Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea
<p>Ocean alkalinity enhancement (OAE) is a climate mitigation strategy aimed at increasing the ocean's capacity to absorb and store atmospheric <span class="inline-formula">CO<sub>2</sub></span>. The effect of OAE depends significantly on local physical a...
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Copernicus Publications
2025-07-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/22/3699/2025/bg-22-3699-2025.pdf |
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| author | F. Liu U. Daewel J. Kossack K. T. Demir H. Thomas H. Thomas C. Schrum C. Schrum |
| author_facet | F. Liu U. Daewel J. Kossack K. T. Demir H. Thomas H. Thomas C. Schrum C. Schrum |
| author_sort | F. Liu |
| collection | DOAJ |
| description | <p>Ocean alkalinity enhancement (OAE) is a climate mitigation strategy aimed at increasing the ocean's capacity to absorb and store atmospheric <span class="inline-formula">CO<sub>2</sub></span>. The effect of OAE depends significantly on local physical and biogeochemical conditions, underscoring the importance of selecting optimal locations for alkalinity addition. Using a regional coupled physical-biogeochemical-carbon model, we examine OAE responses in the North Sea, including <span class="inline-formula">CO<sub>2</sub></span> uptake potential, enhanced carbon storage and cross-shelf export, and the associated changes in the carbonate chemistry. Alkalinity is continuously added as a surface flux in three distinct regions of the North Sea. Our simulations show that the Norwegian Trench and the Skagerrak serve as sinks for added alkalinity, reducing its interaction with the atmosphere. Alkalinity addition along shallow eastern coasts results in a higher <span class="inline-formula">CO<sub>2</sub></span> uptake efficiency (<span class="inline-formula">∼0.79</span> mol <span class="inline-formula">CO<sub>2</sub></span> uptake per mol alkalinity addition) than offshore addition in ship-accessible areas (<span class="inline-formula">∼0.66</span> mol <span class="inline-formula">CO<sub>2</sub></span> uptake per mol alkalinity addition) as offshore alkalinity is more susceptible to deep-ocean loss. Long-term carbon storage, measured by excess carbon accumulation in deep ocean and cross-shelf export below permanent pycnoclines, is similar across the three scenarios and accounts for less than 10 % of total excess <span class="inline-formula">CO<sub>2</sub></span> uptake. The smallest changes in pH occur when alkalinity is added offshore with effects nearly an order of magnitude lower than alkalinity addition in the shallow German Exclusive Economic Zone where pH increases from 8.1 to 8.4. The model's resolution (<span class="inline-formula">∼4.5</span> km in coastal areas) limits its ability to capture rapid, localized carbonate responses, leading to a nearly 10-fold underestimation of chemical perturbations. Thus, finer-scale models are needed to accurately assess near-source alkalinity impacts.</p> |
| format | Article |
| id | doaj-art-441cb305a16d4a6d9b568a1df6ea29ee |
| institution | Kabale University |
| issn | 1726-4170 1726-4189 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj-art-441cb305a16d4a6d9b568a1df6ea29ee2025-08-20T03:56:09ZengCopernicus PublicationsBiogeosciences1726-41701726-41892025-07-01223699371910.5194/bg-22-3699-2025Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North SeaF. Liu0U. Daewel1J. Kossack2K. T. Demir3H. Thomas4H. Thomas5C. Schrum6C. Schrum7Institute of Coastal Systems, Helmholtz-Zentrum Hereon, Geesthacht, GermanyInstitute of Coastal Systems, Helmholtz-Zentrum Hereon, Geesthacht, GermanyInstitute of Coastal Systems, Helmholtz-Zentrum Hereon, Geesthacht, GermanyInstitute of Coastal Systems, Helmholtz-Zentrum Hereon, Geesthacht, GermanyInstitute of Carbon Cycles, Helmholtz-Zentrum Hereon, Geesthacht, GermanyInstitute for Chemistry and Biology of the Marine Environment, Carl von Ossietzky University of Oldenburg, Oldenburg, GermanyInstitute of Coastal Systems, Helmholtz-Zentrum Hereon, Geesthacht, GermanyInstitute of Oceanography, University of Hamburg, Hamburg, Germany<p>Ocean alkalinity enhancement (OAE) is a climate mitigation strategy aimed at increasing the ocean's capacity to absorb and store atmospheric <span class="inline-formula">CO<sub>2</sub></span>. The effect of OAE depends significantly on local physical and biogeochemical conditions, underscoring the importance of selecting optimal locations for alkalinity addition. Using a regional coupled physical-biogeochemical-carbon model, we examine OAE responses in the North Sea, including <span class="inline-formula">CO<sub>2</sub></span> uptake potential, enhanced carbon storage and cross-shelf export, and the associated changes in the carbonate chemistry. Alkalinity is continuously added as a surface flux in three distinct regions of the North Sea. Our simulations show that the Norwegian Trench and the Skagerrak serve as sinks for added alkalinity, reducing its interaction with the atmosphere. Alkalinity addition along shallow eastern coasts results in a higher <span class="inline-formula">CO<sub>2</sub></span> uptake efficiency (<span class="inline-formula">∼0.79</span> mol <span class="inline-formula">CO<sub>2</sub></span> uptake per mol alkalinity addition) than offshore addition in ship-accessible areas (<span class="inline-formula">∼0.66</span> mol <span class="inline-formula">CO<sub>2</sub></span> uptake per mol alkalinity addition) as offshore alkalinity is more susceptible to deep-ocean loss. Long-term carbon storage, measured by excess carbon accumulation in deep ocean and cross-shelf export below permanent pycnoclines, is similar across the three scenarios and accounts for less than 10 % of total excess <span class="inline-formula">CO<sub>2</sub></span> uptake. The smallest changes in pH occur when alkalinity is added offshore with effects nearly an order of magnitude lower than alkalinity addition in the shallow German Exclusive Economic Zone where pH increases from 8.1 to 8.4. The model's resolution (<span class="inline-formula">∼4.5</span> km in coastal areas) limits its ability to capture rapid, localized carbonate responses, leading to a nearly 10-fold underestimation of chemical perturbations. Thus, finer-scale models are needed to accurately assess near-source alkalinity impacts.</p>https://bg.copernicus.org/articles/22/3699/2025/bg-22-3699-2025.pdf |
| spellingShingle | F. Liu U. Daewel J. Kossack K. T. Demir H. Thomas H. Thomas C. Schrum C. Schrum Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea Biogeosciences |
| title | Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea |
| title_full | Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea |
| title_fullStr | Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea |
| title_full_unstemmed | Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea |
| title_short | Evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the North Sea |
| title_sort | evaluating ocean alkalinity enhancement as a carbon dioxide removal strategy in the north sea |
| url | https://bg.copernicus.org/articles/22/3699/2025/bg-22-3699-2025.pdf |
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