We measured the transfer of 12 gases between air and sea at very high wind speeds in two different wind-wave tank labs with fresh water, simulated seawater and seawater. We separated the transfer across the water surface from the transfer through the surface of bubbles. At high winds, the transfer through the free water surface increases very strongly and bubbles become important but only for gases which are very weakly soluble in water. On the ocean, bubbles might be important at lower winds.

Our article presents successful gas exchange measurements obtained in a large-scale wind-wave tank. The adopted box model methodology, experimental produce and instrumentation are described in detail. For the first time, parallel measurements of total transfer velocities for 14 individual gases within a wide range of solubility have been achieved. Various wind speed conditions and the effect of surfactant layers have been investigated providing exciting results.

A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air-Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions, including the measurement of the Schmidt number exponent. Provided the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium, it is possible to scale heat transfer velocities measured by active thermography to gas transfer velocities.