EN
The dependence of the refractive index of artificial and natural Baltic seawater on temperature, n=,(T), has been investigated.The measurements have been carried out at different wavelengths of visible radiation.A second dependence of the refractive index on temperature has been observed. The changes of refractive index with depth, n=n(z), have been investigated in field measurements in the Baltic Sea. The influence of crude oil emulsion on the refractive index is discussed.