THE DYNAMICS OF THE EARTH'S GLOBAL CARBON CYCLE: A MINIMAL MODEL

A so-called minimal dynamical model for the global carbon cycle of the Earth between the mantle and five reservoirs (oceanic crust, continental crust, continental biosphere, ocean + atmosphere, kerogen) is investigated. The dynamical character of the model means that the effective fluxes to or from each of the reservoirs are integrated over the long-term evolution of the Earth. The model takes into account the major feedbacks acting between the geosphere, biosphere and atmosphere. Silicate rock weathering, e.g., acts as a negative feedback and stabilizes the overall temperature of the Earth. The biosphere representation is based on oxygenic photosynthesis. The Earth system evolves under the influence of increasing insolation as external forcing. Special attention is given to geodynamical processes like spreading, subduction, continental growth, and early degassing, i.e. variable ocean mass. We find that different scenarios of ocean chemistry with changes in pH and incorporation of hydrothermal reactions have a strong influence on the early evolution of the Earth. The major pulses of continental growth are connected with a remarkable redistribution of carbon between the reservoirs caused by the action of weathering processes.