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Seasonally flooded forests along tropical rivers cover extensive areas, yet the processes driving air-water exchanges of radiatively active gases are uncertain. To quantify the controls on gas transfer velocities, we combined measurements of water-column temperature, meteorology in the forest and adjacent open water, turbulence with an acoustic Doppler velocimeter, gas concentrations, and fluxes with floating chambers. Under cooling, measured turbulence, quantified as the rate of dissipation of turbulent kinetic energy (epsilon), was similar to buoyancy flux computed from the surface energy budget, indicating convection dominated turbulence production. Under heating, turbulence was suppressed unless winds in the adjacent open water exceeded 1 m/s. Gas transfer velocities obtained from chamber measurements ranged from 1 to 5 cm/hr and were similar to or slightly less than predicted using a turbulence-based surface renewal model computed with measured E and s predicted from wind and cooling.

Plain Language Summary Flooded forests are widespread in the tropics and occur elsewhere. Within the lowland Amazon basin, seasonally inundated forests cover about 15% of the total area and are important to the ecology of the region. Concentrations of greenhouse gases can be high, indicating that flooded forests are likely an appreciable source of these gases to the atmosphere. To understand drivers of gas exchange, measurements of meteorology, temperature, and turbulence in the water were performed in Amazonian flooded forests. While air in flooded forests is often still, water immediately below is in motion and turbulent. The combination of wind-driven flows from outside the forest and nocturnal cooling within the forests indicates that near-surface turbulence is sustained in the flooded forest. Consequently, the extensive area of flooded forests will release appreciable amounts of greenhouse.