Investigating the use of 232Th/230Th as a dust proxy using co-located seawater and sediment samples from the low-latitude North Atlantic

Rowland, George H.; Ng, Hong Chin; Robinson, Laura F.; McManus, Jerry F; Mohamed, K.; McGee, David

doi:10.1016/j.gca.2017.07.033

Cited by 18 publications

(20 citation statements)

References 74 publications

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“…There are few studies that determine the relative solubility of all the elements of interest here. In particular, oceanic Th fractional solubility data are rather limited and range from about 1–29%, in published work (Anderson et al, ; Arraes‐Mescoff et al, ; Hayes et al, ; Robinson et al, ; Rowland et al, ; Roy‐Barman et al, ). Based on time series measurements of Th and Fe at station ALOHA (Hayes, Fitzsimmons, et al, ), it is likely that S Fe / S Th is close to 1, but this may vary regionally and episodically.…”

Section: Methodsmentioning

confidence: 99%

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Hayes

Anderson

Cheng

et al. 2018

Global Biogeochemical Cycles

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The measurable supply of 232Th to the ocean can be used to derive the supply of other elements, which is more difficult to quantify directly. The measured inventory of an element divided by the derived supply yields a replacement time estimate, which in special circumstances is related to a residence time. As a proof of concept, Th‐based supply rates imply a range in the replacement times of the rare earth elements in the North Atlantic that is consistent with the chemical reactivity of rare earth elements related to their ionic charge density. Similar estimates of replacement times for the bioactive trace elements (Fe, Mn, Zn, Cd, Cu, and Co), ranging from <5 years to >50,000 years, demonstrate the broad range of elemental reactivity in the ocean. Here we discuss how variations in source composition, fractional solubility ratios, or noncontinental sources, such as hydrothermal vents, lead to uncertainties in Th‐based replacement time estimates. We show that the constraints on oceanic replacement time provided by the Th‐based calculations are broadly applicable in predicting how elements are distributed in the ocean and for some elements, such as Fe, may inform us on how the carbon cycle may be impacted by trace element supply and removal.

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Section: Methodsmentioning

confidence: 99%

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Hayes

Anderson

Cheng

et al. 2018

Global Biogeochemical Cycles

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“…Changes in 230 Th‐normalized mass fluxes in response to changes in calcium carbonate burial. Core top mass fluxes are reconstructed from depth transects recovered from five seamounts in the tropical Atlantic (Rowland et al, ). Data are represented as deviations from the mass flux or calcium carbonate at the shallowest core top of each seamount; that is, a ΔCaCO 3 of −20% indicates that the calcium carbonate concentration is 20% lower than that of the shallowest core top on that seamount.…”

Section: Uncertainties and Limits Of The Constant 230th Flux Modelmentioning

confidence: 99%

“…The influence of calcium carbonate (CaCO 3 ) dissolution on 230 Th‐normalized mass fluxes may be investigated by looking at core top depth transects, for example, in a study from seamounts across the tropical Atlantic (Rowland et al, ). These sites are primarily composed of CaCO 3 and lithogenic components, and they are proximally located such that the principle deviations in apparent preserved mass flux with depth should result from increasing carbonate dissolution with increasing depth.…”

Section: Uncertainties and Limits Of The Constant 230th Flux Modelmentioning

confidence: 99%

²³⁰Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

Costa

Hayes

Anderson

et al. 2020

Paleoceanog and Paleoclimatol

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230Th normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0–5,000 years ago, or 0–5 ka) and the Last Glacial Maximum (18.5–23.5 ka), and investigated the spatial structure of 230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79–2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48–1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size‐dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (>1,000 m water depth).

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“…COSTA ET AL. Plain, 2004;Pourmand et al, 2004, Pourmand et al, 2007Purcell, 2019;Roberts et al, 2014;Robinson et al, 2008;Rowland et al, 2017;Ruhlemann et al, 1996;Sarin et al, 1979;Saukel, 2011;Scholten et al, 1990, Scholten et al, 2008Serno et al, 2014Serno et al, , 2015Shiau et al, 2012;Shimmield et al, 1986;Shimmield & Mowbray, 1991;Shimmield & Price, 1988;Singh et al, 2011;Skonieczny et al, 2019;Studer et al, 2015;Sukumaran, 1994;Thiagarajan & McManus, 2019;Thöle et al, 2019;Thomas et al, 2007;Thomson et al, 1993, Thomson et al, 1995, Thomson et al, 1999Vallieres, 1997;Veeh et al, 1999Veeh et al, , 2000Veiga-Pires & Hillaire-Marcel, 1999;Voigt et al, 2017;Waelbroeck et al, 2018;Walter et al, 1997;Wengler et al, 2019;Williams et al, 2016;Winckler et al, 2008;Yang & Elderfield, 1990;Yang et al, 1995;Yu, 1994;…”

Section: Paleoceanography and Paleoclimatologyunclassified

“…Changes in 230 Th-normalized mass fluxes in response to changes in calcium carbonate burial. Core top mass fluxes are reconstructed from depth transects recovered from five seamounts in the tropical Atlantic (Rowland et al, 2017). Data are represented as deviations from the mass flux or calcium carbonate at the shallowest core top of each seamount; that is, a ΔCaCO 3 of −20% indicates that the calcium carbonate concentration is 20% lower than that of the shallowest core top on that seamount.…”

Section: 1029/2019pa003820mentioning

confidence: 99%

230Th normalization: New insights on an essential tool for quantifying sedimentary fluxes in the modern and Quaternary ocean

Costa¹

2020

Preprint

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230Th-normalization is a valuable paleoceanographic tool for reconstructing high-resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more complex marine environments, the nuances of 230Th systematics, with regards to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the Late Holocene (0-5000 years ago, or 0-5 ka) and the Last Glacial Maximum (18.5-23.5 ka), and investigated the spatial structure of 230Th-normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79-2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48-1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th-normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic (> 1000 m) marine settings.

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Investigating the use of 232Th/230Th as a dust proxy using co-located seawater and sediment samples from the low-latitude North Atlantic

Cited by 18 publications

References 74 publications

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

²³⁰Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

230Th normalization: New insights on an essential tool for quantifying sedimentary fluxes in the modern and Quaternary ocean

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Investigating the use of 232Th/230Th as a dust proxy using co-located seawater and sediment samples from the low-latitude North Atlantic

Cited by 18 publications

References 74 publications

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

230Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean

230Th normalization: New insights on an essential tool for quantifying sedimentary fluxes in the modern and Quaternary ocean

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Product

Resources

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²³⁰Th Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean