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Sci Rep. 2016 Jul 14;6:29623. doi: 10.1038/srep29623.

Mediterranean circulation perturbations over the last five centuries: Relevance to past Eastern Mediterranean Transient-type events.

Author information

1
Università di Palermo, Dipartimento di Scienze della Terra e del Mare, Via Archirafi 22, 90123 Palermo, Italy.
2
Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research (IDÆA), Spanish Council for Scientific Research (CSIC), Jordi Girona 18, 08034 Barcelona, Spain.
3
University of Cambridge, Department of Earth Sciences, Downing Site, Downing Street, Cambridge CB2 3EQ, United Kingdom.
4
Universitat Autònoma de Barcelona (UAB), Institute of Environmental Science and Technology (ICTA), Edifici Z, Carrer de les Columnes, Campus de la UAB, 08193 Bellaterra (Cerdanyola del Vallès), Barcelona, Spain.
5
UAB, Department of Geography, 08193 Bellaterra (Cerdanyola del Vallès), Barcelona, Spain.
6
Consiglio Nazionale delle Ricerche (CNR), Istituto per l'Ambiente Marino Costiero, Via del Mare 3, 91021 Torretta-Granitola (Trapani), Italy.
7
Vrije Universiteit Amsterdam, Department of Earth Sciences, Faculty of Earth and Life Sciences, de Boelelaan 1085, 1081HV Amsterdam, The Netherlands.
8
ICREA, Catalan Institution for Research and Advanced Studies, 08010, Barcelona, Spain.
9
Hellenic Centre for Marine Research (HCMR), Institute of Oceanography, P.O. Box 712, 19013 Anavyssos, Greece.
10
Department of Ecology and Marine Resources, IMEDEA (CSIC-UIB), Institut Mediterrani d'Estudis Avançats, Miquel Marquès 21, 07190 Esporles, Illes Balears, Spain.
11
Justus-Liebig-University Giessen, Department of Geography, Climatology, Climate Dynamics and Climate Change, Senckenbergstr. 1, 35390 Giessen, Germany.
12
Centre for International Development and Environmental Research, Justus-Liebig-University Giessen, 35390 Giessen, Germany.
13
CNR, Istituto di Scienze Marine, Via Gobetti 101, 40129 Bologna, Italy.
14
Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory 2601, Australia.
15
University of Athens, Faculty of Geology and Geoenvironment, Department of Historical Geology - Paleontology, Panepistimiopolis 15784, Athens, Greece.

Abstract

The Eastern Mediterranean Transient (EMT) occurred in the Aegean Sea from 1988 to 1995 and is the most significant intermediate-to-deep Mediterranean overturning perturbation reported by instrumental records. The EMT was likely caused by accumulation of high salinity waters in the Levantine and enhanced heat loss in the Aegean Sea, coupled with surface water freshening in the Sicily Channel. It is still unknown whether similar transients occurred in the past and, if so, what their forcing processes were. In this study, sediments from the Sicily Channel document surface water freshening (SCFR) at 1910 ± 12, 1812 ± 18, 1725 ± 25 and 1580 ± 30 CE. A regional ocean hindcast links SCFR to enhanced deep-water production and in turn to strengthened Mediterranean thermohaline circulation. Independent evidence collected in the Aegean Sea supports this reconstruction, showing that enhanced bottom water ventilation in the Eastern Mediterranean was associated with each SCFR event. Comparison between the records and multi-decadal atmospheric circulation patterns and climatic external forcings indicates that Mediterranean circulation destabilisation occurs during positive North Atlantic Oscillation (NAO) and negative Atlantic Multidecadal Oscillation (AMO) phases, reduced solar activity and strong tropical volcanic eruptions. They may have recurrently produced favourable deep-water formation conditions, both increasing salinity and reducing temperature on multi-decadal time scales.

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