Snapshot observation of physical structure and stratification in deep-water of the South Caspian Sea (western part)
Abstract. In this article, we describe physical parameters structures and different water masses using CTD measurements in southwestern part of the Caspian Sea (CS) in adjacent to Anzali Port (AP). CTD profilings were conducted along a transect perpendicular to the coastline over 13 stations from the coast down to 720 m in winter 2008. According to the results the continental shelf waters are located in surface mixed layer. Surface mixed layer extends itself down to almost 100 m in outer areas of the continental shelf with a weak seasonal thermocline layer between 80 to 140 m. Freshwaters inflow of local rivers is clearly seen outside continental shelf at the surface layers. Investigating the dissolved oxygen reveals that winter convection is traceable down to 500 m in the lateral waters over the shelf break. Among the deeper stations that are located in continental rise and abyssal plain, 350 m seems to be threshold for penetration of seasonal changes; therefore deeper waters tend to be impermeable against seasonal variances. Despite to the small variations, stability is positive in most region of the study area and temperature plays an important role in static stability and in triggering the lateral mixing. In view of both temperature-salinity and temperature-oxygen distributions in the southwestern part of the CS, three different water masses are separable in cold phase. Snapshot observation of physical properties in the early winter 2008, to some extent revealed that a mixing was triggered at least in the lateral waters of the study area.