Jamshidi, Siamak
(2012)
Variations Of Seawater Properties Of The Southwestern Coastal Waters Of The Caspian Sea.
PhD thesis, Universiti Sains Malaysia.
Abstract
The Caspian Sea is the largest inland saltwater body in the world, but only a few
studies have been conducted on the variations of seawater properties in its southern coastal
waters. This study carried out to determine seawater properties and sea currents for the
purpose of investigating the stratification in water column and interactions among the
physical, water quality, and biological components of the seawater properties. Field
measurements were conducted using two methods: CTD probe profiling deployed once
during each of the four seasons (i.e., winter, spring, summer, and autumn) and using current
meter. The collected data were analyzed using polynomial functions and cubic interpolation
techniques in Matlab programming and regression modeling.
Results showed that the significant changes in seawater properties occurred primarily
within the upper 100 m layer. The seawater temperatures recorded were 9–11 °C (March),
18–19 °C (April), 27–29 °C (August), and 19–20 °C (November) near the surface. A
seasonal thermocline was detected between 20 and 50 m depth in summer at a temperature
gradient of 16 °C. The subsequent destruction of the thermocline layer occurred with the
general cooling of the surface water and deepening of the mixed layer toward the end of
autumn and winter. The mean value of the seawater salinity was 12.33 ppt which its lowest
and highest values were recorded in March and August, respectively. The variations in
seawater density within the upper 100 m layer were considerable (between 1005.78 and
1010.75 kg m-3), but below this layer, the value remained around 1010 kg m-3. The vertical
variations in density agree with variations of temperature in water column, and a pycnocline
was observed at the location of the thermocline. The maximum speed of sound in seawater
was observed at the surface layer, between 1517–1519 m s–1 in August. This value decreased
to about 1453 m s–1 below 450 m.
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