The relationship between near-surface turbulence and gas transfer velocity in freshwater systems and its implications for floating chamber measurements of gas exchange

Vachon, Dominic, Yves T. Prairie, and Jonathan J. Cole

Limnol. Oceanogr., 55(4), 2010, 1723-1732 | DOI: 10.4319/lo.2010.55.4.1723

ABSTRACT: We performed a series of gas exchange measurements in 12 diverse aquatic systems to develop the direct relationship between near-surface turbulence and gas transfer velocity. The relationship was log-linear, explained 78% of the variation in instantaneous gas transfer velocities, and was valid over a range of turbulent energy dissipation rates spanning about two orders of magnitude. Unlike wind-based relationships, our model is applicable to systems ranging in size from less than 1 km² to over 600 km². Gas fluxes measured with our specific model of floating chambers can be grossly overestimated (by up to 1000%), particularly in low-turbulence conditions. In high-turbulence regimes, flux overestimation decreases to within 50%. Direct measurements of turbulent energy dissipation rate provide reliable estimation of the associated gas transfer velocity even at short temporal and spatial scales.