Atmospheric Ocean System

Oceanic Carbon Model, description

The atmospheric CO2 increase is calculated as follows:

N_a = E_fossil + E_land-use - NEP_t - N_o (in Pg C yr^-1)

with:
N_a = atmospheric increase
E_fossil = Energy and industrial emissions
El_and-use = Land-use emissions (including terrestrial uptake by regrowing vegetation)
NEP_t = Terrestrial uptake by full-grown vegetation
N_o = Oceanic uptake.

In the historical period (1765-1970) the model results are validated using data on atmospheric CO₂ concentration and the analysis of C fluxes based on Bern-CC presented in the Third Assessment Report of IPCC (IPCC, 2001).
The OCM computes the air-sea flux based on the CO₂ concentration in the atmosphere and the surface ocean. Initially (1765) these partial pressures were assumed to be equal (278 ppmv). The perturbation of dissolved inorganic carbon is calculated in ten time steps each year and used, in turn, to calculate the new partial pressure of CO₂ in the ocean mixed layer (upper layer).
A positive feedback loop is caused by temperature increases of the ocean (Joos et al., 1999). Higher temperatures influence the chemical CO₂ buffering system which can result in reduced carbon transport from the mixed layer to deeper layers. This may lead to a reduction in oceanic carbon uptake and an increase in the atmospheric CO₂ growth. This feedback is taken into account in the OCM by correcting the calculated partial pressure of CO₂ in the ocean mixed layer with an exponential function using the temperature increase calculated in the Climate Model of IMAGE calculated for this layer.
The calculated partial pressure of CO₂ in the surface layer results in the air-sea CO₂ flux. The carbon flux budget can be drawn up and the atmospheric CO₂ concentration of CO₂ derived, after ten time steps covering one year.

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• to  external references
• to  MNP references