ABSTRACT
The ice sheets of Antarctica and Greenland modulate world climate and control global sea level. Changes in snow and ice extent alter the Earth's albedo and consequently the radiation budgets which drive the atmospheric engine. Ice sheets influence the transfer of energy, mass and momentum between land, ocean and atmosphere and control weather patterns on many temporal and spatial scales. Because the polar ice sheets are inaccessible and inhospitable areas of the Earth's surface, both their historical and contemporary behaviour are poorly mapped and understood. For many parts of the globe, satellite data offer not only the chance to observe large areas synoptically, but also an alternative perspective to ground based observations. Over the hinterlands of Greenland and Antarctica, however, satellite derived data are for the most part, all that are available. In 1977, when the use of satellite imagery was still rare, Swithinbank (1977) wrote that the far side of the Moon was much better mapped than parts of our own planet and noted ' . . . that position errors of more than 100 kmwere found in 1975 on the most up-to-date maps published at any scale of one part of the Antarctic Peninsula'.
