Rainer M. W. Amon

The gas exchange between water bodies and air is difficult to measure, thus the approximations of air–water gas exchange coefficient based solely on wind speed has been widely used. However, such approaches may not work well in river environments. In rivers, water currents may govern gas exchange. Thus, a new approximation for calculating the gas exchange coefficient ( k ) based on the near‐surface velocity scale ( u s ) is suggested and compared to wind‐based estimates. Our velocity scale estimates are based on field observations during summer 2016 on the Yenisei River using an Acoustic Doppler Current Profiler, high‐frequency temperature profilers and a vessel‐mounted meteorological sensors‐suite. The results demonstrate that u s ‐derived gas exchange coefficients are higher than those based solely on wind speed. The results demonstrate that the wind approximation underestimates gas exchange coefficients during low‐wind conditions.