Determination of the lower boundary of the ocean upper mixed layer

Two new methods are considered for determination of thickness of the upper mixed Layer (UML) aimed calculations of large amounts of hydrological observations. The first method is an example of a pure gradient manner of the determination of the lower UML boundary: the correlation between gradients bellow UML and maximum gradients in seasonal thermocline (picnocline) is found. The second method is based on assumptions of hydrological profile structure and optimum approximation in the sense of a root-mean square deviation of the real and automodel profiles. An Universal method for determination of structural elements of profiles is found. Calculation programmes for both methods by using daily temperature profiles for a five-year period (Weather station ''C'') and one survey from 105 hydrological stations for Newfoundland Energy Active area are checked, and good coincidence with real results of the determinations of the UML lower boundary in this region is shown.