Ocean circulation and the ice-temperature conundrum: Unraveling the transition from the Cretaceous greenhouse into today's icehouse world
Zusammenfassung der Projektergebnisse
The Emmy Noether research group focused on identifying past changes in ocean temperature, hydrography and oxygenation across a wide range of different boundary conditions of the Earth’s climate system (ranging from the Late Cretaceous greenhouse to the Neogene’s icehouse world; 115 to 0 Ma). The findings allow new insights into the role of ice sheets in the climate system during that time and, through the combination with foraminifer-based geochemical and biotic data sets, they also help to clarify the effects of ocean temperature and oxygenation changes on ocean circulation and marine ecosystem dynamics. To tackle controversially discussed paleoclimatic and paleoceanographic issues, the proposed project combined “classical” paleoceanographic proxies (e.g., δ18O, Mg/Ca, and assemblage counts) with new proxies that are about to be established. These new proxies include (1) the carbonate “clumped-isotope” paleothermometer (CCIP) and (2) a paleo-oxygenation proxy based on benthic foraminiferal pore characteristics (BFPC). For clumped isotopes, a new calibration has been developed at Goethe University Frankfurt that can be used to reconstruct past temperatures. BFPC as bottom-water oxygenation proxy had been tested and calibrated successfully for different species of benthic foraminifera. Test of these calibration were performed on sediments from the Mediterranean sapropel S1 and the mid-Cretaceous Oceanic Anoxic Event 1a (early Aptian) to provide a test bed for the application of BFPC in geologic times. Within the framework of two PhD projects, several case studies of critical time intervals have been studied. Highlights of these projects are (1) the application of benthic foraminiferal assemblages across a proposed early Maastrichtian glaciation event which suggest changes in ocean circulation rather than ice-sheet build-up occurred across the so-called Campanian-Maastrichtian boundary event; (2) sub-orbitally resolved Mg/Ca and stable isotope records of planktic foraminifera in the North Atlantic across the intensification of Northern Hemisphere glaciation showing the influence of different intermediate-water masses and stratification changes; and (3) the finding that organic-rich intervals associated with the termination of the middle Eocene climatic optimum (MECO) are a widespread feature even in open ocean settings, pointing towards their role as carbon sinks and therefore drivers of the observed changes in pCO2 and CCD. Within the report period, outreach was done in form of articles in public newspapers (Frankfurter Rundschau, local part of Bild, Forschung aktuell) and an interview with the local TV station HR.
Projektbezogene Publikationen (Auswahl)
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(2012): Evolution of mid- to Late Cretaceous oceans-A 55 million year record of Earth’s temperature and carbon cycle. Geology 40: 107-110
Friedrich, O., Norris, R.D. & Erbacher, J.
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(2012): Influence of test size, water depth, and species ecology on Mg/Ca, Sr/Ca, δ18O and δ13C in nine modern species of planktic foraminifers. Earth and Planetary Science Letters 319-320: 133-145
Friedrich, O., Schiebel, R., Wilson, P.A., Weldeab, S., Beer, C.J., Cooper, M.J. & Fiebig, J.
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2012): Campanian-Maastrichtian intermediate- to deep-water changes in the high latitudes: Benthic foraminiferal evidence. Paleoceanography 27
Koch, M.C. & Friedrich, O.
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(2013): Campanian-Maastrichtian ocean circulation in the tropical Pacific. Paleoceanography 28, Issue 3
September 2013, Pages 562–573
Claudia Jung, Silke Voigt, Oliver Friedrich, Mirjam C. Koch, Martin Frank
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(2013): Relationship between the pore density in benthic foraminifera and bottomwater oxygen content. Deep-Sea Research I 76: 85-95
Kuhnt, T., Friedrich, O., Schmiedl, G., Milker, Y., Mackensen, A. & Lückge, A.
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(2014): Automatical and manual analyses of the pore density-to-oxygen relationship in Globobulimina turgida (BAILEY). Journal of Foraminiferal Research 44: 5-16
Kuhnt, T., Schiebel, R., Schmiedl, G., Milker, Y., Mackensen, A. & Friedrich, O.
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(2014): Changes in Southern Ocean bottom water environments associated with the Middle Eocene Climatic Optimum. Palaeogeography, Palaeoclimatology, Palaeoecology 405: 16-27
Möbius, I., Friedrich, O. & Scher, H.D.
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(2014): Empirical calibration of the clumped isotope paleothermometer using calcites of various origins. Geochimica et Cosmochimica Acta 141: 127-144
Wacker, U., Fiebig, J., Schöne, B.R., Bahr, A., Friedrich, O., Tütken, T., Gischler, E. & Joachimski, M.M.
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(2015): Episodes of intensified biological productivity in the subtropical Atlantic Ocean during the termination of the Middle Eocene Climatic Optimum (MECO). Paleoceanography 30
Möbius, I., Friedrich, O., Edgar, K.M. & Sexton, P.F.
