The problem of the solar radiation heat assimilation in the stratum of the ice hummock sail is considered within the frameworks of the problem of quantitative description of hummocky formation evolution. The technique of experimental investigations and the measuring means are described. The results are given of observations on the solar radiation weakening in the stratum of ice hummocks and level ice carried out at the North Pole-35 drifting station and during the Arctic-2008 expedition on board the scientific-research vessel Akademik Fedorov. It is demonstrated that the ice hummock sail stratum assimilates 20-50% of solar radiation more than the level sea ice. The possible explanation of this phenomenon is proposed based on morphometric peculiarities of ice hummock formation.