Salinity profiles of sea ice and snow on sea ice were measured in the Arctic Ocean during the Norwegian Young Sea Ice cruise in 2015 (https://www.npolar.no/en/projects/n-ice2015/), an international sea ice drift expedition led by the Norwegian Polar Institute. Salinity is a key parameter for a range of processes related to biology, photochemistry and physics of sea ice, snow on sea ice as well as atmospheric aerosol. Sea ice cores and snow samples were collected during the sea ice drift expedition from the ice floe and transferred to the ship''s laboratory. The aqueous conductivity of melted sea ice core and snow samples was measured and converted into practical salinity units. Funding was provided by the NERC grant NE/M005852/1, Japan Society for the Promotion of Science (15K16135, 24-4175) and the Centre of Ice, Climate and Ecosystems (ICE) at the Norwegian Polar Institute through the N-ICE project

Surface snow samples were collected daily from a Canadian high Arctic location at Eureka, Nunavut (80N, 86W) from the end of February to the end of March in 2018 and 2019. The snow samples were collected at several sites representing distinct environments: sea ice, inland close to sea level, and a hilltop ~600 m above sea level. Ion Chromatography (IC) analysis was performed for most of the snow samples. Snow salinity measurement is mainly for surface snow. Surface ozone was measured at sea level (from the Zero Altitude PEARL Auxiliary Laboratory (0PAL)) and lower tropospheric BrO (0-4 km) was measured by MAX-DOAS instrument (at ~610 m located at the Polar Environment Atmospheric Research Laboratory (PEARL)). This study was supported by the UK NERC Arctic office via two UK-Canada bursary programs: "The role of tundra snowpack chemistry in the boundary layer bromine budget at Eureka, Canada" (2018), and "A second investigation of the role of tundra snowpack chemistry in the boundary layer ''bromine explosion''" (2019). The Eureka MAX-DOAS BrO measurements made at the PEARL Ridge Laboratory by the Canadian Network for the Detection of Atmospheric Change (CANDAC) was primarily supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canadian Space Agency (CSA), and Environment and Climate Change Canada (ECCC).