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Title: Carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years

Abstract

A computer model has been constructed that considers the effects on the CO/sub 2/ level of the atmosphere, and the Ca, Mg, and HCO/sub 3/ levels of the ocean, of the following processes: weathering on the continents of calcite, dolomite, and calcium-and-magnesium-containing silicates; biogenic precipitation and removal of CaCO/sub 3/ from the ocean; removal of Mg from the ocean via volcanic-seawater reaction; and the metamorphic-magmatic decarbonation of calcite and dolomite (and resulting CO/sub 2/ degassing) as a consequence of plate subduction. Assuming steady state, values for fluxes to and from the atmosphere and oceans are first derived for the modern ocean-atmosphere system. Then the consequences of perturbing steady state are examined by deriving rate expressions for all transfer reactions. These rate expressions are constructed so as to reflect changes over the past 100 my. Results indicate that the CO/sub 2/ content of the atmosphere is highly sensitive to changes in seafloor spreading rate and continental land area, and, to a much lesser extent, to changes in the relative masses of calcite and dolomite. Consideration of a number of alternative seafloor spreading rate formulations shows that in all cases a several-fold higher CO/sub 2/ level for the Cretaceous atmosphere (65-100 mymore » BP) is obtained via the model. Assuming that CO/sub 2/ level and surface air temperature are positively correlated via an atmospheric greenhouse model, they authors predict Cretaceous paleotemperatures which are in rough general agreement with independent published data. Consequently, their results point to plate tectonics, as it affects both metamorphic-magmatic decarbonation and changes in continental land area, as a major control of world climate.« less

Authors:
; ;
Publication Date:
Research Org.:
Yale Univ., New Haven, CT
OSTI Identifier:
6582171
Resource Type:
Journal Article
Journal Name:
Am. J. Sci.; (United States)
Additional Journal Information:
Journal Volume: 283:7
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; CARBON DIOXIDE; ATMOSPHERIC CHEMISTRY; CARBONATES; MINERAL CYCLING; SILICATES; BIOGEOCHEMISTRY; CALCIUM; CLIMATES; GEOCHEMISTRY; MAGNESIUM; MASS BALANCE; MATHEMATICAL MODELS; METAMORPHIC ROCKS; OCEANOGRAPHY; PLATE TECTONICS; SEA-FLOOR SPREADING; SUBDUCTION ZONES; WEATHERING; ALKALINE EARTH METALS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; CHEMISTRY; ELEMENTS; METALS; OXIDES; OXYGEN COMPOUNDS; ROCKS; SILICON COMPOUNDS; TECTONICS; 580400* - Geochemistry- (-1989); 500200 - Environment, Atmospheric- Chemicals Monitoring & Transport- (-1989)

Citation Formats

Berner, R A, Lasaga, A C, and Garrels, R M. Carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years. United States: N. p., 1983. Web. doi:10.2475/ajs.283.7.641.
Berner, R A, Lasaga, A C, & Garrels, R M. Carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years. United States. doi:10.2475/ajs.283.7.641.
Berner, R A, Lasaga, A C, and Garrels, R M. Thu . "Carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years". United States. doi:10.2475/ajs.283.7.641.
@article{osti_6582171,
title = {Carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years},
author = {Berner, R A and Lasaga, A C and Garrels, R M},
abstractNote = {A computer model has been constructed that considers the effects on the CO/sub 2/ level of the atmosphere, and the Ca, Mg, and HCO/sub 3/ levels of the ocean, of the following processes: weathering on the continents of calcite, dolomite, and calcium-and-magnesium-containing silicates; biogenic precipitation and removal of CaCO/sub 3/ from the ocean; removal of Mg from the ocean via volcanic-seawater reaction; and the metamorphic-magmatic decarbonation of calcite and dolomite (and resulting CO/sub 2/ degassing) as a consequence of plate subduction. Assuming steady state, values for fluxes to and from the atmosphere and oceans are first derived for the modern ocean-atmosphere system. Then the consequences of perturbing steady state are examined by deriving rate expressions for all transfer reactions. These rate expressions are constructed so as to reflect changes over the past 100 my. Results indicate that the CO/sub 2/ content of the atmosphere is highly sensitive to changes in seafloor spreading rate and continental land area, and, to a much lesser extent, to changes in the relative masses of calcite and dolomite. Consideration of a number of alternative seafloor spreading rate formulations shows that in all cases a several-fold higher CO/sub 2/ level for the Cretaceous atmosphere (65-100 my BP) is obtained via the model. Assuming that CO/sub 2/ level and surface air temperature are positively correlated via an atmospheric greenhouse model, they authors predict Cretaceous paleotemperatures which are in rough general agreement with independent published data. Consequently, their results point to plate tectonics, as it affects both metamorphic-magmatic decarbonation and changes in continental land area, as a major control of world climate.},
doi = {10.2475/ajs.283.7.641},
journal = {Am. J. Sci.; (United States)},
number = ,
volume = 283:7,
place = {United States},
year = {1983},
month = {9}
}