Overview of the mechanisms that could explain the ‘Boundary Exchange’ at the land–ocean contact

Jeandel, Catherine

doi:10.1098/rsta.2015.0287

Cited by 72 publications

(72 citation statements)

References 80 publications

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“…Nonetheless, the exact mechanisms of BE remain to be elucidated (Jeandel, 2016), and its geographical extension should be better constrained since in such areas seawater  Nd values are not a straightforward water mass tracer. Recently, the first measurements of pore water Nd isotopic composition suggested the contribution of radiogenic pore water Nd to shallow and…”

Section: Accepted Manuscriptmentioning

confidence: 99%

The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data

et al. 2017

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International audienceNeodymium isotopic compositions (143Nd/144Nd or εNd) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have updated a global seawater εNd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive εNd data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (< 10,000 years).At water depths ≥ 1500 m, property-property plots show clear correlations between seawater εNd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater εNd distribution. At ≥ 200 m, basin-scale seawater T-S-εNd diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive εNd values are compared using property-property plots and T-S-εNd diagrams. Archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the Pacific. Both positive and negative offsets exist in the northern North Atlantic. Applying multiple regression analysis to deep (≥ 1500 m) seawater data, we established empirical equations that predict the main, large-scale, deepwater εNd trends from hydrography parameters. Large offsets from the predicted values are interpreted as a sign of significant local/regional influence. Dominant continental influence on seawater and archive εNd is observed mainly within 1000 km from the continents. Generally, seawater and archive εNd values form gradual latitudinal trend in the Atlantic and Pacific at depths ≥ 600 m, consistent with the idea that Nd isotopes help distinguish between northern/southern sourced water contributions at intermediate and deep water depths

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Section: Accepted Manuscriptmentioning

confidence: 99%

The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data

et al. 2017

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“…Rivers are another source of Mn to the ocean (Elderfield, 1976;Aguilar-Islas and Bruland, 2006). While much of the fluvial Mn is removed within the estuaries into the sediments by scavenging and aggregation, a large part may finally be transported to the ocean by diffusion from and resuspension of the sediments (Jeandel, 2016;Charette et al, 2016). Typically, the smaller sediment particles (0.5 µm to 4 µm) have a high Mn content, and, because of their small size, are able to reach the open ocean (Yeats et al, 1979;Sundby et al, 1981;Trefry and Presley, 1982).…”

Section: Introductionmentioning

confidence: 99%

Manganese in the west Atlantic Ocean in the context of the first global ocean circulation model of manganese

et al. 2017

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Dissolved manganese (Mn) is a biologically essential element. Moreover, its oxidised form is involved in removing itself and several other trace elements from ocean waters. Here we report the longest thus far 17 500 km length full-depth ocean section of dissolved Mn in the West Atlantic Ocean, comprising 1320 data values of high accuracy. This is the GA02 transect that is part of the GEOTRACES programme, which aims to understand trace element distributions. The goal of this study is to combine these new observations with a new, state-of-the-art, modelling to give a first assessment of the main sources and redistribution of Mn throughout the ocean. To this end, we simulate the distribution of dissolved Mn using a global-scale circulation model. This first model includes simple parameterisations to account for the sources, processes and sinks of Mn in the ocean. Oxidation and (photo)reduction, aggregation, settling, as well as biological uptake and remineralisation by plankton, are included in the model. Our model provides, together with the observations, the following insights: -The high surface concentrations of manganese are caused by the combination of photoreduction and sources to the upper ocean. The most important sources are sediments, dust, and, more locally, rivers. -Observations and model simulations suggest that surface Mn in the Atlantic Ocean moves downwards into the southward flowing North Atlantic Deep Water (NADW), but because of strong removal rates there is no elevated concentration of Mn visible any more in the NADW south of 40 • N.-The model predicts lower dissolved Mn in surface waters of the Pacific Ocean than the observed concentrations. The intense Oxygen Minimum Zone (OMZ) in subsurface waters is deemed to be a major source of dissolved Mn also mixing upwards into surface waters, but the OMZ is not well represented by the model. Improved high resolution simulation of the OMZ may solve this problem.-There is a mainly homogeneous background concentration of dissolved Mn of about 0.10 nM to 0.15 nM throughout most of the deep ocean. The model reproduces this by means of a threshold on particulate manganese oxides of 25 pM, suggesting that a minimal concentration of particulate Mn is needed before aggregation and removal become efficient.-The observed distinct hydrothermal signals are produced by assuming both a strong source and a strong removal of Mn near hydrothermal vents.

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“…A thorough assessment of the dissolved/particulate partitioning in the buoyant plume is therefore needed to better characterize the export of other hydrothermal trace metals (Waeles et al, 2017) and DREEs in the open ocean. Furthermore, recent studies illustrated that the Nd isotopic composition (ε Nd ) is a key tracer to quantify Nd (and REE) transfer between particulate and dissolved phases (Lacan andJeandel, 2001, 2005;Jeandel et al, 2013;Jeandel, 2016). Therefore, measurements of DREEs and Nd isotopic signature in hydrothermal plumes can provide important new information to address the role of hydrothermal systems as a DREE source or sink to the Oceans.…”

Section: Introductionmentioning

confidence: 99%

Sulfate minerals control dissolved rare earth element flux and Nd isotope signature of buoyant hydrothermal plume (EMSO-Azores, 37°N Mid-Atlantic Ridge)

et al. 2018

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While hydrothermal vents are now thought to be a major source of dissolved iron to the oceans, they have always been considered to be a sink for the dissolved rare-earth elements (DREEs). However, true dissolved REE observations in hydrothermal plumes are still lacking. Here we report for the first time the DREE concentrations and neodymium isotopic compositions (DεNd) of buoyant hydrothermal fluids at Lucky Strike (Mid-Atlantic Ridge). We find that 27 to 62% of total hydrothermal DREEs are rapidly scavenged by anhydrite precipitation at the onset of buoyant plume formation. After this initial loss, all DREEs behave quasi-conservatively within the buoyant plume. Dissolved phase εNd (DεNd) in the evolving plume are identical to black smoker DεNd of +9.0 and contrast radically with DεNd of the local deep water mass at −12.0. Plume DεNd as low as +6.6 may be reconciled by dissolution of newly formed barite in the local environment and carrying seawater DεNd signature. We find, based on the first plume DREE observations, that hydrothermal plumes are in fact a source of DREE to the North Atlantic Deep Water. Precipitation/dissolution processes of hydrothermally-derived minerals, i.e. sulfates in the buoyant plume and Fe oxy-hydroxide in the non-buoyant plume, will likely affect the fate of other Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.trace metals and their isotopic composition.

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Overview of the mechanisms that could explain the ‘Boundary Exchange’ at the land–ocean contact

Abstract: One contribution of 20 to a discussion meeting issue 'Biological and climatic impacts of ocean trace element chemistry'.

Cited by 72 publications

References 80 publications

The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data

The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data

Manganese in the west Atlantic Ocean in the context of the first global ocean circulation model of manganese

Sulfate minerals control dissolved rare earth element flux and Nd isotope signature of buoyant hydrothermal plume (EMSO-Azores, 37°N Mid-Atlantic Ridge)

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