Climate variability controls on CO2 consumption fluxes and carbon dynamics for monsoonal rivers: evidence from Xijiang River, Southwest China

The feedbacks of climate variability on CO2 consumption fluxes and carbon dynamics are thought to play an important role in moderating the global carbon cycle. High‐frequency sampling campaigns and analyses were conducted in this study to investigate temporal variations of river water chemistry and the impacts of climate variability on CO2 consumption fluxes and carbon dynamics for the Xijiang River, Southwest China. Physical processes modify biogeochemical processes, so major ions display different responses to changing discharge. The annual CO2 consumption rate is (6.8 ± 0.2) × 106 ton/year by carbonate weathering and (2.4 ± 0.3) × 106 ton/year by silicate weathering. The annual CO2 consumption flux is much higher than most world rivers, and strong CO2 consumption capacities are observed in catchments in Southwest China. Lower negative δ13CDIC values are found in the high‐flow season which corresponds with high temperatures compared to those in the low‐flow season. High discharge will accelerate material transport, and high temperatures will increase primary production in the catchment, both of which can be responsible for the shift of δ13CDIC values in the high‐flow season. Increased mineral weathering and biological carbon influx in the catchment are the main factors controlling carbon dynamics. Overall, these findings highlight the sensitivity of CO2 consumption fluxes and carbon dynamics in response to climate variability in the riverine systems

Unexpected large evasion fluxes of carbon dioxide from turbulent streams draining the world’s mountains

Inland waters, including streams and rivers, are active components of the global carbon cycle. Despite the large areal extent of the world’s mountains, the role of mountain streams for global carbon fluxes remains elusive. Using recent insights from gas exchange in turbulent streams, we found that areal CO2 evasion fluxes from mountain streams equal or exceed those reported from tropical and boreal streams, typically regarded as hotspots of aquatic carbon fluxes. At the regional scale of the Swiss Alps, we present evidence that emitted CO2 derives from lithogenic and biogenic sources within the catchment and delivered by the groundwater to the streams. At a global scale, we estimate the CO2 evasion from mountain streams to 167 ± 1.5 Tg C yr−1, which is high given their relatively low areal contribution to the global stream and river networks. Our findings shed new light on mountain streams for global carbon fluxes