Hydrological variations of the intermediate water masses of 1 the western Mediterranean Sea during the past 20 ka inferred 2 from neodymium isotopic composition in foraminifera and 3 cold-water corals 4 5

5 Quentin Dubois-Dauphin 1 , Paolo Montagna 2,3 , Giuseppe Siani 1 , Eric Douville 4 , Claudia 6 Wienberg 5 , Dierk Hebbeln 5 , Zhifei Liu 6 , Nejib Kallel 7 , Arnaud Dapoigny 4 , Marie Revel 8 , 7 Edwige Pons-Branchu 4 , Marco Taviani 2,9 , Christophe Colin 1 * 8 9 1 Laboratoire Geosciences Paris-Sud (GEOPS), Université de Paris Sud, Université Paris-Saclay, 91405 Orsay, 10 France. 11 2 ISMAR-CNR, via Gobetti 101, 40129 Bologna, Italy. 12 3 Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964, USA 13 4 Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris14 Saclay, F-91191 Gif-sur-Yvette, France. 15 5 MARUM-Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359 Bremen, 16 Germany. 17 6 State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China. 18 7 Laboratoire Georessources, Matériaux, Environnements et Changements Globaux, LR13ES23, Faculté des 19 Sciences de Sfax, Université de Sfax, BP1171, 3000 Sfax, Tunisia. 20 8 Geoazur, UNS, IRD, OCA, CNRS, 250 rue Albert Einstein, 06500 Valbonne, France 21 9 Biology Department, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, 22 USA. 23 24 25 Correspondence to: Christophe Colin (christophe.colin@u-psud.fr) 26 27 28


156
The WMDW is formed in the Gulf of Lions due to winter cooling and evaporation followed by mixing between

Cold-water coral and foraminifera samples
167 Forty-four CWC samples belonging to the species Lophelia pertusa and Madrepora oculata collected from the 168 Alboran Sea and the Sardinia Channel were selected for this study (Fig. 1). Nineteen fragments were collected at 169 various core depths from a coral-bearing sediment core (RECORD 23; 38°42.18' N; 08°54.75' E; Fig. 1

183
In addition, a deep-sea sediment core (barren of any CWC fragments) was recovered southwest of the Balearic 184 Sea at 622 m water depth during the R/V Le Suroît cruise "PALEOCINAT II" in 1992 (SU92-33; 35°25.38' N; 185 0°33.86' E; Fig. 1). The core unit, which consists of 2.1 m of grey to brown carbonaceous clays, was sub-186 sampled continuously at 5-10 cm intervals for a total number of 24 samples used for δ 18

262
The palaeo-sea surface temperatures (SST) were estimated using the modern analogue technique (MAT) 263 (Hutson, 1980;Prell, 1985), implemented by Kallel et al. (1997) for the Mediterranean Sea. This method directly 264 measures the difference between the faunal composition of a fossil sample with a modern database, and it 265 identifies the best modern analogues for each fossil assemblage (Prell, 1985). Reliability of SST reconstructions 266 is estimated using a square chord distance test (dissimilarity coefficient), which represents the mean degree of 267 similarity between the sample and the best 10 modern analogues. When the dissimilarity coefficient is lower than

287
The εNd record obtained from the CWC samples from the Alboran Sea displays a narrow range from -9.22±0.30 288 to -8.59±0.3, which is comparable to the εNd record of the planktonic foraminifera from the Balearic Sea over 289 the last 13.5 kyr ( Table 2

291
On the contrary, the CWC samples from the Sardinia Channel display a relatively large εNd range, with values 292 varying from -5.99±0.50 to -7.75±0.10 during the Early and Late Holocene, and values as low as -8.66±0.30 293 during the the mid-sapropel S1 deposition (S1a) at ~8.7 ka BP (

302
The age model for the upper 1.2 m of the core SU92-33 was based on 7 AMS-14 C age measurements and a 303 linear interpolation between these ages (Table 3   The  13 C record of C. pachyderma shows a decreasing trend since the LGM with a low variability from ~1.6 ‰ 325 to ~0.6 ‰ (Fig. 2d). The heaviest  13 C values are related to the LGM (~1.6 ‰) while the lightest values (~0.6 326 ‰) characterize the Early Holocene and in particular the period corresponding to the sapropel S1 event in the 327 eastern Mediterranean basin (Fig. 2d).

328
The εNd values of planktonic foraminifera of core SU92-33 from the Balearic Sea vary within a relatively 329 narrow range between -9.50±0.30 and -8.61±0.30, with an average value of -9.06±0.28 (Table 2

380
The range in εNd for the CWC from the Alboran Sea (from -9.22±0.30 to -8.8.59±0.30; Table 2) is very close to 381 the one obtained for the planktonic foraminifera from the Balearic Sea (from -9.50±0.30 to -8.61±0.30; Table 4

396
The SST record displays values centered at around 12°C during the LGM with a subsequent rapid SST decrease 397 towards 9°C , highlighting the onset of the HS1 (Fig. 2a). These values are well comparable to recent high-   (Table 4), synchronous with the HS1 (Fig. 2b) (Fig. 4c). Furthermore, results from the UP10 fraction (particles > 10 m) of the MD99-2343 sediment 438 core (Fig. 4d) (Fig. 5c). However, a stronger LIW and/or a CIW contribution cannot be responsible for εNd values as 490 low as -8.66±0.30 observed during the sapropel S1 event at 8.7 ka BP (Table 1, Fig. 5c

496
The εNd records of the Balearic Sea, Alboran Sea and Sardinia Channel document a temporal variability of the 497 east-west gradient in the western Mediterranean basin during the Holocene. The magnitude of the gradient 498 ranges from ~1.5 to ~3 ε units during the Early and Late Holocene and it is strongly reduced at 8.7 ka BP (from 499 0 to ~0.5 ε unit), coinciding with the sapropel S1 event affecting the eastern Mediterranean basin (Fig. 5). Such