This study investigates the solubility of calcite and aragonite in seawater over a wide range of salinities (5-44 per mil) and temperatures (5-40°C) at 1 atm total pressure. The measurements were conducted using a closed system technique, equilibrating solutions with carbonate solids for periods ranging from 5 days to nearly 2 years. The results, based on over 480 independent measurements, are compared with previous studies, showing that the stoichiometric solubility constants of calcite are generally consistent with those reported by other researchers. However, this study is the only long-term equilibration investigation of aragonite solubility in seawater. The influence of coprecipitates on the solubility behavior of calcium carbonate is found to be negligible within the precision of the measurements. The study also discusses the thermodynamic solubility products of calcite and aragonite and the estimation of total ion activity coefficients in complex electrolyte solutions, providing insights into the solubility behavior of these minerals in seawater.This study investigates the solubility of calcite and aragonite in seawater over a wide range of salinities (5-44 per mil) and temperatures (5-40°C) at 1 atm total pressure. The measurements were conducted using a closed system technique, equilibrating solutions with carbonate solids for periods ranging from 5 days to nearly 2 years. The results, based on over 480 independent measurements, are compared with previous studies, showing that the stoichiometric solubility constants of calcite are generally consistent with those reported by other researchers. However, this study is the only long-term equilibration investigation of aragonite solubility in seawater. The influence of coprecipitates on the solubility behavior of calcium carbonate is found to be negligible within the precision of the measurements. The study also discusses the thermodynamic solubility products of calcite and aragonite and the estimation of total ion activity coefficients in complex electrolyte solutions, providing insights into the solubility behavior of these minerals in seawater.