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XIII-ая конференция

Modelling long-term co-evolution of biosphere and geosphere

Franck S., Bounama C., von Bloh W.

Potsdam Institute for Climate Impact Research, PF 601203, 14412 Potsdam, Germany, +49 331 288 2659, E-mail: franck@pik-potsdam.de

We present a minimal model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, continental biosphere, and the Kerogen, as well as the aggregated reservoir ocean and atmosphere and obtain reasonable values for the present distribution of carbon in the surface reservoirs of the Earth (1). The Earth system model for the long-term carbon cycle is specified by introducing three different types of biosphere: prokaryotes, eucaryotes, and complex multicellular life. They are characterized by different global temperature tolerance windows: prokaryotes [2°C, 100°C], eucaryotes [5°C, 45°C], complex multicellular life [0°C, 30°C]. From the Archaean to the future there always exists a prokaryotic biosphere. 2 Gyr ago eucaryotic life first appears because the global surface temperature reaches the tolerance window for eucaryotes. This moment correlates with the onset of a rapid temperature drop caused by increasing continental area. The resulting increase in the weathering flux takes out carbon dioxide from the atmosphere. In contrast to the eucaryotes the first appearance of complex multicellular life stars with an explosive increase in biomass connected with a strong decrease in Cambrian global surface temperature at about 0.54 Gyr ago. The biological colonization of land surface by metaphyta and the consequent increase in silicate weathering rates caused a reduction in atmospheric carbon dioxide and planetary cooling. After the Cambrian explosion (2) there is a continuous decrease of biomass in all pools. At 0.35 Gyr ago there is a slight drop in all biomass pools connected with the rise of vascular planets. At present the biomass is almost equally distributed between the three pools (3). In contrast to the view of Ward and Brownlee (4), we find that in the long-term future complex organisms do not extinct by an implosion (in contrast to the Cambrian explosion). The ultimate life span of the biosphere is defined by the extinction of prokaryotes in about 1.6 Gyr.

Literature

1. Franck, S., Kossacki, K. J., von Bloh, W., Bounama, C. Long-term evolution of the global carbon cycle: historic minimum of global surface temperature at present // Tellus. 2002. 54B, 325-343.

2. Zhuravlev, A. Y., Riding, R. The ecology of the Cambrian radiation – New York: Columbia University Press, 2001. 525 pages.

3. Von Bloh, W., Bounama, C., Franck, S. Cambrian explosion triggered by geosphere-biosphere feedbacks // Geophys. Res. Lett. 2003. 30 (18). doi: 10.1029/2003GL017928.

4. Ward, P. D., Brownlee, D. The Life and Death of Planet Earth – New York: Henry Holt and Company, 2003. 240 pages.