Ice Sheet And Satellite Altimetry

Since 1991, the altimeters of the ERS European Satellites allow the observation of 80% of the Antarctica ice sheet and the whole Greenland ice sheet: They thus offer for the first time a unique vision of polar ice caps. Indeed, surface topography is an essential data thanks to its capacity to highlight the physical processes which control the surface shape, or to test models. Moreover, the altimeter is also a radar which makes it possible to estimate the snow surface or subsurface characteristics, such as surface roughness induced by the strong katabatic wind or ice grain size. The polar ice caps may not be in a stationary state, they continue to respond to the climatic warming of the beginning of the Holocene, that is 18000 years ago, and possibly start to react to present climatic warming: the altimeter offers the unique means of estimating the variations of volume and thus the contribution of polar ice caps to present sea level change.