Mediterranean Outflow: across the Glacial termination
Dijk, J. van
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The meltdown of the Greenland ice cap could reduce the formation of deep water in the North Atlantic thereby slowing down the Atlantic Meridional Overturning Circulation (AMOC). A reduced overturning might sub sequentially affect the climate of Western Europe. On glacial to interglacial timescales strengthened MOW provided a negative feedback to North Atlantic freshening boosts quickly rebooting a reduced or inactive AMOC. The last glacial to interglacial transition has witnessed several rapid transitions in overturning induced by these changes in the northern salinity budget. This study therefore aimed to reconstruct the density (and strength) of the MOW across the last termination. Trace elemental and clumped isotope temperatures extracted from benthic foraminifera preserved in deep sea sediments in the Gulf of Cadiz provided a high resolution salinity record of the lower core of MOW over the last 21,000 years. Although bottom water salinity was higher in the LGM the lower core reduced in density across the cold H1 and YD stadials. Furthermore stagnation of the water column during the deposition of S1 resulted in a complete shutdown of the lower core of MOW. The deeper branch of Mediterranean Outflow is thus concluded to be incapable of sustaining overturning across the last termination. Additional research should nevertheless aim on reconstructing both the lower and the upper core of outflow. The upper core might turn out to be more influential. An accurate reconstruction of the MOW its flow path and insights into the influence of the Iberian delta on the regional hydrography can resolve several uncertainties. Improvements of the Mg/Ca and clumped isotope thermometry are required in order to further increase the accuracy of the bottom water temperature reconstructions. Moreover, epifaunal benthics supplied the most accurate temperature reconstructions.