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).

Measurements of mean annual temperature in degrees Celsius at 22 sites in Pine Island Glacier, located by hand held Garmin GPS position, and altitude recorded by survey quality Leica GPS. The mean annual temperature of a remote ice sheet site is generally agreed to be equivalent to the temperature measured at 10m depth in a borehole. This dataset records the 10m temperatures at 22 remote sites in the Pine Island Glacier region of the West Antarctic Ice Sheet. Data were recorded on a single thermistor logging thermometer for a period of 12 to 24 hours on the date noted in table (marked in table as ''Single thermistor'') or as the mean of two cables with parallel triple thermistors measured at a single time (date/time noted in table) after a minimum of 12 hours settling in the borehole (marked in table as ''Average of six thermistors''). Measurements were made independently in two boreholes: one drilled to approximately 12m for deployment of a neutron source ice density probe (marked in table as ''10m temperature neutron probe borehole''); one drilled to approximately 50m during recovery of an ice core (marked in table as ''10m temperature ice core borehole''). Some have argued that the mean annual temperature is better measured at 15m in a borehole to remove any trace of the seasonal surface temperature cycle. In the table we additionally record the temperature in the ice core borehole at 15m (marked in table as ''15m temperature ice core borehole'') using a logging PT-100 temperature device (marked in table as ''Single PT-100'').

This dataset contains the position and depth (ice thickness) of three spatially-extensive Internal Reflecting Horizons (IRHs) mapped from ice-penetrating radar data acquired with the British Antarctic Survey''s PASIN and PASIN2 ice radar systems across central East Antarctica. The dataset extends geographically from Dome A to South Pole. Using previous dated IRHs from Winter et al (2019), an independent validation of IRH ages from the South Pole ice-core chronology and a 1-D steady-state model, we assigned ages to our three IRHs: (H1) 38.5 +/- 2.2 ka, (H2) 90.4 +/- 3.57, and (H3) 161.9 +/- 6.76 ka. This study was motivated by the AntArchitecture Action Group of the Scientific Committee for Antarctic Research (SCAR). The project was supported by the National Environmental Research Council (NERC)-funded ONE Planet Doctoral Training Partnership (NE/S007512/1), hosted jointly by Newcastle and Northumbria Universities. The authors thank the BAS science and logistics teams for acquiring both the AGAP PASIN and PolarGAP PASIN2 data which is fully available on the Polar Airborne Geophysics Data Portal of the UK Polar Data Center (https://www.bas.ac.uk/project/nagdp/). BedMachine (version 2) data are available at https://doi.org/10.5067/E1QL9HFQ7A8M.