Ocean alkalinity enhancement (OAE) boosts oceanic CO₂ absorption, offering a climate solution. Using a regional model, we examined OAE in the North Sea, revealing that shallow coastal areas achieve higher CO₂ uptake than offshore where alkalinity is more susceptible to deep-ocean loss. Long-term carbon storage is limited, and pH shifts vary by location. Our findings guide OAE deployment to optimize carbon removal while minimizing ecological effects, supporting global climate mitigation efforts.