Data collected from modern sea ice samples from the Belcher Islands Archipelago, south-eastern Hudson Bay, Canada between April and May 2019 using a Kovacs Mark II core barrel with an internal diameter of 9 cm. Data includes diatom concentrations (valves/ml) from the bottom 5 cm of the sea-ice from each sampling day. Diatom quantification was done using a light microscope (Zeiss Axio Imager.A2 upright research microscope, University of Helsinki) with phase contrast optics at a x1000 magnification
