Exhaustive modelling study of the oceanic neodymium parameters

2 March 2023

Exploring global marine neodymium (Nd) cycling and the interplay between climatic and oceanographic conditions under both modern and palaeoceanographic contexts stands among the important GEOTRACES objectives. This goal requires state of the art modelling and a solid data base, which is proposed in this study: an updated compilation of neodymium parameters comprising 6048 Nd concentrations and 3278 εNd data allowed Robinson and co-authors to implement the neodymium isotopes (¹⁴³Nd and ¹⁴⁴Nd) into the ocean model of the FAMOUS general circulation model (Nd v1.0). Aeolian dust, riverine fluxes, and sedimentary release represent the major interfaces and sources of Nd to the ocean, with reversible scavenging onto biogenic and lithogenic particles coupled with physical ocean circulation governing internal marine Nd cycling. All these sources, sinks and internal processes are tested in Robinson’s modelling exercise. Her conclusion reinforces the important role of the solid particles in driving the Nd oceanic cycle, be they sinking through the water column or sedimented, as seafloor source. However, model-data mismatch in the North Pacific and northern North Atlantic Oceans suggest that certain reactive components of the sediment interact the most with seawater. These results are important for interpreting Nd isotopes in terms of ocean circulation.

**Figure:** The central panel **(g)** displays εNd at the seafloor (i.e. lowermost box of the ocean model) in a simulation using the Nd isotope scheme in FAMOUS general circulation model (Nd v1.0) with superimposed water column measurements (Osborne et al., 2017, 2015; GEOTRACES Intermediate Data Product Group, 2021) from ≥3000 m shown by filled coloured circles on the same colour scale. The surrounding panels **(a)**–**(f)** and **(h)**–**(m)** display depth profiles of simulated (coloured lines, one per sensitivity simulation with varied reversible scavenging efficiency) and measured (filled circles) εNd, respectively. Larger shifts in the εNd between simulations highlight the region’s most sensitive to the efficiency of reversible scavenging.

Reference:

Robinson, S., Ivanovic, R., Gregoire, L., Tindall, J., van de Flierdt, T., Plancherel, Y., Pöppelmeier, F., Tachikawa, K., & Valdes, P. (2022). Simulating marine neodymium isotope distributions using ND v1.0 coupled to the ocean component of the FAMOUS-MOSES1 climate model: sensitivities to reversible scavenging efficiency and benthic source distributions. Access the paper:10.5194/egusphere-2022-606

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