The ocean surface mixed layer mediates the transfer of heat, freshwater, momentum and trace gases between atmosphere, sea ice and ocean, thus playing a central role in the dynamics of our climate. This session will focus on the surface mixed layer globally, from the coastal ocean to the deep ocean. We will review recent progress in understanding the key dynamical and biogeochemical processes taking place in the mixed layer: surface waves, Langmuir circulations and turbulence, shear-induced mixing, internal waves, coherent structures, fronts, frontal instabilities, entrainment and detrainment at the mixed layer base, convection, restratification, dynamics of the euphotic layer, carbon and nutrient cycling, etc. The improvement of the representation of surface mixed layer processes in numerical models is a complex and pressing issue: this session will bring together new advances in the representation of mixed layer processes in high resolution numerical models, as well as evaluation of mixed layer properties in climate models using most recent observational datasets. The coupling of the ocean and atmospheric boundary layers as well as the special processes occurring under sea ice and in the marginal sea ice zone will be given special consideration. This session welcomes all contributions related to the study of the oceanic mixed layer independent of the time- and space scales considered. This includes small scale process studies, short-term forecasting of the mixed layer characteristics for operational needs, studies on the variability of the mixed layer from sub-seasonal to multi annual time scales and mixed layer response to external forcing. The use of multiple approaches (coupled numerical modeling, reanalyses, observations) is encouraged.