International Geologiical Congress - Oslo 2008


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EGC-01 General contributions to environmental geochemistry - Part 1


Changes of inorganic carbon and pH in the world ocean on geological time scale


Petr Makkaveev, Shirshov Institute of Oceanology RAS (Russian Federation)


Carbon system of the World Ocean is constantly changing. Temporal scale of these changes varies from a few seconds to a time comparable with the age of the Earth. Every temporal scale corresponds to its characteristic spatial scale from size of the molecule to all the Earth.
Changes of the carbon equilibrium in the waters of the World Ocean during the longest time period were estimated with a help of mathematical modeling. The largest-scale component of variability of the carbon equilibrium of the World Ocean water is connected with processes of the Earth evolution and magma degassing. In general content of carbon forms in the ocean-atmosphere system was decreasing during last 2.5 billon years.
The second large-scale component of the carbon system variability in water that was acquired as a result of the modeling has a period of 150?200 million years. This component can be connected to the rhythms of substance circulation in the Earth mantle.
These changes affect carbon of the atmosphere, hydrosphere, the Earth's crust and the Earth mantle. The designing of conditions of carbon equilibrium in the ocean shows the existence of two more variability cycles by the Quaternary period. One cycle has a period of 90?120 thousands years, another - 20-30 thousand years.
One can suppose that these cycles are connected with the changes of the Earth's orbit parameters and angle of the incline of the Earth's centre. The character of these cyclical changes of pH in the water and content of the dissolved carbon is asymmetrical. A period when the content of carbon in the water is growing and the pH values are decreasing takes about 10?20% of the cycle time. The remaining time period reflects the content of carbon in the ocean?atmosphere system.
The calculations show that in the nearest future (50-200 years) one can expect a decrease of CO2 level both in the Ocean water and the atmosphere.


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