Abstract
Whitecap foam, created by breaking waves, is a ubiquitous ocean surface feature. Full understanding of its role in the air-sea interaction is crucial for precise momentum flux parameterization which directly influences forecast accuracy, especially in hurricanes where whitecaps are pervasive. Despite its importance, the role of whitecap foam in air-sea interaction remains largely unexplored. This study uses a wind-wave tank and an artificial foam generator to study the impact of whitecap residual foam on air-sea coupling. We find that foam reduces momentum flux, indicative of a smoothed surface roughness, and reduces wave form stress across all wind speeds, with a more pronounced effect in surfactant-rich water. Foam also alters wave characteristics and airflow separation. These findings offer new insights into whitecap residual foam's role in air-sea coupling and have implications for modelling hurricanes and other wind driven processes.