Anschütz et al. (2026): Not one shoe fits all: Applicability of hydrodynamic models for the simulation of ocean alkalinity enhancement in the Baltic Sea
Anna-Adriana Anschütz, Thomas Neumann, Peter Holtermann and Hagen Radtke, IN: Journal of Marine Systems, https://doi.org/10.1016/j.jmarsys.2026.104226
Ocean alkalinity enhancement (OAE) has become the focus of intensive research as a potential method for future carbon dioxide removal (CDR). In the Baltic Sea, the deposition of alkaline minerals on the seafloor is one of the considered options, as their dissolution raises local alkalinity. Once the additional alkalinity reaches the sea surface, it increases the ocean’s potential for uptake of atmospheric CO₂. A reliable estimation of the vertical transport of dissolved constituents is therefore essential for a model’s applicability to ocean alkalinisation research. While concentrations of seawater ingredients are often straightforward to measure, the corresponding transports of these ingredients by advection and turbulent diffusion are not. Based on an example from the study of ocean alkalinity enhancement, the authors demonstrate that these transport estimates can exhibit a considerable range of uncertainty even when well-calibrated models are employed. To evaluate the reliability of such estimates by current physical ocean models, they recreated a passive tracer release experiment in the Gotland Deep (Baltic Sea) in three model setups: two hydrodynamic models with differing vertical coordinate systems, including two resolutions for one of the models.