6.4.1.2. Sinks of Atmospheric CO2

The surface ocean also acts as a natural sink for atmospheric CO2, with an annual removal flux of 92Gt carbon. The interaction of CO2 between atmosphere and surface ocean was more fully addressed in section 5.3.1.2 (Equations 14 to 17). The other major natural sink is the primary productivity of land vegetation (photosynthesis), which sequesters 61.4Gt carbon every year (Schimel et al., 1995). The regrowth of Northern Hemisphere forests represents the only major anthropogenic sink of atmospheric CO2, although enhanced fertilisation effects due to elevated CO2 concentrations and other climatic feedbacks have also been considered.