Laboratory Experiments on CO2 Gas Exchange with Wave Breaking

Abstract

The CO2 gas transfer velocity (KCO2 ) at air–sea interface is usually parameterized with the wind speed, but to a great extent it is defined by waves and wave breaking. To investigate the direct relationship between KCO2 and waves, laboratory experiments are conducted in a wind-wave flume. Three types of waves are forced in the flume: modulational wave trains generated by a wave maker, wind waves with 10-m wind speed ranging from 4.5 to 15.5 m s21, and (mechanically generated) modulational wave trains coupled with superimposed wind force. The wave height and wave orbital velocity are found to be well correlated with KCO2 whereas wind speed alone cannot adequately describe KCO2 . To reconcile the measurements, nondimensional equations are established in which gas transfer velocity is expressed as a main function of wave parameters and an additional secondary factor to account for influence of the wind.