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PreprintCited by 81Marine and coastal ecosystemsCO2 Sequestration and Geologic InteractionsClimate Change and Geoengineering

Seawater carbonate system considerations for ocean alkalinity enhancement research

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Schulz, Kai G., Bach, Lennart T., Dickson, Andrew G.·2023·State of the Planet
DOI 10.5194/sp-2023-12

Preprint — published as 10.5194/sp-2-oae2023-2-2023 · Paper page

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Abstract

Abstract. Ocean alkalinity enhancement (OAE) is a proposed marine carbon dioxide removal (mCDR) approach that has the potential for large-scale uptake of significant amounts of atmospheric carbon dioxide (CO2). Removing anthropogenic legacy CO2 will be required to stabilise global surface temperatures below the 1.5–2 ∘C Paris Agreement target of 2015. In this chapter we describe the impacts of various OAE feedstocks on seawater carbonate chemistry, as well as pitfalls that need to be avoided during sampling, storage, and measurement of the four main carbonate chemistry parameters, i.e. dissolved inorganic carbon (DIC), total alkalinity (TA), pH, and CO2 fugacity (fCO2). Finally, we also discuss considerations in regard to calculating carbonate chemistry speciation from two measured parameters. Key findings are that (1) theoretical CO2 uptake potential (global mean of 0.84 mol of CO2 per mole of TA added) based on carbonate chemistry calculations is probably secondary in determining the oceanic region in which OAE would be best; (2) carbonate chemistry sampling is recommended to involve gentle pressure filtration to remove calcium carbonate (CaCO3) that might have been precipitated upon TA increase as it would otherwise interfere with a number of analyses; (3) samples for DIC and TA can be stabilised to avoid the risk of secondary CaCO3 precipitation during sample storage; and (4) some OAE feedstocks require additional adjustments to carbonate chemistry speciation calculations using available programs and routines, for instance if seawater magnesium or calcium concentrations are modified.

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  • Beyond carbon dioxide removal (CDR), OAE holds the potential to regionally mitigate ocean acidification.

    “Beyond carbon dioxide removal (CDR), OAE holds the potential to regionally mitigate ocean acidification (Schulz et al., 2023).”

    From Biogeochemical responses to ocean alkalinity enhancement in the North China Sea (2026) · cites this paper as Schulz et al., 2023

    The Abstract identifies OAE as a carbon dioxide removal approach, and §1.2 says alkalinity additions affect seawater pH. Those passages support a potential effect on acidification, but our copy does not establish that OAE could mitigate ocean acidification at a regional scale; its discussion of regional differences concerns CO₂ uptake. (LLM, conf=0.77)

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Research works printed but not linked: 31

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Cited by

Sorted by citations

Authors
Schulz, K. G., Bach, L. T., & Dickson, A. G.
Affiliations
  • Southern Cross University (AU)
  • University of Tasmania (AU)
  • Scripps Institution of Oceanography (US)
Corresponding author
Schulz, Kai G.
ORCID
Venue
State of the Planet
Publisher
Copernicus GmbH
Published
2023-07-03
Volume
2-oae2023
Pages
1-14
ISSN
2752-0706 (ISSN-L)
DOI
10.5194/sp-2023-12
OpenAlex
W4389055956
Cited by
81
References
0
Citations by year
2026: 17 · 2025: 18 · 2024: 30 · 2023: 16
FWCI
10.89
Type
journal article
Language
en
Open access
Licence
Locations
  • State of the Planet (publishedVersion, cc-by)
  • Helmholtz Centre for Ocean Research Kiel (GEOMAR) (acceptedVersion, other-oa)
  • Informationszentrum Lebenswissenschaften (ZB MED) (submittedVersion, cc-by)
Funders
  • ClimateWorks Foundation (22-0296)
  • Prince Albert II of Monaco Foundation (n/a)
  • Australian Research Council (FT200100846)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal ecosystems
  • Physical Sciences › Environmental Science › Environmental Engineering › CO2 Sequestration and Geologic Interactions
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate Change and Geoengineering
Keywords
ocean alkalinity enhancement, marine carbon dioxide removal, seawater carbonate chemistry, dissolved inorganic carbon, total alkalinity, pH, fugacity of CO2, carbonate speciation, calcium carbonate precipitation

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