scholarly journals Adjoint sensitivity of the air-sea CO<sub>2</sub> flux to ecosystem parameterization in a three-dimensional global ocean carbon cycle model

2007 ◽  
Vol 4 (2) ◽  
pp. 1377-1404 ◽  
Author(s):  
J. F. Tjiputra ◽  
A. M. E. Winguth
Keyword(s):  
Carbon Cycle ◽  
Marine Ecosystem ◽  
Three Dimensional ◽  
Co2 Flux ◽  
Global Ocean ◽  
Ecosystem Structure ◽  
Cycle Model ◽  
Ocean Carbon Cycle ◽  
Carbon Cycle Model ◽  
Ocean Carbon

Abstract. The regional sensitivity of air-sea CO2 flux to ecosystem components and parameters in a three-dimensional ocean carbon cycle model is estimated using an adjoint model. Adjoint sensitivities to the global air-sea CO2 flux reveal that the biological component of the model is significant in the high latitudes of both hemispheres and in the Equatorial Pacific. More detailed analysis indicates that zooplankton grazing activity plays a major role in the carbon exchange in the above regions. The herbivores' ingestion parameter in the model regulates the flux of remineralized (i.e. regenerated) biogenic nutrients; thus, substantially controls the biological production and the concentration of dissolved inorganic carbon (DIC) in the euphotic zone. Over a 10-year period, reducing the herbivores' ingestion parameter in the model by 25% could increase the global uptake of atmospheric carbon by 6 Pg C. Thus, climate induced changes in the marine ecosystem structure are of importance for the future uptake of atmospheric CO2.

scholarly journals An isopycnic ocean carbon cycle model

2009 ◽  
Vol 2 (2) ◽  
pp. 1023-1079 ◽  
Author(s):  
K. M. Assmann ◽  
M. Bentsen ◽  
J. Segschneider ◽  
C. Heinze
Keyword(s):  
Carbon Cycle ◽  
Global Ocean ◽  
System Modelling ◽  
Surface Boundary ◽  
Cycle Model ◽  
Biological Production ◽  
Carbon Cycle Model ◽  
Export Production ◽  
Sensitivity Studies ◽  
Ocean Carbon

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.

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