Seasonal variations of vertical water structure in the deep water of the southern Caspian Sea

Seasonal changes in the vertical structure of temperature and salinity data, during winter, spring and summer in the south Caspian Sea, measured at one Transect and studied at 9 stations during 2013-2014. Comparison of the depth of the mixed layer estimated by two visual and threshold methods. The results showed that the threshold method estimates the depth of the mixed layer less. The depth of mixing layer in winter will be in peak with the air cooling and decreases with the start of the heating season. The temperature in the mixing layer varies in winter, spring and summer, between 10- 12˚C, 5˚16-5˚C and 25.5˚С-25˚C, respectively. The thermocline located on the bottom of the merged layer, consists of two sections, a seasonal thermocline (10-50 m deep) and a permanent thermocline (50-150 m). The seasonal thermocline is caused by the air warming in the spring, and its slope reaches the maximum in summer as the air temperature rises. Under the thermocline is a deep-layer that the temperature and salinity variations are insignificant.

Keywords:

Thermocline , Seasonal variation , Southern Caspian Sea