Through observations and modeling, scientists have long known that large, deep currents in the Pacific, Atlantic and Indian oceans flow southward, converging on Antarctica. After entering the Southern Ocean they overturn — bringing water up from the deeper ocean — before moving back northward at the surface. This overturning completes the global circulation loop, which is important for the oceanic uptake of carbon and heat, the resupply of nutrients for use in biological production, as well as the understanding of how ice shelves melt._Lauren Hinkel | Oceans at MIT