Spatial heterogeneity and lake morphology affect diffusive greenhouse gas emission estimates of lakes

Abstract Most estimates of diffusive flux ( F ) of methane (CH 4 ) and carbon dioxide (CO 2 ) from lakes are based on single‐point flux chamber measurements or on piston velocity ( k ) modeled from wind speed and single‐point measurements of surface water gas concentrations ( C aq ). We analyzed spatial variability of F of CH 4 and CO 2 , as well as C aq and k in 22 European lakes during late summer. F and k were higher in the lake centers, leading to considerable bias when extrapolating single‐point chamber measurements to whole‐lake estimates. The ratio of our empirical k estimates to wind speed‐modeled k was related to lake size and shape, suggesting a lake morphology effect on the relationship between wind speed and k . This indicates that the error inherent to established wind speed models can be reduced by determining k and C aq at multiple sites on lakes to calibrate wind speed‐modeled k to the local system.