Mapping Vertical Ice Sheet Melt Profiles using Spaceborne Multi-frequency Microwave Radiometry

The Greenland and Antarctica ice sheets are major and increasingly important contributors to the global sea level rise through the melting of the ice masses. Thus, monitoring and understanding their evolution is more important than ever. However, the understanding of the ice sheet melt is hindered because of the limitations in the current observational melt products. The products report only the top layer surface melt and do not convey information on the deeper melt/refreeze processes. The reason is the relatively high frequency used in the products. The solution is to use multi-frequency observations from L-band (1.4 GHz) to Ka-band (37 GHz) available from spaceborne microwave radiometers. The range of frequencies allow the retrieval of melt water profiles as the emission at higher frequencies originates from shallow surface layers, while the lower frequencies originate deeper and are consequently influenced by the seasonal melt water in a thicker surface layer. We simulated brightness temperatures at 1.4, 6.9, 10, 19 and 37 GHz with the MEMLS (Microwave Emission Model of Layered Snowpacks) emission model with liquid water content (LWC) profiles modeled for the DYE-2 experimental site in Greenland using an energy balance model, which was calibrated with in situ temperature and snow wetness profiles. The MEMLS model was run using the same snow density and temperature profiles as the energy balance model, but some of the snow structural parameters were adjusted so that the simulated TB values corresponded to the values measured by the SMAP (1.4 GHz) and AMSR2 (6.9, 10, 19 and 37 GHz) microwave radiometers during the frozen conditions. During the melt season, LWC and temperature profiles were fed to the emission model from the energy balance model. The simulated TB values corresponded to the measured TB demonstrating that the observations carry information on the melt evolution at different depths. The TB measurements can then be inverted to LWC profiles. The process can be applied to the twice daily continent scale measurements of the satellite instruments to map the LWC profiles for tracking the melt evolution in the different layers of the ice sheet. In this presentation, we will show the most recent results of this analysis.