Waves and air‐sea fluxes from a drifting ASIS buoy during the Southern Ocean Gas Exchange experiment

Abstract

The Southern Ocean, while widely acknowledged as playing a major role within the Earth's climate system, remains the most poorly sampled and understood of the world's ocean basins. The High Latitude Surface Flux Working Group of U.S. CLIVAR (Climate Variability and Predictability, part of the World Climate Research Programme) has accordingly identified as a key priority the need for further measurements in the Southern Ocean. During the 2008 Southern Ocean Gas Exchange experiment, an Air‐Sea Interaction Spar (ASIS) buoy was deployed to measure air‐sea fluxes, surface waves, and mean properties of the upper ocean and lower atmosphere. During its eight‐day deployment in the Atlantic sector of the Southern Ocean, the drifting buoy captured two storm events, with winds reaching 20 m s−1 and waves approaching 6 m significant height. The wavefield was observed to be dominated by swell waves except for the storm periods. In a combined analysis using data from two other ASIS deployments, existing relations for fetch limited wave growth were evaluated. Measured moisture flux showed good comparison with previous findings indicating a near‐constant Dalton number. The drag coefficient was found to be significantly higher than previous parameterization predictions, due to an effect of swell wave interaction with the atmospheric turbulence. This enhanced momentum flux in the swell dominated seas of the Southern Ocean must be accounted for in regional bulk flux relations.