Effects of Reversal of Water Flow in an Arctic Floodplain River on Fluvial Emissions of CO₂ and CH₄

Abstract

When organic matter from thawed permafrost is released, the sources and sinks of greenhouse gases (GHGs), like carbon dioxide (CO2) and methane (CH4) in Arctic rivers will be influenced in the future. However, the temporal variation, environmental controls, and magnitude of the Arctic riverine GHGs are largely unknown. We measured in situ high temporal resolution concentrations of CO2, CH4, and oxygen (O2) in the Ambolikha River in northeast Siberia between late June and early August 2019. During this period, the largely supersaturated riverine CO2 and CH4 concentrations decreased steadily by 90% and 78%, respectively, while the O2 concentrations increased by 22% and were driven by the decreasing water temperature. Estimated gas fluxes indicate that during late June 2019, significant emissions of CO2 and CH4 were sustained, possibly by external terrestrial sources during flooding, or due to lateral exchange with gas‐rich downstream‐flowing water. In July and early August, the river reversed its flow constantly and limited the water exchange at the site. The composition of dissolved organic matter and microbial communities analyzed in discrete samples also revealed a temporal shift. Furthermore, the cumulative total riverine CO2 emissions (36.8 gC‐CO2 m−2) were nearly five times lower than the CO2 uptake at the adjacent floodplain. Emissions of riverine CH4 (0.21 gC‐CH4 m−2) were 16 times lower than the floodplain CH4 emissions. Our study revealed that the hydraulic connectivity with the land in the late freshet, and reversing flow directions in Arctic streams in summer, regulate riverine carbon replenishment and emissions.

Seasonality of methane and carbon dioxide emissions in tropical seagrass and unvegetated ecosystems

“…The correction of the HydroC-CH 4 data was done similarly, except that this sensor does not need drift correction 24 . The lag correction was done using a t63-to-temperature linear relationship provided by the manufacturer during calibration for the two pump models (SBE 5M and 5T).…”

A snap-shot assessment of carbon emission and export in a pristine river draining permafrost peatlands (Taz River, Western Siberia)

“…This recognition has motivated research aimed at understanding climate impacts on the sources and sinks of GHG in high latitude inland waters Hutchins et al, 2019;Zolkos et al, 2019;Dean et al, 2020). Of these numerous studies, only a few were conducted in the permafrost-affected rivers, typically at the scale of small watersheds (Denfeld et al, 2013;Serikova et al, 2018;Ji et al, 2020;Castro-Morales et al, 2022). Yet our knowledge of C cycling in so-called middle eight Arctic rivers (Severnaya Dvina, Pechora, Pur, Taz, Khatanga, Olenek, Yana, Indigirka) remains incomplete, preventing accurate quantification and prediction of C source-sink functions and responses to climate change.…”