We studied the spatial and temporal distribution of the hydrated calcium carbonate mineral ikaite in sea ice off Terre Adélie, Antarctica, in relation to biogeochemical parameters such as alkalinity and phosphate. The quantity of ikaite was determined on different spatial scales in young ~3 month old landfast sea ice, as well as in older fast ice and glacial ice. Values of up to 125 mg L^–1 ikaite were measured. The highest concentrations were found in the older landfast sea ice. Stratigraphic investigations revealed an enrichment of the mineral within the top layers of the ice, with a marked decrease to below 1 mg L^–1 near the bottom. Our results indicate a heterogeneous distribution of ikaite in sea ice. Furthermore we could not find a clear relationship between quantity of ikaite and alkalinity or phosphate levels. It appears that these parameters may have changed with time after precipitation of ikaite had occurred, due to diffusion processes subsequent to precipitation. CaCO₃*6H₂O is thought to precipitate in the presence of high phosphate concentrations. Unexpected findings of ikaite in continental Antarctic firn ice indicate that the mineral is transported from the sea ice to the Antarctic continent by aeolian processes, thus supporting previous reports. The quantitative determination of ikaite and biogeochemical parameters in sea ice provides a first insight into the processes involved in calcium carbonate precipitation and a better understanding of its role in polar CO₂ cycling.