Surface velocities of grounded ice are an important input parameter for mass flux calculations and ice-sheet modelling. As on-site measurements in remote areas are sparse, satellite-based measurements have to be used to obtain area-wide surface velocities. For this purpose synthetic aperture radar data from various sensors are routinely employed. Depending on the availability of adequate SAR image pairs, the surface velocity is derived by radar interferometry, speckle or feature tracking. The accuracy of the applied methods heavily depends on external input parameters (e.g. elevation model) and the processing history. In this case study we aim to put error margins on the evaluated surface velocities by comparing the data with available on-site GPS measurement. The study focuses on the hinterland of the German overwintering station Neumayer III (Antarctica) and complements pre-site surveys for a future deep drill site. We analyse the dependency of external elevation models for the interferometric approach by comparing surface velocities based on Antarctic-wide elevation models (from satellite altimetry and photoclinometry), with surface velocities based on local elevation models (from differential SAR interferometry). The interferometric approach is restricted to the availability of coherent SAR image pairs and does not cover the floating ice shelves. We fill these gaps with data from lower-resolved speckle and feature tracking.The main goal is to point out the inaccuracy/accuracy of surface velocity fields. As a geophysical product a map of surface velocities next to the German overwintering station Neumayer III is presented. In combination with ice-thickness measurements in the area the mass flux and its uncertainties are estimated. In the future we aim to use these velocities for the derivation of stress and strain rates in complex flow regimes, such as triple points on the nearby ice domes. These areas are of particular interest for ice coring, ice sheet modelling, radio-echo sounding and seismic studies.
Helmholtz Research Programs > PACES I (2009-2013) > TOPIC 1: The Changing Arctic and Antarctic > WP 1.1: Role of Ice Sheets in the Earth System