HR: 08:00h
AN: PP51G-01    [Abstracts]
TI: Separating Palaeoproductivity and Preservation
AU: Versteegh, G J
EM: gerardv@nioz.nl
AF: Hanse Wissenschaftskolleg, Hanse Wissenschaftskolleg Lehmkuhlembusch 4, Delmenhorst, D-27753 Germany
AU: * Zonneveld, K A
EM: zonnev@uni-bremen.de
AF: FB 5-Geowissenschaften, Bremen University, Postfach 330440, Bremen, D-28334 Germany
AB: Understanding climate related changes in concentration and isotopic composition of the atmospheric carbon pool, is a prerequisite for understanding anthropogenic or natural climate forcing. The deep ocean includes the largest pool of carbon and has major influence on the atmosphere on decadal and longer time scales. Its carbon budget depends on export production rate and ventilation steered organic matter (OM) degradation. However, its influence over time is poorly quantified mainly since current proxies for productivity often suffer from modification e.g., dissolution, aerobic decay, or migration. This is often neglected, resulting in misleading interpretations and forcing-mechanism propositions. Separating diagenesis from productivity forms a key question in world-wide operating research programs such as IMAGES (International Marine Global Change Study), JGOFS (Joint Global Ocean Flux Studies) and WCRP (World Climate Research Program). Here we circumvent such modifications by using recognizable OM particles that remain at a stable position within the sediments and for which the degradation rates for various environments are known. Compilation of data on postdepositional aerobic OM degradation at natural oxidation fronts in sediments of the late Quaternary Madeira Abyssal Plain f-turbidite and the last eastern Mediterranean sapropel (S1) reveals a stable ranking of the OM components with respect to their degree of degradation. In contrast to previous work, which mainly emphasises the effects of decay, we use this to separate degradation from bioproductivity. Application of our method will be documented by a reconstruction of past export productivity and deep ocean ventilation of the eastern South Atlantic Ocean and the Southern Ocean (Atlantic sector) since 145,000 BP. We will show that export productivity is regionally defined whereas ventilation and oxygen content variations of the deep ocean occur basin-wide. We indicate that a more active working "biological pump" as a cause for lower glacial atmospheric [CO$_{2}$], might have been overestimated and address possible effects of ventilation changes and post depositional aerobic OM decay on the atmospheric \Delta$^{14}$C
DE: 4805 Biogeochemical cycles (1615)
DE: 4850 Organic marine chemistry
DE: 1806 Chemistry of fresh water
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1635 Oceans (4203)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting