Assessment the Synoptic Variability of Vertical Thermal Structure in Baltic Sea Waters on the Base of in-situ Measurements

The thermal regime of sea's active layer is determined by its interaction with atmosphere, thermal balance, wind and convective water mixing. The question about assessment of synoptic variability of thermal stratification in Baltic Sea waters has not yet solved. The purpose of the present work was to determine the bounds of synoptic variability of vertical temperature profiles T(z) at the all seasons on the example of Bornholm Basin in the Baltic Sea. On the base of the large array of episodic measurements at the international stations BY, situated in key regions of the Baltic Sea, the principles of annual rhythmic of vertical distribution of water temperature are given in the paper [1]. However, this data does not allow separate the synoptic variability from seasonal and inter-annual diapasons, since measurements at fixed horizon belong to different synoptic events at different years. During 1978-1988 the State Oceanographic Institute (Leningrad/Saint-Petersburg Branch) on the base of Russian RV "Rudolf Samoylovich" was carrying out observations of hydrological and hydro-chemical elements of Baltic Sea waters at the stations BY [2]. The originality of carried out work is that for the first time continuous series of measurements for elements of vertical thermo-haline structure with duration from day to several months and discreteness of 3 hour were executed. These observations got name "Multi-daily Stations". This data alongside with the data of episodic observations allows separate synoptic variability of water temperature profile and assess its degree. Vertical thermal structure of sea waters has been typified based on the parameters of profile geometry. The degree of synoptic variability in each element of profile T(z) for all the seasons has determined. It has been showed, that the enthalpy is the optimal thermal regime parameter for separating the synoptic diapason from others. It has also been showed, that synoptic variability of water temperature in deep layer is not significant. References 1. Terziev, F.S., Rozhkov, V.A., Smirnova, A.I.// Hydrometeorology and Hydro-chemistry of USSR seas, Vol. III. The Baltic Sea, Issue 2. Hydro-chemical Conditions and Oceanographic Basis for Biological Productivity, pp. 149-197, 1994 2. Davidan, I.N., Gusev, A.K., Savchuk, O.P., Chernyshova, E.S., Shadrin, P.S.// Representativity of seasonal surveys in the Baltic sea/ Proc. of III BASYS Annual Science Conf., Warnemünde, Germany, 20 - 22.09.1999. Paper SP 8 - 7, p. 83