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

Type Article
Date 2017-01
Language English
Author(s) Dubois-Dauphin QuentinORCID1, Montagna Paolo2, 3, Siani Giuseppe1, Douville Eric4, Wienberg Claudia5, Hebbeln Dierk5, Liu Zhifei6, Kallel Nejib7, Dapoigny Arnaud4, Revel Marie8, Pons-Branchu Edwige4, Taviani Marco2, 9, Colin Christophe1
Affiliation(s) 1 : Univ Paris Saclay, Univ Paris Sud, Lab Geosci Paris Sud GEOPS, F-91405 Orsay, France.
2 : ISMAR CNR, Via Gobetti 101, I-40129 Bologna, Italy.
3 : Columbia Univ, Lamont Doherty Earth Observ, 61 Route 9W, Palisades, NY 10964 USA.
4 : Univ Paris Saclay, CEA CNRS UVSQ, Lab Sci Climat & Environm, LSCE IPSL, F-91191 Gif Sur Yvette, France.
5 : Univ Bremen, MARUM Ctr Marine Environm Sci, Leobener Str, D-28359 Bremen, Germany.
6 : Tongji Univ, State Key Lab Marine Geol, Shanghai 200092, Peoples R China.
7 : Univ Sfax, Lab Georessources Mat Environm & Changements Glob, LR13ES23, Fac Sci Sfax, BP1171, Sfax 3000, Tunisia.
8 : CNRS, OCA, IRD, Geoazur,UNS, 250 Rue Albert Einstein, F-06500 Valbonne, France.
9 : Woods Hole Oceanog Inst, Dept Biol, 266 Woods Hole Rd, Woods Hole, MA 02543 USA.
Source Climate Of The Past (1814-9324) (Copernicus Gesellschaft Mbh), 2017-01 , Vol. 13 , N. 1 , P. 17-37
DOI 10.5194/cp-13-17-2017
WOS© Times Cited 13
Note Special issues. Human–land–sea interactions in the Mediterranean Basin: a Holocene perspective Editor(s): M.-A. Sicre, J. Guiot, L. Carozza, N. Combourieu Nebout, B. Martrat, and M.-F. Loutre
Abstract

We present the neodymium isotopic composition (epsilon Nd) of mixed planktonic foraminifera species from a sediment core collected at 622m water depth in the Balearic Sea, as well as epsilon Nd of scleractinian cold-water corals (CWC; Madrepora oculata, Lophelia pertusa) retrieved between 280 and 442m water depth in the Alboran Sea and at 414m 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 (delta O-18) and carbon (delta C-13) isotopes. The foraminiferal and coral epsilon Nd values from the Balearic and Alboran seas are comparable over the last similar to 13 kyr, with mean values of -8.94 +/- 0.26 (1 sigma; n = 24) and -8.91 +/- 0.18 (1 sigma; n = 25), respectively. Before 13 ka BP, the foraminiferal epsilon Nd 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 epsilon Nd values. The slight epsilon Nd increase after 13 ka BP is associated with a decoupling in the benthic foraminiferal delta C-13 composition between intermediate and deeper depths, which started at similar to 16 ka BP. This suggests an earlier stratification of the water masses and a subsequent reduced contribution of unradiogenic epsilon Nd from deep waters. The CWC from the Sardinia Channel show a much larger scatter of epsilon Nd 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 epsilon Nd values of the Sardinian CWC become more unradiogenic (8.38 +/- 0.47; n = 3 at similar to 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 (similar to 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.

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Dubois-Dauphin Quentin, Montagna Paolo, Siani Giuseppe, Douville Eric, Wienberg Claudia, Hebbeln Dierk, Liu Zhifei, Kallel Nejib, Dapoigny Arnaud, Revel Marie, Pons-Branchu Edwige, Taviani Marco, Colin Christophe (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. Climate Of The Past, 13(1), 17-37. Publisher's official version : https://doi.org/10.5194/cp-13-17-2017 , Open Access version : https://archimer.ifremer.fr/doc/00420/53193/