Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage
The clear predictions of the silicic acid leakage hypothesis (SALH) resulted in a number of studies of downcore opal records from the tropical Pacific. The original SALH predicts that unused silicic acid, due to Fe-driven changes in Si versus N limitation, escaped from the glacial Southern Ocean to...
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American Geophysical Union
2010
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Online Access: | http://hdl.handle.net/2429/40061 https://doi.org/10.1029/2010GB003821 |
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ftunivbritcolcir:oai:circle.library.ubc.ca:2429/40061 2023-05-15T18:18:57+02:00 Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage Calvert, Stephen E. Francois, Roger University of British Columbia. Pacific Centre for Isotopic and Geochemical Research 2010 http://hdl.handle.net/2429/40061 https://doi.org/10.1029/2010GB003821 eng eng American Geophysical Union Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ Francois, Roger CC-BY-NC-ND Low-temperature Geochemistry Text Article 2010 ftunivbritcolcir https://doi.org/10.1029/2010GB003821 2019-10-15T18:07:43Z The clear predictions of the silicic acid leakage hypothesis (SALH) resulted in a number of studies of downcore opal records from the tropical Pacific. The original SALH predicts that unused silicic acid, due to Fe-driven changes in Si versus N limitation, escaped from the glacial Southern Ocean to equatorial upwelling regimes where it enhanced diatom productivity, thereby decreasing coccolith growth and lowering atmospheric CO2. In contrast to SALH predictions, however, sedimentary records from the eastern equatorial Pacific (EEP) do not show enhanced opal burial during the Last Glacial Maximum (LGM) but higher rates of opal burial during the deglaciation and marine isotopic stage 3 (MIS3). The peak in opal productivity during the deglaciation has been attributed to increased supply of nutrient-rich waters driven by stronger upwelling of deep water in the Southern Ocean at the end of last glacial period. The large peak in opal burial observed in a number of EEP cores during MIS3 was interpreted as evidence for Si leakage when Southern Ocean diatom productivity was limited by both low dust flux and extended sea ice. On the other hand, the paradoxical LGM decline in pal accumulation in the EEP was explained by enhanced dust input that lowered the diatom Si:C uptake ratio. Here we use a combination of molecular fingerprints of algal productivity and radioisotope tracers of sedimentation to revisit opal burial in the EEP, in particular during the MIS3 “opal peak.” An increase in algal productivity is not supported by the sedimentary concentration of brassicasterol, an organic molecule commonly found in diatoms, or by the ratio of (231Pa/230Th)xs,0, a proxy for opal export production. We therefore conclude that the large peak in opal burial during MIS3 reflects enhanced preservation of diatoms. Building on mechanisms invoked in previous studies, we hypothesize that opal burial in the EEP is controlled both by the physiological response of diatoms to low-latitude Fe inputs and by the high-latitude processes leading to silicic acid leakage. An edited version of this paper was published by AGU. Copyright 2010 American Geophysical Union. Science, Faculty of Earth and Ocean Sciences, Department of Reviewed Faculty Article in Journal/Newspaper Sea ice Southern Ocean University of British Columbia: cIRcle - UBC's Information Repository Pacific Southern Ocean Global Biogeochemical Cycles 24 4 n/a n/a |
institution |
Open Polar |
collection |
University of British Columbia: cIRcle - UBC's Information Repository |
op_collection_id |
ftunivbritcolcir |
language |
English |
topic |
Low-temperature Geochemistry |
spellingShingle |
Low-temperature Geochemistry Calvert, Stephen E. Francois, Roger Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage |
topic_facet |
Low-temperature Geochemistry |
description |
The clear predictions of the silicic acid leakage hypothesis (SALH) resulted in a number of studies of downcore opal records from the tropical Pacific. The original SALH predicts that unused silicic acid, due to Fe-driven changes in Si versus N limitation, escaped from the glacial Southern Ocean to equatorial upwelling regimes where it enhanced diatom productivity, thereby decreasing coccolith growth and lowering atmospheric CO2. In contrast to SALH predictions, however, sedimentary records from the eastern equatorial Pacific (EEP) do not show enhanced opal burial during the Last Glacial Maximum (LGM) but higher rates of opal burial during the deglaciation and marine isotopic stage 3 (MIS3). The peak in opal productivity during the deglaciation has been attributed to increased supply of nutrient-rich waters driven by stronger upwelling of deep water in the Southern Ocean at the end of last glacial period. The large peak in opal burial observed in a number of EEP cores during MIS3 was interpreted as evidence for Si leakage when Southern Ocean diatom productivity was limited by both low dust flux and extended sea ice. On the other hand, the paradoxical LGM decline in pal accumulation in the EEP was explained by enhanced dust input that lowered the diatom Si:C uptake ratio. Here we use a combination of molecular fingerprints of algal productivity and radioisotope tracers of sedimentation to revisit opal burial in the EEP, in particular during the MIS3 “opal peak.” An increase in algal productivity is not supported by the sedimentary concentration of brassicasterol, an organic molecule commonly found in diatoms, or by the ratio of (231Pa/230Th)xs,0, a proxy for opal export production. We therefore conclude that the large peak in opal burial during MIS3 reflects enhanced preservation of diatoms. Building on mechanisms invoked in previous studies, we hypothesize that opal burial in the EEP is controlled both by the physiological response of diatoms to low-latitude Fe inputs and by the high-latitude processes leading to silicic acid leakage. An edited version of this paper was published by AGU. Copyright 2010 American Geophysical Union. Science, Faculty of Earth and Ocean Sciences, Department of Reviewed Faculty |
author2 |
University of British Columbia. Pacific Centre for Isotopic and Geochemical Research |
format |
Article in Journal/Newspaper |
author |
Calvert, Stephen E. Francois, Roger |
author_facet |
Calvert, Stephen E. Francois, Roger |
author_sort |
Calvert, Stephen E. |
title |
Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage |
title_short |
Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage |
title_full |
Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage |
title_fullStr |
Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage |
title_full_unstemmed |
Sedimentary opal records in the eastern equatorial Pacific: It is not all about leakage |
title_sort |
sedimentary opal records in the eastern equatorial pacific: it is not all about leakage |
publisher |
American Geophysical Union |
publishDate |
2010 |
url |
http://hdl.handle.net/2429/40061 https://doi.org/10.1029/2010GB003821 |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
Sea ice Southern Ocean |
genre_facet |
Sea ice Southern Ocean |
op_rights |
Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ Francois, Roger |
op_rightsnorm |
CC-BY-NC-ND |
op_doi |
https://doi.org/10.1029/2010GB003821 |
container_title |
Global Biogeochemical Cycles |
container_volume |
24 |
container_issue |
4 |
container_start_page |
n/a |
op_container_end_page |
n/a |
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1766195739024687104 |