Particle number flux of airborne snow particles was measured near-continuously at 1-min resolution above the sea ice surface from October 2019 to July 2020 during the year-round MOSAiC expedition. Sensors where mounted at 0.08 m and 10 m on the mast in MetCity on the MOSAiC ice floe drifting during the measurement period within an area of 79.2 N to 88.6 N and 2.7 W to 133.6 E. The SPC measurements were part of the BAS measurement suite during MOSAiC to quantify sea salt aerosol production from blowing snow above sea ice and potential impacts on clouds and climate. Instrument and data quality checks during the year-round campaign were carried out by BAS scientists and the MOSAiC ATMOS team. Funding was provided by UKRI Natural Environment Research Council (NERC) project "Sea Salt Aerosol above Arctic Sea Ice - sources, processes and climate impacts" (SSAASI-CLIM) grant NE/S00257X/1. The project was part of the international Multi-disciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) with the tag MOSAiC20192020.

Ground truth measurements in the form of snow/ice cores were obtained from three sites in 2006: Rothschild Island, Latady Island and Smyley Island. The sites selected corresponded to the position of Automatic Weather Stations (AWS) deployed during the previous season. At both the Rothschild Island and Smyley Island sites the AWS - due to an unprecedented amount of snowfall - had been buried. Therefore, two cores, 8m and 12m in length, were obtained from the approximate position of the AWS, in addition to the sampling of a snow pit. At the Latady Island site, the top 60cm of the 5m AWS was protruding above the surface - again, due to an unprecedented amount of snowfall. A diagonally descending trench was dug to recover the AWS and two cores were collected at this site. This work was carried out as part of a project to understand how air mass origin and meteorology affect the mass accumulation of snow in areas of the Antarctic Peninsula, and how the atmosphere''s properties are preserved in the snow, Photographs of the expedition showing the ground layout, the situation of the cores and what was done when they were gathered are available and stored with the data.

The Antarctic snow accumulation map is derived from a compilation of field measurements. Satellite observations from AMSR-E and AVHRR (Advanced Microwave Scanning Radiometer-EOS and Advanced Very High Resolution Radiometer) instruments are used to guide the interpolation. The effective resolution of the map is approximately 100 km. The estimates of root mean square percentage error apply to regional averages at scales of around 100 km by 100 km. On smaller scales, additional deviations of 30% r.m.s. are likely. Values for locations subject to melt may be unreliable. Units are (kg/m2/a), or (mm/a) water equivalent.

Three micro-power Automatic Weather Stations (AWS) with two sonic ranging sensors were deployed at field-sites situated at Rothschild Island, Latady Island and Smyley Island in January 2005. The AWS instruments included a wind vane and two humicaps on the mast and two sonic ranging sensors mounted on separate horizontal scaffold poles. The AWS data collected contributed to a project concerned with understanding how air mass origin and meteorology affect the mass accumulation of snow in areas of the Antarctic Peninsula, and how the atmosphere''s properties are preserved in the snow.

These datasets show how lake water-pressure fluctuated through time over several months in seasonally-frozen catchments in winter. These catchments were in three settings: the lowland Finnish Arctic, an alpine valley and a high cirque in Switzerland. The water-pressure data are accompanied by water temperature and (except for Orajarvi), ground temperature for the same periods. Together, they were used to detect and quantify the water content of snow falling on the lake surfaces. The locations, method of data collection and analysis and the results are described in detail in Pritchard, H. D., Farinotti, D., & Colwell, S. (2021). This work was funded by Natural Environment Research Council (UK) core funding to the British Antarctic Survey, and a fellowship from the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, CH-8903 Birmensdorf, Switzerland.