mathias Göckede1, Fanny Kittler1, Min Jung Kwon1, Ina Burjack1, Martin Heimann1,2, Olaf Kolle1, Nikita Zimov3, and Sergey Zimov3 1Department Biogeochemical Systems, Max-Planck Institute for Biogeochemistry, Jena, Germany
2Division of Atmospheric Sciences, Department of Physics, University of Helsinki, Finland
3North-East Science Station, Pacific Institute for Geography, Far-Eastern Branch of Russian Academy of Science, Chersky, Republic of Sakha (Yakutia), Russia
Abstract. Hydrologic conditions are a key factor in Arctic ecosystems, with strong influences on ecosystem structure and related effects on biogeophysical and biogeochemical processes. With systematic changes in water availability expected for large parts of the Northern high latitude region in the coming centuries, knowledge on shifts in ecosystem functionality triggered by altered water levels is crucial for reducing uncertainties in climate change predictions. Here, we present findings from paired ecosystem observations in Northeast Siberia that comprise a drained and a control site. At the former, the water table has been artificially lowered by up to 30 cm in summer for more than a decade. This sustained primary disturbance in hydrologic conditions has triggered a suite of secondary shifts in ecosystem properties, including vegetation community structure, snow cover dynamics, and radiation budget, all of which influence the net drainage effects. Reduced heat conductivity in dry organic soils was identified as the dominating drainage effect on energy budget and soil thermal regime. Through this effect, reduced heat transfer into deeper soil layers leads to shallower thaw depths, initially leading to a stabilization of organic permafrost soils, while the long-term effects on permafrost temperature trends still need to be assessed. At the same time, more energy is transferred back into the atmosphere in the drained area, with the largest fraction attributed to the sensible heat flux. Accordingly, this increase in vertical heat transfer will act as a positive feedback to permafrost degradation triggered by the warming of the lower atmospheric surface layer.

Citation: Göckede, M., Kittler, F., Kwon, M. J., Burjack, I., Heimann, M., Kolle, O., Zimov, N., and Zimov, S.: Shifts in permafrost ecosystem structure following a decade-long drainage increase energy transfer to the atmosphere, but reduce thaw depth, The Cryosphere Discuss., https://doi.org/10.5194/tc-2016-212, in review, 2016.
Mathias Göckede et al.
Mathias Göckede et al.
Mathias Göckede et al.

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Short summary
Shifts in hydrologic conditions will be a key factor for the sustainability of Arctic ecosystems under future climate change. We analyzed through a long-term manipulation experiment how a permafrost ecosystem reacts to sustained dry conditions. Our experiments demonstrate that drainage leads to changes in several important ecosystem characteristics. Both positive and negative feedback loops to climate change were identified, so the net impact assessment needs to consider their complex interplay.
Shifts in hydrologic conditions will be a key factor for the sustainability of Arctic ecosystems...
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