مدل سازی عددی توده ی آب چگال خزر شمالی با استفاده از مدل HYCOM

This study investigates the formation of dense water masses in the northern Caspian Sea and their effects on the outflow through the Apsheron Strait. To achieve this, the ocean model HYCOM was used for a 10-year period (1992–2001). The model has a horizontal grid resolution of approximately 3.5 km and consists of 49 hybrid layers. The barotropic and baroclinic time steps were set at 18 and 180 seconds, respectively. The equation of state is based on the UNESCO equation with 17 degrees of freedom, and the Mellor–Yamada turbulence scheme with a 2.5-level closure was applied. In this study, sea ice was included in the model, which is often neglected in previous works, resulting in a longer model run time compared to past studies. The results show that in some parts of the northern Caspian Sea, water begins to freeze in late autumn, with the ice thickness reaching up to about 55 cm. Considering the process of ice formation in marine environments, variations in salinity beneath the ice layer were also examined, showing the highest salinity values during the cold seasons, reaching up to approximately 14 PSU. The results further indicate that the outflow velocity, which is directly influenced by atmospheric forcing, varies not only across different months of the year but also between different years. For instance, a comparison of outflow variations between 1997 and 2001 shows that the velocity in 2001 was higher than the average velocity in 1999. This difference could be attributed to changes in atmospheric forcing or to the filling time of the northern Caspian Sea basin.