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We develop a physical model capable of simulating the mean echo power ofCryoSat-2 SAR- and SARIn-mode waveforms over sea-ice-covered regions. Themodel simulations are used to show the importance of variations in the radarbackscatter coefficient with incidence angle and surface roughness for theretrieval of surface elevation of both sea ice floes and leads. The physicalmodel is used to fit CryoSat-2 waveforms to enable retrieval of surfaceelevation through the use of lookup tables and a bounded trust region Newtonleast-squares fitting approach. The use of a model to fit returns from seaice regions offers advantages over currently used threshold retrackingmethods, which are here shown to be sensitive to the combined effect ofbandwidth-limited range resolution and surface roughness variations. Laxon etal. (2013) have compared ice thickness results from CryoSat-2 and IceBridge,and found good agreement; however consistent assumptions about the snow depthand density of sea ice were not used in the comparisons. To address thisissue, we directly compare ice freeboard and thickness retrievals from thewaveform-fitting and threshold tracker methods of CryoSat-2 to OperationIceBridge data using a consistent set of parameterizations. The purpose ofthe comparison is to highlight the physical basis between differences in theretracking methods. For three IceBridge campaign periods from March2011 to March 2013, mean differences (CryoSat-2 – IceBridge) of 0.144 and1.351 m are found between the freeboard and thicknessretrievals, respectively, using a 50% sea ice floe threshold retracker, while meandifferences of 0.019 and 0.182 m are found when using the waveform-fitting method. This suggests the waveform-fitting technique is capable ofbetter reconciling the sea ice thickness data record from laser and radaraltimetry data sets through the usage of consistent physical assumptions

An improved CryoSat-2 sea ice freeboard retrieval algorithm through the use of waveform fitting