Effects of Plunging Breakers on the Gas Contents in the Oceans

The aeration of the ocean contributes to the transfer of oxygen, nitrogen and carbon dioxide between the ocean and the atmosphere. Breaking waves are known to enhance the aeration process by increasing the turbulent mixing and entraining air bubbles. One type of breaking waves, the plunging breaker, can entrain large quantities of air bubbles to depths as large as 10 to 20 metres. The resulting increase of the air-water interface area and the increase of the gas saturation concentration with the depth induce a massive augmentation of air-water gas transfer. The aeration characteristics of plunging breakers in the deep sea are presented using a similarity with plunging jets. A method is developed to predict the sizes of the entrained bubbles, the resulting interface area, the maximum penetration depth and the air-water gas transfer. The results are consistent with experimental observations and emphasise the role of plunging breakers in the aeration process. The authors develop also a prediction model of the gas transfer rate due to plunging breaking waves in deep sea during a storm even