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Glacial-interglacial pCO2 Variations and the Rain Ratio Hypothesis: Implications for Sedimentary Carbonate Preservation/Dissolution Processes
Munhoven, Guy
2008Symposium 'Climate change: from the geologic past to the uncertain future: A tribute to André Berger'
 

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Keywords :
Glacial-interglacial; Atmospheric CO2; Carbonate; Preservation/dissolution
Abstract :
[en] A reduction of the carbonate-carbon to organic-carbon export rain ratio during glacial times has been for years one of the favourite hypotheses to explain the glacial-interglacial atmospheric CO2 variations. This hypothesis have been tested and implications for the dynamics of sedimentary carbonate preservation and dissolution explored with MBM, a multi-box model of the ocean carbon cycle, fully coupled to the transient early diagenesis model MEDUSA. With this coupled model, a peak reduction of the rain ratio by 40% at the Last Glacial Maximum (LGM) was found to produce a net atmospheric pCO2 reduction of about 40 ppm. Changing shelf carbonate accumulation rates and continental weathering inputs produced a 55-60 ppm reduction. The combination of the two mechanisms generates a 90-95 ppm pCO2 change, which compares well with the observations. However, the resulting model sedimentary record is at odds with actual sedimentary records. Changing carbonate accumulation rates on the continental shelf and variable weathering fluxes depress the calcite saturation horizon (CSH) by about 1 km at the LGM; rain ratio variations depress it by another km. In addition to this large amplitude for the CSH, the changing rain ratio also leads to transition zone changes in the model sedimentary record that are opposite in phase with data-based reconstructions.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Munhoven, Guy ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) - Pétrologie, géochimie endogènes et pétrophysique
Language :
English
Title :
Glacial-interglacial pCO2 Variations and the Rain Ratio Hypothesis: Implications for Sedimentary Carbonate Preservation/Dissolution Processes
Publication date :
27 May 2008
Event name :
Symposium 'Climate change: from the geologic past to the uncertain future: A tribute to André Berger'
Event organizer :
Université catholique de Louvain
Event place :
Louvain-la-Neuve, Belgium
Event date :
from 26-04-2008 to 29-04-2008
By request :
Yes
Audience :
International
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Available on ORBi :
since 25 May 2010

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