BedMachine Antarctica Version 4

BedMachine Antarctica Version 4 provides Antarctic subglacial bed topography deduced by subtracting ice thickness from the surface elevation, using mass conservation ( Morlighem et al., 2011 ), Ice Flow Perturbation Analysis (IFPA) ( Ockenden et al. , 2026), and other methods. Surface elevations are obtained from the Reference Elevation Model of Antarctica (REMA) ( Howat et al. , 2019). A major contribution to BedMachine Antarctica is a continental-scale elevation map of Antarctica’s subglacial topography produced by applying the physics of ice flow to ice surface maps and incorporating geophysical ice thickness observations. The surface evelation and ice thickness are in ice equivalent as they include a firn air content correction. The elevation of the top of the snow, which is provided by REMA, can be calculated by adding the firn depth correction provided in the BedMachine Antarctica netCDF file ( Morlighem et al., 2020, Supplemantary Information). In BedMachine Antarctica, heights are referenced to mean sea level as realized by the EIGEN-6C4 geoid, horizontal positions are referenced to the WGS84 ellipsoid and projected coordinates to Antarctic Polar Stereographic projection (EPSG:3031). The data were collected between 1 January 1970 and 1 October 2019. The nominal year of this data set is 2015 and refers to the year of the reference surface digital elevation model. The output product is generated at a 500 m resolution. The accuracy of the Antarctic subglacial bed elevations is no better than 50 meters.