Tracing water mass mixing in the Cape Basin and the restricted Angola Basin with radiogenic neodymium isotopes

In the frame of GEOTRACES cruise GA08, Rahlf et al. (2020, see reference below) determined seawater profiles of dissolved radiogenic neodymium isotope signatures (εNd) and neodymium concentrations across the restricted western Angola Basin and along the northern Cape Basin to investigate mixing and provenance of water masses. Nd isotope compositions of deep water masses in both basins primarily reflect conservative water mass mixing, except the central Angola Basin, which is significantly overprinted by terrestrial inputs. Bottom waters of the Cape Basin show some excess Nd concentrations released from detrital sediments, however, without significantly changing their Nd isotopic compositions ranging between εNd -9.6 and 10.5. Highly unradiogenic εNd signatures of up to -17.6 in the upper water column originate from a west African coastal plume in the Angola Basin and from Mozambique Channel surface waters advected into the Cape Basin.

19 Rahlf

Figure: Nd isotope distributions in the western Angola Basin (left section) and the northern Cape Basin (right section) along the cruise track of GA08, combined with isotope data obtained further south from cruise ANT-XXIIV/3 (Stichel et al., 2012). Dashed lines indicate approximate boundaries of the prevailing water masses. The figure is adopted from Rahlf et al. (2020). Click here to view the figure in new window.

References:

Rahlf, P., Hathorne, Ed., Laukert, G., Gutjahr, M., Weldeab, S., Frank, M. (2020). Tracing water mass mixing and continental inputs in the southeastern Atlantic Ocean with dissolved neodymium isotopes. Earth Planet. Sci. Lett., in press, DOI: 10.1016/j.epsl.2019.115944.

Stichel, T., Frank, M., Rickli, J., Haley, B.A. (2012). The hafnium and neodymium isotope composition of seawater in the Atlantic sector of the Southern Ocean. Earth Planet. Sci. Lett. 317–318, 282–294.

Latest highlights

Science Highlights

Thorium-Protactinium fate across the tropical Atlantic Ocean: what reveals the water column-sediment coupling

Twenty seawater profiles and twenty core-top 231-protactinium and 230-thorium analyses were realised by Ng and colleagues along five depth transects across the northern tropical Atlantic open ocean.

18.01.2021

Science Highlights

Constraining Oceanic Copper Cycling through Artificial Intelligence and Ocean Circulation Inverse Model

Using available observations of dissolved copper, artificial neural networks, and an ocean circulation inverse model, authors calculated a global estimate of the 3-dimensional distribution and cycling of dissolved copper in the ocean

15.01.2021

Science Highlights

Particulate rare earth elements distributions, processes and characterisation of nepheloids in the North Atlantic

Lagarde et al. realised the first basin scale section of particulate rare earth elements concentrations across the North Atlantic Ocean.

06.01.2021

Science Highlights

Isopycnal mixing controls protactinium and thorium distributions in the Pacific Southern Ocean

Pavia and co-workers determined the physical and chemical speciation as well as the vertical distribution of Protactinium-231 and Thorium-230 at 12 stations across the Southern Pacific Antarctic Circumpolar Current…

13.12.2020

Rechercher