Late Pliocene variations of the Mediterranean outflow.

Khélifi, Nabil, Sarntheim, Michael, Frank, Martin , Andersen, Nils and Garbe-Schönberg, Dieter (2014) Late Pliocene variations of the Mediterranean outflow. Marine Geology, 357 . pp. 182-194. DOI 10.1016/j.margeo.2014.07.006.

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Late Pliocene changes in the advection of Mediterranean Outflow Water (MOW) derivates were reconstructed at northeast Atlantic DSDP/ODP sites 548 and 982 and compared to records of WMDW at West Mediterranean Site 978. Neodymium isotope (εNd) values more positive than −10.5/−11 reflect diluted MOW derivates that spread almost continuously into the northeast Atlantic from 3.7 to 2.55 Ma, reaching Rockall Plateau Site 982 from 3.63 to 2.75 Ma. From 3.4 to 3.3 Ma average MOW temperature and salinity increased by 2°–4 °C and ~1 psu both at proximal Site 548 and distal Site 982. The rise implies a rise in flow strength, coeval with a long-term rise in both west Mediterranean Sea surface salinity by almost 2 psu and average bottom water salinity (BWS) by ~1 psu, despite inherent uncertainties in BWS estimates. The changes were linked with major Mediterranean aridification and a drop in African monsoon humidity. In contrast to model expectations, the rise in MOW salt discharge after 3.4 Ma did not translate into improved ventilation of North Atlantic Deep Water, since it possibly was too small to significantly influence Atlantic Meridional Overturning Circulation. Right after ~2.95 Ma, with the onset of major Northern Hemisphere Glaciation, long-term average bottom water temperature (BWT) and BWS at Site 548 dropped abruptly by ~5 °C and ~1–2 psu, in contrast to more distal Site 982, where BWT and BWS continued to oscillate at estimates of ~2 °C and 1.5–2.5 psu higher than today until ~2.6 Ma. We relate the small-scale changes both to a reduced MOW flow and to enhanced dilution by warmwaters of a strengthenedNorth Atlantic Current temporarily replacingMOWderivates at Rockall Plateau.

Document Type: Article
Keywords: Pliocene, Onset of major Northern Hemisphere, Glaciation, Mediterranean Sea Mediterranean OutflowWater North African aridification, Atlantic Meridional Overturning Circulation, Intermediate waters
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
Publisher: Elsevier
Projects: IODP, Laptev Sea System, Transdrift, Future Ocean
Date Deposited: 05 Jan 2015 09:09
Last Modified: 23 Sep 2019 20:48

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