Improved retrieval of sea ice thickness from SMOS and CryoSat-2

We investigate the potential of a synergetic combination of data from ESA's SMOS and CryoSat-2 mission for sea ice thickness retrieval. SMOS and CryoSat-2 provide complementary information because of their different spatio-temporal sampling and resolution, and because of the complementary uncertainty due to the fundamental difference of the radiometric and altimetric measurement principle. The main limitations of the ice thickness retrieval depend on the emission e-folding depth and the vertical resolution of the effective radar pulse-length, respectively. It is shown that the combination of SMOS and CryoSat-2 considerably reduces the uncertainty with respect to the products derived from the single sensors. The RMS error is reduced from 76 to 66 cm and the squared correlation coefficient increases from 0.47 to 0.61 in comparison to validation data of NASA's Operation IceBridge campaign, 2013. Furthermore, we demonstrate the applicability of the Optimal Interpolation method for the generation of a combined product based on weekly CryoSat-2 averages.