How it works
Bedmap3 grids ice thickness, bed and surface elevation over Antarctica at 500 m, with a mask of
grounded ice, floating ice shelves and rock. Each array is a cloud-optimised GeoTIFF on source.coop
with overviews, so the page reads only the window round the line and block, at the level whose
pixels suit its length: a few requests for a line across the continent as for one across a glacier.
Each sample becomes three bands: rock up to the bed, water from the bed to the ice base (under a
floating shelf) or to sea level (the open sea), and ice from its base to its surface. Grounded ice
rests on its bed; floating ice has its base at its surface less its thickness. The cut face of the
block is the section itself, the other three faces are the same bands along the block's edges, and
its top surfaces are the bed, the ice and the sea from the same grid. With the block on both sides of
the line, the ice is taken off the right-hand side to show the bed under it (unflooded and not
rebounded), and the block can be bent over the Earth's curve, for a line across the continent.
A drill site is a red rod from the bed up through the surface, with the ice thickness, bed and
their uncertainties read there at Bedmap3's full 500 m. While B is placed on the map, a dashed guide
runs from A through the site to the map's edge, and the hint says how far the line to the cursor
passes from the site (Escape starts again).
REMA gives heights above the WGS84 ellipsoid; the page subtracts the EGM2008 geoid (as the Geoid
page does) so its line sits with Bedmap3's and GEBCO's heights above sea level. Where REMA and
Bedmap3's surface part, that is the datum, the date and the resolution of each source, and worth a
look. GEBCO 2026 is the ice surface in Antarctica and the sea floor beyond, in longitude and
latitude, sampled through the projection.
- Bedmap3: Pritchard, H.D., Fretwell, P.T., Fremand, A.C., et al. (2025) Bedmap3 updated ice bed, surface and thickness gridded datasets for Antarctica. Sci Data 12, 414; data from the UK Polar Data Centre (CC BY 4.0), copied to source.coop.
- REMA v2: Howat, I. et al., Polar Geospatial Center; the 100 m, 500 m and 1 km mosaics from rema-ovr.
- GEBCO Compilation Group (2026) GEBCO 2026 Grid, on source.coop.