Report of a Physical Oceanography Research Project over the Southern Continental Shelf of the Caspian Sea

Abstract The study presents monthly variations of seawater properties, monitoring water column stability and stratification over the southern shelf of the Caspian Sea which depends on collecting data. Field measurements were carried out during 13 cruises along the southern boundary of the sea. Spatial and temporal distributions of temperature, salinity and density were investigated. Monthly changes of water temperature at the sea surface (ΔT 20 C   ) were under influence of the climate changes in the region. Physical structure of water column in the southern Caspian Sea is characterized by a significant seasonal thermocline formed approximately between 20-50m depths. Water column out of the shelf was strongly stratified in midsummer (ΔT 16 C   ). Shallow water over the continental shelf was moderately well mixed. Destruction of the thermocline occurred with the general cooling of the sea surface water and deepening of the mixed layer from late of autumn to mid winter. Frequency of stability across the surface mixed layer and thermocline was more than deeper levels. Structures of thermocline and pycnocline were characterized by a significant homogeneity, especially in offshore stations during the year. Because of high correlation between density and temperature in the Caspian Seawater, a strong seasonal pycnocline was observed in the position of the thermocline. Monthly changes of physical characteristics of seawater were mainly limited to the upper 100 m layers. Below this layer, monthly changes of seawater parameters were minor. Variations of salinity were about 12.4 during the time of measurements.