Evidence for the importance of bubbles in increasing air–sea gas flux

Abstract

Two models have been proposed to account for gas exchang between the atmosphere and the oceans: one involves direct transport of the gas through a surface boundary layer¹; the other also includes a substantial enhancement of the gas flux due to bubbles formed by breaking waves^2,3. In a long time-series of dissolved oxygen measurements, Wallace and Wirick⁴ observed sharply increased fluxes that seemed to be associated with wave activity. But the lack of vertical resolution meant that they could not rule out water advection and entrapment, rather than bubble-mediated air injection, as the cause of the increased flux. They were also unable to calculate transfer coefficients. Here we report simultaneous in situ observations from a vertical array of dissolved-gas sensors and a variety of other instruments during a single storm event. Our results confirm the importance of bubbles for the gas-transfer process. They also imply that existing transfer coefficients underestimate the transfer of weakly soluble gases during periods of bubble penetration.