1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
2DTU Space, National Space Institute, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Received: 04 May 2016 – Published in The Cryosphere Discuss.: 06 Jun 2016
Abstract. A new methodology for retrieval of glacier and ice sheet elevations and elevation changes from CryoSat-2 data is presented. Surface elevations and elevation changes determined using this approach show significant improvements over ESA's publicly available CryoSat-2 elevation product (L2 Baseline-B). The results are compared to near-coincident airborne laser altimetry from NASA's Operation IceBridge and seasonal height amplitudes from the Ice, Cloud, and Elevation Satellite (ICESat).
Revised: 18 Oct 2016 – Accepted: 19 Oct 2016 – Published: 01 Dec 2016
Applying this methodology to CryoSat-2 data collected in interferometric synthetic aperture mode (SIN) over the high-relief regions of the Greenland Ice Sheet we find an improvement in the root-mean-square error (RMSE) of 27 and 40 % compared to ESA's L2 product in the derived elevation and elevation changes, respectively. In the interior part of the ice sheet, where CryoSat-2 operates in low-resolution mode (LRM), we find an improvement in the RMSE of 68 and 55 % in the derived elevation and elevation changes, respectively. There is also an 86 % improvement in the magnitude of the seasonal amplitudes when compared to amplitudes derived from ICESat data. These results indicate that the new methodology provides improved tracking of the snow/ice surface with lower sensitivity to changes in near-surface dielectric properties.
To demonstrate the utility of the new processing methodology we produce elevations, elevation changes, and total volume changes from CryoSat-2 data for the Greenland Ice Sheet during the period January 2011 to January 2015. We find that the Greenland Ice Sheet decreased in volume at a rate of 289 ± 20 km3a−1, with high interannual variability and spatial heterogeneity in rates of loss. This rate is 65 km3a−1 more negative than rates determined from ESA's L2 product, highlighting the importance of CryoSat-2 processing methodologies.
Nilsson, J., Gardner, A., Sandberg Sørensen, L., and Forsberg, R.: Improved retrieval of land ice topography from CryoSat-2 data and its impact for volume-change estimation of the Greenland Ice Sheet, The Cryosphere, 10, 2953-2969, doi:10.5194/tc-10-2953-2016, 2016.