Mesoscale variability in the Black Sea: satellite observations and laboratory experiments

Blokhina, Marina (2003) Mesoscale variability in the Black Sea: satellite observations and laboratory experiments. Masters thesis, Memorial University of Newfoundland.

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Abstract

The circulation in the Black Sea is characterized by a strong basin-wide current along the shore in the cyclonic direction known as the Rim Current. Satellite and field data demonstrate that this circulation is subject to mesoscale variability in the form of meanders, intense jets, eddies and filaments. In this thesis the surface circulation of the Black Sea is simulated in the laboratory experiments and analyzed using the satellite data. This work focuses on improvement of methods for analyzing the satellite images in order to investigate the Black Sea mesoscale dynamics and to understand the physics of eddies, air-sea interaction and circulation. In this work we develop a new approach to the measurement of velocity and vorticity fields of the upper layer of the Black Sea, using direct observations made by National Oceanic and Atmospheric Administration (NOAA) Advanced Very-High Resolution Radiometer (AVHRR) during 2000-2002 years. The analysis is based on the Maximum Cross Correlation (MCC) analysis and Particle Image Velocimetry (PIV) method. The application of these two techniques to the Black Sea investigation reveals the large scale dynamic feature of circulation, as well as many details of mesoscale vortical activity. The results demonstrate the main characteristics of the Black Sea circulation. In particular, the Black Sea Rim Current is well defined by an average velocity of 20 cm/s. The Rim Current intensifies along the Turkish coast and displays a meandering structure with essential seasonal variability. -- The unstable cyclonic boundary current was modeled in a new series of laboratory experiments on a rotating platform using a scaled model of the Black Sea. The dynamical similarity of the important dimensionless control parameters, including the normalized Rossby deformation radius, the Rossby number and the Ekman number, was satisfied in the experiments. The results demonstrate the development of baroclinic instability due to fresh water discharge imitating the river inflow in the Black Sea. Persistent transient features of the circulation, such as the so-called Batumi Eddy and the Sevastopol Eddy as well as other features, were reproduced in the experiments when the background rotation rate of the system was varied.

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