On this MSc thesis we use two radar altimetry mission data in order to study the evolution oof the Greenland ice sheet during the period 2013-2014. The Throughout Earth’s history the cryosphere, and more specifically its ice sheets, have responded to every major climate change event by expanding or retreating its extension pulled on the direction of the new climatic situation. Thus, for the currently ongoing climate change, the Antarctic and Greenland Ice Sheets hold a significant relevance as they are one of the most sensitive indicators of climatic changes. On this scenario, this thesis project studies the process of characterizing the mass changes on the Greenland Ice Sheet (GrIS) making use of satellite radar altimetry data provided by the K band altimetry mission SARAL/Altika. The data have been obtained from the RADS radar altimetry data base of the TU Delft. One of the main focuses has been put into the characteristics of employing the radar altimetry techniques over ice sheets and the specific phenomena that need to be taken into account when computing range values. The slope-induced deviations have been estimated by calculating the along- and across-track surface slopes on the nadir direction and correcting for the deviation caused by these on the range estimates. The result has been satisfactory when compared with an independent DEM. On a second phase of the project, the elevation changes have been computed at the intersections between ascending and descending tracks, the crossover points. Three methods have been used to analyse these elevation changes: an overall GrIS estimate that uses all crossover points as equal; a regionalized averaging method for the crossover points; and a Laplacian differential molecule method for adding a dynamic dimension to the regionalized data and thus have a smoother and better covered GrIS data. The regionalized methods have yielded a distribution of elevation changes where the north- western and north-eastern coastal areas are where the main ice loss is measured, while the interior areas show no change or a slight increase on the southern interior area. By using the elevation change estimates, annual volume changes have been derived for each of the methods mentioned above. The resulting estimates are similar from one method to the other, giving an average of -272 ± 55 km /yr for the January 2013 - December 2014 period. When translated into annual mass balances using an effective ice density of 900 kg/m a total mass change of -245 ± 50 Gt/yr is obtained. This thesis has successfully calculated annual mass change estimates for the GrIS using SARAL/Altika measurements, results that come into agreement with the ones obtained in other independent studies. In addition, it has confirmed the validity of the applied methods for the correction of slope-induced deviations and the calculation of regionalized elevation changes. The availability of longer period data records and an improved re-tracking procedure could significantly improve the accuracy of the final results.