The formation of sea ice entails intricate alterations in carbonate chemistry

Abstract

During the formation of sea ice, there are significant alterations in carbonate chemistry. Specifically, our focus was on the influence of the ikaite formation on the carbonate chemistry in the sea ice. Although ikaite, hydrated calcium carbonate (CaCO3·6H2O), is known to form inorganically during the sea ice formation process, the changes in carbonate chemistry during sea ice formation including the precipitation of ikaite has not been identified precisely. We conducted measurements of changes in total alkalinity and calcium ions to confirm the formation of calcium carbonate within the sea ice. Surprisingly, our results revealed a discrepancy between the changes in total alkalinity and calcium ion concentrations. These small yet significant differences may, in part or entirely, be attributed to variations in boron concentrations, which contribute to changes in alkalinity. Our laboratory study has provided new insights into intricate alterations in carbonate chemistry that occur during the formation of sea ice in polar environments.