Spatiotemporal variations of pCO2 and δ13C-DIC in subarctic streams in northern Sweden.

Current predictions of climate-related changes in high-latitude environments sugges major effects on the C export in streams and rivers. To what extent this will also affect the stream water CO₂ concentrations 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 (δ¹³) 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 inpCO₂ with an average concentration of 850 µatm. The variability in pCO₂ across streams was poorly related to vegetation cover, and carbonaceous bedrock influence was manifested in high DIC concentrations but not reflected in either stream pCO₂ or δ¹³. Stream waterpCO₂ values were highest during winter base flow when we also observed the lowest δ¹³ values, and this pattern is interpreted as a high contribution from CO₂ from soil respiration. Summer base flow δ¹³ 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 watel CO₂ and quantify their relative importance. [ABSTRACT FROM AUTHOR]