Coupling and decoupling of barium and radium-226 along the GEOVIDE GEOTRACES section

Because radium-226 (226Ra) and barium (Ba) are both alkaline earth metals and thus display similar chemical behaviours, studying their fate in contrasting environments is of prime interest. With this aim, Le Roy and co-workers (2018, see reference below) realised a high resolution description of the distribution of these tracers along the GEOVIDE section (GA01, see section map here). Using an optimum multi parameter analysis of their data, they figured out that:

– both tracers can be considered as conservative of water mass transport in the deep open ocean part of the section;

– non conservative and decoupled behaviours are observed at the ocean boundaries, namely:

  • in the eastern part of the section, the deepest waters (North East Atlantic Deep Water) display high Ba and 226Ra concentrations, which could reflect either an accumulation in this “old” water mass or diffusion from the sediment below;
  • contrastingly, depletion of both tracers in the upper layers of the West European basin likely reflects biological stripping;
  • at the land-ocean contact, as for example close to the Greenland and Newfoundland coasts, marked decoupled behaviours reflect the different main input sources of both tracers (rivers for Ba, sediment for 226Ra).

18 LeRoy
Distribution of dissolved 226Ra/Ba ratio (a) measured along the GEOVIDE section and the difference between the measured concentrations and those calculated by the optimum multiparameter (OMP) analysis for 226Ra (b), Ba (c) and  226Ra/Ba ratio (d) along the GA01 section. Positive anomalies (in Red) reflect recent tracer addition, while negative ones (in blue) reflect recent tracer removal. Station numbers are found above the panels. Click here to view the figure larger.


Le Roy, E., Sanial, V., Charette, M. A., van Beek, P., Lacan, F., Jacquet, S. H. M., Henderson, P. B., Souhaut, M,. García-Ibáñez, Maribel I., Jeandel, C.,Pérez, F., F., Sarthou, G. (2018). 226Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01. Biogeosciences, 15(9), 3027–3048.

Latest highlights

Science Highlights

Particulate fluxes and circulation in a changing Arctic Ocean: tracer data and modeling

A complete review of published and new water column profiles of 230Th and 231Pa concentrations and neodymium (Nd) isotopic compositions collected in the Amerasian Basin of the Arctic Ocean between 1983 and 2015 was performed by Grenier and co-workers (2019, see reference below). This review allowed them to identify regional and temporal variability of geochemical […]


Science Highlights

Who produces methylmercury in the global ocean?

The UNEP Minamata Convention was ratified in August 2017 and aims to protect human health from mercury exposure by reducing anthropogenic, inorganic, mercury emissions. The most toxic and biomagnifying mercury species, methylmercury, is not emitted from anthropogenic or natural sources, but produced in the ocean from inorganic mercury. Marine mercury methylation has been confirmed for […]


Science Highlights

Oceanic Margins as sources of lithogenic particulate and dissolved iron in the North Pacific Ocean

Three GEOTRACES Japanese cruises on board the R/V Hakuho Maru allowed establishing basin-scale and full-depth sectional distributions of total dissolvable iron (tdFe), dissolved iron (dFe), and labile particulate iron (lpFe=tdFe – dFe) in the North Pacific Ocean. Zheng and Sohrin (2019, see reference below) also discuss aluminum (Al) and manganese (Mn) data in this work. […]


Science Highlights

Informative zinc isotopic fractionation in the Southern Ocean

Ellwood and co-workers (2020, see reference below) established the distribution of dissolved and particulate zinc (dZn and pZn respectively) and its isotopes in the Subantarctic Zone South of Tasmania. Concentration profiles show that zinc has a longer regeneration length scale than phosphorus and of cadmium, but shorter than copper. Modelling of the particulate profiles produced […]