Enhanced western mediterranean rainfall during past interglacials driven by North Atlantic pressure changes

Type Article
Date 2020-07
Language English
Author(s) Dixit Yama1, 2, Toucanne SamuelORCID1, Fontanier Christophe3, 4, 5, Pasquier Virgil2, Lora Juan M.6, 7, Jouet Gwenael1, Tripati Aradhna1, 2, 6, 7
Affiliation(s) 1 : IFREMER, Laboratoire Géophysique et enregistrement Sédimentaire, CS10070, 29280, Plouzané cedex, France
2 : Université de Brest - UMR 6538 CNRS/UBO, LGO, IUEM, 29280, Plouzané, France
3 : Université de Bordeaux, CNRS, Environnements et Paléo-environnements Océaniques et Continentaux, UMR 5805, F-33600, Pessac, France
4 : FORAM, Research Group, F-49140, Villevêque, France
5 : Université d’Angers, F49035, Angers, France
6 : Department of Atmospheric and Oceanic Sciences, Institute of the Environment and Sustainability, Center for Diverse Leadership in Science, University of California, Los Angeles, USA
7 : Department of Earth, Planetary, and Space Sciences, Center for Diverse Leadership in Science, University of California, Los Angeles, USA
Source Quaternary International (1040-6182) (Elsevier BV), 2020-07 , Vol. 553 , P. 1-13
DOI 10.1016/j.quaint.2020.08.017
Keyword(s) Western mediterranean, Interglacials, Mg/ca-SST, Ba/Ca-salinity, Sapropel, Foraminifera
Abstract

There is increasing concern with anthropogenic greenhouse gas emissions that ocean warming, in concert with summer and winter precipitation changes, will induce anoxia in multiple ocean basins, such as in the Mediterranean Sea. Although the hydrological changes in the eastern Mediterranean are quite well constrained, quantitative evidence of changes in sea surface temperature (SST) and winter rainfall in the western Mediterranean across the past interglacials is relatively scarce. In this study, we use a combination of trace element (Ba/Ca and Mg/Ca) and stable oxygen isotope composition of planktonic foraminifera from a sediment core located off the Golo River, Corsica (northern Tyrrhenian Sea) to reconstruct variations in SSTs and sea surface salinities (SSS) during the Holocene (MIS 1) and warm periods of the past two interglacials (MIS 5, 7). We also analyse PMIP3 model simulations for the mid-Holocene to investigate the mechanism for moisture transport in the western Mediterranean. Our Mg/Ca-SSTs, Ba/Ca-salinity and derived δ18O-seawater records suggest that the warm periods of the Last interglacials were characterized by high river discharge and lower SSS in the northern Tyrrhenian Sea. Since this region is ideally located on the trajectory of wintertime storm tracks across the North Atlantic into the Mediterranean Sea and is also outside the influence of the ITCZ-controlled summer monsoon rains, we suggest enhanced winter rainfall during the past interglacials. Our analysis of PMIP3 model simulations for mid-Holocene also support increased south-westerly moisture transport into the western Mediterranean originating from the North Atlantic. We also find evidence that long-term amplitude of the salinity decrease tightly follows eccentricity. We suggest that these hydrologic changes in the western Mediterranean, and the northern Mediterranean borderlands as a whole, were a contributing factor, together with local cyclogenesis and African summer monsoon rainfall, to basin-wide anoxia in the past. Our findings offer new constraints to the amplitude and cause of winter rainfall changes in the Mediterranean during past warm periods.

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