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).

This dataset contains rates of mass change and cumulative mass change and their associated uncertainty for the Antarctic Ice Sheet (in its entirety and split into West Antarctica, East Antarctica and the Antarctic Peninsula), the Greenland Ice Sheet, and their sum between 1992 and 2020. The data are reconciled estimates of mass balance from three independent satellite-based techniques: altimetry, gravimetry and input-output method. This dataset is part of the Ice Sheet Mass Balance Intercomparison Exercise (IMBIE). This work is an outcome of the Ice Sheet Mass Balance Inter-Comparison Exercise IMBIE) supported by the ESA Climate Change Initiative and the NASA Cryosphere Program. Andrew Shepherd was additionally supported by a Royal Society Wolfson Research Merit Award and the UK Natural Environment Research Council Centre for Polar Observation and Modelling (cpom30001).

This dataset consists of the time series of mass change of the Greenland Ice Sheet and its contribution to global sea level between 1980 and 2018 derived from satellite measurements. The dataset presented here is a reconciled estimate of mass balance estimates from three independent satellite-based techniques - gravimetry, altimetry and input-output method - and its associated uncertainty. This dataset is part of the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). The total mass change as well as the partition between surface and dynamics mass balance are provided in this dataset. This work is an outcome of the Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) supported by the ESA Climate Change Initiative and the NASA Cryosphere Program. Andrew Shepherd was additionally supported by a Royal Society Wolfson Research Merit Award and the UK Natural Environment Research Council Centre for Polar Observation and Modelling (cpom30001). ***** PLEASE BE ADVISED TO USE UPDATED DATA ***** The expanded data set (see 'Related Data Set Metadata' link below) has an additional 24 months of measurements, and also includes data for Antarctica.