Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle
The Southern Ocean is widely thought to play an important role in atmospheric CO₂ change over glacial-interglacial cycles. It has been suggested that as the region that ventilates the majority of the world’s carbon-rich deep waters today, reduced exchange between deep waters and the atmosphere in th...
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University of St Andrews
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Online Access: | http://hdl.handle.net/10023/20385 https://doi.org/10.17630/10023-20385 |
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ftstandrewserep:oai:research-repository.st-andrews.ac.uk:10023/20385 2023-07-02T03:30:02+02:00 Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle Crumpton-Banks, Jessica Georgina Magdalen Burke, Andrea Rae, James William Buchanan Natural Environment Research Council (NERC) vi, 238 p. 2020-07-31T11:45:48Z http://hdl.handle.net/10023/20385 https://doi.org/10.17630/10023-20385 en eng University of St Andrews The University of St Andrews Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle (thesis data 1) Crumpton-Banks, J.G.M., University of St Andrews. DOI: https://doi.org/10.17630/48e0f7a2-95de-4914-b880-85b897736e0e Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle (thesis data 2) Crumpton-Banks, J.G.M., University of St Andrews. DOI: https://doi.org/10.17630/87cf5912-7441-44e3-b43e-86818f84526e https://doi.org/10.17630/48e0f7a2-95de-4914-b880-85b897736e0e https://doi.org/10.17630/87cf5912-7441-44e3-b43e-86818f84526e http://hdl.handle.net/10023/20385 https://doi.org/10.17630/10023-20385 Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ 2025-06-26 Thesis restricted in accordance with University regulations. Electronic copy restricted until 26th June 2025 Palaeoceanography Southern Ocean Foraminifera CO₂ Glacial-interglacial Boron isotopes Climate QE39.5P25C8 Paleoceanography--Antarctic Ocean Chemical oceanography--Antarctic Ocean Foraminifera--Antarctic Ocean Thesis Doctoral PhD Doctor of Philosophy 2020 ftstandrewserep https://doi.org/10.17630/10023-2038510.17630/48e0f7a2-95de-4914-b880-85b897736e0e10.17630/87cf5912-7441-44e3-b43e-86818f84526e 2023-06-13T18:26:45Z The Southern Ocean is widely thought to play an important role in atmospheric CO₂ change over glacial-interglacial cycles. It has been suggested that as the region that ventilates the majority of the world’s carbon-rich deep waters today, reduced exchange between deep waters and the atmosphere in the Southern Ocean acted to draw down CO₂ over glacial timescales. However, direct evidence of the Southern Ocean’s role in glacial CO₂ drawdown has been lacking thus far. Here I apply the boron-isotope pH-proxy to foraminifera from the Antarctic Zone sediment core PS1506 over the last glacial cycle. The low boron concentrations in these polar foraminifera makes these samples particularly sensitive to boron blank and so a close examination of the sources of blank, and an assessment of the precision of blank measurements, has been made. The ratios of trace elements to calcium in foraminiferal shells are widely applied as proxies for palaeoenvironmental parameters such as temperature. As Southern Ocean carbonate sediments are particularly prone to dissolution, which can affect trace element concentrations, an assessment of dissolution has been made. Firstly, dissolution experiments were conducted to constrain the impact of dissolution in a controlled setting, and secondly, shell mass and trace elements were evaluated for the downcore record. Imaging reveals similar etching textures in both experimentally dissolved samples and deglacial intervals, when shell mass is also low and several trace elements exhibit an excursion to lower values. Boron isotope data for PS1506 show that during the penultimate interglacial, surface water pH was low. At the onset of atmospheric CO₂ drawdown, pH increased, indicating low CO₂ surface waters. This is consistent with the signature predicted for a more stratified Southern Ocean, and is evidence that stratification in the Antarctic Zone acted to contribute to CO₂ drawdown early in the transition to a glacial state. "This work was supported by the Natural Environmental Research Council ... Doctoral or Postdoctoral Thesis Antarc* Antarctic Antarctic Ocean Southern Ocean University of St Andrews: Digital Research Repository Antarctic Antarctic Ocean Southern Ocean The Antarctic |
institution |
Open Polar |
collection |
University of St Andrews: Digital Research Repository |
op_collection_id |
ftstandrewserep |
language |
English |
topic |
Palaeoceanography Southern Ocean Foraminifera CO₂ Glacial-interglacial Boron isotopes Climate QE39.5P25C8 Paleoceanography--Antarctic Ocean Chemical oceanography--Antarctic Ocean Foraminifera--Antarctic Ocean |
spellingShingle |
Palaeoceanography Southern Ocean Foraminifera CO₂ Glacial-interglacial Boron isotopes Climate QE39.5P25C8 Paleoceanography--Antarctic Ocean Chemical oceanography--Antarctic Ocean Foraminifera--Antarctic Ocean Crumpton-Banks, Jessica Georgina Magdalen Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle |
topic_facet |
Palaeoceanography Southern Ocean Foraminifera CO₂ Glacial-interglacial Boron isotopes Climate QE39.5P25C8 Paleoceanography--Antarctic Ocean Chemical oceanography--Antarctic Ocean Foraminifera--Antarctic Ocean |
description |
The Southern Ocean is widely thought to play an important role in atmospheric CO₂ change over glacial-interglacial cycles. It has been suggested that as the region that ventilates the majority of the world’s carbon-rich deep waters today, reduced exchange between deep waters and the atmosphere in the Southern Ocean acted to draw down CO₂ over glacial timescales. However, direct evidence of the Southern Ocean’s role in glacial CO₂ drawdown has been lacking thus far. Here I apply the boron-isotope pH-proxy to foraminifera from the Antarctic Zone sediment core PS1506 over the last glacial cycle. The low boron concentrations in these polar foraminifera makes these samples particularly sensitive to boron blank and so a close examination of the sources of blank, and an assessment of the precision of blank measurements, has been made. The ratios of trace elements to calcium in foraminiferal shells are widely applied as proxies for palaeoenvironmental parameters such as temperature. As Southern Ocean carbonate sediments are particularly prone to dissolution, which can affect trace element concentrations, an assessment of dissolution has been made. Firstly, dissolution experiments were conducted to constrain the impact of dissolution in a controlled setting, and secondly, shell mass and trace elements were evaluated for the downcore record. Imaging reveals similar etching textures in both experimentally dissolved samples and deglacial intervals, when shell mass is also low and several trace elements exhibit an excursion to lower values. Boron isotope data for PS1506 show that during the penultimate interglacial, surface water pH was low. At the onset of atmospheric CO₂ drawdown, pH increased, indicating low CO₂ surface waters. This is consistent with the signature predicted for a more stratified Southern Ocean, and is evidence that stratification in the Antarctic Zone acted to contribute to CO₂ drawdown early in the transition to a glacial state. "This work was supported by the Natural Environmental Research Council ... |
author2 |
Burke, Andrea Rae, James William Buchanan Natural Environment Research Council (NERC) |
format |
Doctoral or Postdoctoral Thesis |
author |
Crumpton-Banks, Jessica Georgina Magdalen |
author_facet |
Crumpton-Banks, Jessica Georgina Magdalen |
author_sort |
Crumpton-Banks, Jessica Georgina Magdalen |
title |
Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle |
title_short |
Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle |
title_full |
Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle |
title_fullStr |
Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle |
title_full_unstemmed |
Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle |
title_sort |
geochemical reconstructions of southern ocean ph and temperature over the last glacial cycle |
publisher |
University of St Andrews |
publishDate |
2020 |
url |
http://hdl.handle.net/10023/20385 https://doi.org/10.17630/10023-20385 |
op_coverage |
vi, 238 p. |
geographic |
Antarctic Antarctic Ocean Southern Ocean The Antarctic |
geographic_facet |
Antarctic Antarctic Ocean Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Antarctic Ocean Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctic Ocean Southern Ocean |
op_relation |
Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle (thesis data 1) Crumpton-Banks, J.G.M., University of St Andrews. DOI: https://doi.org/10.17630/48e0f7a2-95de-4914-b880-85b897736e0e Geochemical reconstructions of Southern Ocean pH and temperature over the last glacial cycle (thesis data 2) Crumpton-Banks, J.G.M., University of St Andrews. DOI: https://doi.org/10.17630/87cf5912-7441-44e3-b43e-86818f84526e https://doi.org/10.17630/48e0f7a2-95de-4914-b880-85b897736e0e https://doi.org/10.17630/87cf5912-7441-44e3-b43e-86818f84526e http://hdl.handle.net/10023/20385 https://doi.org/10.17630/10023-20385 |
op_rights |
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ 2025-06-26 Thesis restricted in accordance with University regulations. Electronic copy restricted until 26th June 2025 |
op_doi |
https://doi.org/10.17630/10023-2038510.17630/48e0f7a2-95de-4914-b880-85b897736e0e10.17630/87cf5912-7441-44e3-b43e-86818f84526e |
_version_ |
1770274294121627648 |