Particulate iron dynamics during FeCycle in subantarctic waters southeast of New Zealand

Frew, Russell; Hutchins, David A.; Nodder, Scott D.; Sañudo‐Wilhelmy, Sergio A.; Tovar-Sánchez, Antonio; Leblanc, Karine; Hare, Clinton E.; Boyd, Philip W.

doi:10.1029/2005gb002558

Cited by 123 publications

(201 citation statements)

References 83 publications

(116 reference statements)

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“…Increases in the apparent solubility when considering the longer-term processing of lithogenic particles, similar to that for Th, have been reported for Fe (Boyd et al, 2010;Frew et al, 2006;Hansard et al, 2009). On this basis, we infer a general similarity in the dissolution of relatively insoluble lithogenic elements such as Fe, Nd, etc.…”

Section: Dissolved Metal Fluxes Based On Dissolved 232 Th Fluxesmentioning

confidence: 59%

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

Hayes

Anderson

Fleisher

et al. 2013

Earth and Planetary Science Letters

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Dissolved 232 Th is added to the ocean though the partial dissolution of lithogenic materials such as aerosol dust in the same way as other lithogenically sourced and more biologically important trace metals such as Fe. Oceanic 230 Th, on the other hand, is sourced primarily from the highly predictable decay of dissolved 234 U. The rate at which dissolved 232 Th is released by mineral dissolution can be constrained by a Th removal rate derived from 230 Th: 234 U disequilibria, assuming steady-state. Calculated fluxes of dissolved 232 Th can in turn be used to estimate fluxes of other lithogenically sourced dissolved metals as well as the original lithogenic supplies, such as aerosol dust deposition, given the concentration and fractional solubility of Th (or other metals) in the lithogenic material. This method is applied to 7 water column profiles from the Innovative North Pacific Experiment (INOPEX) cruise of 2009 and 2 sites from the subtropical North Pacific. The structure of shallow depth profiles suggests rapid scavenging at the surface and at least partial regeneration of dissolved 232 Th at 100-200 m depth. This rapid cycling could involve colloidal Th generated during mineral dissolution, which may not be subject to the same removal rates as the more truly dissolved 230 Th. An additional deep source of 232 Th was revealed in deep waters, most likely dissolution of seafloor sediments, and offers a constraint on dissolved trace element supply due to boundary exchange.

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Section: Dissolved Metal Fluxes Based On Dissolved 232 Th Fluxesmentioning

confidence: 59%

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

Hayes

Anderson

Fleisher

et al. 2013

Earth and Planetary Science Letters

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“…In the lower panels, sites where simultaneous total 234 Th, large particle 234 Th, and large particle element measurements have been made are shown as filled squares (this study) and circles (Lemaitre et al, 2016;Planquette et al, 2011;Weinstein and Moran, 2005). Prior 234 Th studies where large particle E: 234 Th values were extrapolated from other data are indicated by diamonds (Bown et al, 2011;Dulaquais et al, 2014) and trap-only studies by nabla (Collier et al, 2000;Frew et al, 2006;Lamborg et al, 2008;Martin, 1990;Martin et al, 1985, 1980, Martin and Knauer, 1984, 1983Migon et al, 2002;Noble et al, 2012;Pohl et al, 2004;Quetel et al, 1993;Schüßler et al, 1997;Stanley et al, 2004). 234 Th.…”

Section: Discussionmentioning

confidence: 98%

“…Bishop et al, 1977;Frew et al, 2006;Weinstein and Moran, 2004) and often limited to a select few metals (e.g. Bishop and Fleisher, 1987;Lam et al, 2006) or a single location (e.g.…”

Section: Element Concentrations In Large Particlesmentioning

confidence: 99%

An investigation of basin-scale controls on upper ocean export and remineralization

Black¹

2018

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The biological carbon pump (BCP) helps to moderate atmospheric carbon dioxide levels by bringing carbon to the deep ocean, where it can be sequestered on timescales of centuries to millennia. Climate change is predicted to decrease the efficiency of the global BCP, however, the magnitude and timescale of this shift is largely uncertain and will likely impact some areas of the global ocean more significantly than others. Therefore, it is imperative that we (1) accurately quantify surface export and remineralization of particulate organic carbon (POC) via the BCP over large regions of the global ocean, (2) examine the factors controlling these POC fluxes and their variability, which includes the cycling of biologically-relevant trace metals, and (3) establish if and how the BCP is changing over time.This thesis focuses on addressing various aspects of these objectives using the 234 Th-238 U method across basin-scale GEOTRACES transects. First, the export and remineralization of POC were examined across large gradients in productivity, upwelling, community structure, and dissolved oxygen in the southeastern tropical Pacific Ocean. Although low oxygen zones are traditionally thought to have decreased POC flux attenuation relative to other regions of the global ocean and the low oxygen Pacific locations followed this pattern, regions that were functionally anoxic had enhanced attenuation in the upper 400 m. Second, trace metal export and remineralization were quantified across the Pacific transect. Because many trace metals are necessary for the metabolic functions of marine organisms and can co-limit marine productivity, the controls on the cycling of trace metals in the upper ocean were examined. Lastly, POC export was determined across two transects in the Western Arctic Ocean, where light and nutrient availability drive the biological pump. Upper ocean export estimates in the central basin did not reflect a substantial change in the biological pump compared to studies from the last three decades, however, an extensive maximum in 234 Th relative to 238 U deeper in the water column indicated that rapid vertical transport had occurred, which could suggest a more efficient biological pump in the Arctic Ocean.

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“…This implies either that seasonal dFe patterns in spring-summer are dominated by external inputs (mediated by physical mixing) or that the signal of biology is dominated by recycling terms. For example, a number of attempts to construct dFe budgets have highlighted the so-called "ferrous wheel" as the dominant Fe flux term (e.g., Strzepek et al, 2005;Frew et al, 2006;Boyd and Ellwood, 2010). The "ferrous wheel" encompasses Fe recycling processes associated with zooplankton grazing, higher trophic levels, bacterial turnover, as well as dissolution of particle Fe (e.g., Strzepek et al, 2005;Frew et al, 2006;Tovar-Sanchez et al, 2007;Nicol et al, 2010).…”

Section: Future Challengesmentioning

confidence: 99%

“…For example, a number of attempts to construct dFe budgets have highlighted the so-called "ferrous wheel" as the dominant Fe flux term (e.g., Strzepek et al, 2005;Frew et al, 2006;Boyd and Ellwood, 2010). The "ferrous wheel" encompasses Fe recycling processes associated with zooplankton grazing, higher trophic levels, bacterial turnover, as well as dissolution of particle Fe (e.g., Strzepek et al, 2005;Frew et al, 2006;Tovar-Sanchez et al, 2007;Nicol et al, 2010). While we might imagine greater herbivory and associated Fe recycling to be associated with higher Chl-a levels, which would then be in accord with the associated high values of dFe, we lack quantitative data.…”

Section: Future Challengesmentioning

confidence: 99%

A global compilation of dissolved iron measurements: focus on distributions and processes in the Southern Ocean

et al. 2012

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Abstract. Due to its importance as a limiting nutrient for phytoplankton growth in large regions of the world's oceans, ocean water column observations of concentration of the trace-metal iron (Fe) have increased markedly over recent decades. Here we compile >13 000 global measurements of dissolved Fe (dFe) and make this available to the community. We then conduct a synthesis study focussed on the Southern Ocean, where dFe plays a fundamental role in governing the carbon cycle, using four regions, six basins and five depth intervals as a framework. Our analysis highlights depth-dependent trends in the properties of dFe between different regions and basins. In general, surface dFe is highest in the Atlantic basin and the Antarctic region. While attributing drivers to these patterns is uncertain, inter-basin patterns in surface dFe might be linked to differing degrees of dFe inputs, while variability in biological consumption between regions covaries with the associated surface dFe differences. Opposite to the surface, dFe concentrations at depth are typically higher in the Indian basin and the Subantarctic region. The inter-region trends can be reconciled with similar ligand variability (although only from one cruise), and the inter-basin difference might be explained by differences in hydrothermal inputs suggested by modelling studies ) that await observational confirmation. We find that even in regions where many dFe measurements exist, the processes governing the seasonal evolution of dFe remain enigmatic, suggesting that, aside from broad Subantarctic -Antarctic trends, biological consumption might not be the major driver of dFe variability. This highlights the apparent importance of other processes such as exogenous inputs, physical transport/mixing or dFe recycling processes. Nevertheless, missing measurements during key seasonal transitions make it difficult to better quantify and understand surface water replenishment processes and the seasonal Fe cycle. Finally, we detail the degree of seasonal coverage by region, basin and depth. By synthesising prior measurements, we suggest a role for different processes and highlight key gaps in understanding, which we hope can help structure future research efforts in the Southern Ocean.

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Particulate iron dynamics during FeCycle in subantarctic waters southeast of New Zealand

Cited by 123 publications

References 83 publications

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes

An investigation of basin-scale controls on upper ocean export and remineralization

A global compilation of dissolved iron measurements: focus on distributions and processes in the Southern Ocean

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