During several austral summers covering a 13 year period, we collected a random sample of body feathers from chicks of 11 sympatric species of Procellariiform (wandering albatross Diomedea exulans -79 individuals in total-, black-browed albatross Thalassarche melanophris - 51-, grey-headed albatross T. chrysostoma - 58 -, light-mantled sooty albatross Phoebetria palpebrata - 34 -, northern giant petrel Macronectes halli - 59 -, southern giant petrel M. giganteus - 60 -, white-chinned petrel Procellaria aequinoctialis - 39 -, blue petrel Halobaena caerulea - 19 - , Antarctic prion Pachyptila desolata - 19 -, South Georgian diving petrel Pelecanoides georgicus - 2 - and common diving petrel P. urinatrix - 6 -) to analyse Delta15N and Delta13C.

The dataset contains 3 data files. Firstly, it contains one set of stable isotope compositions expressed as delta13C, d15N, d34S values recovered from fish muscle from a variety of species captured in September 2019 across the Barents Sea as part of the joint IMR-PINRO Barents Sea Ecosystem Survey. Samples were collected by Dr Matthew Cobain and Dr Kim Vane, and isotope data analysed at the university of Southampton. A second dataset contains delta13C and delta18O compositions of fish otolith carbonate recovered from a subset of the same fish. A final sheet contains the full metadata associated with each fish sampled on the survey. All samples were processed by Dr Matthew Cobain or Prof Clive Trueman and stable isotope values determined at the University of Southampton. Funding: Project was funded under the NERC Changing Arctic Ocean project, Coldifsh (NE/R012520/1).

This dataset provides stable isotope values (delta13C, delta15N) of 174 bone collagen samples collected in the western South Atlantic. Collagen was extracted from bone samples for six whale species as follows: Antarctic blue whale (n = 20), fin whale (n = 64), humpback whale (n = 46), sei whale (n = 40), southern right whale (n = 1), and sperm whale (n = 3). Bone samples were collected from ex-whaling sites across three locations in the western South Atlantic: the Falkland Islands, South Georgia, and the South Orkneys. This samples were used to estimate niche partitioning and diet specialism of whale species in the western South Atlantic. Funding: NE/L002507/1 (a NERC-Cambridge ESS Doctoral Training Partnership studentship from the Natural Environment Research Council awarded to Danielle L. Buss) and the Ecosystems component of the British Antarctic Survey Polar Science for Planet Earth Programme, funded by NERC.

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).