The importance of inland water CO2, CH4, N2O to summertime greenhouse gas exchange with the atmosphere in arctic tundra lowlands

Inland waters in Arctic landscapes act as conduits of terrestrial material by transporting and processing it, subsequently exchanging the greenhouse gases (GHG) carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) with the atmosphere. To quantify the role of inland water emissions in the Arctic GHG budget, it is necessary to assess their emissions in relation to the terrestrial sink capacity. We present measurements of dissolved CO₂, CH₄ and N₂O from lake, pond and low order fluvial systems across two summers (2016-2017) in the Indigirka River lowlands. During May-July 2017, the region experienced a large flood of which we captured the tail end. Using remote sensing images to up-scale inland water emissions to an area of approximately 18 km² we calculated combined carbon (C) emissions, CO₂-C and diffusive CH₄-C. Considering N₂O emissions in terms of their radiative forcing showed that they were negligible compared to CO₂ and CH₄ emissions. Our results shows that in the northeast Siberian Arctic tundra, CO₂ and CH₄ emissions from inland waters are a significant component (potentially up to 25 %) of the landscape C exchange with the atmosphere. Accurately integrating these into regional carbon budgets is essential for forecasting, climate-impact-assessment and to better constrain the feedback to climate warming.