Physical processes at the ocean-atmosphere interface have a large effect on climate and weather by controlling the transfer of momentum and mass. Without wave breaking, transport between the ocean and the atmosphere is through slow conduction and molecular diffusion, while wave breaking is a transitional process from laminar to turbulent flow. When waves are breaking, the surface experiences dramatic changes, with sea spray ejection in the atmosphere and air entrainment into the ocean water. In this talk I will discuss recent efforts in my group towards improving parameterizations of gas transfer and sea spray production through a multi-scale approach. We combine detailed laboratory experiments and numerical simulations on turbulent multiphase flows, including wave breaking, bubble break-up in turbulence and spray production by bubble bursting with a statistical description of breaking waves to develop a general theoretical framework. This framework aims to account for the complex nature of wave breaking and air entrainment, a two-phase turbulent process, and the very large range of scales involved in the process, from wave statistics scales of order of km, O(1m-1km), to wave breaking dynamics, O(1-10m), air bubble entrainment, bubble dynamics in turbulence and finally bubble bursting at the first surface, O(microns to mm).