Iranian Journal of Geophysics

Iranian Journal of Geophysics

Seasonal changes of stability and double diffusive processes in the pit of the Strait of Hormuz

Document Type : Research Article

Authors
Farzaneh Mohammadpour 1
Maryam ُSoyuf Jahromi 2
Samad Hamzei 3
1 M.Sc., Department of Nonliving Resources of Atmosphere and Ocean, Faculty of Marine Science and Technology, University of Hormozgan, Bandar Abbas, Iran
2 Assistant Professor, Department of Nonliving Resources of Atmosphere and Ocean, Faculty of Marine Science and Technology, University of Hormozgan, Bandar Abbas, Iran
3 Assistant Professor, Iranian National Institute for Oceanography and Atmospheric Science, Tehran, Iran
10.30499/ijg.2024.435204.1565
Abstract
Oceanic pits are often unknown due to their enclosed nature and lack of exchange with the surrounding environment, and they are often overlooked and neglected by researchers. The study area of the current research is a pit located in the Strait of Hormuz, near the south of Greater Tunb Island, which has not been previously studied. Its depth is more than 185 meters, with longitude coordinates of 55.321 degrees East and latitude of 26.122 degrees North. However, the depth of these coordinates has been recorded as 68 meters on GEBCO's international website. The seasonal data used are temperature and salinity obtained from one seasonal field measurement of the Persian Gulf Explorer in 2018 which were measured using a CTD (Conductivity, Temperature, and Depth) instrument with a time step of one second. Then the related graphs of temperature, salinity and potential density were plotted and analyzed in Ocean Data View (ODV) software package. Moreover, the Brunt-Väisälä buoyancy frequency and Turner’s angle were calculated and plotted using ODV. The average values of each component were calculated by the weighted averaging method in ODV. The results showed that the pit is generally stable. The surface layer of winter had a higher density than the other seasons, but the summer unexpectedly had a higher density than the other seasons in the deep trapped water of the pit. The results also showed that all three states of stability, instability and double diffusion convection occur in all seasons in the pit. The layers which mostly consist of double diffusion convection were observed in the following order: summer, winter, spring and autumn, respectively. The salt finger regime in warm seasons (spring and summer) and the diffusive convection regime in cold seasons (autumn and winter) had a greater contribution to creating double diffusion convection. The strong diffusive regime in warm and cold season  seasons was9% and 4%, respectively, and the weak diffusive regime in warm and cold season seasons was 5% and 22%, respectively. Meanwhile, the strong salt finger regime in warm and cold seasons was 18% and 8%, respectively and the weak salt finger regime in warm and cold seasons was 21% and 9%, respectively. The relationship between temperature and stability clearly showed that there was no seasonal thermocline layer in autumn and winter. In summer, the thermocline layer is stable and the surface mixed layer was highly unstable. Surprisingly, both the most stable and unstable layers were located in deep waters of spring. In general, autumn was the most stable season and spring was the most unstable season according to the measured data of the Persian Gulf Explorer (2018) in the pit of Strait of Hormuz, near the south of Greater Tunb.
Keywords
Brunt-vaisala frequency
diffusive convection
double diffusion
ODV
salt fingering
turner angle

Subjects

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Iranian Journal of Geophysics
Volume 19, Issue 6
January and February 2026
Pages 31-43