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

Abstract

Most estimates of diffusive flux (F) of methane (CH4) and carbon dioxide (CO2) 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 (Caq). We analyzed spatial variability of F of CH4 and CO2, 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 Caq at multiple sites on lakes to calibrate wind speed-modeled k to the local system. Key Points Diffusive greenhouse gas flux from lakes has a distinct within-lake distribution Single-point estimates can lead to biased diffusive gas flux estimates The relationship of wind speed at 10 m with piston velocity varies within lakes ©2013. American Geophysical Union. All Rights Reserved.