The transfer of CO2 from the atmosphere to the ocean is partly mediated by wave breaking in open seas. Indeed, when a wave breaks, it traps large volumes of air that will fragment and generate submillimetric bubbles. These small bubbles rise slower to the surface, and dissolve faster into the ocean. However, the distribution of bubble size in a turbulent flow, in particular the submillimetric diameters, remains an open question. In collaboration with L. Deike from Princeton University, we have developed a dual approach, experimental & numerical to identify the physical processes at play in bubble fragmentation. To do so, we inject a controlled volume of air within a turbulent flow, and we track the fragmentation dynamics. Combining an experimental approach & direct numerical simulations, I will present how we develop models to explain the distribution of small bubble size in turbulent flows.