MIS-11: A Super-Interglacial with enhanced North Atlantic Deep Water Circulation

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The Atlantic Meridional Circulation (AMOC) is an essential component of the heat fluxes in the climate system, whose change is difficult to predict with regard to future climate warming. In this project, we focus on the Marine Isotope Stage (MIS) 11, which led to a 30,000 year long warm period about 410,000 years ago with similar orbital parameters as compared to today. A large part of the Greenland ice sheet had melted and as a result the global sea level was significantly higher than today. Traditional nutrient proxies provide evidence of strong deep water formation during this particular warm period. In order to reconstruct the provenance of the water masses, their flow paths, and the mixing ratios, the isotope ratio 143Nd/144Nd in the authigenic phase of deep-sea sediments has proved to be a very useful tracer. In this project, we have extracted the Nd isotopic composition from such authigenic Fe-Mn deposits on numerous ODP/IODP sediment cores, for the duration of MIS-11 and the previous ice age MIS-12 (including Termination V). In the Atlantic Ocean, a significant increase of less radiogenic neodymium is measurable, which probably shows a stronger deep water formation even during periods of increased ice loss on Greenland. The investigated sediments map the entire deep Atlantic from north to south, as well as some regions with direct regional influence on the Nd isotope compostion (near Iceland) and the Labrador Sea. In addition to a strong deep circulation during MIS-11, an important contribution of Arctic water (the Iceland-Scotland Ridge Overflow) and a long-lasting influence of water from the Labrador Sea could thus be demonstrated. In the deep West Atlantic very unradiogenic Nd isotope values are found throughout the interglacial period. In this extension project, we would like to improve the temporal resolution of Nd isotope investigations of some sediment cores from the Labrador Sea and Cape Basin and accomplish publications of the large amount of results, but with particular focus on the comparison of MIS-11, the Holocene, and a future warmer climate.