Extensive observations of sea ice cover are essential for understanding the development of these ice masses and of their interactions with other components of the climate system. Among the least known parameters of sea ice cover are snow and ice thicknesses. Both parameters are crucial for the calculation of heat and salinity fluxes between the ocean and the atmosphere over ice covered areas. Snow and ice are good thermal conductors and have relatively high albedo, but their impact can vary considerably depending on thickness. Sensitivity studies using several global circulation models have also indicated that accurate values for the snow and ice thicknesses are required for consistent predictions.
Comparison to other instruments
Feasibiltiy of concept
The results of ground-based experiments suggest to us that observations of diffuse halos can indeed be used to estimate sea ice thickness (see Table 1 in Haines et al. 1997).
Experimental setup of in-situ ice thickness measurements in Haines et al. (1997). Ice thickness was retrieved using only reflectance measurements; transmission measurements were used only for estimating the anisotropy of brine pockets and absorption by algae.
Ground-based observations suggest that halo observations can also reveal snow thickness. (See VĂ¡rnai, T., and R. F. Cahalan, 2009: Modeling and analysis of offbeam lidar returns from thick clouds, snow, and sea ice. International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, American Nuclear Society, ISBN: 978-0-89448-069-0)
Retrieval methodology
Snow and ice thickness is retrieved by comparing THOR observations to simulated data generated by a three-dimensional Monte Carlo radiative transfer model for a wide range of snow and ice conditions.
Time-integrated return signals for various snow and ice conditions, as simulated by a Monte Carlo radiative transfer model