Radiocarbon Data Reveal Contrasting Sources for Carbon Fractions in Thermokarst Lakes and Rivers of Eastern Canada (Nunavik, Quebec)

Greenhouse gas emissions from permafrost organic carbon decomposition in lakes and rivers can accelerate global warming. We used radiocarbon (14C) measurements to determine the predominant sources of dissolved (DOC), particulate (POC), inorganic (DIC), methane (CH4) five thermokarst three an area widespread degradation Northern Quebec assess contributions thawing other old (fixed before CE 1950) reservoirs. compared emission pathways (dissolved ebullition), seasons (summer winter), surface soil type (mineral peat soils). Modern after was dominant source DOC, DIC, CH4 non-peatland aquatic systems, while POC sediment were predominantly fixed last millennia. In peatland modern important lake ebullition CO2, CH4. contrast, POC, CH4, river DIC dominated by millennial-old carbon. winter, 14C age increased, but did not change. Our results point a clearly older overall for relative lakes. The younger ages DOC all suggest that recent primary productivity strongly influences large total CO2 this area, as diffusion fluxes greatly exceed fluxes.