In this thesis I develop novel methods and datasets, based on the processing of CryoSat-2 satellite radar altimeter data, to improve the understanding of retrieving measurements of surface elevation and elevation change over the Antarctic and Greenland ice sheets.
First, I used 6 years of CryoSat-2 altimetry to create a model of the surface height of the Antarctic Ice Sheet and ice shelves. Posted at a resolution of 1 km, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells North of 88 ° S are interpolated using ordinary kriging. Taking into account slope-dependent errors and the distribution of slopes across the ice sheet, I estimated the average accuracy of the DEM to be 9.5 m - a value that is comparable to, or better than that of other models derived from satellite radar and laser altimetry.
Next, I developed a new technique to retrieve estimates of the depth distribution of radar backscatter from CryoSat-2 altimeter waveforms using a backscatter model. I then applied this model to chart spatial and temporal variatibility in radar backscatter and, for the first time, explicitly estimate radar penetration depth across the interior of the Greenland Ice Sheet. I then used this information to correct for artefacts in elevation trends derived from Cryosat-2 pulse-limited altimetry resulting from an episodic melt event which reset the radar scattering horizon. Incorporating the penetration depth into the surface height retrieval, I find improved agreement when compared to independent airborne laser altimeter data recorded over the same time period.
Finally, I used CryoSat-2 altimetry to estimate seasonal elevation changes in the Greenland Ice Sheet. Using regional climate model simulations of height fluctuations due to surface process alone, I demonstrate that CryoSat-2 observations track elevation changes driven by melting and snowfall accumulation in the ice sheet ablation zone. I then mapped spatial and temporal variations in seasonal elevation change, demonstrating the ability of CryoSat-2 to monitor changes in Greenland which arise due to its meteorology.
