Citation
Disclaimer
The ice thickness and bed topography are model outputs and are not free of error (especially in regions where ice thickness measurements are sparse). This dataset is a work in progress and we encourage users to send us feedback so that we keep improving it.
Projection
The projection is Polar Stereographic South (71ºS, 0ºE), which corresponds to ESPG 3031
Reading with MATLAB
MATLAB now has an extensive library for NetCDF files.
filename = 'BedMachineAntarctica-2019-09-04.nc';
x = ncread(filename,'x');
y = ncread(filename,'y');
bed = ncread(filename,'bed')'; %Do not forget to transpose
%Display bed elevation
imagesc(x,y,bed); axis xy equal; caxis([-1000 3000]);
Converting Heights to WGS84
All heights are referenced to mean sea level (using the geoid EIGEN-6C4). To convert the heights to heights referenced to the WGS84 ellipsoid, simply add the geoid height:
\(𝑧_{𝑒𝑙𝑙𝑖𝑝𝑠𝑜𝑖𝑑} = 𝑧_{𝑔𝑒𝑜𝑖𝑑}+𝑔𝑒𝑜𝑖𝑑\)
Surface height and firn depth correction
All the quantities provided in BedMachine are in ice equivalent. This affects primarily the upper surface of the ice, to which we have subtracted a firn depth correction to account for the presence of air in the firn layer. The ice thickness is also in ice equivalent. To recover the top of the surface dem from RAME in WGS84:
\(𝑧_{REMA} = surface + firn + geoid \)
where “firn” is the firn depth correction, “surface” is the surface height, and “geoid” is the geoid height. All these quantities are provided in the netCDF file.
Acknowledgements and references
This project is performed at Dartmouth and the University of California Irvine under a contract with the National Aeronautics and Space Administration (Sea Level Rise Program #NNX14AN03G and MEaSURES-3) and the National Science Foundation (Thwaites #1739031).
The ice thickness data are from:
The bathymetry data are from:
The surface velocity data used by MC are from:
The surface mass balance is from RACMO 2.3 1 km:
The surface topography map is from:
The mask is derived from: