2 Antarctica explored
Until recently, our picture of Antarctica was based on sparse terrestrial surveys, beginning with overland expeditions in the 1890s (green). These were often driven by personal ambition, while the establishment of national research bases from the 1920s onwards (blue) tended to be politically motivated. Although aircraft surveys since the 1940s (red) provide us with the best estimate of the thickness of the Antarctic ice sheet, satellite measurements in the 1990s (greyscale) let us monitor the height and flow rate of the sheet with unprecedented detail.