A total of 24 depth profiles were measured during this deployment. In the marginal ice zone in summer and spring, the sea ice cover controls the biogeochemistry and the physical structure of the water column, including the distribution of Chl a and density as well as bacterial activity . Thus, exactly as in Wohl et al. , vertical profiles were classified by sea ice cover (SIC) at the time of sampling (Figure ). Details of the Chl a measurements, the analytical chemistry, measurement noise and the cruise track are presented in the supplementary text.