Denmark Strait water circulation traced by heterogeneity in neodymium isotopic compositions

Seawater neodymium isotopic composition (εNd) and rare earth element (REE) concentrations were measured along four hydrologic sections within the East Greenland Current (EGC), between the Fram and the Denmark Straits, during summer 1999. EGC intermediate waters, between 77°N and 70°N, displaying similar hydrological characteristics as Denmark Strait Overflow Water (DSOW), had very constant REE characteristics and εNd value of −10.9. This constancy reveals the absence of lithogenic input, from the East Greenland margin, into intermediate waters in this area, corroborating previous dissolved aluminum data. The DSOW was characterized by εNd=−8.4±1.4. This value can be explained by the imprint of lithogenic formations, mainly basaltic, bordering the Denmark Strait on the intermediate waters described above. However, granitic Precambrian formations seem to contribute, although more slightly, to defining the DSOW Nd signature. This double influence could explain the heterogeneity of the Denmark Strait waters. These results provide a better understanding of the DSOW Nd signature, allowing a better use of this tracer in the study of present and past North Atlantic Deep Water dynamics. Atlantic Water was present at a station located at the mouth of Nansen Fjord, on the western side of Denmark Strait. We suggest that this water reaches the fjord intermittently as isolated water lenses or eddies detached from the northward flowing branch of the Irminger current.