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6.4.1. Carbon Dioxide and the Carbon Cycle

Carbon in the form of CO2, carbonates and organic compounds is cycled between the main reservoirs of its biogeochemical system: the atmosphere, ocean, land and marine biota, and over geologic time scales, the sediments and rocks (Butcher et al., 1992). This is schematised in Figure 6.1.

The global carbon cycle, like other biogeochemical cycles, exists in dynamic equilibrium. Today, the atmosphere stores approximately 750 billion tonnes (Gt) of carbon (in the form of CO2). The deep ocean represents an enormous store of carbon, with over 38,000Gt, whilst the surface ocean contains roughly 1,000Gt (Schimel et al., 1995).