Concentrations of dissolved ²³⁰Th in the ocean water column increase with depth due to scavenging and downward particle flux. Due to the ²³⁰Th scavenging process, any change in the calcium carbonate (CaCO₃) fraction of the marine particle flux due to changes in biological CaCO₃ hard-shell production as a consequence of progressing ocean acidification would be reflected in the dissolved ²³⁰Th activity. Our prognostic simulations with a biogeochemical ocean general circulation model using different scenarios for the reduction of CaCO₃ production under ocean acidification and different greenhouse gas emission scenarios - the Representative Concentration Pathways (RCPs) 8.5 to 2.6 - reveal the potential for deep ²³⁰Th measurements to detect reduced CaCO₃ production at the sea surface. The time of emergence of an acidification-induced signal on dissolved ²³⁰Th is of the same order of magnitude as for alkalinity measurements. Interannual and decadal variability in factors other than a reduction in CaCO₃ hard-shell production may mask the ocean-acidification-induced signal in dissolved ²³⁰Th and make detection of the pure CaCO₃-induced signal more difficult so that only really strong changes in marine CaCO₃ export would be unambiguously identifiable soon. Nevertheless, the impacts of changes in CaCO₃ export production on marine ²³⁰Th are stronger than those for changes in POC (particulate organic carbon) or clay fluxes.