| Volumes and Issues Contents of Issue 2 |
www.geosci-model-dev-discuss.net/2/1023/2009/
doi:10.5194/gmdd-2-1023-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
An isopycnic ocean carbon cycle model
1Bjerknes Centre for Climate Research, Bergen, Norway
2Geophysical Institute, University of Bergen, Bergen, Norway
3Nansen Remote Sensing and Environmental Research Centre, Bergen, Norway
4Max-Planck Institute for Meteorology, Hamburg, Germany
Abstract. The carbon cycle is a major forcing component in the global climate system. Modelling studies aiming to explain recent and past climatic changes and to project future ones thus increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here we present first results from a newly developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents interior ocean transport of biogeochemical tracers well and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the biogeochemical code for use with an isopycnic coordinate are in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. Use of a prognostic slab atmosphere allows us to assess the effect of the changes in export production on global ocean carbon uptake and atmospheric CO2 levels. Sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of modelled air-sea fluxes and nutrient distributions.
Discussion Paper (PDF, 7677 KB) Interactive Discussion (Closed, 6 Comments) Final Revised Paper (GMD)
Citation: Assmann, K. M., Bentsen, M., Segschneider, J., and Heinze, C.: An isopycnic ocean carbon cycle model, Geosci. Model Dev. Discuss., 2, 1023-1079, doi:10.5194/gmdd-2-1023-2009, 2009. Bibtex EndNote Reference Manager XML
