Study of physical properties and surface circulation of the Caspian Sea using HYCOM model

The Caspian Sea, the world’s largest inland enclosed body of water, is divided into three distinct basins: northern, middle, and southern (Aubrey et al., 1994). Its enclosed nature, combined with the growing intensity of oil extraction in recent years, has raised significant concerns regarding biological contamination. The Caspian Sea is of considerable scientific interest due to its unique oceanographic characteristics. Given the scarcity of observational data in the region, numerical modeling provides an effective approach for advancing our understanding of the physical processes occurring in the sea. Over the past decade, several numerical models have been employed to investigate the physical oceanographic properties of the Caspian Sea. For instance, Ibrayev et al. (2010) and Gunduz and Özsoy (2014) explored seasonal circulation using a coupled model incorporating sea hydrodynamics, air-sea interactions, and sea ice thermodynamics. Kara et al. (2010) used the HYCOM model to examine the influence of freshwater inflows on seasonal variations in salinity and the surface circulation patterns of the Caspian Sea. Shieh et al. (2016) applied the COHERENS (Coupled Hydrodynamical Ecological Model for Regional Shelf Seas) framework to assess the impact of wind and thermal forcing on seasonal variability in the basin. In this study, we use the HYCOM ocean model to investigate key physical parameters—temperature, salinity, and density—as well as the circulation patterns of the Caspian Sea. A notable feature of our approach, in contrast to earlier works such as Shieh et al. (2016), is the inclusion of sea ice processes. Ice plays a critical role in the northern Caspian due to its significant thermodynamic influence on the distribution of temperature and salinity.