Alkalinity enhancement in subduction regions and the global ocean

Efficiency, earth system feedbacks, and scenario sensitivity

Bibliographic Data

ID15546999
AuthorsTanvi Nagwekar (0000-0002-6866-2508, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, corresponding author), Christopher Danek (0000-0002-4453-1140, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, corresponding author), Miriam Seifert (0000-0002-2570-5475, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, corresponding author), Judith Hauck (0000-0003-4723-9652, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, corresponding author)
Year2025
Volume21
Issue1
Pages014031-014031
Publication date2025-12-08
Open AccessYes
TypeARTICLE
VenueEnvironmental Research Letters (JOURNAL)
Journal identifiersISSN: 1748-9326 • E-ISSN: 1748-9326
PublisherIOP Publishing (PUBLISHER • GB)
DOI10.1088/1748-9326/ae293b
OpenAlexW4417136886
LanguageEN
References cited56

Ocean alkalinity enhancement (OAE) refers to the addition of alkaline material to the surface ocean, which shifts carbonate chemistry towards more oceanic uptake of atmospheric CO 2 . This study compares global OAE with regionally focused deployment in subduction regions of the Southern Ocean, Northwest Atlantic, and Norwegian-Barents Sea. We conducted ensemble simulations using an emissions-driven Earth System Model (ESM) under high- (SSP3-7.0) and low-emissions (SSP1-2.6) scenarios. By 2100, subduction region OAE was nearly as efficient (SSP3-7.0: 0.71 ± 0.03, SSP1-2.6: 0.60 ± 0.04) as global deployments (SSP3-7.0: 0.73 ± 0.01, SSP1-2.6: 0.64 ± 0.03). However, the ESM simulations did not reproduce the efficient vertical carbon transport seen in a previous ocean-only study, as strong internal variability and climate feedbacks to OAE hampered deep ocean carbon storage. The excess ocean CO 2 uptake and atmospheric CO 2 reduction were scenario-dependent (15%–19% and 22%–41% lower under SSP1-2.6 compared to SSP3-7.0, respectively). The pathways of excess ocean CO 2 uptake and atmospheric CO 2 reduction diverged between the scenarios after the mid-2060s, when atmospheric CO 2 peaked and then declined under SSP1-2.6, with a substantially larger relative land carbon loss in SSP1-2.6 than in SSP3-7.0 for regional OAE deployment. Furthermore, the emissions-driven ensemble simulations showed that climate feedbacks introduced substantial uncertainty in early decades of regional OAE efficiency, posing challenges for near-term monitoring, reporting, and verification. Reviewing our and previous model experiments revealed a strong linear relationship between added alkalinity and oceanic CO 2 uptake and atmospheric reduction, highlighting that first-order effects of OAE on carbonate chemistry are well understood and consistently represented, while the effects of carbon and climate feedbacks (13%–20%) and scenario sensitivity are smaller but non-negligible. Overall, our study shows that subduction regions can be a viable option for OAE; however, their efficiency is limited by these feedbacks and scenario sensitivity, which must be accounted for in future regional OAE interventions

Alkalinity · Carbon cycle · Carbon fibers · Carbonate · Climate model · Earth (classical element · Earth system science · Global change · Subduction · CO2 Sequestration and Geologic Interactions · Marine and coastal ecosystems · Methane Hydrates and Related Phenomena

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