Thorium distributions in high- and low-dust regions and the significance for iron supply
Thorium and uranium isotopes (²³²Th, ²³⁰Th, ²³⁸U, and ²³⁴U) were investigated to refine their use for estimating mineral dust deposition and Fe delivery to the ocean. U concentrations and isotope ratios were consistent with conservative behavior and can safely be described using published U‐salinity...
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| Format: | Article |
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American Geophysical Union (AGU)
2019
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| Online Access: | http://hdl.handle.net/1721.1/120502 https://orcid.org/0000-0002-5609-8241 https://orcid.org/0000-0002-6394-1866 |
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| author | Hayes, Christopher Tyler McGee, William David Rosenblum, Jeffrey Laurence Boyle, Edward A |
| author2 | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences |
| author_facet | Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Hayes, Christopher Tyler McGee, William David Rosenblum, Jeffrey Laurence Boyle, Edward A |
| author_sort | Hayes, Christopher Tyler |
| collection | MIT |
| description | Thorium and uranium isotopes (²³²Th, ²³⁰Th, ²³⁸U, and ²³⁴U) were investigated to refine their use for estimating mineral dust deposition and Fe delivery to the ocean. U concentrations and isotope ratios were consistent with conservative behavior and can safely be described using published U‐salinity relationships and global average seawater isotopic composition. Near Barbados, waters affected by the Amazon outflow contained elevated ²³²Th. This signals one region where the thorium‐dust method is inaccurate because of a confounding continental input. Dissolved ²³²Th fluxes in this region suggest that Amazonian Fe supply to the adjacent open ocean is much larger than local atmospheric deposition. The colloidal content of dissolved Th south of Bermuda was found to be quite small (2–6%), similar to that found north of Hawaii, despite the order of magnitude higher dust deposition in the Atlantic. This finding supports the assumption that dissolved ²³²Th and ²³⁰Th are scavenged at the same rate despite their different sources and also sheds light on the increase of dissolved ²³²Th fluxes with integrated depth. Outside the region influenced by Amazon River waters, dissolved ²³²Th fluxes are compared with Bermudan aerosol Fe deposition to estimate that fractional Th solubility is around 20% in this region. Finally, new dissolved and soluble Fe, Mn, and Cr data from the subtropical North Pacific support the idea that Fe concentrations in the remote ocean are highly buffered, whereas ²³²Th has a larger dynamic range between high‐ and low‐dust regions. Keywords: aerosol dust; Amazon River; Bermuda; Hawaii; Barbados |
| first_indexed | 2024-09-23T14:53:24Z |
| format | Article |
| id | mit-1721.1/120502 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T14:53:24Z |
| publishDate | 2019 |
| publisher | American Geophysical Union (AGU) |
| record_format | dspace |
| spelling | mit-1721.1/1205022022-09-29T11:16:37Z Thorium distributions in high- and low-dust regions and the significance for iron supply Thorium distributions in high- and low-dust regions and the significance for iron supply: Marine Thorium and Iron Cycles Hayes, Christopher Tyler McGee, William David Rosenblum, Jeffrey Laurence Boyle, Edward A Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology. Department of Urban Studies and Planning Boyle, Edward Hayes, Christopher Tyler McGee, William David Rosenblum, Jeffrey Laurence Boyle, Edward A Thorium and uranium isotopes (²³²Th, ²³⁰Th, ²³⁸U, and ²³⁴U) were investigated to refine their use for estimating mineral dust deposition and Fe delivery to the ocean. U concentrations and isotope ratios were consistent with conservative behavior and can safely be described using published U‐salinity relationships and global average seawater isotopic composition. Near Barbados, waters affected by the Amazon outflow contained elevated ²³²Th. This signals one region where the thorium‐dust method is inaccurate because of a confounding continental input. Dissolved ²³²Th fluxes in this region suggest that Amazonian Fe supply to the adjacent open ocean is much larger than local atmospheric deposition. The colloidal content of dissolved Th south of Bermuda was found to be quite small (2–6%), similar to that found north of Hawaii, despite the order of magnitude higher dust deposition in the Atlantic. This finding supports the assumption that dissolved ²³²Th and ²³⁰Th are scavenged at the same rate despite their different sources and also sheds light on the increase of dissolved ²³²Th fluxes with integrated depth. Outside the region influenced by Amazon River waters, dissolved ²³²Th fluxes are compared with Bermudan aerosol Fe deposition to estimate that fractional Th solubility is around 20% in this region. Finally, new dissolved and soluble Fe, Mn, and Cr data from the subtropical North Pacific support the idea that Fe concentrations in the remote ocean are highly buffered, whereas ²³²Th has a larger dynamic range between high‐ and low‐dust regions. Keywords: aerosol dust; Amazon River; Bermuda; Hawaii; Barbados National Science Foundation (U.S.) (Award EAR-1439559) 2019-02-19T19:42:15Z 2019-02-19T19:42:15Z 2017-01 2016-08 Article http://purl.org/eprint/type/JournalArticle 0886-6236 http://hdl.handle.net/1721.1/120502 Hayes, Christopher T., Jeffrey Rosen, David McGee, and Edward A. Boyle. “Thorium Distributions in High- and Low-Dust Regions and the Significance for Iron Supply.” Global Biogeochemical Cycles 31 (January 2017): 328-347 © 2017 American Geophysical Union https://orcid.org/0000-0002-5609-8241 https://orcid.org/0000-0002-6394-1866 en_US https://doi.org/10.1002/2016GB005511 Global Biogeochemical Cycles Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf American Geophysical Union (AGU) Prof. Boyle via Chris Sherratt |
| spellingShingle | Hayes, Christopher Tyler McGee, William David Rosenblum, Jeffrey Laurence Boyle, Edward A Thorium distributions in high- and low-dust regions and the significance for iron supply |
| title | Thorium distributions in high- and low-dust regions and the significance for iron supply |
| title_full | Thorium distributions in high- and low-dust regions and the significance for iron supply |
| title_fullStr | Thorium distributions in high- and low-dust regions and the significance for iron supply |
| title_full_unstemmed | Thorium distributions in high- and low-dust regions and the significance for iron supply |
| title_short | Thorium distributions in high- and low-dust regions and the significance for iron supply |
| title_sort | thorium distributions in high and low dust regions and the significance for iron supply |
| url | http://hdl.handle.net/1721.1/120502 https://orcid.org/0000-0002-5609-8241 https://orcid.org/0000-0002-6394-1866 |
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