Vorarbeiten zum geplanten Projekt Das Mittel-Pleistozän: führte marine biologische Produktivität zur Änderung von pCO2?

• Antragstellerin: Professorin Dr. Liselotte Diester-Haass
• Fachliche Zuordnung: Paläontologie
• Förderung: Förderung von 2012 bis 2013
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 237930779

The Mid Pleistocene transition (MPT), the period between about 1200 to 700 ky marks the transition from the 40 ky to a 100 ky world, and the development of thicker ice sheets without any change in the mode of orbital forcing, and a decrease in atmospheric pCO2 by about 30 ppm. The cause is not yet well understood. I plan to investigate possible causes in a broader project:. My aim is to test the greenhouse forcing hypothesis: was marine biological productivity globally enhanced in glacial and interglacial periods during the MPT leading to storage of carbon in deep ocean basins? Did terrestrial input of nutrients and organic detritus during this period of a shift in global aridity (de Menocal, 1995) foster productivity, lead to lighter d13C in foraminiferal shells and drop in pCO2atm.? Was the paleoproductivity increase restricted to the subantarctic ocean (Martinez-Garcia et al., 2009) or was there a global increase in marine productivity?Preliminary studies are necessary before applying for funds for a broader study. First I want to compare in about 100 samples from ODP Site 1090 paleoproductivity estimates based on accumulation rates of benthic foraminifera (BFAR) with geochemically established paleoproductivity data in the same intervals with high and low productivity (Martinez-Garcia et al., 2009; 2011). If the results do not agree, I have to find possible reasons.Second, I want to test whether the number of available isotope data from several ODP Sites, published by Raymo et al. (1997), is sufficient to see the relation between productivity changes and carbon and oxygen isotope changes, or whether it is necessary to have isotope data from exactly the same samples as for BFAR studies. It is important to see, for example, whether increases in productivity are related to lighter carbon isotope values, as has been observed in the Late Miocene Biogenic Bloom period and attributed to input of light terrestrial organic matter (Diester-Haass et al., 2005; 2006) or whether increased productivity is related to heavier isotope carbon values, that might be explained by withdrawal of light carbon from the global carbon reservoir ( as observed at the Oligocene/Miocene transition (Diester-Haass et al., submitted). Do changes occur simultaneously or are lead-lag phenomena observed? To clarify this question for future work we propose to make a test at Site 607. I plan to study about 100 samples for BFAR-productivity and ask K. Billups to study stable isotopes in the same samples. The result of this comparison (productivity versus Raymo isotope data and productivity versus Billups isotope data) allows to decide whether the future project needs funds for isotope data or whether existing datare sufficient.

• DFG-Verfahren: Sachbeihilfen
• Internationaler Bezug: USA
• Beteiligte Person: Professorin Dr. Katharina Billups