Article (Scientific journals)
MODELING THE PHANEROZOIC CARBON-CYCLE AND CLIMATE - CONSTRAINTS FROM THE SR-87-SR-86 ISOTOPIC RATIO OF SEAWATER
François, Louis; WALKER, J. C. G.
1992In American Journal of Science, 292 (2), p. 81-135
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Abstract :
[en] A numerical model describing the coupled evolution of the biogeochemical cycles of carbon, sulfur, calcium, magnesium, phosphorus, and strontium has been developed to describe the long-term changes of atmospheric carbon dioxide and climate during the Phanerozoic. The emphasis is on the effects of coupling the cycles of carbon and strontium. Various interpretations of the observed Phanerozoic history of the seawater Sr-87/Sr-86 ratio are investigated with the model. More specifically, the abilities of continental weathering, volcanism, and surface lithology in generating that signal are tested and compared. It is suggested that the observed fluctuations are mostly due to a changing weatherability over time. It is shown that such a conclusion is very important for the modelling of the carbon cycle. Indeed, it implies that the conventional belief that the evolution of atmospheric carbon dioxide and climate on a long time scale is governed by the balance between the volcanic input of CO2 and the rate of silicate weathering is not true. Rather carbon exchanges between the mantle and the exogenic system are likely to have played a kev role too. Further, the increase of the global weathering rates with increasing surface temperature and/or atmospheric CO2 pressure usually postulated in long-term carbon cycle and climate modelling is also inconsistent with the new model. Other factors appear to have modulated the weatherability of the continents through time, such as mountain building and the existence of glaciers and ice sheets. Based on these observations, a history of atmospheric carbon dioxide and climate during Phanerozoic time, consistent with the strontium isotopic data, is reconstructed with the model and is shown to be compatible with paleoclimatic indicators, such as the timing of glaciation and the estimates of Cretaceous paleotemperatures.
Disciplines :
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Author, co-author :
François, Louis  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Modélisation du climat et des cycles biogéochimiques
WALKER, J. C. G.;  The University of Michigan > Department of Geological Sciences
Language :
English
Title :
MODELING THE PHANEROZOIC CARBON-CYCLE AND CLIMATE - CONSTRAINTS FROM THE SR-87-SR-86 ISOTOPIC RATIO OF SEAWATER
Publication date :
1992
Journal title :
American Journal of Science
ISSN :
0002-9599
Publisher :
Kline Geology Laboratory
Volume :
292
Issue :
2
Pages :
81-135
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 24 May 2010

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