Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods
Changes in bioavailable dust-borne iron (Fe) supply to the iron-limited Southern Ocean may influence climate by modulating phytoplankton growth and CO 2 fixation into organic matter that is exported to the deep ocean. The chemical form (speciation) of Fe impacts its bioavailability, and glacial weat...
Published in: | Proceedings of the National Academy of Sciences |
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Online Access: | http://www.osti.gov/servlets/purl/1483093 https://www.osti.gov/biblio/1483093 https://doi.org/10.1073/pnas.1809755115 |
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ftosti:oai:osti.gov:1483093 2023-07-30T04:07:00+02:00 Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods Shoenfelt, Elizabeth M. Winckler, Gisela Lamy, Frank Anderson, Robert F. Bostick, Benjamin C. 2023-06-28 application/pdf http://www.osti.gov/servlets/purl/1483093 https://www.osti.gov/biblio/1483093 https://doi.org/10.1073/pnas.1809755115 unknown http://www.osti.gov/servlets/purl/1483093 https://www.osti.gov/biblio/1483093 https://doi.org/10.1073/pnas.1809755115 doi:10.1073/pnas.1809755115 54 ENVIRONMENTAL SCIENCES 2023 ftosti https://doi.org/10.1073/pnas.1809755115 2023-07-11T09:30:11Z Changes in bioavailable dust-borne iron (Fe) supply to the iron-limited Southern Ocean may influence climate by modulating phytoplankton growth and CO 2 fixation into organic matter that is exported to the deep ocean. The chemical form (speciation) of Fe impacts its bioavailability, and glacial weathering produces highly labile and bioavailable Fe minerals in modern dust sources. However, the speciation of dust-borne Fe reaching the iron-limited Southern Ocean on glacial–interglacial timescales is unknown, and its impact on the bioavailable iron supply over geologic time has not been quantified. Here we use X-ray absorption spectroscopy on subantarctic South Atlantic and South Pacific marine sediments to reconstruct dust-borne Fe speciation over the last glacial cycle, and determine the impact of glacial activity and glaciogenic dust sources on bioavailable Fe supply. We show that the Fe(II) content, as a percentage of total dust-borne Fe, increases from ~5 to 10% in interglacial periods to ~25 to 45% in glacial periods. Consequently, the highly bioavailable Fe(II) flux increases by a factor of ~15 to 20 in glacial periods compared with the current interglacial, whereas the total Fe flux increases only by a factor of ~3 to 5. The change in Fe speciation is dominated by primary Fe(II) silicates characteristic of glaciogenic dust. Furthermore, our results suggest that glacial physical weathering increases the proportion of highly bioavailable Fe(II) in dust that reaches the subantarctic Southern Ocean in glacial periods, which represents a positive feedback between glacial activity and cold glacial temperatures. Other/Unknown Material Southern Ocean SciTec Connect (Office of Scientific and Technical Information - OSTI, U.S. Department of Energy) Southern Ocean Pacific Proceedings of the National Academy of Sciences 115 44 11180 11185 |
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SciTec Connect (Office of Scientific and Technical Information - OSTI, U.S. Department of Energy) |
op_collection_id |
ftosti |
language |
unknown |
topic |
54 ENVIRONMENTAL SCIENCES |
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54 ENVIRONMENTAL SCIENCES Shoenfelt, Elizabeth M. Winckler, Gisela Lamy, Frank Anderson, Robert F. Bostick, Benjamin C. Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods |
topic_facet |
54 ENVIRONMENTAL SCIENCES |
description |
Changes in bioavailable dust-borne iron (Fe) supply to the iron-limited Southern Ocean may influence climate by modulating phytoplankton growth and CO 2 fixation into organic matter that is exported to the deep ocean. The chemical form (speciation) of Fe impacts its bioavailability, and glacial weathering produces highly labile and bioavailable Fe minerals in modern dust sources. However, the speciation of dust-borne Fe reaching the iron-limited Southern Ocean on glacial–interglacial timescales is unknown, and its impact on the bioavailable iron supply over geologic time has not been quantified. Here we use X-ray absorption spectroscopy on subantarctic South Atlantic and South Pacific marine sediments to reconstruct dust-borne Fe speciation over the last glacial cycle, and determine the impact of glacial activity and glaciogenic dust sources on bioavailable Fe supply. We show that the Fe(II) content, as a percentage of total dust-borne Fe, increases from ~5 to 10% in interglacial periods to ~25 to 45% in glacial periods. Consequently, the highly bioavailable Fe(II) flux increases by a factor of ~15 to 20 in glacial periods compared with the current interglacial, whereas the total Fe flux increases only by a factor of ~3 to 5. The change in Fe speciation is dominated by primary Fe(II) silicates characteristic of glaciogenic dust. Furthermore, our results suggest that glacial physical weathering increases the proportion of highly bioavailable Fe(II) in dust that reaches the subantarctic Southern Ocean in glacial periods, which represents a positive feedback between glacial activity and cold glacial temperatures. |
author |
Shoenfelt, Elizabeth M. Winckler, Gisela Lamy, Frank Anderson, Robert F. Bostick, Benjamin C. |
author_facet |
Shoenfelt, Elizabeth M. Winckler, Gisela Lamy, Frank Anderson, Robert F. Bostick, Benjamin C. |
author_sort |
Shoenfelt, Elizabeth M. |
title |
Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods |
title_short |
Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods |
title_full |
Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods |
title_fullStr |
Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods |
title_full_unstemmed |
Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods |
title_sort |
highly bioavailable dust-borne iron delivered to the southern ocean during glacial periods |
publishDate |
2023 |
url |
http://www.osti.gov/servlets/purl/1483093 https://www.osti.gov/biblio/1483093 https://doi.org/10.1073/pnas.1809755115 |
geographic |
Southern Ocean Pacific |
geographic_facet |
Southern Ocean Pacific |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
http://www.osti.gov/servlets/purl/1483093 https://www.osti.gov/biblio/1483093 https://doi.org/10.1073/pnas.1809755115 doi:10.1073/pnas.1809755115 |
op_doi |
https://doi.org/10.1073/pnas.1809755115 |
container_title |
Proceedings of the National Academy of Sciences |
container_volume |
115 |
container_issue |
44 |
container_start_page |
11180 |
op_container_end_page |
11185 |
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1772820048412409856 |