New neodymium data in the North East Atlantic Ocean allow progressing on the behaviour of this geochemical tracer

High-resolution vertical profiles of neodymium (Nd) concentrations and isotopic compositions were measured at the eastern part of the US GEOTRACES North Atlantic Zonal Transect (GA03, Gulf of Cadiz – Mauritanian Shelf – Cape Verde Islands). This allowed documenting impacts of different environmental settling on the tracer’s behaviours: the Mediterranean Outflow Waters (MOW), the Saharan dust plume, the Mauritanian margin with nepheloid layers and an Oxygen Minimum Zone (OMZ).

Distinguishing water masses in this oceanic area was a difficult task due to the relative uniformity of their Nd isotopic composition. Except in the Gulf of Cadiz, where MOW displays distinctively more radiogenic values than the surrounding waters (indicating the advection from the western North Atlantic Central Water from the West Atlantic).

Other striking features are: highest Nd concentrations below the Saharan dust plume with non radiogenic Nd; first documented release of mostly scavenged Nd within an OMZ; and, a prominent benthic nepheloid layer at the bottom of the Mauritanian margin, which favours the release of non radiogenic Nd. Thorough treatments of these data allow disentangling horizontal transports from biogeochemical processes in this area.

15 Stichel

Figure: Map of the cruise track and stations with a section along GA03 (Cape Verde Islands – Mauritanian Shelf – Gulf of Cadiz, from left to right) showing measured Nd concentrations (colour shading) overlain by the ratio of expected to actual Nd concentrations (iso-lines). Values >1 indicate excess of Nd with respect to water mass mixing, which is particularly the case within the OMZ at ~500m between section distance 0 and ~2500km. Click here to view the figure larger.

 

Reference:

Stichel, T., Hartman, A. E., Duggan, B., Goldstein, S. L., Scher, H., & Pahnke, K. (2015). Separating biogeochemical cycling of neodymium from water mass mixing in the Eastern North Atlantic. Earth and Planetary Science Letters, 412, 245–260. doi:10.1016/j.epsl.2014.12.008 Click here to access the paper.

Latest highlights

Science Highlights

Surprisingly heavy silicon isotopes in the surface and deep Arctic Ocean

Brzezinski and his colleagues report on a comprehensive study of the Arctic Ocean silicic acid concentrations and silicon isotopic composition…

14.09.2021

Science Highlights

Unique winter dataset of particulate and dissolved cadmium in the Indian sector of the Southern Ocean

Cloete and collaborators analysed particulate and dissolved cadmium at 7 stations in austral winter along a North South section off South Africa.

06.09.2021

Science Highlights

A new proxy for ocean iron bioavailability

The approach established and verified in this study, opens a new way for determining dissolved iron bioavailability in samples across the ocean.

23.07.2021

Science Highlights

Scavenging differentiates the distribution of cadmium, nickel, zinc and copper in the North Pacific Ocean

Zheng and co-authors observed sectional distributions of cadmium, nickel, zinc, and copper in the North Pacific Ocean during three GEOTRACES related cruises…

19.07.2021

Rechercher