On the generation and evolution of internal solitary waves in the southern Red Sea

Satellite observations recently revealed trains of internal solitary waves (ISWs) in the off-shelf region between 16.0 degrees N and 16.5 degrees N in the southern Red Sea. The generation mechanism of these waves is not entirely clear, though, as the observed generation sites are far away (50 km) from the shelf break and tidal currents are considered relatively weak in the Red Sea. Upon closer examination of the tide properties in the Red Sea and the unique geometry of the basin, it is argued that the steep bathymetry and a relatively strong tidal current in the southern Red Sea provide favorable conditions for the generation of ISWs. To test this hypothesis and further explore the evolution of ISWs in the basin, 2-D numerical simulations with the nonhydrostatic MIT general circulation model (MITgcm) were conducted. The results are consistent with the satellite observations in regard to the generation sites, peak amplitudes and the speeds of first-mode ISWs. Moreover, our simulations suggest that the generation process of ISWs in the southern Red Sea is similar to the tide-topography interaction mechanism seen in the South China Sea. Specifically, instead of ISWs arising in the immediate vicinity of the shelf break via a hydraulic lee wave mechanism, a broad, energetic internal tide is first generated, which subsequently travels away from the shelf break and eventually breaks down into ISWs. Sensitivity runs suggest that ISW generation may also be possible under summer stratification conditions, characterized by an intermediate water intrusion from the strait of Bab el Mandeb.

Citation

Guo D, Akylas TR, Zhan P, Kartadikaria A, Hoteit I (2016) On the generation and evolution of internal solitary waves in the southern Red Sea. Journal of Geophysical Research: Oceans 121: 8566–8584. Available: http://dx.doi.org/10.1002/2016JC012221.

Acknowledgements

The authors would like to thank Prof. Sigurjon Jonsson and Wenbin Xu for ordering and helping process the satellite SAR images from European Space Agency: https://earth.esa.int/web/guest/data-access, and the ARAMCO Oil Company for supplying sea level data from tide gauges. The authors would also like to thank the anonymous reviewers and editors for their valuable comments and suggestions. The research reported in this manuscript was supported by King Abdullah University of Science and Technology. This research made use of the resources of the Supercomputing Laboratory and/or computer clusters of King Abdullah University of Science and Technology. The data used in this study could be requested from the corresponding author (Ibrahim.hoteit@kaust.edu.sa).