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Ikaite (CaCO3•6H2O) is a metastable calcium carbonate mineral that forms at low temperature and/or high pressure. Ikaite precipitates in sea ice and may play a significant role in air–sea CO2 exchange in ice covered seas and oceans. However, the spatial and temporal dynamics of ikaite in sea ice are poorly understood due to few available measurements and time consuming analytical techniques. Here, we present a new method for quantifying ikaite in sea ice and compare it with a more time-consuming imaging technique currently in use. In short, sea ice cores were melted at low temperatures (−1), lower concentrations in 1.5 m thick first–year sea ice (45 µmol kg−1) and low concentrations in 3.3 m thick multi–year sea ice (3 µmol kg−1). Highest concentrations were observed in the upper ice layers at all stations and layers where sea ice algae were present. The higher abundance of ikaite in young first–year sea ice indicates that its concentrations will likely increase in the Arctic as a result of the recent rapid decline of the multi–year ice cover and increasing presence of seasonal sea ice. As a result, it is likely that ikaite will play a more significant role in air–sea CO2 exchange in ice–covered seas in the future.