The Sub-Mesoscale Ocean Dynamics Experiment (S-MODE) is a NASA Earth Venture Suborbital-3 (EVS-3) mission. S-MODE will use measurements from a novel combination of platforms and instruments, along with data analysis and modeling, to test the hypothesis that submesoscale ocean dynamics make important contributions to vertical exchange of climate and biological variables in the upper ocean. This will require coordinated application of newly-developed in situ and remote sensing techniques, and it will provide an unprecedented view of the physics of submesoscale eddies and fronts and their effects on vertical transport in the upper ocean.