CryoSat-2 and the Polar Ice Sheets
Shepherd, Andrew1; McMillan, Malcolm1; Hogg, Anna1; Muir, Alan2; Ridout, Andy2; Galin, Natalia3; Cullen, Robert4; Gourmelen, Noel5; Dehecq, Amaury6; Wingham, Duncan7; Briggs, Kate1; Ticconi, Francesca1
1University of Leeds, UNITED KINGDOM; 2Unviersity College London, UNITED KINGDOM; 3NOAA, UNITED STATES; 4ESA, NETHERLANDS; 5Unviersity of Edinburgh, UNITED KINGDOM; 6University of Strasbourg, FRANCE; 7University College London, UNITED KINGDOM
Following a successful launch in April 2010, CryoSat-2 has acquired almost two years of measurements with which to study the ice sheets of Antarctica and Greenland. This presentation summarises the scientific and technical progress of the satellite mission to date, with a focus on several key scientific achiecements related to the study of contiental ice.
We have examined interferometric data from CryoSat-2 acquired over the open ocean for the purpose of calibration, and this analysis demonstrates that the system performance greatly exceeds the pre-launch specfication. The interferometer measures across-track surface slopes with a precision of 25 micro-radians and an accuracy of 10 micro-radians, which may be compared with a pre-launch estimation of 100 micro-radians. The elevation measurement over the ice sheets combines the interferometer measurement of across track slope with the range measurement deduced from the SAR echoes. We have examined the performance of the range estimation, and determined the range precision to be 19 cm RMS at 20 Hz. We have examined the retrieval of the phase information over the ice sheets, and found the phase estimates to be robust and little affected by the uncertain ice sheet topography. Based on the calibration of the interferometer, the contribution of the across track slope error is, at 0.4 mm, negligible.
During the first two years of operation, data from CryoSat-2 have provided remarkable insight into the glaciology of the polar ice sheets. The mission data have been used to produce digital elevation models of the Greenland and Antarctic ice sheet, and to study dynamical changes associated with the movement of continental ice and with the movement of water at the base of Antarctica. When operating in interferemetric mode, key glaciological features are resolved with unprecedented detail. In this paper, we present a series of case studies which exemplify the system performance over the continental ice sheets, including the ability to survey coastal regions that present a challenge to conventional pulse-limited altimeters, the ability to track changes in ice sheet elevation and volume in key sectors of known imbalance, and the ability to study the evolution of Antarctic subglacial lakes.