Methane fluxes and isotopic composition over heterogeneous landscapes of Arctic permafrost and Siberian peatlands (MICHAEL)

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Arctic permafrost landscape and Siberian peatlands represent globally important sources of the greenhouse gas methane. Under warming climate, feedback mechanisms will further enhance methane emissions. However, only few sites with continuous measurements of methane fluxes are available in the Russian Arctic and Siberia, and they serve as reference for estimations on regional scales. Further, local small-scale heterogeneities of land cover within a landscape are understood to be one of the main sources of the uncertainty in the observed methane fluxes. A combination of several measurement methods for high spatio-temporal resolution of methane fluxes as well as of the heat and moisture budget is needed. This lack of data limits further land-cover and emission model development. Therefore, the project MICHAEL aims at i) providing high spatio-temporal resolution of methane emissions, of the turbulent heat fluxes and the isotopic composition using novel observational techniques in addition to those commonly used and ii) further develop land-surface models and parameterizations by taking into account landscape heterogeneities more adequately. Two sites are chosen for field campaigns: the Samoylov Station in the Lena River Delta and Mukhrino in the central part of West Siberia. The special focus is on small-scale variability and the impact of contrasting landscape features. During the project, continuous ground-based methane fluxes obtained using eddy-covariance and automatic chamber methods are enhanced with additional ground-based observational sites and combined with unmanned aerial system (UAS) measurements of surface and meteorological parameters, components of the surface heat balance, methane fluxes, profiles of methane concentration and methane isotopic composition. Three UAS are applied: a fixed-wing system for meteorological measurements including turbulence and radiation, a quadrocopter for obtaining vertical profiles of the methane concentration and for taking air samples that are analyzed for methane isotopic composition, and a tiltrotor system providing fluxes of methane. The UAS are operated at different locations within a radius of up to 10 km around the observatories, depending on wind direction, atmospheric stability and land surface to enable footprint calculations. Based on the results the accuracy of traditional eddy-covariance and chamber methods is evaluated and upscaling/downscaling methods are revised.Numerical simulations are used to derive the 3D variability of methane emitted into the atmosphere, using land-surface modelling to represent turbulent exchange over heterogeneous surface, and high-resolution atmospheric modelling to embed the measurements in the context of synoptic conditions. A numerical land-surface model containing also the carbon cycle is adapted to the considered landscapes. The modelling results are evaluated against observations and the impact of landscape heterogeneities is quantified.