How do polynyas affect global ocean circulation?
Although relatively small in area, coastal polynyas play a disproportionately important role in many important physical and biological processes in the high-latitude Southern Ocean, as well as having an impact on global ocean circulation. Coastal polynyas in some areas around Antarctica are important contributors to global ocean circulation. Vertical mixing of ocean water, known as ‘overturning circulation’ or ‘thermohaline circulation’, is an important aspect of the global current system that is driven primarily by rising and sinking of water masses at high latitudes in both the northern and southern hemispheres. Salt is expelled as the ocean water freezes to form sea ice. This creates dense brine that sinks and flows down the continental shelf of Antarctica to form Antarctic Bottom Water – the densest water in the open ocean. This water flows outward from the Southern Ocean and through other ocean basins as part of the global ocean circulation ‘conveyor belt’ that distributes heat, n
