Marine Isotope Stage 11 in the eastern Mediterranean Sea: Nearest analog to the present day?
Zusammenfassung der Projektergebnisse
The similarity in the configuration of the Earth’s orbital parameters and resulting insolation patterns during marine isotopic stage 11 (~400 kyr ago) and the current interglacial, the Holocene, has often been used as an argument to investigate climate trends of MIS11 reconstructed from geological archives could in order to evaluate current and future climate trends. In this study, paleoclimatic and paleoceanographic information has been extracted in the climatically sensitive Mediterranean Sea in one ODP core (ODP Site 964) and one gravity core (GeoTü SL96) throughout marine isotope stage 11 (MIS 11), the Holocene (MIS 1) and adjacent glacial stages. Oxygen isotope ratios and faunal events were combined to develop an age model for the cores. The implied high sedimentation rates allowed for an exceptionally high resolution in the obtained time series. In both records, the isotopically detected deglaciation initiating MIS11 appears to have remained virtually unnoticed by the ecosystem and circulation patterns in the basin until the second insolation peak, 20 kyr into the interglacial, has been reached, triggering the establishment of warm-water fauna in the basin during a period characterised by significant freshwater flux and bottom water stagnation and development of organic-rich sapropel in the deeper part of the basin. Whereas stable isotope records of MIS 11 and MIS 1 are comparable in GeoTü-SL96, exceptionally light oxygen isotopic values for this region are seen at ODP Site 964 during a brief interval in this core, which also corresponds with the deposition of an organic rich sapropel layer in this core during MIS 11. XRF measurement data were used to detect the true thickness, elemental composition and the origin of sediments deposited during the MIS11 freshwater pulse to the basin. Using Ba and Mn concentrations it was possible to detect the original sapropel thickness at ODP Site 964, whereas surprisingly there is clear evidence that no sapropel has been formed at that time in GeoTü SL96. The main freshwater source during MIS11 appears to have been the Nile river discharge (Ti/Al and K/Al ratio) connected with the tropical monsoonal system driven by summer insolation. Although the large isotopic excursion indicates more freshwater than in the Holocene, lack of a sapropel at GeoTü-SL96 indicates a lesser degree of anoxia in the eastern Mediterranean than in the early Holocene. The peak interglacial conditions of MIS11 developed during the sapropel event. Reconstructed SST reached values similar to, but not higher than those observed at the position of the cores today, but the warm-water foraminiferal fauna continued to dominate the sites until well into the glacial MIS10. This transition was associated with a small increase in primary productivity, indicated by an increase in the abundance of benthic foraminifera and a significant decrease in alkenone-derived SST. The observed mismatch in the alignment of the monsoon-driven freshwater events in MIS 11 and MIS 1 with respect to the respective deglaciation invalidates the expected analogy between the two periods. Instead, MIS 11 in the Mediterranean Sea proved to be characterised by a unique climatic development including phenomena not observed in the Holocene despite the analogous insolation trends at that time.
Projektbezogene Publikationen (Auswahl)
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2006. Reconstruction of paleo-SST in the eastern Mediterranean during Marine Isotope Stage 11 by transfer functions. Forams 2006, Natal, Brazil. Anuário do Instituto de Geosciências – UFRJ, 29(19): 614
Numberger, L., Kucera, M., Hemleben, Ch.
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2007. Large difference between MIS 12 and MIS 10 in the eastern Mediterranean Sea. ICP IX, 2007, Shanghai, China. Abstracts and Programme, p. 81
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, H.
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2007. Marine Isotope Stage 11 in the eastern Mediterranean Sea. INQUA 2007, Cairns, Australia. Abstracts and Programme, p. 72
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, H.
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2007. Marine Isotope Stage 11 in the eastern Mediterranean Sea. INQUA-Morss Workshop on MIS 11, 2007, Woods Hole, USA
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, Hoffmann, R.
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2007. Morphotypes of Globigerinoides ruber (white) in the eastern Mediterranean Sea. TMS Foraminifera and Nannofossil Groups Joint Spring Meeting, Angers. Abstracts and Programme, p. 106
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, H., Hoffmann, R., Wunderlich, M.
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2007. Reconstruction of paleo-SST in the eastern Mediterranean during Marine Isotope Stage 11 by planktonic foraminifera counts and stable isotopes. IODP-ICDP Kolloquium 2007, Potsdam, Germany. Abstracts and Programme
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, H., Röhl, U., Badawi, A., van Raden, U., Hoffmann, R.
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2007. Habitats of Globigerinoides ruber (d’Orbigny) in the eastern Mediterranean Sea since the Marine Isotopic Stage 12. IODP-ICDP Kolloquium 2008, Hannover, Germany. Abstracts and Programme, p.99
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, Hoffmann, R.
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2007. Habitats of Globigerinoides ruber (d’Orbigny) in the eastern Mediterranean Sea since the Marine Isotopic Stage 12. Oxygen isotopes as tracers of Mediterranean climate variability: linking past present and future, 2008, Pisa, Italy. Abstracts and Programme, p.53
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, Hoffmann, R.
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2008. Habitats of Globigerinoides ruber (d’Orbigny) in the eastern Mediterranean Sea since the Marine Isotopic Stage 12. TMS Foraminifera and Nannofossil Groups Joint Spring Meeting, Tübingen. Abstracts and Programme, p. 40
Numberger, L., Kucera, M., Hemleben, Ch., Mackensen, A., Schulz, H., Hoffmann, R., Wunderlich, M.
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2009. Habitats, abundance patterns and isotopic signals of morphotypes of the planktonic foraminifer Globigerinoides ruber (d’Orbigny) in the eastern Mediterranean Sea since the Marine Isotopic Stage 12. Marine Micropaleontology
Numberger, L., Hemleben, Ch., Hoffmann, R., Mackensen, A., Schulz, H., Wunderlich, J-M., Kucera, M.
