High-resolution neodymium characterization along the Mediterranean margins and modelling of epsilon(Nd) distribution in the Mediterranean basins

Type Article
Date 2016-09
Language English
Author(s) Ayache Mohamed1, Dutay Jean-Claude1, Arsouze ThomasORCID2, 3, Revillon Sidonie4, Beuvier Jonathan5, 6, Jeandel Catherine7
Affiliation(s) 1 : Univ Paris Saclay, LSCE, IPSL, CEA,CNRS,UVSQ, F-91191 Gif Sur Yvette, France.
2 : Univ Paris Saclay, ENSTA ParisTech, 828 Bd Marechaux, F-91762 Palaiseau, France.
3 : Ecole Polytech, Meteorol Dynam Lab, Palaiseau, France.
4 : UBO, CNRS, Lab Domaines Ocean, IUEM,SEDISOR,UMR6538, Plouzane, France.
5 : Mercator Ocean, Ramonville St Agne, France.
6 : Meteo France, Toulouse, France.
7 : Univ Toulouse, CNRS, CNES, LEGOS,IRD,UPS, Toulouse, France.
Source Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2016-09 , Vol. 13 , N. 18 , P. 5259-5276
DOI 10.5194/bg-13-5259-2016
WOS© Times Cited 17

An extensive compilation of published neodymium (Nd) concentrations and isotopic compositions (Nd IC) was realized in order to establish a new database and a map (using a high-resolution geological map of the area) of the distribution of these parameters for all the Mediterranean margins. Data were extracted from different kinds of samples: river solid discharge deposited on the shelf, sedimentary material collected on the margin or geological material outcropping above or close to a margin. Additional analyses of surface sediments were done in order to improve this data set in key areas (e.g. Sicilian strait). The Mediterranean margin Nd isotopic signatures vary from non-radiogenic values around the Gulf of Lion, (epsilon(Nd) values similar to -11) to radiogenic values around the Aegean and the Levantine sub-basins up to +6. Using a high-resolution regional oceanic model (1/12 degrees of horizontal-resolution), epsilon(Nd) distribution was simulated for the first time in the Mediterranean Sea. The high resolution of the model provides a unique opportunity to represent a realistic thermohaline circulation in the basin and thus apprehend the processes governing the Nd isotope distribution in the marine environment. Results are consistent with the preceding conclusions on boundary ex-change (BE) as an important process in the Nd oceanic cycle. Nevertheless this approach simulates a too-radiogenic value in the Mediterranean Sea; this bias will likely be corrected once the dust and river inputs will be included in the model. This work highlights that a significant interannual variability of epsilon(Nd) distribution in seawater could occur. In particular, important hydrological events such as the Eastern Mediterranean Transient (EMT), associated with deep water formed in the Aegean sub-basin, could induce a shift in epsilon(Nd) at deep/intermediate depths that could be noticeable in the eastern part of the basin. This underlines that the temporal and geographical variations of epsilon(Nd) could represent an interesting insight of Nd as tracer of the Mediterranean Sea circulation, in particular in the context of palaeo-oceanographic applications.

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Ayache Mohamed, Dutay Jean-Claude, Arsouze Thomas, Revillon Sidonie, Beuvier Jonathan, Jeandel Catherine (2016). High-resolution neodymium characterization along the Mediterranean margins and modelling of epsilon(Nd) distribution in the Mediterranean basins. Biogeosciences, 13(18), 5259-5276. Publisher's official version : https://doi.org/10.5194/bg-13-5259-2016 , Open Access version : https://archimer.ifremer.fr/doc/00639/75064/