Samples of snow, sea ice, seawater (0.5 m and 5 m depths) and meltponds were collected from two ice-covered stations located in the Barents Sea (81 N), during the "Nansen Legacy Q3" summer cruise of the Norwegian research vessel Kronprins Haakon on 26-28 August 2019. Perfluoroalkyl substances (PFAS) concentrations, salinity and stable oxygen isotopes were measured in all samples to determine sources and environmental fate of PFAS during late summer. NERC ENVISION Doctoral Training Centre (NE/L002604/1). NERC and the German Federal Ministry of Education and Research (BMBF) funded Changing Arctic Ocean program EISPAC project (NE/R012857/1). The Nansen Legacy research is funded by the Research Council of Norway (# 276730).

The long term monitoring of water chemistry in Signy Island lakes is unique in polar limnology, in its duration (30+ years), detail, and range of sites. It details seasonal patterns of snow and ice cover, inorganic nutrient status and chlorophyll-a and includes vertical profiles of various physical chemical parameters. There are detailed data for several study lakes and twice/thrice yearly analyses for all the Signy Island lakes. Temperature and light climate has been studied in certain lakes using automatic data loggers. Micrometeorological monitoring with additional data loggers provided data on solar radiation (PAR, UVR), air temperature, humidity and wind conditions. Data are collected by chemical analysis, use of temperature, pH light probes and observation. The ''grand prix'' was the sampling of 16 lakes in a short period (approx. one week), this was carried out perhaps two or three times a year. Approximately three to five lakes were sampled monthly or fortnightly in more detail, these were representative of the 16 lakes. Comparative studies were also undertaken in the Arctic. The long-term programme was established in 1971, although some observations were made in 1963/1964 and 1969/1970. The programme finished in 2004. As the exact months of the data collection were not provided, and the metadata standard requires a YYYY-MM-DD format, this dataset has been dated as 1st January for start date, and 31st December for stop date.