Variability of the Mediterranean Outflow on glacial-interglacial and millennial time scales

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Mediterranean Outflow Water (MOW) has exerted significant influence on the Late Pleistocene paleoceanography and climate evolution in the North Atlantic region through its contribution to the mid-depth Atlantic salinity budget. The MOW has been strongly influenced by changes in sea level due to the shallow (286 m) sill depth of the Strait of Gibraltar but also by changes in the hydrology of the Mediterranean Sea and the tropical Atlantic gyre. In this study we propose to reconstruct in detail the flow path, flow strength and past mixing of MOW with other eastern North Atlantic water masses through radiogenic isotope analyses of neodymium (Nd) and lead (Pb), which have the potential to unravel the evolution of MOW at unprecedented detail and precision. We will extract the dissolved radiogenic isotope signatures of bottom waters from authigenic ferromanganese coatings of bulk sediments. The isotope composition of the clay fraction will provide independent constraints on the past flow paths of the water masses. The study will be carried out on a suite of well-dated cores of hemipelagic sediments from the Portuguese margin, the Gulf of Cadiz, and from the Alboran Sea in the Western Mediterranean, which will allow the reconstruction of MOW dynamics in the eastern Atlantic Ocean back to approximately 30 ka. A lot of recent evidence points to a critical role of MOW for oceanographic changes during the last major climatic transition (Termination 1), which is why particular emphasis will be on a high resolution record of MOW variability during this period of time.