Air–sea gas exchange in rough and stormy seas measured by a dual-tracer technique

Abstract

THE transfer of dissolved atmospheric gases across the air/sea interface is a strong function of wind speed and state of the sea surface. The form of the dependence on wind velocities is needed to calculate oceanic sources and sinks of climatically significant gases, particularly carbon dioxide¹ and dimethylsulphide^2,3. Previous measurements at sea have used techniques that reveal this dependence only when averaged over weeks or months^4,5, making it impossible to study the effects of high winds, which are generally episodic. Here we report first results from the application of a tracer technique which enables accurate measurements to be made over periods of 24–72 hours, including the first determination of gas exchange in storm conditions. Our results support the wind-speed dependence suggested by Liss and Merlivat⁶ on the basis of lake and wind-tunnel experiments, and are consistent with most measurements made by the radon-deficit technique. They suggest slower rates for CO₂exchange than those obtained by ¹⁴C budgeting, and favour recent lower estimates^1,7 of the global oceanic sink for anthropogenic CO₂.