Humans have released ~500 billion tons of carbon to the atmosphere. About 30% have been taken up by the oceans. The uptake leads to changes in ocean chemistry resulting in a decrease of seawater pH and carbonate ion concentration, commonly referred to as ocean acidification. The availability of carbonate ions is crucial for marine calcifying organisms to form their skeletons or shells that are made of different crystalline forms of calcium carbonate, such as calcite and aragonite. Aragonite is more soluble than calcite. Thus, the saturation state of aragonite can be taken as an indicator for ocean acidification. The animation shows how aragonite saturation at the ocean's surface is projected to decrease towards the end of the 21st century as man-made carbon dioxide accumulation in the atmosphere continues to rise. Nowadays, coral reefs are mainly found in regions where open-ocean aragonite saturation is 3.0 or higher. Currently, this value is reached in about 50% of the world's ocean. Projections indicate that the size of areas providing aragonite saturation levels of 3.0 or higher will shrink to less than 5% until the end of the 21st century. By that time, large parts of the Southern Ocean will experience conditions that may lead to a dissolution of skeletons and shells due to extremely low aragonite saturation (less than 1). Ocean acidification constitutes a serious hazard to global marine ecosystem and marine resources such as fisheries, food supply and tourism.
This animation was generated as part of a project funded by The Nature Conservancy, the National Science Foundation and JAMSTEC.