Combination of laser and radar altimeter height measurements to estimate snow depth during the 2004 Antarctic AMSR‐E Sea Ice field campaign

Abstract

Among the most important parameters needed to evaluate the present and future state of Antarctic sea ice cover is the ice thickness. The retrieval of ice thickness using remote sensing techniques has been hampered by the absence of a capability to remotely measure snow thickness covering the sea ice. Data sets collected with Johns Hopkins Applied Physics Laboratory's Delay‐Doppler Phase Monopulse (D2P) radar and NASA's Airborne Topographic Mapper (ATM) scanning lidar during NASA's Antarctic AMSR‐E Sea Ice field campaign over the Bellingshausen Sea are used to demonstrate the potential of a remote‐sensing technique for retrieval of snow cover thickness from an airborne platform. The technique takes advantage of the fact that the radar is most sensitive to the snow‐ice interface while the lidar responds to the highly optically reflective snow surface. The difference between the radar‐ and laser‐determined surfaces yields an estimate of snow thickness that appears to be reasonably consistent with expected values. The technique requires careful registration of the instrument footprints. Because there was no absolute range calibration of the lidar due to predeployment scheduling difficulties, the vertical offset between the instruments was resolved by determining the difference between measurements over leads. Elsewhere over sea ice the radar‐defined surface is generally below the laser‐defined surface consistent with the radar defining the snow‐ice interface. Over a relatively small portion of the data, we observed opposite relationship between the sensor‐defined surfaces for which we discuss a plausible physical explanation.