As geophysical fluids, the ocean and atmosphere share many common traits, including well-mixed boundary layers adjacent to the air-sea interface. The thermodynamic properties of these layers are influenced by exchanges across the top of the marine atmospheric boundary layer (MABL) and the base of the ocean mixed layer (OML), but also by ocean-atmosphere exchanges of heat, freshwater, and momentum across the air-sea interface. Because the ocean is 1000 times more dense than the atmosphere, fluxes of heat or momentum across the air-sea interface induce responses with different timescales for the atmosphere and ocean. Ocean-atmosphere communication, therefore, is achieved through a tangled series of cross-scale interactions between the OML and MABL.

In this talk, I will introduce some examples of coupled cross-scale interactions from around the globe, followed by a discussion of how uncertainties in bulk surface flux estimates could lead to misinterpretation of the role of ocean-atmosphere coupling for these phenomena. I will conclude with an overview of ongoing community efforts to develop observational strategies of the coupled boundary layers to advance process understanding and, ultimately, improve predictions by coupled forecast models.