Monthly Determination of Surface Elevation Changes fromCryoSat Data

摘要

More recently we have extended our work to improve detection of the position of the POCA in CryoSat records, and from that the measurement of monthly changes in the height of ice caps in the Canadian and Norwegian Arctic (Gray et al., 2015). By developing a 'retracker' that estimates the POCA position in a CryoSat waveform from the maximum slope on the first significant leading edge of the return, we can measure individual point elevations on ice caps to an accuracy of -1-1.5 m. However, by comparingspatial averages at different time periods, height change can be estimated with sub-meter accuracy. The repeat orbit period of CryoSat is 369 days, but it contains a 30-day orbit sub-cycle that enables approximately monthly measurements of the surface elevation of ice caps by averaging many thousands of individual returns. When applied to Barnes Ice Cap, Baffin Island, for example, this enables the nearly continuous monitoring of surface mass balance conditions (Fig. 3). An analysis of CryoSat recordsfrom the same period each year can then provide information on the annual mass balance. Comparisons between CryoSat-derived height changes on Devon Ice Cap and those recorded with an automated snow depth sounder show close correspondence, with the CryoSat measurements recording a mean height change of -0.72 ±0.5 m for 2011, compared to -0.64 ±0.03 m recorded by the in situ sensor (Gray et al., 2015).