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Middle eocene seawater pH and atmospheric carbon dioxide concentrations
1Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK. T. H. Huxley School, Royal School of Mines, Imperial College, Prince Consort Road, London SW7 2BP, UK.
Atmospheric carbon dioxide levels influence ocean pH. Analyzing boron isotopes in ancient plankton fossils reveals middle Eocene Pacific Ocean pH, suggesting carbon dioxide concentrations were similar to today.
Area of Science:
- Paleoceanography
- Geochemistry
- Climate Science
Background:
- Atmospheric carbon dioxide partial pressure (pCO2) influences surface ocean chemistry and seawater pH.
- Seawater pH is a critical factor in marine ecosystems and global carbon cycling.
- Understanding past atmospheric CO2 levels is crucial for predicting future climate change.
Purpose of the Study:
- To reconstruct the pH-depth profile of the middle Eocene tropical Pacific Ocean.
- To estimate atmospheric pCO2 levels during the middle Eocene epoch.
- To assess the relationship between atmospheric CO2 and ocean pH in a past climate scenario.
Main Methods:
- Utilizing the boron isotope composition (delta11B) of fossil planktonic foraminifera.
- Analyzing foraminifera that calcified at various water depths to establish a pH-depth profile.
- Applying geochemical proxies to ancient marine sediment cores from the tropical Pacific.
Main Results:
- A detailed pH-depth profile for the middle Eocene tropical Pacific was successfully constructed.
- The study indicates that seawater pH varied with depth during this period.
- Reconstructed atmospheric pCO2 levels were found to be comparable to, or slightly higher than, present-day concentrations.
Conclusions:
- The boron isotope proxy is effective for reconstructing ancient ocean pH profiles.
- Middle Eocene atmospheric pCO2 levels were similar to modern levels, despite different global conditions.
- This research provides valuable insights into the long-term carbon dioxide-ocean pH relationship.
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