Spatiotemporal variations ofpCO2and δ13C‐DIC in subarctic streams in northern Sweden

Abstract

Current predictions of climate‐related changes in high‐latitude environments suggest major effects on the C export in streams and rivers. To what extent this will also affect the stream water CO2concentrations is poorly understood. In this study we examined the spatiotemporal variation in partial pressure of CO2(pCO2) and in stable isotopic composition of dissolved inorganic carbon (δ13C‐DIC) in subarctic streams in northern Sweden. The selected watersheds are characterized by large variations in high‐latitude boreal forest and tundra and differences in bedrock. We found that all streams generally were supersaturated inpCO2with an average concentration of 850 µatm. The variability inpCO2across streams was poorly related to vegetation cover, and carbonaceous bedrock influence was manifested in high DIC concentrations but not reflected in either streampCO2or δ13C‐DIC. Stream waterpCO2values were highest during winter base flow when we also observed the lowest δ13C‐DIC values, and this pattern is interpreted as a high contribution from CO2from soil respiration. Summer base flow δ13C‐DIC values probably are more affected by in situ stream processes such as aquatic production/respiration and degassing. A challenge for further studies will be to disentangle the origin of stream water CO2and quantify their relative importance.