This study proposes a coordinated large-scale mooring-based observational experiment in the Eurasian and Canadian basins of the Arctic Ocean. The widely spaced array of moorings will emphasize the largest-scale modes of variability, including basin-scale shifts of the Arctic Ocean circulation and water mass structure. The overall purpose of the experiment is to provide a quantitative, observationally based assessment of circulation, water mass transformations, biogeochemical fluxes, key mechanisms of variability in the Arctic Ocean, and its links to the lower-latitude processes. Coupled with existing oceanographic datasets, the observational data obtained in this experiment will enhance our understanding of Arctic Ocean variability on a broad range of time scales (from hours to years) and space scales (from meters to basin-scales). Linked with North Atlantic observations provided by the international ASOF (Arctic/Subarctic Ocean Fluxes), our large-scale oceanographic survey will provide a unique opportunity for coordinated long-term measurements over a vast polar/sub-polar region.