Data collected from sea ice cores and ice-ocean interface water in Svalbard fjords, Tempelfjorden and Van Mijenfjorden, in April 2021, and laboratory-based data collected at UiT The Arctic University of Norway on Van Mijenfjorden ice algal cultures in 2021

Data collected from sea ice cores and ice-ocean interface water in two Svalbard fjords, Tempelfjorden and Van Mijenfjorden, include sea ice algal gross primary productivity (GPP), photophysiology, chlorophyll a (Chl a), community composition as well as general sea ice characteristics (snow depth, ice thickness, draft, freeboard), bulk-ice salinity, temperature, inorganic bulk and brine nutrients concentrations (nitrite + nitrate (NO2 + NO3), phosphate (PO4), silicic acid (Si(OH)4)) and molar ratios (N:P, N:Si), particulate organic carbon-nitrogen (POC/N) and molar ratios (POC:PON), dissolved inorganic carbon (DIC). The sea ice cores, and ice-ocean interface water were collected at three sampling sites on three different days. First, at one site at Tempelfjorden (TF1, 78.41 ºN, 17.08 ºE) on 12 April, 2021, being freshwater influenced by the tidewater glacier Tunabreen, and then at two sites at Van Mijenfjorden, site 1 (VM1, 77.80 ºN, 15.76 ºE) on 17 April, 2021, and site 2 (VM2, 77.82 ºN, 15.71 ºE) on 14 April, 2021.