G24A-01 INVITED
Glaciological studies of the evolution of ice sheets in a warming climate.
The last 10-15 years have witnessed tremendous improvements in our ability to study ice sheets in Antarctica and Greenland, thanks to the advent of satellite missions (ERS-1/2, Radarsat-1, Envisat, GRACE, ICESAT, ALOS, MODIS, ASTER) and the deployment of modern sensors onboard aircrafts (lidar, radar sounder) and on the ground (GPS, seismometer, AWS). Geodesy has been played a central piece in those efforts. As these new tools became available and unveiled unknown details about the present-day status of these ice sheets, the influence of humans started to perturb the system beyond what any of us was ready to accept. In Greenland, we learned in the 1990s that the ice sheet was shrinking as a result of coastal thinning. In the 2000s, we witnessed major glaciological changes that tripled the mass deficit in only 11 years. While these changes only represent a trickle of melt water in the vast oceans, they took place sooner, more rapidly, and more strongly than expected. Following the realization that large-scale models fail to predict this evolution, a race with time began with laser, sounders, InSAR, GPS, seismometer, cameras to determine what causes these glaciers to change so rapidly and what this means for the future. The roles of surface melt water, ice- quakes, calving dynamics, melting of calving faces by warm ocean waters, or sub-glacial hydrology are investigated in more details, ice motion, surface elevation and thickness are mapped at the continental scale with high precision, leaving a frantic trail of exploration and discoveries of how little we knew, and how little we know. In Antarctica, immutable continent far from human influence, we witnessed some of the most spectacular glaciological changes in the wake of the collapse of the Larsen ice shelves. Satellite data reveal that places believed to be vulnerable to climate change and inherently unstable are indeed changing rapidly at present, over large areas. Even East Antarctica is sending eye-opening signs of changes to come. Antarctica remains frantically cold, yet its surrounding ocean is changing, and the ice sheet is responding beyond what numerical or conceptual models anticipated. In this talk, I will attempt to synthesize these advances, the challenges that lay ahead and what the coming century may hold.