Ocean carbon cycle in Earth system modelling
Dr Michio Kawamiya, Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology, Japan

Dr Michio Kawamiya received his PhD in Oceanography from the University of Tokyo, Japan in 1997. He since has held research positions at the University of Tokyo and the University of Kiel, Germany and JAMSTEC. He has been a Group Leader at JAMSTEC since 2004. His interests include modelling of carbon cycle and ocean ecosystem, and global warming projection. He is currently a member of the national committee for IGBP.

Presentation (568kb)

It has been recognised through modelling efforts that climate–carbon cycle interactions may form a positive feedback loop for the global warming. Actual extent of the feedback is, however, strongly model dependent. This situation necessitates an organised activity to compare results from various models and discuss what causes such differences between models. An international project C4MIP (Coupled Carbon-Cycle Climate Model Inter-comparison Project) has been established in order to facilitate such comparative studies and discussions made under C4MIP are likely to be reflected in the 4th assessment report of IPCC (Intergovernmental Panel on Climate Change). All the eleven models participating in C4MIP show an agreement in that CO₂ uptake by both the land and the ocean is reduced due to future warming, although the increase of atmospheric CO₂ concentration varies among models between 20ppm and 200ppm by the end of the 21st century. Eight models attribute most of the changes to the land, while three attribute it comparably to both the land and the ocean. Although the role of the ocean does not appear to be dominant in the climate–carbon cycle feedback, local response of the North Atlantic in our simulation is as strong as in the land areas with an intense feedback, and will be discussed in more details in the presentation. Furthermore, there are some inconsistencies between results from ocean carbon cycle models and those from observation-based studies. For example, air-sea CO₂ fluxes obtained by inversion techniques and carbon isotope analysis yield much larger interannual variations than those by forward numerical models. Such problems may indicate that the oceanic feedback in the climate–carbon cycle system is currently underestimated.