Articles | Volume 21, issue 1
https://doi.org/10.5194/bg-21-261-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-21-261-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| Highlight paper
| 
16 Jan 2024
Research article | Highlight paper |
| 16 Jan 2024
| 16 Jan 2024
The additionality problem of ocean alkalinity enhancement
Lennart Thomas Bach
CORRESPONDING AUTHOR
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
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Cited
38 citations as recorded by crossref.
- No compromise in efficiency from the co-application of a marine and a terrestrial CDR method Y. Moustakis et al. https://doi.org/10.1038/s41467-025-59982-x
- Manganese Oxide-Mediated Reactions with Olivine Dissolution Products: A Double-Edged Sword for Ocean Alkalinity Enhancement W. Zhuang et al. https://doi.org/10.1021/acs.est.5c16120
- Global carbonate chemistry gradients reveal a negative feedback on ocean alkalinity enhancement N. Lehmann & L. Bach https://doi.org/10.1038/s41561-025-01644-0
- An improved model of particle attenuation reduces estimates of Southern Ocean carbon transfer efficiency A. Oetjens et al. https://doi.org/10.1038/s43247-025-03090-7
- Ocean Carbon Dioxide Removal and Storage C. Lee et al. https://doi.org/10.1021/acs.chemrev.5c00433
- Review and syntheses: Ocean alkalinity enhancement and carbon dioxide removal through marine enhanced rock weathering using olivine L. Geerts et al. https://doi.org/10.5194/bg-22-355-2025
- Inorganic carbon exports from coastal wetlands can offset part of blue carbon systems’ CO2 removal L. Xue et al. https://doi.org/10.1016/j.scib.2026.04.052
- Removal of dissolved inorganic carbon from seawater for climate mitigation: potential marine ecosystem impacts G. Hooper et al. https://doi.org/10.3389/fclim.2025.1528951
- Ocean alkalinity enhancement in an estuary M. Ho et al. https://doi.org/10.3389/fclim.2025.1665329
- Direct effects of ocean alkalinity enhancement in the Baltic Sea–results from in-silico experiments A. Anschütz et al. https://doi.org/10.3389/fclim.2025.1450468
- Impulse response functions as a framework for quantifying ocean-based carbon dioxide removal E. Yankovsky et al. https://doi.org/10.5194/bg-22-5723-2025
- Blue carbon ecosystems and coral reefs as coupled nature-based climate solutions M. Fakhraee https://doi.org/10.1038/s41893-026-01768-0
- Site selection for ocean alkalinity enhancement informed by passive tracer simulations Y. Guo et al. https://doi.org/10.1038/s43247-025-02480-1
- Hawaiian beaches as natural analogues for enhanced silicate weathering of olivine M. Kreuzburg et al. https://doi.org/10.1088/1748-9326/ae130c
- Alkalinity enhancement with sodium hydroxide in coastal ocean waters C. Wynn-Edwards et al. https://doi.org/10.1038/s41598-025-31606-w
- Calcite is an efficient and low-cost material to enhance benthic weathering in shelf sediments of the Baltic Sea M. Fuhr et al. https://doi.org/10.1038/s43247-025-02079-6
- A high-resolution nested model to study the effects of alkalinity additions in Halifax Harbour, a mid-latitude coastal fjord A. Laurent et al. https://doi.org/10.5194/bg-23-115-2026
- Substantial inter-model variation in OAE efficiency between the CESM2/MARBL and ECCO-Darwin ocean biogeochemistry models M. Tyka et al. https://doi.org/10.5194/bg-23-4943-2026
- Seawater carbonate chemistry based carbon dioxide removal: towards commonly agreed principles for carbon monitoring, reporting, and verification P. Halloran et al. https://doi.org/10.3389/fclim.2025.1487138
- Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea F. Liu et al. https://doi.org/10.5194/bg-22-3699-2025
- Laying waste to the deep: parallel narratives of marine carbon dioxide removal and deep-seabed mining S. Lidström et al. https://doi.org/10.1038/s44183-024-00075-5
- Mapping the global variation in the efficiency of ocean alkalinity enhancement for carbon dioxide removal M. Zhou et al. https://doi.org/10.1038/s41558-024-02179-9
- A tracer study for the development of in-water monitoring, reporting, and verification (MRV) of ship-based ocean alkalinity enhancement A. Subhas et al. https://doi.org/10.5194/bg-22-5511-2025
- An assessment of ocean alkalinity enhancement using aqueous hydroxides: kinetics, efficiency, and precipitation thresholds M. Ringham et al. https://doi.org/10.5194/bg-21-3551-2024
- Perspectives and challenges of marine carbon dioxide removal A. Oschlies et al. https://doi.org/10.3389/fclim.2024.1506181
- Reviews and syntheses: Potential and limitations of oceanic carbon dioxide storage via reactor-based accelerated weathering of limestone T. Huysmans et al. https://doi.org/10.5194/bg-22-5557-2025
- A numerical assessment of ocean alkalinity enhancement efficiency on a river-dominated continental shelf—a case study in the northern Gulf of Mexico Y. Ou et al. https://doi.org/10.1088/1748-9326/adaa8b
- Closing the comparability gap in mCDR with Triple REAL filters Q. Chen et al. https://doi.org/10.1016/j.scib.2026.06.038
- Effects of ocean alkalinity enhancement on plankton in the Equatorial Pacific J. Guo et al. https://doi.org/10.1038/s43247-025-02248-7
- The Verification Challenge of Marine Carbon Dioxide Removal K. Fennel https://doi.org/10.1146/annurev-marine-032123-025717
- Can enhanced alkalinity store carbon durably? T. Isson & A. West https://doi.org/10.1126/science.adz2620
- The CDR potential of olivine-based enhanced rock weathering in marine systems: a case study for the coastal zone of France L. Geerts et al. https://doi.org/10.1088/1748-9326/addf60
- Metrics for quantifying the efficiency of atmospheric CO2 reduction by marine carbon dioxide removal (mCDR) K. Yamamoto et al. https://doi.org/10.1088/1748-9326/ad7477
- Assessing the efficacy of river-based ocean alkalinity enhancement for carbon sequestration under high emission pathways X. Zhu et al. https://doi.org/10.5194/bg-22-7293-2025
- The coupled uncertainties in carbon dioxide removal and transient climate response to cumulative CO2 emissions C. Di Natale et al. https://doi.org/10.1088/1748-9326/ae20a5
- Imprint of minute hydrocarbon seepage on solid phase and pore water geochemistry in organic-poor subseafloor sediment E. Schnabel et al. https://doi.org/10.5194/bg-23-1383-2026
- Regional ocean biogeochemical modeling challenges for predicting the effectiveness of marine carbon dioxide removal N. Ward et al. https://doi.org/10.3389/fclim.2025.1640617
- Assessing the limitations of commercial sensors and models for supporting marine carbon dioxide removal monitoring: a case study T. Stewart et al. https://doi.org/10.3389/fclim.2025.1649723
38 citations as recorded by crossref.
- No compromise in efficiency from the co-application of a marine and a terrestrial CDR method Y. Moustakis et al. https://doi.org/10.1038/s41467-025-59982-x
- Manganese Oxide-Mediated Reactions with Olivine Dissolution Products: A Double-Edged Sword for Ocean Alkalinity Enhancement W. Zhuang et al. https://doi.org/10.1021/acs.est.5c16120
- Global carbonate chemistry gradients reveal a negative feedback on ocean alkalinity enhancement N. Lehmann & L. Bach https://doi.org/10.1038/s41561-025-01644-0
- An improved model of particle attenuation reduces estimates of Southern Ocean carbon transfer efficiency A. Oetjens et al. https://doi.org/10.1038/s43247-025-03090-7
- Ocean Carbon Dioxide Removal and Storage C. Lee et al. https://doi.org/10.1021/acs.chemrev.5c00433
- Review and syntheses: Ocean alkalinity enhancement and carbon dioxide removal through marine enhanced rock weathering using olivine L. Geerts et al. https://doi.org/10.5194/bg-22-355-2025
- Inorganic carbon exports from coastal wetlands can offset part of blue carbon systems’ CO2 removal L. Xue et al. https://doi.org/10.1016/j.scib.2026.04.052
- Removal of dissolved inorganic carbon from seawater for climate mitigation: potential marine ecosystem impacts G. Hooper et al. https://doi.org/10.3389/fclim.2025.1528951
- Ocean alkalinity enhancement in an estuary M. Ho et al. https://doi.org/10.3389/fclim.2025.1665329
- Direct effects of ocean alkalinity enhancement in the Baltic Sea–results from in-silico experiments A. Anschütz et al. https://doi.org/10.3389/fclim.2025.1450468
- Impulse response functions as a framework for quantifying ocean-based carbon dioxide removal E. Yankovsky et al. https://doi.org/10.5194/bg-22-5723-2025
- Blue carbon ecosystems and coral reefs as coupled nature-based climate solutions M. Fakhraee https://doi.org/10.1038/s41893-026-01768-0
- Site selection for ocean alkalinity enhancement informed by passive tracer simulations Y. Guo et al. https://doi.org/10.1038/s43247-025-02480-1
- Hawaiian beaches as natural analogues for enhanced silicate weathering of olivine M. Kreuzburg et al. https://doi.org/10.1088/1748-9326/ae130c
- Alkalinity enhancement with sodium hydroxide in coastal ocean waters C. Wynn-Edwards et al. https://doi.org/10.1038/s41598-025-31606-w
- Calcite is an efficient and low-cost material to enhance benthic weathering in shelf sediments of the Baltic Sea M. Fuhr et al. https://doi.org/10.1038/s43247-025-02079-6
- A high-resolution nested model to study the effects of alkalinity additions in Halifax Harbour, a mid-latitude coastal fjord A. Laurent et al. https://doi.org/10.5194/bg-23-115-2026
- Substantial inter-model variation in OAE efficiency between the CESM2/MARBL and ECCO-Darwin ocean biogeochemistry models M. Tyka et al. https://doi.org/10.5194/bg-23-4943-2026
- Seawater carbonate chemistry based carbon dioxide removal: towards commonly agreed principles for carbon monitoring, reporting, and verification P. Halloran et al. https://doi.org/10.3389/fclim.2025.1487138
- Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea F. Liu et al. https://doi.org/10.5194/bg-22-3699-2025
- Laying waste to the deep: parallel narratives of marine carbon dioxide removal and deep-seabed mining S. Lidström et al. https://doi.org/10.1038/s44183-024-00075-5
- Mapping the global variation in the efficiency of ocean alkalinity enhancement for carbon dioxide removal M. Zhou et al. https://doi.org/10.1038/s41558-024-02179-9
- A tracer study for the development of in-water monitoring, reporting, and verification (MRV) of ship-based ocean alkalinity enhancement A. Subhas et al. https://doi.org/10.5194/bg-22-5511-2025
- An assessment of ocean alkalinity enhancement using aqueous hydroxides: kinetics, efficiency, and precipitation thresholds M. Ringham et al. https://doi.org/10.5194/bg-21-3551-2024
- Perspectives and challenges of marine carbon dioxide removal A. Oschlies et al. https://doi.org/10.3389/fclim.2024.1506181
- Reviews and syntheses: Potential and limitations of oceanic carbon dioxide storage via reactor-based accelerated weathering of limestone T. Huysmans et al. https://doi.org/10.5194/bg-22-5557-2025
- A numerical assessment of ocean alkalinity enhancement efficiency on a river-dominated continental shelf—a case study in the northern Gulf of Mexico Y. Ou et al. https://doi.org/10.1088/1748-9326/adaa8b
- Closing the comparability gap in mCDR with Triple REAL filters Q. Chen et al. https://doi.org/10.1016/j.scib.2026.06.038
- Effects of ocean alkalinity enhancement on plankton in the Equatorial Pacific J. Guo et al. https://doi.org/10.1038/s43247-025-02248-7
- The Verification Challenge of Marine Carbon Dioxide Removal K. Fennel https://doi.org/10.1146/annurev-marine-032123-025717
- Can enhanced alkalinity store carbon durably? T. Isson & A. West https://doi.org/10.1126/science.adz2620
- The CDR potential of olivine-based enhanced rock weathering in marine systems: a case study for the coastal zone of France L. Geerts et al. https://doi.org/10.1088/1748-9326/addf60
- Metrics for quantifying the efficiency of atmospheric CO2 reduction by marine carbon dioxide removal (mCDR) K. Yamamoto et al. https://doi.org/10.1088/1748-9326/ad7477
- Assessing the efficacy of river-based ocean alkalinity enhancement for carbon sequestration under high emission pathways X. Zhu et al. https://doi.org/10.5194/bg-22-7293-2025
- The coupled uncertainties in carbon dioxide removal and transient climate response to cumulative CO2 emissions C. Di Natale et al. https://doi.org/10.1088/1748-9326/ae20a5
- Imprint of minute hydrocarbon seepage on solid phase and pore water geochemistry in organic-poor subseafloor sediment E. Schnabel et al. https://doi.org/10.5194/bg-23-1383-2026
- Regional ocean biogeochemical modeling challenges for predicting the effectiveness of marine carbon dioxide removal N. Ward et al. https://doi.org/10.3389/fclim.2025.1640617
- Assessing the limitations of commercial sensors and models for supporting marine carbon dioxide removal monitoring: a case study T. Stewart et al. https://doi.org/10.3389/fclim.2025.1649723
Saved (final revised paper)
Latest update: 12 Aug 2026
Editorial statement
Reaching the Paris Agreement targets to limit global warming to 1.5 or 2°C implies not only reducing emissions, but also active carbon dioxide removal from the atmosphere. While land-based carbon dioxide removal or negative emission technologies have received most attention, ocean solutions are increasingly being considered. Ocean alkalinity enhancement (OAE), or alkalinization, is one promising ocean-based carbon dioxide technology. However, any new carbon dioxide removal technique needs thorough investigations for its effectiveness, longevity, benefits and lack of disbenefits, financial viability, social acceptance and governability. The paper by Bach is a nice illustration of the type of research that must be done if we are to consider large scale application of OAE. It focuses on the additionality problem of ocean alkalinity enhancement, specifically it investigates how the addition of alkalinity modifies the natural alkalinity cycle and in that way the efficiency of carbon dioxide sequestration.
Reaching the Paris Agreement targets to limit global warming to 1.5 or 2°C implies not only...
Short summary
Ocean alkalinity enhancement (OAE) is a widely considered marine carbon dioxide removal method. OAE aims to accelerate chemical rock weathering, which is a natural process that slowly sequesters atmospheric carbon dioxide. This study shows that the addition of anthropogenic alkalinity via OAE can reduce the natural release of alkalinity and, therefore, reduce the efficiency of OAE for climate mitigation. However, the additionality problem could be mitigated via a variety of activities.
Ocean alkalinity enhancement (OAE) is a widely considered marine carbon dioxide removal method....
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