Unprecedented Fe delivery from the Congo River margin to the South Atlantic Gyre

Vieira, Lúcia Helena; Krisch, Stephan; Hopwood, Mark J.; Beck, Aaron J.; Scholten, Jan; Liebetrau, Volker; Achterberg, Eric P.

doi:10.1038/s41467-019-14255-2

Cited by 35 publications

(46 citation statements)

References 67 publications

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“…where FTE-a is the offshore advective flux of TE, w is the net offshore advection velocity (0.6 ± 0.3 cm s -1 ) along the SAC in (Charette et al, 2016;Sanial et al, 2018;Vieira et al, 2020). This method provides the integrated net fluxes of TEs, considering all the possible inputs (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Comparing the shelf-ocean TE fluxes from this study with previous studies, all the TE fluxes are normalised to the area of the shelf-ocean cross section. The areas of shelf-ocean cross section from the reference regions are summarised in Table D2 ( Emery, 1966;Windom et al, 2006;Hooker et al, 2013;Vieira et al, 2020). In this study, the 228 Ra-derived shelf-ocean Co fluxes range from 3.8 to 22 × 10 3 nmol m -2 d -1 in the Argentine margin and from 4.3 to 6.2 × 10 3 nmol m -2 d -1 in the Cape margin of the 40 o S transect in the South Atlantic.…”

Section: Trace Element Inputs In the South Atlanticmentioning

confidence: 99%

“…In this study, the 228 Ra-derived shelf-ocean Co fluxes range from 3.8 to 22 × 10 3 nmol m -2 d -1 in the Argentine margin and from 4.3 to 6.2 × 10 3 nmol m -2 d -1 in the Cape margin of the 40 o S transect in the South Atlantic. In comparison, previous studies have applied the TE/ 228 Ra approach to estimate the shelf Co fluxes in several continental margins: the western North Atlantic (1.6 × 10 5 nmol m -2 d -1 , Charette et al, 2016), the Peruvian shelf (1.4 × 10 5 nmol m -2 d -1 , Sanial et al, 2018) and the Congo-offshelf 3 o S (2.8 × 10 6 nmol m -2 d -1 , Vieira et al, 2020). Although these fluxes are about one and two orders of magnitude respectively higher than the estimates in the South Atlantic, these regions are also associated with low oxygen which is prone to result in higher Co fluxes.…”

Section: Trace Element Inputs In the South Atlanticmentioning

confidence: 99%

“…Previous work has assessed TE input to the wider South Atlantic from rivers (Vieira et al, 2020), atmospheric dust (Gaiero et al, 2013), shelf sediments (Graham et al, 2015), the Agulhas current (Paul et al, 2015) and hydrothermal vents . There are also studies of TE distributions in some areas of the South Atlantic (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Subsequent downward mixing from the surface can also be used to assess vertical mixing in the upper water column (Charette et al, 2007;Sarmiento et al, 1976;van Beek et al, 2008). Radium-228 has also been used as a conservative tracer to estimate submarine groundwater discharge (SGD) (Windom et al, 2006;Moore et al, 2008;Kwon et al, 2014;Rodellas et al, 2015;Le Gland et al, 2017), river inputs (Vieira et al, 2020), continental shelf (van der Loeff et al, 1995;Charette et al, 2016;Sanial et al 2018;Kipp et al, 2018a) and hydrothermal inputs (Kipp et al, 2018b).…”

Section: Introductionmentioning

confidence: 99%

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Radium-228-derived ocean mixing and trace element inputs in the South Atlantic

Hsieh¹,

Geibert²,

Woodward³

et al. 2020

Preprint

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Abstract. Trace elements play important roles as micronutrients in modulating marine productivity in the global ocean. The South Atlantic around 40° S is a prominent region of high productivity and a transition zone between the nitrate-depleted Subtropical Gyre and the iron-limited Southern Ocean. However, the sources and fluxes of trace elements to this region remain unclear. In this study, the distribution of the naturally occurring radioisotope 228Ra in the water column of the South Atlantic (Cape Basin and Argentine Basin) has been investigated along a 40° S zonal transect to estimate ocean mixing and trace element supply to the surface ocean. Ra-228 profiles have been used to determine the horizontal and vertical mixing rates in the near-surface open ocean. In the Argentine Basin, horizontal mixing from the continental shelf to the open ocean shows an eddy diffusion of Kx = 1.7 ± 1.4 (106 cm2 s−1) and an integrated advection velocity w = 0.6 ± 0.3 cm s−1. In the Cape Basin, horizontal mixing is Kx = 2.7 ± 0.8 (107 cm2 s−1) and vertical mixing Kz = 1.0–1.5 cm2 s−1 in the upper 600 m layer. Three different approaches (228Ra-diffusion, 228Ra-advection and 228Ra/TE-ratio) have been applied to estimate the dissolved trace-element fluxes from shelf to open ocean. These approaches bracket the possible range of off-shelf fluxes from the Argentine margin to be: 3.8–22 (× 103) nmol Co m−2 d−1, 7.9–20 (× 104) nmol Fe m−2 d−1 and 2.7–6.5 (× 104) nmol Zn m−2 d−1. Off-shelf fluxes from the Cape margin are: 4.3–6.2 (× 103) nmol Co m−2 d−1, 1.2–3.1 (× 104) nmol Fe m−2 d−1 and 0.9–1.2 (× 104) nmol Zn m−2 d−1. On average, at 40° S in the Atlantic, vertical mixing supplies 0.4–1.2 nmol Co m−2 d−1, 3.6–11 nmol Fe m−2 d−1, and 13–16 nmol Zn m−2 d−1 to the euphotic zone. Compared with atmospheric dust and continental shelf inputs, vertical mixing is a more important source for supplying dissolved trace elements to the surface 40° S Atlantic. It is insufficient, however, to provide the trace elements removed by biological uptake. Other inputs (e.g. particulate, or from winter deep-mixing) are required to balance the trace element budgets in this region.

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Section: Discussionmentioning

confidence: 99%

Section: Trace Element Inputs In the South Atlanticmentioning

confidence: 99%

Section: Trace Element Inputs In the South Atlanticmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Radium-228-derived ocean mixing and trace element inputs in the South Atlantic

Hsieh¹,

Geibert²,

Woodward³

et al. 2020

Preprint

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Distribution and Flux of Trace Metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and U) in the Amazon and Pará River Estuary and Mixing Plume

Hollister

Léon

Scholten³

et al. 2022

Preprint

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Distinct drivers of two size fractions of operationally dissolved iron in a temperate river

Logozzo

Hosen

McArthur

et al. 2023

Limnology & Oceanography

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Riverine dissolved iron (Fe) affects water color, nutrients, and marine carbon cycling. Fe size and coupling with dissolved organic matter (DOM), in part, modulates the biogeochemical roles of riverine Fe. We used size fractionation to operationally define dissolved Fe (< 0.22 μm) into soluble (< 0.02 μm) and colloidal (0.02–0.22 μm) fractions in order to characterize the downstream drivers, concentrations, and fluxes of Fe across season and hydrologic regime at the freshwater Connecticut River mainstem, which we sampled bi‐weekly for 2 yrs. Drivers of colloidal and soluble Fe concentrations were markedly different. The response of colloidal Fe concentration to changes in discharge was modulated by water temperature; colloidal Fe decreased with increasing discharge at temperatures < 10.5°C, but increased with increasing discharge at temperatures > 10.5°C. Conversely, soluble Fe concentrations were only positively correlated to discharge at high temperatures (> 20°C). Soluble Fe was strongly positively correlated to a humic‐like DOM fluorescence component, suggesting coupling with DOM subsets, potentially through complexation. While average colloidal Fe fluxes varied twofold seasonally, soluble Fe fluxes varied ninefold; therefore, soluble Fe variability was more important to the overall dissolved Fe variability than colloidal Fe, despite lower concentrations. Seasonal Fe fluxes were decoupled from discharge: dissolved and soluble Fe fluxes were greatest in the fall, whereas discharge was greatest in the spring. Fluxes of soluble Fe, which may be more bioavailable and more likely to be exported to the ocean, were lowest in the summer when downstream biological demand is high, having implications for primary productivity and iron uptake.

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Unprecedented Fe delivery from the Congo River margin to the South Atlantic Gyre

Cited by 35 publications

References 67 publications

Radium-228-derived ocean mixing and trace element inputs in the South Atlantic

Radium-228-derived ocean mixing and trace element inputs in the South Atlantic

Distribution and Flux of Trace Metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and U) in the Amazon and Pará River Estuary and Mixing Plume

Distinct drivers of two size fractions of operationally dissolved iron in a temperate river

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