Comparison of floating chamber and eddy covariance measurements of lake greenhouse gas fluxes

Fluxes of carbon dioxide (CO2) and methane (CH4) from lakes may have a large impact on the magnitude of the terrestrial carbon sink. Traditionally lake fluxes have been measured using the floating chamber (FC) technique; however, several recent studies use the eddy covariance (EC) method. We present simultaneous flux measurements using both methods at lake Tamnaren in Sweden during field campaigns in 2011 and 2012. Only very few similar studies exist. For CO2 flux, the two methods agree relatively well during some periods, but deviate substantially at other times. The large discrepancies might be caused by heterogeneity of partial pressure of CO2 (pCO(2w)) in the EC flux footprint. The methods agree better for CH4 fluxes. It is, however, clear that short-term discontinuous FC measurements are likely to miss important high flux events.