Hindering effects of tides on the intrusion of the Gulf of Aden Intermediate water

Daquan Guo1, Fengchao Yao2, Peng Zhan3, George Krokos4 and Ibrahim Hoteit3, (1)King Abdullah University of Science and Technology, Thuwal, Saudi Arabia, (2)King Abdullah University of Science and Technology, Red Sea Research Center, Thuwal, Saudi Arabia, (3)Earth Sciences and Engineering Program, King Abdullah University of Science and Technology (KAUST), Jeddah, Saudi Arabia, (4)King Abdullah University of Science and Technology, Division of Physical Science and Engineering, Thuwal, Saudi Arabia
As a semi-enclosed marginal sea, the Red Sea communicates with the open ocean through only one narrow strait in the south. It thus features a relatively complete and independent circulation system. The semi-isolation property makes the Red Sea an ideal arena to investigate the tidal influence on the general circulations.

In this study, based on the 3D high-resolution non-hydrostatic Red Sea general circulation model, by configuring with and without tidal forcing implementation, we found that one of the most important circulation feature, the intrusion of GAIW during summer time, is strongly affected by the tidal influences. With the tides included, the along-axis extension of the intrusion has been reduced by maximum of 1.0 degree; the cross-axis transects structure are similar but shows colder feature of intermediate water; the volume transports are reduced by 20 percent on average. Analysis through vertical mixing parameters of the square of Buoyancy Frequency, the square of vertical gradient of along-axis velocity and the logarithm of Richardson number at the base of 10 indicate that the reason is likely due to the enhancement of the vertical movements along the thermocline and near the bottom topography when introducing the tides into the model. The tidal mixing is more likely increasing the roughness of the interfaces between the layers, which enlarges the friction force and results in the hindering of the intrusion.