On the control of the carbon-oxygen system

Abstract

The dynamical aspects of the carbon-oxygen system in the ocean and atmosphere are considered. The analysis is based on the stoichiometry of the main reactions, relevant continuity constraints and assumptions about feedback from the state of the system. It is found that silicate weathering, though necessary for the forcing of the system, may be unimportant for the control of the system. It is thus fully possible that the stability is taken care of by feedback on the burials of carbonate, reduced carbon and sulphide, which flows may have the potential to be very sensitive to modest perturbations of the state of the ocean-atmosphere system. It is shown that the coupling between the carbon and oxygen cycles becomes stronger, if silicate weathering is less important for the control, which has interesting consequences. In general, the need to keep the carbon cycle balanced on the long time scale characterizing the oxygen cycle has important implications. If feed back from pCO₂ on silicate weathering is sufficiently weak, we thus find that a positive feedback from pO₂ on the rate of burial of reduced carbon may be favourable for the stability of the system, contrary to what is commonly assumed. It is discussed how the frequency of forest fire may have a key position in the control system together with the degree of oxygen depletion in oceanic deep water, since these phenomena may provide “switches” for the formation of charcoal (i.e. deposition of reduced carbon) and burial of sulfide.