Global continental and marine detrital εNd: An updated compilation for use in understanding marine Nd cycling

Robinson, Suzanne; Ivanovic, Ruza; Flierdt, Tina van de; Blanchet, Cécile; Tachikawa, Kazuyo; Martin, E. E.; Cook, C.; Williams, T.; Gregoire, Lauren; Plancherel, Yves; Jeandel, Catherine; Arsouze, Thomas

doi:10.1016/j.chemgeo.2021.120119

Cited by 35 publications

(35 citation statements)

References 118 publications

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“…Neodymium (Nd) isotopic ratios are commonly measured in biogenic material, such as fish teeth or foraminifer shells, or in the associated Fe-Mn oxyhydroxide fractions of the sediment, as tracers of bottom water circulation (e.g., Frank, 2002;Goldstein and Hemming, 2003). In the ocean, each water mass is tagged with a distinctive Nd isotopic composition (typically expressed using the epsilon notation ε Nd ), which reflects, to a large extent, that of the continental masses surrounding their source region (e.g., Tachikawa et al, 2017;Robinson et al, 2021). While Nd isotopes have proven particularly helpful for reconstructing past ocean circulation patterns over various geological timescales, their application to contourite sediment accumulations at ocean margins, such as the Demerara Rise, can be skewed by sedimentary processes related to strong bottom current activity, such as winnowing and reworking.…”

Section: Introductionmentioning

confidence: 99%

Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise

et al. 2021

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Contourite sediment accumulations at continental margins are related to strong bottom water circulation, where intense winnowing can result in neoformation of authigenic grains of glauconite at the seafloor. In this study, we investigated whether such glauconite grains could faithfully record ambient bottom-water neodymium (Nd) isotopic compositions, and hence be used as paleoceanographic archives. To this purpose, we measured Nd isotopic compositions (εNd) in a series of glauconitic grains, foraminiferal assemblages, leached Fe-Mn oxyhydroxide phases, and detrital clays separated from a contourite sediment record at the Demerara slope off French Guiana (IG-KSF-11; 2370 m water depth), at a location where the present-day εNd distribution along the water column is well characterised. We show that the εNd composition of core-top glauconite grains (−12.0 ± 0.5) agrees with the expected NADW-like seawater signature at the same location and water depth (−11.6 ± 0.3), while departing from measured εNd values for corresponding detrital clays (−11.3 ± 0.2), foraminiferal (−10.9 ± 0.2), and Fe-Mn oxyhydroxide fractions (−9.2 ± 0.2). This finding indicates that glauconitic grains at this particular location are probably best suited for paleoceanographic reconstructions than foraminifera and leached Fe-oxyhydroxide fractions, which appear to be influenced by sediment redistribution and the presence of terrestrial continental Fe-oxides, respectively. Using rare earth elements (REE), we tentatively propose that the acquisition of seawater Nd isotopic signatures by glauconite is controlled by the presence of authigenic REE-bearing phosphate-rich phases intertwined within clay mineral sheets, while confirming previous findings that the process of glauconitisation results in the progressive loss of REE within glauconitic grains. Preliminary paleoceanographic implications suggest strengthened bottom-water circulation of the glacial analogue of NADW at this particular location and water depth, with a εNd signature (between −10.8 and −11.5) similar to that of modern NADW.

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Section: Introductionmentioning

confidence: 99%

Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise

et al. 2021

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“…Sea ice changes may have played a role in deep Cape Basin εNd and δ 13 C shifts during this time, although sea‐salt sodium (ssNa, a proxy for sea ice extent) records show less variability at this time compared to late MIS 5 (Figure 5c) (Wolff et al., 2006). For the mid‐depth site U1479, εNd variability may have also been influenced by changes in the NADW εNd endmember, which a recent study has suggested to be sensitive to the extent of land ice cover (Zhao et al., 2019) (Figure 5c), especially over the northeastern Canada cratons characterized by the most negative εNd values (Batchelor et al., 2019; Robinson et al., 2021).…”

Section: Discussionmentioning

confidence: 98%

Little Change in Ice Age Water Mass Structure From Cape Basin Benthic Neodymium and Carbon Isotopes

Hines

Bolge

Goldstein

et al. 2021

Paleoceanog and Paleoclimatol

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A common conception of the deep ocean during ice age episodes is that the upper circulation cell in the Atlantic was shoaled at the Last Glacial Maximum compared to today, and that this configuration facilitated enhanced carbon storage in the deep ocean, contributing to glacial CO2 draw‐down. Here, we test this notion in the far South Atlantic, investigating changes in glacial circulation structure using paired neodymium and benthic carbon isotope measurements from International Ocean Discovery Program Site U1479, at 2,615 m water depth in the Cape Basin. We infer changes in circulation structure across the last glacial cycle by aligning our site with other existing carbon and neodymium isotope records from the Cape Basin, examining vertical isotope gradients, while determining the relative timing of inferred circulation changes at different depths. We find that Site U1479 had the most negative neodymium isotopic composition across the last glacial cycle among the analyzed sites, indicating that this depth was most strongly influenced by North Atlantic Deep Water (NADW) in both interglacial and glacial intervals. This observation precludes a hypothesized dramatic shoaling of NADW above ∼2,000 m. Our evidence, however, indicates greater stratification between mid‐depth and abyssal sites throughout the last glacial cycle, conditions that developed in Marine Isotope Stage 5. These conditions still may have contributed to glacial carbon storage in the deep ocean, despite little change in the mid‐depth ocean structure.

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“…where α GRL is the vector equal to α GRL for grid cells against the coast of Greenland and equal to 1 otherwise, ε sed is the column vector of the ε Nd map of Robinson et al (2021) repeated at all depths throughout the water column, z bot is the vector of the depths of the bottom of each model grid cell, ∆z is the vector of the height of each model grid cell, and f topo is a mask equal to 1 for grid cells on the seafloor and equal to 0 otherwise. (Functions and operations in Eq.…”

Section: Sedimentsmentioning

confidence: 99%

“…Riverine ε Nd values are taken from the global map of interpolated sedimentary ε Nd by Robinson et al (2021), which we also use for the sedimentary source, so that the RNd riverine source is given by R eff sed s river . We note that the sedimentary ε Nd map of Robinson et al (2021) overlays the nearest continental ε Nd signal where sediment thickness is more than 1 km, such that the ε Nd of the GNOM v1.0 riverine sources are mostly from continental measurements that lie within or close to the river drainage basins. Riverine ε Nd values are shown in Fig.…”

Section: Riversmentioning

confidence: 99%

“…Samarium-147 ( 147 Sm) decays to neodymium-143 ( 143 Nd) with a half-life of 106 Gyr. The Sm:Nd ratio is largely uniform in most continental rocks and lower than the bulk Earth value (DePaolo and Wasserburg, 1976;McCulloch and Wasserburg, 1978;Goldstein et al, 1984), therefore the Nd isotope ratio R = 143 Nd/ 144 Nd is mainly a reflection of the amount of time the Nd in a rock has been a part of the continental crust, with lower values indicating older ages and longer crustal residence times (DePaolo and Wasserburg, 1976;McCulloch and Wasserburg, 1978;Goldstein and Hemming, 2003;Jeandel et al, 2007;van de Flierdt et al, 2016;Robinson et al, 2021). Because R variations are typically small, Nd isotope signatures are usually defined as…”

Section: Introductionmentioning

confidence: 99%

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GNOM v1.0: An optimized steady-state model of the modern marine neodymium cycle

Pasquier

Hines

Liang

et al. 2021

Preprint

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Abstract. Spatially distant sources of neodymium (Nd) to the ocean that carry different isotopic signatures (εNd) have been shown to trace out major water masses, and have thus been extensively used to study large-scale features of the ocean circulation both past and current. While the global marine Nd cycle is qualitatively well understood, a complete quantitative determination of all its components and mechanisms, such as the magnitude of its sources and the paradoxical conservative behavior of εNd, remains elusive. To make sense of the increasing collection of observational Nd and εNd data, we develop the global neodymium ocean model (GNOM) v1, the first inverse model of the global marine biogeochemical cycle of Nd. The GNOM is embedded in a data-constrained steady-state circulation that affords spectacular computational efficiency, which we leverage to estimate biogeochemical parameters via systematic objective optimization. Owing to its matrix representation, the GNOM model is additionally amenable to novel diagnostics that allow us to investigate open questions about the Nd cycle with unprecedented accuracy. The GNOM is open-source and freely accessible, is written in Julia, and its code is easily understandable and modifiable for further developments and experiments.

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Global continental and marine detrital εNd: An updated compilation for use in understanding marine Nd cycling

Cited by 35 publications

References 118 publications

Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise

Neodymium Isotopes in Glauconite for Palaeoceanographic Reconstructions at Continental Margins: A Preliminary Investigation From Demerara Rise

Little Change in Ice Age Water Mass Structure From Cape Basin Benthic Neodymium and Carbon Isotopes

GNOM v1.0: An optimized steady-state model of the modern marine neodymium cycle

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