Atmospheric physical processes regulating diurnal and seasonal variations in CO2 fluxes over a large reservoir

Abstract:

As the role of carbon emissions from inland waters in regional and global carbon budget has become increasing apparent, better understanding the influence of environmental variables on CO2 exchange requires direct, long-term eddy covariance measurements of CO2 fluxes across the water-atmosphere interface. Here we provide analysis of CO2 fluxes over a large southern inland water body of Ross Barnett Reservoir in central Mississippi in 2008. It is found that greater atmospheric instability at night leads to approximately 70% greater CO₂ effluxes than during daytime. Frequent synoptic weather events associated with extratropical cyclones induce CO₂ flux pulses, resulting in further increase in annual CO₂ effluxes by 16%. Therefore, our measurements indicate that CO₂ emission rates from global inland waters, which do not account for the influence of these atmospheric physical processes on CO₂ exchange across the water-air interface, are likely underestimated by approximately 42%. Field measurements and modeling efforts to estimate CO₂ emissions should consider this daytime-nighttime efflux difference and the missing emissions during these synoptic weather events.