Small particles (known as aerosol) in the atmosphere play several critical roles. They affect the transmission of sunlight to the underlying surface; they affect the formation of clouds, and they host and enhance important chemical reactions. When they are deposited on ice they leave a record of past conditions that can be accessed by drilling ice cores. The most significant aerosol component over marine areas is sea salt aerosol. Over most of the world''s oceans this is created by bubble bursting in sea spray. However there is strong evidence that another source of sea salt aerosol is important in the polar regions, and that this ultimately derives from the surface of sea ice. The existence of this source forms the basis for a proposed method using ice core data for determining changes in sea ice extent over long time periods. Additionally sea salt aerosol, along with salty sea ice surfaces, is the host for the production of halogen compounds which seem to play a key role in the oxidation chemistry of the polar regions. It is therefore important to understand the sources of polar sea salt aerosol and therefore to be able to predict how they may vary with, and feedback to, climate. It was recently proposed that the main source of this polar sea salt aerosol was the sublimation of salty blowing snow. The idea is that snow on sea ice has a significant salinity. When this salty snow is mobilised into blowing snow, sublimation from the (top of) the blowing snow layer will allow the formation of sea salt aerosol above the blowing snow layer, that can remain airborne after the blowing snow has ceased. First calculations suggested that this would provide a strong source of aerosol (greater than that from open ocean processes over an equivalent area). It was proposed that this would have a strong influence on polar halogen chemistry and a noticeable influence on halogens at lower latitudes. However, this was based on estimates of the relevant parameters as there were no data about aerosol production from this source, and almost no data about blowing snow over sea ice in general. Participation in a rare sea ice cruise onboard the German ice breaker Polarstern operated by Alfred-Wegener-Institut (AWI) provided the opportunity to access the sea ice covered Weddell Sea during Austral winter 2013. Snow on sea ice was sampled at various locations, and the snow salinity was subsequently measured in the ship''s laboratory.

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

Two consecutive cruises in the Weddell Sea, Antarctica, in winter/spring 2013 provided the first direct observations of sea salt aerosol (SSA) production from blowing snow above sea ice, thereby validating a model hypothesis to account for winter time SSA maxima in polar regions not explained otherwise. Concentration, size distribution and chemical composition of airborne snow particles, sea salt aerosol and snow on sea ice where measured on board RV Polarstern as well as on the sea ice during ice stations. Funding was provided by NERC projects NE/J023051/1 and NE/J020303/1.

The dataset contains oxygen stable isotope and salinity measurements from water samples collected from sea ice and meltwater pools in April 2016 in the region of South Georgia, Signy and deep within the Weddell Sea pack ice during the marine survey JR15006. The d18O and salinity measurements from sea ice and meltwater sources complement the same analysis from CTD casts and underway non-toxic flow water system on the RRS James Clark Ross during the JR15006. Establishing d18O and salinity values for saline water and oceanic freshwater components can be used to identify sources and changes of freshwater contributions to the ocean.

Perfluoroalkyl substances (PFAS) concentrations in artificial sea ice experiments at the Roland von Glasow Air-Sea-Ice Chamber (RvG-ASIC) at the University of East Anglia, UK. Experiments involved investigating chemical contaminant behaviours during sea ice formation and melt in order to assess possible exposure risk to sea ice biota. 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). British Antarctic Survey Collaboration Voucher. EUROCHAMP-2020 Infrastructure Activity under grant agreement (No 730997).

Persistent organic pollutant concentrations in artificial sea ice experiments at the Roland von Glasow Air-Sea-Ice Chamber (RvG-ASIC) at the University of East Anglia, UK. Experiments involved investigating chemical contaminant behaviours during sea ice formation and melt in order to assess possible exposure risk to sea ice biota. Funding was provided by: 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). British Antarctic Survey Collaboration Voucher. EUROCHAMP-2020 Infrastructure Activity under grant agreement (No 730997).

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).