The Black Sea general circulation and climatic temperature and salinity fields

Abstract

The Black Sea is a nearly enclosed ocean basin, exhibiting many features common with larger ocean basins. Lacking an open boundary and having a limited exchange with sources of fresh and salt water, this basin is an ideal laboratory for developing and evaluating numerical circulation models. The present report describes one numerical model of the Black Sea, developed by Bulgarian and Russian scientists. The new approach has the advantages of both diagnostic models (incorporation of experimental data) and prognostic models (producing hydrodynamical adjustment and filtered fields). Successive application of diagnostic and prognostic models is used. The temperature and salinity fields obtained from observations, and currents obtained from diagnostic models, are used as the initial approximation to the prognostic model. Judicious selection of an integration time prevents over-smoothing of the results while preserving the stability of the solution. Using this model, caculations have been made at 25 levels over a grid interval of 0.25° (latitude) by 0.5°. Input data consist of nearly 50,000 observations taken over nearly 100 years, averaged over 0.5° by 0.5° cells. Seasonal fields of temperature, salinity, and velocity form the output of these experiments. The results provide the basis for various hypotheses that must be tested using future field observations and more sophisticated models.