THE NEW VISION OF ICE SHEET THANKS TO 20 YEARS OF ALTIMETRY

摘要

Altimetry is probably one of the most powerful toolsrnfor the observation of the sea ice and of ice sheet. 5rnyears ago, a synthesis presented in Venice, at the “15rnyears of Progress in Radar Altimetry” Symposium,rnconcluded that altimetry has provided a strong newrnvision for ice sheet modeling. It allows us to maprntopography with an unprecedented precision but alsornbalance velocity or geothermal flux, to detectrnsubglacial lakes and hydrological networks, to pointrnout several physical processes such as longitudinalrnstresses, sliding, to test and constrain ice sheetrnmodelling… These 15 years were also enough tornprovide mass balance of the Greenland and Antarcticarnice sheets and to detect important ice discharge ofrnseveral glaciers, such as the Pine Island one. To finish,rnit was concluded that altimetry was a unique remoternsensing tool for sea ice thickness … Yet, nothing wasrnsaid about subglacial lake discharges, nothing aboutrnimpressive acceleration of loss of mass for severalrnglaciers of both ice sheets, little about the space andrntime mapping of ice sheet mass balance. We proposernhere a new synthesis of our knowledge of therncryosphere thanks to 20 years of ERS and Envisatrnaltimetry. We will focus on the most recent impressivernprogress above ice sheet provided by Envisat RA2.