Temporal change in the extinction coefficient of snow on the Greenland ice sheet from an analysis of Seasat and Geosat altimeter data

The extinction coefficient of snow, k_e, along the central portion of the Greenland ice sheet is mapped using data from the Seasat (1978) and Geosat (1985) altimeters. The extinction coefficient is obtained by fitting altimeter waveforms with a surface/volume scattering model. It was found that in the lower latitudes the Seasat and Geosat extinction coefficients are very nearly the same, while in the higher latitudes the Seasat k_e values exceed the Geosat values by over 100%. By analyzing 18-months of the Geosat data, the author quantified the natural variability inherent in the extinction coefficient measurements. The results show that the observed temporal variation in the extinction coefficient from 1978-1985 is three times larger than the natural variability. This indicates that the average grain size of the near surface snow in this region may have decreased during the time span between the two altimeter datasets