WUN Earth Systems virtual seminar: Modelling the ocean carbon cycle - lessons from the past and entering new territory for the future
Christopher Heinze, Bergen University
Further details at: http://wun.ac.uk/events/horizons-earth-systems-4
The ocean is the major long-term sink for human-produced CO2 emitted to the atmosphere. The ocean is also major factor in natural glacial-interglacial atmospheric CO2variations. We employ prognostic ocean carbon cycle models for determining in which way the ocean carbon cycle interacts with climate. In order to exploit the information from the sedimentary paleo-climate record for a calibration and proper design of ocean carbon cycle process representations in models we have developed the method of synthetic sediment cores.
An early diagenesis model was coupled with a biogeochemical ocean general circulation model to allow the build-up of time dependent sediment layers under each grid point of the model. An age transport model was developed for each sediment weight fraction in order to allow proper synchronisation of observed sediment cores with the modelled record. The method in principles allows to directly using CaCO3, opal, as well as δ13C data (planktonic, benthic) from sediment core data for the calibration of carbon cycle model parameters such as the CaCO3:POC rain ratio, stoichiometry of carbon and nutrients in particulate matter, and also circulation fields as functions of climatic state variables. Thus there is some hope to optimally estimate the governing model parameters for natural carbon cycle climate feedbacks through systematic combination of models and the paleo-climatic records.
This will also be of use for a better quantification of future carbon cycle climate feedbacks. However, there are processes, for which no paleo-analogue is readily available:
- In the on-going anthropocene quickly new amounts of carbon are emitted to the atmosphere-ocean-land system, while the glacial-interglacial changes were mainly redistributions of carbon within the Earth system.
- The timing of the anthropogenic CO2 increase is much faster than glacial-interglacial changes.
- The extent to which carbon will accumulate in the atmosphere and upper ocean is and will be significantly higher than during glacial-interglacial transitions.
We have to prepare for this new territory with a broad range of possible scenarios, through inclusion of findings from laboratory and mesocosm experiments in ocean models, through developments of early warning indicators for checking whether potential feedback process in fact are in place, and with high quality observational data syntheses as a basis for adequate modelling.