| Summary: | Due to a strong Arctic warming trend, potentially large greenhouse gas emissions from Arctic and sub- Arctic areas are of concern. The Lena River Delta located in north-east Siberia is the largest delta within the Arctic Circle, characterized by wetland ecosystems and wet polygonal tundra environments. These environments are currently thought to be sinks for carbon dioxide and sources of methane. Tower-based eddy covariance is the most widely used direct method for quantifying exchanges of momentum, energy and trace gases between the surface and the atmosphere. However, they cover a relatively small footprint and constitute point measurements relative to the vast extend of tundra ecosystems. To improve spatial coverage and spatial representativeness of these direct flux measurements, airborne eddy covariance flux measurements across large areas are required. We used the helicopter-carried measurement system “Helipod” equipped with a turbulence probe, fast temperature and humidity sensors, and a fast response gas analyzer to measure turbulent fluxes of heat, carbon dioxide, and methane across the Lena River Delta in Russia in 2012 and 2014. The 2014 campaign covered several periods of the season from April to August 2014. Wavelet transforms are used to improve spatial resolution of the flux measurements and footprint analysis is applied to find relations between surface fluxes and biophysically relevant land cover properties. Strong regional differences in trace gas fluxes were detected, indicating a non-uniform distribution of sources especially in wet sedge-, moist grass-, and moss-dominated tundra. In contrast, the sensible heat flux showed less variability across the investigation area. The obtained results are essential in understanding the role of Arctic ecosystems in the greenhouse gas budgets and to evaluate regional scale model simulations.
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