A comparison of several models of carbon turnover in the ocean with respect to their distributions of transit time and age, and responses to atmospheric CO₂ and ¹⁴C

Abstract

Five models of carbon depth distribution in the world ocean are compared with respect to carbon transit-time distribution, age distribution, and integrated responses to histories of fossil CO, and weapons "C. Two models represent the ocean as two well-mixed layers and differ only in the relative sizes of these compartments. The remaining three models consider 19 well-mixed layers and differ in the patterns of carbon transfer among the layers. All five models are required to be compatible with a preindustrial depth profile of natural I F , which is used to fix the values of transfer coefficients. Within this constraint the five models exhibit significantly different responses to fossil CO, and weapons 'F regimes. Of the estimated 134 x 10" g of fossil carbon produced in the period 1860-1975, the models estimate a net uptake range of 24 x 10" to 66 x 1Ol5 gC by the ocean. For weapons 14C the range is 6.0 x lo2 to 1.0 x lo3 kg I4C. Each of these models shows shifts in the implied role of the terrestrial biota between net carbon source and sink, with the latter role dominating in the last years of the simulated period. The largest estimate of source strength for the five models was 0.74 x 10l5 gC yr-l, in contrast to the fossil CO, production rate of -5 x loL5 gC yr-' in 1975. The five models were also used to predict atmospheric CO, levels during the period 1975-2300 for a logistic source that would ultimately release 5000 x 10" gC.

Carbon dioxide increase: the implications at the ecosystem level*

“…Calculations developed to reconcile the observed change in the atmospheric CO2 concentration with estimates of carbon uptake by the oceans and estimates of the increased emission of CO2 from the burning of fossil fuels (Broecker et al, 1979;Killough & Emanuel, 1981;Keeling et al, 1982) indicate the existence of a net sink for carbon, in addition to the sink provided by the oceans. An increase in terrestrial storage of cdrbon in vegetation, stimulated by increased atmospheric CO2, has been suggested as a means by which the terrestrial biosphere could have acted as a net carbon sink with respect to the atmosphere (Bacastow & Keeling, 1973;Oeschger et al, 1975).…”

The Response of CO2 Evolution from Soils to Global Temperature Changes

“…Over the past decade numerous publications have dealt w r ith the global carbon cycle [1][2][3][4][5][6]. It has been stressed that only an accurate understanding of all its aspects wall finally provide the knowledge which is necessary, to answer reliably questions about the future consequences inherent in the evolution of CO2 from fossil fuel burning.…”

Carbon dioxide, climate and the deep ocean circulation: Carbon chemistry model

“…The upwelling returns the deep water to surface. This is a diffusion and advection model where the rate of mixing is calculated from oceanographic data of the rate of 14C and 3H20 from atomic bombs has mixed into the ocean [ 16]. The models adjust the chemistry in each layer according to the carbonate equilibrium reactions.…”