HR: 13:55h
AN: PP43E-02    [Abstracts]
TI: Calcium Carbonate Dissolution in Sinking Particulate Matter
AU: * Jokulsdottir, T
EM: tinna@uchicago.edu
AF: University of Chicago, 5734 S. Ellis Ave., Chicago, IL 60637, United States
AU: Archer, D
EM: d-archer@uchicago.edu
AF: University of Chicago, 5734 S. Ellis Ave., Chicago, IL 60637, United States
AB: Atmospheric carbon dioxide is sequestered into the deep ocean via sinking particles that are produced in the euphotic zone. These particles are composed of organic carbon, calcium carbonate and silica that remineralizes as the particles sink through the water column. Calcium carbonate is a key component in ballasting the particles; according to model calculations it has the potential to determine to a large degree the strength of the biological pump. Understanding the mechanisms of calcite dissolution in the water column are important to the understanding of cycling of organic and inorganic material in the ocean. We have developed an idealized, mechanistic model of particles sinking to the deep ocean, in which settling velocity is calculated from first principles. Calcium carbonate (calcium + aragonite) dissolution is both biologically and thermodynamically mediated. Opal dissolution and organic carbon respiration are temperature dependent. Global compilations of sediment trap data are used to constrain poorly known parameters such as the CaCO₃ dissolution constant and organic carbon respiration rates. Coupling our sinking particle model to a sediment diagenesis model, we are able to reproduce global burial and sea floor dissolution rates within a factor of 2. A higher export ratio has been hypothesized to lower the glacial pCO₂ level. Stratification and circulation changes associated with global warming is likely to bring about a change in export production, thus possibly changing the export ratio (orgC/CaCO₃) of material sinking out of the euphotic zone. We explore the response of the lysocline to changes in export ratio.
DE: 4255 Numerical modeling (0545, 0560)
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4806 Carbon cycling (0428)
DE: 4926 Glacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting