Model-calculated aragonite saturation states throughout the surface ocean in 2000, 2050, and 2099. Aragonite is a form of calcium carbonate often used by calcifying organisms to create shells and skeletons. Saturation state measures the amount of calcium and carbonate, the mineral building blocks of aragonite, present in the water. In areas where the aragonite saturation state is below 1 (shades of red), most exposed aragonite structures will dissolve. However, the growth of calcifying organisms may decrease with declining saturation state, even if it remains above 1. This model predicts that as ocean acidification continues over the next 90 years, surface aragonite saturation states will drop throughout the global oceans. By 2099, only tropical and subtropical waters may have saturation levels high enough to support the growth of calcifying organisms such as some mollusks, crustaceans, and corals.

Surface values were calculated with the Community Climate System Model 3.1 of the National Center for Atmospheric Research.

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