Influence of deep-sea benthic processes on atmospheric CO2

Abstract Understanding ocean—atmosphere carbon-cycle interactions requires attention to the potential importance of marine benthic processes, particularly deep-sea carbonate dissolution. However, because of the wide array of processes that control marine carbonate dissolution rates, it is difficult to identify which processes dominate rates of response to global carbon-cycle perturbations. This paper describes a model that simulates atmospheric CO2, ocean chemistry and sediment carbonate content in a time-dependent fashion. Response times are assessed through an analysis of a series of perturbation experiments in which a pulse of CO2 is added to the model atmosphere. The results of these experiments suggest that the relatively rapid buffering of atmospheric CO2 by seawater is controlled by the rate of ocean mixing and accounts for about 60 % of the total buffering by the ocean-sediment system. The more gradual buffering of atmospheric CO2 and seawater by carbonate sediments is controlled by the rate of sedimentation of carbonate particles, but the rate of this buffering is slower than previously thought because the dissolution or precipitation of carbonates does not produce dissolved carbonate ions on a mole-for-mole basis.