Seminar: Sandra Raab

This study focuses on hydrological patterns within a floodplain tundra site near Chersky, Northeast Siberia. We compared a wet control area with an area affected by a drainage ring built in 2004 to study the effect of water availability on carbon production and transport. Water table depths at both areas were continuously monitored with a distributed sensor network over the summer seasons 2016-2020. The spatio-temporal dynamics of water table depth revealed systematic differences between control and drained area. The drained area showed a stronger decrease in water tables towards peak summer season in July and stronger reactions to precipitation events. The control area responded less pronounced to short-term changes. At the drained area, the main groundwater flow direction was stable throughout the measurement period. Total CO2 fluxes (including lateral and vertical fluxes) showed distinctive patterns throughout the growing season: summer fluxes were relatively low and indicated CO2 uptake; autumn (starting in September) fluxes were much higher and indicated a CO2 source. Spatial carbon patterns showed that DOC is the dominant fraction, followed by DIC and POC. A carbon isotope (δ13C-DIC, δ13C-DOC and ∆14C-DOC) analysis gave hints about production processes, source areas and age of the dissolved carbon in water with distinctive patterns between drained and control area. The understanding of these production and redistribution processes is essential for interpreting the carbon budget in disturbed permafrost.