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3.17.1 Overview

This model overlays the dissolved inorganic carbon biogeochemistry model (the ``dic'' package) over a 2.8$ ^o$ global physical model. The physical model has 15 levels, and is forced with a climatological annual cycle of surface wind stresses Trenberth et al. [1989], surface heat and freshwater fluxes Jiang et al. [1999] with additional relaxation toward climatological sea surface temperature and salinity Levitus and T.P.Boyer [1994a,b]. It uses the Gent and and McWilliams Gent and McWilliams [1990] eddy parameterization scheme, has an implicit free-surface, implicit vertical diffusion and uses the convective adjustment scheme. The files for this experiment can be found in the verification directory under tutorial_global_oce_biogeo.

The biogeochemical model considers the coupled cycles of carbon, oxygen, phosphorus and alkalinity. A simplified parameterization of biological production is used, limited by the availability of light and phosphate. A fraction of this productivity enters the dissolved organic pool pool, which has an e-folding timescale for remineralization of 6 months [following Yamanaka and Tajika, 1997]. The remaining fraction of this productivity is instantaneously exported as particulate to depth [Yamanaka and Tajika, 1997] where it is remineralized according to the empirical power law relationship determined by Martin et al [1987]. The fate of carbon is linked to that of phosphorus by the Redfield ratio. Carbonate chemistry is explicitly solved Follows et al. [ress] and the air-sea exchange of CO$ _2$ is parameterized with a uniform gas transfer coefficient following Wanninkhof [1992]. Oxygen is also linked to phosphorus by the Redfield ratio, and oxygen air-sea exchange also follows Wanninkhof [1992]. For more details see Dutkiewicz et al. [2005].

The example setup described here shows the physical model after 5900 years of spin-up and the biogeochemistry after 2900 years of spin-up. The biogeochemistry is at a pre-industrial steady-state (atmospheric ppmv is kept at 278). Five tracers are resolved: dissolved inorganic carbon ($ DIC$ ), alkalinity ($ ALK$ ), phosphate ($ PO4$ ), dissolved organic phosphorus ($ DOP$ ) and dissolved oxygen ($ O2$ ).

Figure 3.20: Modelled annual mean air-sea CO$ _2$ flux (mol C m$ ^{-2}$ y$ ^{-1}$ ) for pre-industrial steady-state. Positive indicates flux of CO$ _2$ from ocean to the atmosphere (out-gassing), contour interval is 1 mol C m$ ^{-2}$ y$ ^{-1}$ .
\includegraphics[width=\textwidth,height=.3\textheight]{s_examples/global_oce_biogeo/co2flux.eps}

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Next: 3.17.2 Equations Solved Up: 3.17 Biogeochemistry Tutorial Previous: 3.17 Biogeochemistry Tutorial   Contents
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