Mesoscale eddies play a key role in setting the climate of the global ocean system via the transport of heat, salt, momentum and trace biogeochemical constituents. The ability to fully resolve mesoscale eddies throughout the entire ocean is a computational grand challenge. One path forward is to model the ocean with multiple scales, thus allowing resolution and computational resources to be directed toward those regions of the ocean most influenced by mesoscale eddies. The Model for Prediction Across Scales (MPAS) project allows for a multi-scale representation of the global ocean through use of a conforming,variable-resolution finite-volume scheme. Both test-bed and real-world configurations of MPAS-Ocean indicate that regional representation of mesoscale eddies and their influence on the broader circulation can be carried out with a high level of accuracy. Looking forward, the simulation of important climate processes, such as ocean-ice shelf interaction and coastal biogeochemistry, are tractable with this modeling approach.