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FP5

ORFOIS Résumé de rapport

Project ID: EVK2-CT-2001-00100
Financé au titre de: FP5-EESD
Pays: Germany

BOGCM HAMOCC run, glacial

A model of the marine carbon cycle (HAMOCC3, Hamburg Model of the Ocean Carbon Cycle) was driven off-line by glacial oceanic circulation and dust input fields. As a novelty developed within ORFOIS, the model incorporates both the open and the closed system components that constitute the marine carbon cycle. The newly added open system component consists of Aeolian dust and fluvial CaCO3 input (the latter kept constant in both experiments) and subsequent burial and dissolution of CaCO3 in the sediment. The closed system component consists of the biological pump, the counter pump as well as the internal redistribution by the oceanic circulation.

Thus the model used here can be considered an improvement over the more often used and easier to handle but less realistic closed system models, in which river input of CaCO3 is used to balance the loss from burial to the sediment. The closed system models proved to be fairly insensitive to changes in the potential driving mechanisms for glacial pCO2 reduction.

The oceanic response to the glacial forcing is decreased total CO2, increased total alkalinity, and decreased PO4. The atmospheric pCO2 drops to some 230 ppm after 8,000 years of integration. The drawback is that the lysocline is below the sea floor everywhere (not shown). We still think that we have identified and installed a potentially crucial and efficient mechanism to lower pCO2. This is one step forward to identify the control mechanisms for glacial/ interglacial pCO2 changes, which have been tried to identify and simulate now for more than 20 years.

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Grassl HARTMUT, (Director)
Tél.: +49-40-41173233
Fax: +49-40-41173298
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