Satellite altimeter measurements of the geoid in sea ice zones

Abstract

The Seasat radar altimeter provided surface height measurements to a precision better than 10cm over the open ocean, The data have been used to produce maps of the ocean geoid which reveal details of sub-surface topography such as sea mounts, ocean trenches and mid-ocean ridges /1/. In areas of the ocean covered by sea ice, however, the quasi-specular ice returns which occurred were incorrectly handled by the on-board processor. This resulted in a significant decrease in the precision of the surface height estimates. Consequently, researchers have generally eliminated data from regions where sea ice is suspected to have been present, including large areas of the Antarctic ocean. We have developed a technique for significantly improving the height measurements over such areas permitting the mapping of the geoid in such regions. The short wavelength RMS deviation of elevation measurements from collinear passes over such areas has been reduced from 1.032m to 0.632m. The application of the technique to ERS-1 altimeter data will be particularly important, since coverage of a substantial area of the Arctic ocean (up to 82° latitude) will be possible for the first time