Extreme floods increase CO₂ outgassing from a large Amazonian river

Abstract

Large Amazonian rivers are characteristically subject to seasonal floods. We examine how inundation extent affects the partial pressure of carbon dioxide (pCO 2 ) and CO 2 outgassing in the Madeira River, a large tributary to the Amazon River. We show data from nine field campaigns performed between 2009 and 2011, complemented with data from one additional campaign in April 2014 that is representative of the largest flood on record. Both the pCO 2 (range, 835-9694 latm) and CO 2 outgassing (range, 641-12,253 mg C m 22 d 21 ) had large seasonal variability (with peaks during high water), and fit exponential relationships with water level. CO 2 outgassing per unit area in 2014 was 50% higher than the other highest rate in our dataset. Reconstruction of CO 2 fluxes since 1968 indicates that extreme-flood years outgas 20% more CO 2 per unit area than years without reported occurrence of extreme floods. Our findings indicate a positive feedback between climate change, extreme flooding, and CO 2 outgassing from river water.

Carbon Dioxide Fluxes to the Atmosphere From Waters Within Flooded Forests in the Amazon Basin

“…While our time series data support previous studies that CO 2 concentrations and fluxes vary seasonally, the frequency of our measurements further illustrated that variability was high at each site and during each measurement period. We corroborate previous studies reporting higher CO 2 concentrations and fluxes during the high water period for Amazonian rivers (Almeida et al, ; Amaral et al, ; Devol et al, ; Richey et al, ) and floodplain lakes (Abril et al, ; Rudorff et al, ). The seasonal pattern can be explained by (i) increases in water depth that increase depth integrated respiration (Devol et al, ; Forsberg et al, ) and (ii) the extent of inundation of the floodplains.…”

Radon‐traced pore‐water as a potential source of CO2 and CH4 to receding black and clear water environments in the Amazon Basin

“…reported by Abril et al (2014), likely due to our surveys extending further upstream where pCO 2 was considerably higher. Receding white river (Madeira) observations are higher than those reported at the mouth ( 1300 latm) by Abril et al (2014), but lower than the 4100 latm reported further upstream by Almeida et al (2017). Clear rivers had the lowest pCO 2 of the three water types which is consistent with other studies Rasera et al 2013;Abril et al 2014).…”

Variations in dissolved greenhouse gases (CO<sub>2</sub>, CH<sub>4</sub>, N<sub>2</sub>O) in the Congo River network overwhelmingly driven by fluvial-wetland connectivity

“…The global organic carbon degradation by net heterotrophy of rivers and streams given by Battin et al (2008) of 0.2 PgC yr −1 is insufficient to sustain global riverine CO 2 emissions given by the most recent estimates of 0.7-1.8 PgC yr −1 (Raymond et al, 2013;Lauerwald et al, 2015), suggesting an important role of lateral CO 2 inputs in sustaining emissions to the atmosphere from rivers. In a regional et al, 2016), in sharp contrast to the extensive and sustained work that has been done on the Amazon river basin (Alsdorf et al, 2016). The Congo basin has a wide range of contrasting tributaries (differing in lithology, soil characteristics, vegetation, rainfall patterns, etc.)…”