Current estimates of CO2 flux from inland waters often rely on limited point in time measurements, therefore, short time variation of gas exchange and mechanisms controlling the flux are particularly understudied. Here we present the results of a global synthesis of eddy fluxes from 25 globally distributed aquatic sites. The objective of this study was to quantify the magnitudes and variation of CO2 fluxes and investigate their responses to environmental controls across half-hourly to seasonal time scales. The coupled observations of in-water physical and biogeochemical parameters with meteorology and eddy covariance fluxes were analyzed using decomposed correlation and wavelength coherence analysis to quantify the critical time scales that are associated with the variability of CO2 flux and related drivers. The flux rates were synthesized according to time scale, climate, and water body type.
The shoreter temporal CO2 flux variation was attributed to wind speed, solar radiation cycle, vapor pressure deficit, temperature gradients at water-air interface, and ecosystem productivity. The emergent plant coverage distinguished wetlands from lakes and reservoirs, and determined a clear carbon uptake response to environmental drivers. We found an inconsistent latitudinal pattern of CO2 fluxes correlated with proxies of ecosystems productivity, suggesting that waterbody-specific characteristics play an important role in controlling flux magnitudes and variation. The results presented here highlight the importance of quantifying variation of trace gas fluxes at multi-temporal scales towards improving the understanding of the carbon cycle and linked ecological processes.