Tropisch-polare Klimaverknüpfungen im Nordatlantik während des letzten Interglazials
Zusammenfassung der Projektergebnisse
The last interglacial or Marine Isotope Stage (MIS) 5e, which lasted from about ~129 to 116 thousand years ago (ka), holds important implications for the projected global warming, as this geological interval was significantly warmer than preindustrial. Paleo-data obtained in the frame of the DFG grant helped to improve our current understanding of the MIS 5e paleoceanography in the subarctic and (sub)tropical North Atlantic, providing new insights into ice-sheets dynamics and cross-latitudinal climatic teleconnections. In the frame of the project, a multi-proxy dataset comprising stable oxygen and carbon isotope compositions, alkenone-derived sea surface temperatures (SST), planktic foraminiferal assemblages, ice-rafted debris (IRD) and X-ray fluorescence (XRF) elemental data was produced using high-quality marine sediments from the Nordic Seas, the Bahama region and the Tobago Basin (southeastern Caribbean Sea). New data from the Nordic Seas (M23351, ODP Site 986) suggest that deglacial meltwater strongly influenced the Nordic Seas during early MIS 5e (~129-125 ka). In particular, stable oxygen and carbon isotope records and IRD content reveal major freshwater additions from the disintegrating Svalbard-Barents Sea Ice Sheet and the northeastern Greenland Ice Sheet until ~125 ka. The data also indicate that a thick deglacial meltwater lid hindered a northward propagation of warm and saline Atlantic Water at the sea surface during early MIS 5e. As a result, full resumption of the Atlantic Meridional Overturning Circulation (AMOC) with modern-like deep-water overflows from the Nordic Seas established only in the mid-MIS 5e. Although influence of the Atlantic Water at the sea surface during the penultimate deglaciation, including early MIS 5e, was notably decreased, its inflow into the Nordic Seas never completely ceased. Indeed, a thorough inspection of the data (e.g., occurrences of B. megastoma, magnetic susceptibility) suggests that the Atlantic Water penetrated polewards during the penultimate deglaciation, likely underneath the low-density halocline layer. This revised view is crucial for understanding variations in the vertical water mass structure in the Nordic Seas, which influences deep-water formation and overflow into the open North Atlantic. Comparison of published data from the Labrador Sea with the new records from the Nordic Seas provides evidence for a millennial-scale sea surface cooling and reduction in vertical water convection during early MIS 5e (at ~126.5 ka), which appears to follow a meltwater discharge event attributed to melting of the Greenland Ice Sheet. Furthermore, a multiproxy dataset from the Bahama region (core MD99-2202) reveals, for the first time, a comparable early-MIS 5e cooling event in the subtropical North Atlantic. The cooling was associated with a sudden southward displacement of the Intertropical Convergence Zone (ITCZ), presumably in relation to a temporary reduction in deep-water formation and weakening of the AMOC strength. These observations lead to the inference that the persistent ocean freshening in the high northern latitudes during early MIS 5e accounted for unstable deep-water formation and a particularly sensitive climatic regime, associated with the abrupt warm-cold switches which could be traced across various oceanic basins. In addition, data from the Tobago Basin (core MD99-2198) suggest warming of the tropical North Atlantic during cold events in the high northern latitudes, i.e., in agreement with temperature development in Antarctica. Therefore, it was argued that the ocean properties in the region were influenced by the bipolar seesaw and AMOC variations, and importantly, not only during the last (de)glacial period, but also during stadial-interstadial climate variability of the generally warmer MIS 5a-5d and, possibly, during the penultimate glacial-interglacial transition.
Projektbezogene Publikationen (Auswahl)
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MIS5e hydrographic shifts linked to Poster meltwater discharges from the East Greenland margin. European Geosciences Union (EGU) General Assembly 2016, Vienna (Austria), 17-22 April 2016
Zhuravleva, A., Bauch, H. A., and Van Nieuwenhove, N.
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Atlantic water heat transfer through the Arctic Gateway (Fram Strait) during the Last Interglacial. (2017) Global and Planetary Change, 157, 232-243
Zhuravleva, A., Bauch, H. A., and Spielhagen, R. F.
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Last Interglacial (MIS5e) hydrographic shifts linked to meltwater discharges from the East Greenland margin. (2017) Quaternary Science Reviews, 164, 95-109
Zhuravleva, A., Bauch, H. A., and Van Nieuwenhove, N.
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Meltwater release from a receding East Greenland ice sheet margin after the penultimate glacation. 5th International Conference on Palaeo-Arctic Spatial and Temporal (PAST) Gateways, Kristineberg Field Station, Sven Lovén Centre/University of Gothenburg Fiskebäckskil (Sweden), May 22-26, 2017
Bauch, H. A, Zhuravleva, A., and Van Nieuwenhove, N.
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MIS5e cycle offshore the Little Bahama Bank: Large-scale ocean dynamics versus sea-level fluctuations. European Geosciences Union (EGU) General Assembly 2017, Vienna (Austria), April 23-28, 2017
Zhuravleva, A., Bauch, H. A., and Kandiano, E.
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(2018) Last interglacial ocean changes in the Bahamas: climate teleconnections between low and high latitudes. Climate of the Past, 14, 1361-1375
Zhuravleva, A., and Bauch, H. A.
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Atlantic Water heat transfer through the Arctic Poster Gateway (Fram Strait) during the Last Interglacial. 6th International Conference on Palaeo-Arctic Spatial and Temporal (PAST) Gateways, Durham (UK), April 16- 20, 2018
Zhuravleva, A., Bauch, H. A., and Spielhagen, R. F.
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Response of the tropical oceanatmosphere system to high-latitude forcing during Dansgaard-Oeschger events. Goldschmidt Conference, Virtual, 4-9 July 2020
Zhuravleva, A., Hüls, M., Tiedemann, R., and Bauch, H. A.
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(2021) A 125-ka record of northern South American precipitation and the role of high-to-low latitude teleconnections. Quaternary Science Reviews, 270, 107159
Zhuravleva, A., Hüls, M., Tiedemann, R., and Bauch H. A.
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Changes in intermediate water circulation in the tropical North Atlantic during the Last Interglacial. Goldschmidt Conference, Honolulu (USA), 10-15 July 2022
Zhuravleva, A., Bauch, H. A., Frank, M., Hathorne, E., Laukert, G., Filippova, A. and Kienast, M.
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The last interglacial cycle in the SE Caribbean and its relation to riverine (Orinoco-Amazon) discharge variability. 14th International Conference on Paleoceanography, Bergen (Norway), 29 August - 2 September 2022
Zhuravleva, A., Bauch, H. A., Fahl, K., and Kienast, M.
