Variability of (sub)surface water masses at the Iberian Margin during the mid-Pleistocene

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During the mid-Pleistocene (0.7 – 1.2 Ma), glacial cyclicity shifted from 41 kyrs to 100 kyrs. This period, the “Mid-Pleistocene Revolution” (MPR), was accompanied by a fundamental change of the climate system, documented by rapid growth of glacial ice volume, cooling in the North Atlantic and enhanced monsoonal strength. Concomitant shifts in atmospheric circulation should have affected the wind-driven oceanic surface circulation such as the North Atlantic subtropical gyre. As an important heat and salt reservoir, the latter con-stitutes a pivotal part of the Atlantic thermohaline circulation. A better understanding of its long-term evolution with respect to the MPR is important but not well-constrained by data so far. To fill this gap, the pro-posed project aims on the reconstruction of mid-Pleistocene sea-surface and thermocline temperatures and salinities at the Iberian Margin (Site U1385, IODP Exp. 339). This will be done by combined δ18O and Mg/Ca analyses on shallow and deep dwelling planktonic foraminifera in ~0.5 to 1 kyr resolution. The southern Iberian Margin is ideally suited for the proposed paleoceanographic study since surface waters at this location are influenced by high-latitude climate processes but are also affected by subtropical gyre waters. Benthic records, on the other hand, can be linked to Antarctic climate fluctuations reflecting changes in ice volume. This particular situation allows the determination of inter-hemispheric phase relations within the ocean-atmospheric system with great stratigraphic confidence. The generated data will document how changed boundary conditions, in particular ice volume, influenced the spatial extension and characteristics of subtropical gyre waters.