Seasonal variation of the double diffusion processes at the Strait of Hormuz
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Seasonal variation of the double diffusion processes at the Strait of Hormuz AZIZPOUR Jafar1*, CHEGINI Vahid1, SIADATMOUSAVI Seyed Mostafa2 1 Iranian National Institute for Oceanography and Atmospheric Science, Tehran 1411813389, Iran 2 Iran University of Science and Technology, Tehran 1684613114, Iran
Received 14 November 2015; accepted 24 February 2016 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2017
Abstract
Profiles of salinity and temperature were measured in the strait of Hormuz (SH) during the winter of 2012, spring and summer of 2013. To investigate the double diffusion (DD) processes, Turner (TU) angle values are calculated in all the stations in the SH. Different TU angle values correspond to salt fingering (SF), diffusive convection (DC) and stable stratification. The distributions of the two forms of DD were plotted vertically along transects in the eastern, central and western part of the SH, and corresponding DD processes were described. The results show that both SF and DC occurred in most part of the study area. Two different water masses (the Indian Ocean surface water and the Persian Gulf water) were evident at the SH, and SF and DC were evident at the interface of two water masses. Due to evaporation, SF occurred in the surface layer of most Stations throughout the year. In the eastern part of the SH, occurrences of DC were more feasible in wintertime. SF was the main phenomenon at the end of hot season. For central part, SF occurred throughout the year in water column. In the western part, water column was stable in summer and DC happened in most part of water column in winter. Key words: double diffusion, diffusive convection, salt fingering, Turner angle, Strait of Hormuz Citation: Azizpour Jafar, Chegini Vahid, Siadatmousavi Seyed Mostafa. 2017. Seasonal variation of the double diffusion processes at the Strait of Hormuz. Acta Oceanologica Sinica, 36(1): 26–34, doi: 10.1007/s13131-017-0990-6
1 Introduction The Persian Gulf (PG) is a shallow, semi-enclosed basin, which is connected to the Gulf of Oman and Indian Ocean through the Strait of Hormuz (SH). The Persian Gulf water (PGW) is one of the most saline water masses in the world. The PGW flushes out of the PG as a deep outflow and induces a surface inflow of the Indian Ocean surface water (IOSW), driving an inverse-estuarine type water exchange through the SH (Johns et al., 2003; Yao, 2008). Indeed the SH plays a critical role in determining the circulation in the PG by constricting the water exchange between the PG and the open ocean. Water exchange through the SH is forced primarily by the large annual evaporation over the PG, which drives fresher inflow of water from the Gulf of Oman in the northern part and a deep outflow of dense water from southern part of the SH (Fig. 1). These two water masses exist throughout the year in the SH. The SH located on a boundary between the extra-tropical weather system from the northwest, and the tropical weather system of the Indian Ocean from southeast, which are aff
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