This dataset comprises measurements from moored CTD instruments, collected by the Mooring Dirigibile Italia (MDI), which is managed by the Institute of Polar Sciences of the National Research Council (CNR). The data was gathered at Kongsfjorden, Svalbard Island, since 29 May 2016 . This dataset is also part of the SIOS-Svalbard Integrated Arctic Earth Observing System, developed to observe the impacts of climate change, including the rapid loss of sea ice cover, the retreat of local glaciers, and the Atlantification of Arctic seas. Measured properties are: sea-water pressure, temperature, potential temperature, practical salinity, density, turbidity, fluorescence, PAR and dissolved oxygen in sea-water. The acquisition of this time series data is still ongoing and will continue, bolstered by the inclusion of this infrastructure within the framework of the Italian PNRR project ITINERIS. This ensures sustained data collection and further enhances our understanding of the observed environmental changes.

ISotopic and physical-chemical MOnitoring of GLACial drainages and sea water in the Ny-Ålesund area (Svalbard) The dataset includes vertical profiles of physical-chemical performed on-site in different sites along the fjord in Kongsfjorden.

The automated nivological station was installed in November 2020 in a flat area over the tundra about 80 meters far from the Gruvebadet Atmospheric Laboratory and nearby a snow sampling site from where weekly snow samples are collected for chemical analysis. Sensors (NESA LU06) have been calibrated by their companies before installation and are connected to a datalogger for continuous acquisition. For all the parameters, data are logged with 10-minute time resolution and then averaged over 1 hour. This activity is carried out by the Aldo Pontremoli Centre part of the Joint Research Agreement ENI-CNR, in the framework of the SnowCorD project (SIOS Core Data).

The Aldo Pontremoli Mooring (MAP), operated by the Institute of Polar Sciences of the National Research Council (CNR), has been active in the Kongsfjord, located in the Svalbard archipelago, since September 11, 2020. It is situated near the mouth of Bayelva River mouth and is influenced by land terminating glaciers and the release of permafrost. Currently, the mooring line is equipped with various instruments positioned at depths ranging from 22 to 97 meters within the water column. These instruments collect a wide array of physical and biogeochemical Essential Ocean Variables, including seawater pressure, temperature, conductivity, salinity, currents, dissolved oxygen concentration, pH, particle fluxes and dissolved carbon dioxide concentration. This activity is part of the Svalbard Integrated Arctic Earth Observing System (SIOS), which aims to monitor the impacts of climate change, such as the rapid loss of sea ice cover, the retreat of local glaciers, and the Atlantification of Arctic seas. Time series acquisition is ongoing and will continue, supported by funding from JRA ENI-CNR. The project's goal is to analyse the environmental feeback related to the material released into the marine environment due to permafrost melting. Reactivated permafrost can have significant consequences for both climate and the environment by contributing to the release of greenhouse gases into the atmosphere and pollutants into aquatic ecosystems.

The Mooring Dirigibile Italia (MDI), operated by the Institute of Polar Sciences of the National Research Council (CNR), has been active in the Kongsfjord of the Svalbard archipelago since September 9, 2010. The mooring line is equipped with various instruments placed at depths ranging from 30 to 90 meters in the water column. These instruments collect a wide range of physical and biogeochemical Essential Ocean Variables, including seawater pressure, temperature, conductivity, currents, dissolved oxygen concentration, PAR, fluorescence, turbidity, particle fluxes, nutrients, and ocean sound. This activity is part of the SIOS (Svalbard Integrated Arctic Earth Observing System), designed to monitor the impacts of climate change, such as the rapid loss of sea ice cover, the retreat of local glaciers, and the Atlantification of Arctic seas. Time series acquisition is ongoing and will continue, supported by the integration of this infrastructure into the Italian Marine Data Portal, developed under the ITINERIS PNRR project. This project also funds the enhancement of the research infrastructure with new sensors to improve measurement resolution, expand the number of EOVs measured, and support the continuous collection of long-term data. These efforts will further deepen our understanding of the observed environmental changes.

Aerosol size distribution (10-500 nm) measured by a APS 3321

Activities: - PM1 sampling by a High-Volume Sampler (TECORA eco-highvol equipped with digital PM1 sampling inlet, nominal flow 500 lpm) on pre-washed and pre-baked quartz-fiber filters (PALL, Ø= 18cm). Sampling time: 3-4 days per sample. - Off-line filter based AMS characterization of water soluble non-refractory sulfate, nitrate, ammonium, chloride, and organic mass (NR-PM1). - Off-line filter-based spectroscopic characterization of the water-soluble organic mass in term of chemical functional groups and specific markers by means of proton-Nuclear Magnetic Resonance spectroscopy (H-NMR). - Source apportionment of organic aerosol by means of multivariate statistical techniques (namely Positive Matrix Factorization, PMF, and other factor analysis methods) applied on both AMS and NMR spectral datasets. Available data: -NMR functional groups (Aromatics, anomeric/vynilic, H-C-O, H-C-C=, H-C) -NMR tracers: Levoglucosan, Methane-sulphonic acid (MSA), Hydroxymethane-sulphonic acid (HMSA), Amines (mono-, di- and tri-methyl amines, etc.) -HR-TOF-AMS (off-line): main species (Org, SO4, NO3, NH4, Chl), elemental ratios (OM:OC, O:C, H:C) & tracer fragments (m/z43, 44, 60 etc.) -NMR & AMS OA source apportionment

Aerosol scattering coefficient at 1 wavelength (530 nm) measured using a nephelometer M903 manufactured by Radiance Research and absorption coefficient at 7 wavelengths (370, 470, 520, 590, 660, 880, 950 nm) measured using an AETHALOMETER AE33 from Aerosol Magee Scientific.

Atmospheric Gondola for Aerosol Profiles (AGAP) The scientific goals of AGAP are to develop novel aerosol payloads and evaluate the vertical distribution of aerosol properties in the Arctic Boundary Layer. Dataset consists in Aerosol vertical profiles gridded at a 50 m spatial resolution: R, T, P, RH, Aerosol size distribution, BC concentration, O3. Maximum altitudes 1500 m.

Spatial variability: validation dataset on pops concentrations in snow (SVAL-POPS) We aim to measure the spatial variability of chosen persistent organic pollutants levels in the snow. The samples will represent three spatial scales: 2-5 m spacing, 0.5-1 km distance, and two sites across Svalbard: Ny Ålesund and Hornsund. These will be compared thanks to a laboratory crosscheck.