p. 23 - 30 SPACE-TIME SCALE DEPENDENCE OF THE HORIZONTAL EXCHANGE COEFFICIENTS Vasile Diaconu Romanian Marine Research Institute Constanta Abstract Using sea current time series recorded over the Romanian Black Sea shelf, the increase of the horizontal exchange coefficients from nearshore to offshore waters, as well as the differences in their values above and below the seasonal thermocline were shown. Their dependence on the 2/3 power of the averaging period was preved valid for period up to 12 hours.