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Carbon cycle and climate change during the Cretaceous inferred from a biogeochemical carbon cycle model
Author(s) -
Tajika Eiichi
Publication year - 1999
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1046/j.1440-1738.1999.00238.x
Subject(s) - carbon cycle , cretaceous , geology , biogeochemical cycle , paleoclimatology , carbon fibers , total organic carbon , climate change , paleoceanography , paleontology , atmospheric sciences , earth science , oceanography , chemistry , environmental chemistry , ecology , materials science , ecosystem , composite number , composite material , biology
The carbon cycle and climate change during the Cretaceous are reconstructed by using a carbon cycle model, and discussed. The model takes into account the effects of the enhanced magma eruption and organic carbon burial rates, both of which characterize the carbon cycle during the Cretaceous. The result for the CO 2 variation is roughly consistent with the pattern of paleoclimate change inferred from the geological record. The CO 2 level during the mid‐Cretaceous is estimated to be 4–5 times the present atmospheric level, corresponding to a surface temperature of 20–21°C. The warm, equable Cretaceous resulted from the effects of tectonic forcing such as enhanced CO 2 degassing, although the enhanced organic carbon burial has a tendency to decrease the CO 2 level. The organic carbon burial rate during the Cretaceous is generally larger than those for the Cenozoic, and is characterized by three major peaks (~ 1.5–1.8 times the present‐day value) corresponding to the major oceanic anoxic events. In the case for the extensive mantle plume degassing, although the CO 2 levels are only 10% higher than those for the standard case during 120–100 Ma, the causes for the enhanced CO 2 levels would be quite different. If the globally averaged surface temperature had increased due to paleogeographic forcing effects, the greenhouse effect of CO 2 (and thus the CO 2 level) should be lower than the values estimated for the standard case. If the CO 2 levels are similar to, but the surface temperature is higher than, those for the standard case, either the parameter β (an influence of the Himalayas–Tibetan Plateau on the global weathering today) may be unreasonably large or the dependence of the silicate weathering rate on the CO 2 partial pressure and the surface temperature should be much weaker than those previously proposed.