Glaciers and ice sheets modulate global sea level by storing water deposited as snow on the surface, and discharging water back into the ocean through melting. Their physical state can be characterized in terms of their mass balance and dynamics. To estimate the current ice mass balance, and to predict future changes in the motion of the Greenland and Antarctic ice sheets, it is necessary to know the ice sheet thickness and the physical conditions of the ice sheet surface and bed. This information is required at fine resolution and over extensive portions of the ice sheets.
In this innovative development supported in part by NASA ESTO, airborne tomographic ice sounding technology was used to successfully image the reflectivity and topography of the surface as well as the reflectivity of the ice sheet base and ice sheet thickness. From the surface topography and ice thickness measurements, the 3D basal topography can be computed. For the first time, one is able to “see” through kilometers-thick ice sheets and measure the 3D bottom topography and its scattering properties, across a several-kilometers-wide swath. Validation with independent measurements indicates that this technique provides accurate topographic measurement of ice sheet surface and bed, and can be used for local ice sheet bed mapping.
The tomographic sounding processing system is composed of several major modules: a sub-aperture, back-projection azimuth compression with ray-bending correction; a MUSIC/ML arrival angle estimation to estimate surface/bed return arrival angles; and post-processing modules including data regrid and DEM (digital elevation model) mosaic. It produces the ice thickness map and the bedmap as the final product.
This work was done by Xiaoqing Wu, Ernesto Rodriguez, and Anthony Freeman of Caltech; and Ken Jezek of Ohio State University for NASA’s Jet Propulsion Laboratory. NPO-48638
This Brief includes a Technical Support Package (TSP).

Airborne Tomographic Swath Ice Sounding Processing System
(reference NPO-48638) is currently available for download from the TSP library.
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