Nordic Seas and Subarctic Atlantic water masses traced by neodymium isotopes
The neodymium isotopic composition (Nd I.C.) is a tracer of oceanic circulation and of ocean/continent matter exchanges. We measured this parameter in almost 200 seawater samples from the Nordic Seas (Greenland, Iceland and Norwegian) and the Subarctic Atlantic (north of 50°N). The interpretation of...
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|Format:||Doctoral or Postdoctoral Thesis|
|Summary:||The neodymium isotopic composition (Nd I.C.) is a tracer of oceanic circulation and of ocean/continent matter exchanges. We measured this parameter in almost 200 seawater samples from the Nordic Seas (Greenland, Iceland and Norwegian) and the Subarctic Atlantic (north of 50°N). The interpretation of these data in relation with the hydrology and the geology of the studied area allowed to improve our knowledge of the circulation and the tracer Nd CI. The study of the isotopic signature of the Subarctic Intermediate Water (SAIW), the Norwegian Sea Deep Water and the Subpolar Mode Water (SPMW) allowed us to better understand their history (pathways, mixings). In particular, we confirm the SAIW originates in the Labrador Current and we suggest that the SPMW is the result of a two end-member mixture : Central North Atlantic Water and waters from the Labrador Current. Nd I.C. are in good agreement with the commonly accepted scenarios of the formation of the upper and lower layers of the North Atlantic Deep Water (NADW). On the other hand they suggest a North East Atlantic Deep Water composition significantly different from that of the middle layer of the NADW. This point will require further studies. We firmly confirm that the Nd IC is conservative in the absence of terrigeneous input. We show the influence of granitic derived sediments on water masse Nd I.C. and confirm that of basaltic derived sediments. We suggest that the Nd IC partially lost the memory of water mass history during sediment/ocean interactions, within high hydraulic energy areas. Lastly, we suggest that passed erosion variations would modify NADW signature as much as or maybe more than circulation variations. La composition isotopique de néodyme (C.I. de Nd) est un traceur de circulation océanique et d'échanges de matière océan/continent. Nous avons mesuré cette grandeur sur près de 200 échantillons d'eau de mer des mers Nordiques (Groenland, Islande, Norvège) et de l'Atlantique Subarctique (au nord de 50°N). L'interprétation de ces données en ...|