ICESat's contribution to advancing our understanding of ice sheet processes (Invited)

The ICESat mission lasted for almost 7 years from January 2003 to October 2009, and for most of this period its laser altimeter acquired surface elevations along repeated ground tracks. The unique capabilities of ICESat - high along-track resolution and vertical precision, and accurate repeatability of ground tracks - proved invaluable for detailed studies of ice sheet processes. Amongst the most significant findings were discoveries related to Antarctica’s subglacial hydrology, including the first detailed observations of subglacial lake filling and draining, and a comprehensive inventory of active subglacial lakes. This application exploited the fact that the ice surface above the lake rises and falls in response to changes in the lake volume. ICESat data also contributed significantly to studies of Antarctic ice shelves, whose stability is known to be a strong constraint on grounded ice mass change. Repeated tracks acquired at different phases of the ocean tide revealed the flexure across the grounding line, leading to improved mapping of the grounding zone including ice plains. ICESat has also contributed to other studies of ice shelf stability and ice/ocean interactions including evolution of rifts, tides, and basal melting.