Impact of the Long-Term Drainage on the Eddy-Covariance Fluxes in Northern High Latitude Permafrost Regions

In the context of global climate change, permafrost thaw in northern high-latitude territories is becoming a major concern due to the vast amount of organic carbon that is stored within this region. To accurately predict the feedback between Arctic permafrost carbon pools and future climate change, detailed insight into current carbon cycle processes and their environmental controls is imperative. A highly valuable data source for this purpose are continuous observations of turbulent exchange fluxes of carbon (e.g. CO₂ and CH₄ fluxes) and energy (e.g. fluxes of sensible and latent heat) with the eddy-covariance technique, in combination with the monitoring of environmental parameters such as e.g. air or soil temperature and moisture, radiation,  atmospheric turbulence, water table levels, precipitation, and snow depth.

In this study, we evaluate the effect of drainage on vertical carbon fluxes and environmental parameters within a Northeast Siberian wet tundra permafrost ecosystem. Our experiment includes two co-located eddy-covariance sites, one reflecting disturbed conditions affected by a drainage system which was built in 2004, and the other as an undisturbed control site. Both towers were identically outfitted with eddy covariance instruments mounted on 5 m tall towers on the floodplain of the Kolyma River near Chersky (68.75 º N, 161.33º E) in Northeast Siberia, Russia. The dataset analyzed here covers the period from July 2013 to December 2021, including continuous coverage throughout the winter seasons. We present a statistical analysis of the long-term trends in the environmental parameters and surface-atmosphere exchange fluxes at both sites. In addition, we relate the carbon and heat fluxes at both sites in the spectral and temporal domain to the inter-annual variability in climate conditions, which include extremes in both summer (temperature, precipitation) and winter (snow cover) conditions. Finally, we show the annual carbon budget of both sites, with a specific focus on the long-term impact of the drainage on carbon cycle process.