The role of inland freshwaters in summer CO2, CH4 and N2O emissions from north-eastern Siberian Arctic tundra

Inland waters are an ubiquitous feature of Arctic landscapes, with carbon (C) and nutrient cycles that are closely coupled to terrestrial processes. They act as important conduits of terrestrial matter by not only transporting but also actively storing and processing it, subsequently emitting greenhouse gases (GHG) of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)to the atmosphere. Amplified climate warming at northern high-latitudes is changing contemporary carbon and nitrogen cyclesand driving permafrost thawing which has the potential to mobilise organic matter from vast stocks stored in Arctic tundra permafrost soils. Released carbon and nitrogen becomes available to degradation producing GHGs which inland waters emit to the atmosphere, thus forming a positive feedback to climate change.
GHG emissions from tundra ecosystems vary regionally with local environmental and climate factors. Dissolved GHG concentrations in collected samples from the Indigirka watershed were measured and fluxes computed during three growing seasons (2015, 2016, 2017) to provide insight into the role of each type of aquatic system in this region. Fluvial CO2 and CH4fluxes (85.7 ± 29.7 mmol C/m2/ d, 10.6 ± 27.3 mmol C/m2/ d, respectively mean ± STD) were the highest, followed by pond fluxes (30.0 ± 21.0 mmol C/m2/ d, 4.9 ± 9.4 mmol/m2/ d) and finally fluxes from lake sites (8.6 ± 7.6 mmol C/m2/ d, 0.84± 0.57 mmol/m2/ d).
The aim of this study was to quantify the effect of inland water emissions on the landscape C exchange. This was done by using remote sensing information to upscale emissions and integrate them into the terrestrial C exchange of the study area. As N2O has a large warming potential and received scant attention in the Arctic biome so far its contribution to terrestrial aquatic fluxes wasalso assessed. The effect of an extensive flooding event in 2017 on the landscape GHG exchange was also evaluated since increased flooding occurrence is what climate change might hold for this region. Greater insight into these aspects will increase understanding of GHG dynamics among inland waters in the north-eastern Siberian Arctic tundra lowlands which is essential for forecasting, climate-impact-assessment and to better constrain the feedback to climate warming.