Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
Clim. Past, 13, 17-37, 2017
http://www.clim-past.net/13/17/2017/
doi:10.5194/cp-13-17-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
10 Jan 2017
Hydrological variations of the intermediate water masses of the western Mediterranean Sea during the past 20 ka inferred from neodymium isotopic composition in foraminifera and cold-water corals
Quentin Dubois-Dauphin1, Paolo Montagna2,3, Giuseppe Siani1, Eric Douville4, Claudia Wienberg5, Dierk Hebbeln5, Zhifei Liu6, Nejib Kallel7, Arnaud Dapoigny4, Marie Revel8, Edwige Pons-Branchu4, Marco Taviani2,9, and Christophe Colin1 1Laboratoire Geosciences Paris-Sud (GEOPS), Université de Paris Sud, Université Paris-Saclay, 91405 Orsay, France
2ISMAR-CNR, via Gobetti 101, 40129 Bologna, Italy
3Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964, USA
4Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
5MARUM Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359 Bremen, Germany
6State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
7Laboratoire Georessources, Matériaux, Environnements et Changements Globaux, LR13ES23, Faculté des Sciences de Sfax, Université de Sfax, BP1171, 3000 Sfax, Tunisia
8Geoazur, UNS, IRD, OCA, CNRS, 250 rue Albert Einstein, 06500 Valbonne, France
9Biology Department, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA
Abstract. We present the neodymium isotopic composition (εNd) of mixed planktonic foraminifera species from a sediment core collected at 622 m water depth in the Balearic Sea, as well as εNd of scleractinian cold-water corals (CWC; Madrepora oculata, Lophelia pertusa) retrieved between 280 and 442 m water depth in the Alboran Sea and at 414 m depth in the southern Sardinian continental margin. The aim is to constrain hydrological variations at intermediate depths in the western Mediterranean Sea during the last 20 kyr. Planktonic (Globigerina bulloides) and benthic (Cibicidoides pachyderma) foraminifera from the Balearic Sea were also analyzed for stable oxygen (δ18O) and carbon (δ13C) isotopes. The foraminiferal and coral εNd values from the Balearic and Alboran seas are comparable over the last  ∼  13 kyr, with mean values of −8.94 ± 0.26 (1σ; n =  24) and −8.91 ± 0.18 (1σ; n =  25), respectively. Before 13 ka BP, the foraminiferal εNd values are slightly lower (−9.28 ± 0.15) and tend to reflect higher mixing between intermediate and deep waters, which are characterized by more unradiogenic εNd values. The slight εNd increase after 13 ka BP is associated with a decoupling in the benthic foraminiferal δ13C composition between intermediate and deeper depths, which started at  ∼  16 ka BP. This suggests an earlier stratification of the water masses and a subsequent reduced contribution of unradiogenic εNd from deep waters. The CWC from the Sardinia Channel show a much larger scatter of εNd values, from −8.66 ± 0.30 to −5.99 ± 0.50, and a lower average (−7.31 ± 0.73; n =  19) compared to the CWC and foraminifera from the Alboran and Balearic seas, indicative of intermediate waters sourced from the Levantine basin. At the time of sapropel S1 deposition (10.2 to 6.4 ka), the εNd values of the Sardinian CWC become more unradiogenic (−8.38 ± 0.47; n =  3 at  ∼  8.7 ka BP), suggesting a significant contribution of intermediate waters originated from the western basin. We propose that western Mediterranean intermediate waters replaced the Levantine Intermediate Water (LIW), and thus there was a strong reduction of the LIW during the mid-sapropel ( ∼  8.7 ka BP). This observation supports a notable change of Mediterranean circulation pattern centered on sapropel S1 that needs further investigation to be confirmed.

Citation: Dubois-Dauphin, Q., Montagna, P., Siani, G., Douville, E., Wienberg, C., Hebbeln, D., Liu, Z., Kallel, N., Dapoigny, A., Revel, M., Pons-Branchu, E., Taviani, M., and Colin, C.: Hydrological variations of the intermediate water masses of the western Mediterranean Sea during the past 20 ka inferred from neodymium isotopic composition in foraminifera and cold-water corals, Clim. Past, 13, 17-37, doi:10.5194/cp-13-17-2017, 2017.
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