Animation of the saturation state of surface water with respect to aragonite. Shown is the annual mean (ΔCO₃^2-) for aragonite in µmol kg^-1, i.e., the carbonate ion concentration above that which would exist if the same water were in equilibrium with aragonite, a metastable form of CaCO₃. The magenta line, which first becomes visible in 2025 (in the Weddell Sea), separates saturated waters (orange colors) from undersaturated waters (blue colors). By the end of this century, undersaturation spreads throughout the entire Southern Ocean (all ocean south of 60°S) and into a portion of the subarctic Pacific. For more details, see Orr et al. (2005, Nature).
[Movie credit: James Orr, LSCE/CEA-CNRS France]