Abstract
Various CTD data obtained in the Oman Sea are analyzed to explain structural features of intrusive layering. Special attention is compensated to thermohaline intrusions observed in layers (depth ranges of 150 m to 450 m, 150 m to 350 m, 100 m to 350 m and 150 m and 400 m in the winter, spring, summer and autumn, respectively). The temperature and salinity profiles in thermohaline intrusion have sawtooth structure in all stations, while they have step structure in density field. Based on interpretations, detailed estimates of thickness are about 10 to 20 meters. The T-S diagrams show the positions of the outflow intrusion with different thicknesses and depths for all seasons in the Oman Sea. Vertical profiles of temperature and salinity show two boundaries in the upper and lower layers. They are prone to double diffusive convection. Salt fingering and diffusive convection can be seen in both the upper and lower boundaries, and salt fingering is stronger at the lower boundary. Diffusive convection also is visible from the surface to the mid-depth of the plume outflow, and the diffusive intrusion is more severe at the upper boundary than the surface and deep. The intensity of double diffusion in the bottom border is greater than the upper boundary. At the deeper parts, the stratification is completely stable. Variations of the positions of greatest salinities in different diagrams are due to changing water masses for different locations and depths and paths of intrusive flow.
Highlights
Diffusive convection is visible from the surface to the mid-depth of the plume outflow, and the diffusive intrusion is more severe at the upper boundary than the surface and deep
Vertical profiles and the cross-sections of temperature, salinity and potential density in Oman Sea along the Persian Gulf outflow indicate the seasonal variation of vertical extension as well as the depth of the intrusion between the Strait of Hormuz and the Ra’s Al Hadd
Persian Gulf outflow enters the Oman Sea with high salinity, these isopycnal waters intrudes into the Oman Sea and creates a tongue of warm and salty water in subsurface, overlying colder and fresher water
Summary
[8] has investigated in some parts of the Persian Gulf and Oman Sea there are complex layered structures and inversions in vertical profiles of salinity and temperature. [12] studied thermohaline intrusion layers in the frontal zone in the North Pacific Ocean that is prone to salt fingering They showed that salinity inversions in thermohaline structure are due to intrusive movements. [14] estimated turbulent diapycnal eddy diffusivity and small-scale mixing processes throughout the Sermilik Fjord They concluded that double-diffusive convection in thermohaline staircase structure was between the depths 150 - 450 m, in the open ocean in which the water of this Fjord enters. The focus of our investigation is to study the lateral convection across the Persian Gulf outflow front and structure of interleaving of the thermohaline front in the Oman Sea in different seasons using field data.
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