Figure 7.11. (a) The Revelle factor (or buffer factor) as a function of CO₂ partial pressure (for temperature 25°C, salinity 35 psu, and total alkalinity 2,300 µmol kg^–1) (Zeebe and Wolf-Gladrow, 2001, page 73; reprinted with permission, copyright 2001 Elsevier). (b) The geographical distribution of the buffer factor in ocean surface waters in 1994 (Sabine et al., 2004a; reprinted with permission, copyright 2004 American Association for the Advancement of Science). High values indicate a low buffer capacity of the surface waters.