Simulating Ocean Alkalinity Enhancement along the European Coast in an Earth System Model

To assess the potential of coastal ocean alkalinity enhancement as a CO₂ removal option for climate change mitigation, the Flexible Ocean and Climate Infrastructure (FOCI) earth system model was used to simulate alkalinity addition at the European coast open to the North Atlantic. FOCI has a global ocean resolution of 0.5° which can be regionally refined to 0.1° with a two-way nesting approach. The model was run in emission driven mode, starting with a linear ramp up from 2025 to 2035, after which alkalinity equivalent of 1Gt Ca(OH)₂ per year was added in both resolution configurations from year 2035 to 2100 along the European coastline in a high and low emission scenario. To assess regional efficacies, the coast was divided into subsections. We illustrate the importance of adequate model resolution for simulating coastal alkalinity deployment, and show how each coastal region has a different CO₂ uptake efficiency that is caused by differences in the regional environmental and hydrodynamic conditions.