Permafrost Carbon Network

thermokarst lakescottongrasstussocksthermokarstyedoma

Working Group: Anaerobic and Aerobic Carbon Fluxes

Background and Objectives:

Hydrological conditions and processes are critical for ecosystem carbon cycling, both through their control of dominant microbial mineralization pathways that determine the relative rates of carbon dioxide and methane production and through lateral movement of carbon from terrestrial to aquatic ecosystems. Climate change and permafrost thaw will alter the hydrology at high latitudes, with implications at both local scales as well as at the pan-arctic scale. Consequently, the impact of permafrost thaw on carbon cycling and storage at high latitudes will be intrinsically linked to altered hydrological conditions and need to be considered together.

Some question that this working group addresses:

  • How do permafrost characteristics influence post-thaw hydrology and greenhouse gas fluxes from lakes and wetlands?
  • Which regions in the pan-arctic can we expect to be particularly sensitive to future enhanced methane emissions due to permafrost thaw?
  • How well do empirical observations and bottom up estimates of methane emissions agree with forward models and inverse model results?
  • Under what conditions will permafrost thaw render soil carbon vulnerable to downstream waterborne transport, and how is this carbon processed in streams, lakes and in the ocean?
  • For more details on this working group send an email to David Olefeldt


     

    completed synthesis products

    Environmental and physical controls on northern terrestrial methane emissions across permafrost zones

    As a first product, we have compiled a database of chamber-based methane data from wetland ecosystems across the permafrost zones, based on studies published over the last three decades. The results stress the interacting effects of site wetness, vegetation composition and soil temperature in controlling methane emissions – all variables that change following permafrost thaw in wetlands. In contrast, we did not find any conclusive evidence that permafrost thaw will enhance methane emissions as a result of increased soil organic carbon stores that become available for microbial degradation.

    Olefeldt D, Turetsky MR, Crill PM, McGuire AD (2013) Environmental and physical controls on northern terrestrial methane emissions across permafrost zones. Global Change Biology, 19, 589–603, doi: 10.1111/gcb.12071

     

    Climate-sensitive northern lakes and ponds are critical components of methane release

    In a second product, members of the Permafrost Carbon Network estimated methane emissions from lakes. By compiling previously reported measurements taken at a total of 733 northern water bodies -- from small ponds formed by beavers to large lakes formed by permafrost thaw or ice-sheets -- researchers were able to more accurately estimate emissions over large scales. With climate warming, particularly at high northern latitudes, longer ice-free seasons in combination with permafrost thaw is likely to fuel methane release from lakes, potentially causing their emissions to increase 20-50 precent before the end of this century. Such a change would likely generate a positive feedback on future warming, causing emissions to increase even further

    Wik M, Varner RK, Anthony KW, MacIntyre S, Bastviken D (2016) Climate-sensitive northern lakes and ponds are critical components of methane release. Nature Geosci, doi:10.1038/ngeo2578

     

    Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

    A review by Vonk et al. 2015 gives an overview of the current state of knowledge regarding how permafrost thaw affects aquatic systems. The review describes the general impacts of thaw on aquatic ecosystems, pathways of organic matter and contaminant release and degradation, resulting emissions and burial, and effects on ecosystem structure and functioning. The paper concludes with an overview of potential climate effects and recommendations for future research.

    Vonk JE, Tank SE, Bowden WB, Laurion I, Vincent WF, Alekseychik P, Amyot M, Billet MF, Canário J, Cory RM, Deshpande BN, Helbig M, Jammet M, Karlsson J, Larouche J, MacMillan G, Rautio M, Walter Anthony KM, Wickland KP (2015) Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems. Biogeosciences, 12, 7129-7167. doi: 10.5194/bg-12-7129-2015

     

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    Map with study locations

    Click on the map for more details on study locations for CH4 flux measurements used in Olefeldet et al. 2013

    Map_methane