  For accurate forecast of climate change, sea ice mass balance, ocean
circulation and sea- atmosphere interactions is required to have long term
records of Sea Ice Thickness (SIT). Different approaches have been applied to
retrieve SIT and only satellite altimetry, radar or laser, have been proven to
provide hemispheric estimates of SIT distribution over a sufficient thickness
range. To simplify the algorithm for SIT retrieval from RA, constant ice
density has been applied until now, which lead to different results for derived
SIT and SID, in dependence on input information for sea ice density and snow
depth. The purpose of this paper is to select algorithm for SID and SIT
retrieval from RA, using statistical, sensitivity analyses and independent
observations of SID from moored ULS, or on Submarine. The impact of ice density
and snow depth on accuracy of the retrieved SIT has been examined, applying
sensitivity analyses, and the propagated uncertainties have been summarised.
Accuracy of algorithms for snow depth retrieval in the Arctic have been
discussed and it is concluded that the assumption of half snow depth over First
Year Ice (FYI) will lead always to underestimation of SIT and SID derived from
RA and is not applicable for SIT retrieval from RA, using the equation for
hydrostatic equilibrium. Algorithms for freeboard depended ice densities and
SIT retrieval from RA have been developed and a FD algorithm for SIT retrieval
from RA has been selected, based on statistical, sensitivity analyses and
comparison with collocated observations of SID from moored ULS and on Submarine
. ESA (ERS1, 2, ENVISAT, CryoSat2), future ESA (Sentinel) and NASA satellite
and airborne missions, climate and numerical forecast programs will benefit the
results of this paper.
