Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 3, 143-167, 2010
http://www.geosci-model-dev.net/3/143/2010/
doi:10.5194/gmd-3-143-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
 
16 Feb 2010
An isopycnic ocean carbon cycle model
K. M. Assmann1, M. Bentsen1,2, J. Segschneider3, and C. Heinze1,4 1Bjerknes Centre for Climate Research, Bergen, Norway
2Nansen Remote Sensing and Environmental Research Centre, Bergen, Norway
3Max-Planck Institute for Meteorology, Hamburg, Germany
4Geophysical Institute, University of Bergen, Bergen, Norway
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, 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 well the interior ocean transport of biogeochemical tracers 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 ocean biogeochemistry model HAMOCC, for use with an isopycnic coordinate, were 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. The 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 nutrient distributions and liniting factors of biological production.

Citation: Assmann, K. M., Bentsen, M., Segschneider, J., and Heinze, C.: An isopycnic ocean carbon cycle model, Geosci. Model Dev., 3, 143-167, doi:10.5194/gmd-3-143-2010, 2010.
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