Satellite altimetry observations of the Black Sea level

Abstract

The paper is devoted to the application of satellite altimetry from the TOPEX/Poseidon and ERS‐1 missions to the Black Sea. We use the NASA Ocean Altimeter Pathfinder Project collinear data set and monthly climatic hydrography to restore the dynamical sea level, that which connected with the Black Sea circulation. Two realizations are created from collinear and grid data sets. The Black Sea hydrographic survey data collected by the Cooperative Marine Science Programme for the Black Sea are used for validation of both products. The estimated rms accuracy of the Black Sea dynamical level is about 3 cm. The grid data product is used for the analysis of seasonal and mesoscale variability of the Black Sea level. The observations show that the Black Sea circulation has strong seasonal variation. It attenuates in summer to autumn and intensifies in winter to spring. This variability is accompanied by a western‐phase propagation of the sea level. A simple two‐layer model of the wind‐induced circulation in the rectangular basin provides an interpretation of these results. It is shown that the seasonal variability of the geostrophic circulation is most likely produced by the annual changes of the wind stress curl. The western phase propagation is treated as the radiation of Rossby waves from the eastern coast of the basin. Typical periods of the mesoscale oscillations of the dynamical sea level are estimated from the TOPEX/Poseidon altimeter time series in different parts of the Black Sea by means of a spectral analysis. The strongest mesoscale oscillations have periods of about 120 days and are located in the southeastern part of the basin, where the Rim Current bifurcates, and off the Crimean peninsula, where the Rim Current meanders as a result of the local orography.