Field measurements during the Barex-95 expedition in the marginal ice zone of the Barents Sea provided new data of solar radiation under different conditions of cloudiness and sea ice cover during the thawing. We found a strong dependence of angular and spectral redistribution of radiation on cloud optical thickness and surface albedo. We developed a Monte Carlo model for radiative transfer through a homogeneous cloud layer above sea ice with given concentration and homogeneous snow on top. This simple Monte Carlo model reproduced the observed angular distribution of solar intensity and cloud albedo as a function of solar zenith angle, optical thickness of the clouds, and surface albedo. The model allowed us to estimate the influence of surface tilt on irradiance and to give a qualitative explanation of how the sea ice relief transforms during summer. Data of short wave radiation below clouds enabled the estimation of the effect of clouds on the distribution of radiative heating of the upper ocean for spectral ranges 350--1000 and 400--700 nm (photosynthetically active radiation range). Spectral sensitivity of absorption of solar radiation in clouds relatively decreases radiative heating in the upper centimeters of the water up to 25 and 5% for 350--1000 and 400--700 nm, respectively. ¿ 2001 American Geophysical Union