Characteristics and seasonal variability of internal tides in the southern South China Sea. (April 2015)

• Record Type: Journal Article
• Authors: Shang, Xiaodong; Liu, Qian; Xie, Xiaohui; Chen, Guiying; Chen, Rongyu
• Is Part Of: Deep sea research. Volume 98(2015)
• Page Start: 43
• Page End: 52
• Publication Date: 2015-04
• Subjects: Internal tides -- Seasonal variation -- South China Sea; Oceanography -- Periodicals; Océanographie -- Périodiques; 551.4605
• DOI: 10.1016/j.dsr.2014.12.005
• Languages: English
• ISSNs: 0967-0637

Abstract

Abstract: Two sets of current mooring records at the same location are used to investigate the generation and temporal variation of internal tides (ITs) near reefs in the southern South China Sea (SCS). The total records covered more than 900 days. ITs in this region are dominated by mode-1 diurnal motions, which are mainly composed of O 1, P 1 and K 1 constituents. The major axes of both diurnal barotropic and baroclinic tidal ellipses are oriented in the northeast-southwest direction. The ITs over the entire observation period clearly show an approximately 14-day spring-neap cycle. Meanwhile, the diurnal ITs also displayed an evident seasonal change: their energy was higher in summer and winter than in spring and autumn. The modal decomposition of diurnal motion shows that their time-averaged kinetic energy in summer and winter was about 1.2 kJ/m 2, which was approximately 60% higher than the values in spring and autumn. The same seasonal variation also occurred at the diurnal barotropic tides with prominent O 1, P 1 and K 1 constituents. Because stratification does not show a significant seasonal variation in the southern SCS, the enhanced diurnal ITs in winter and summer can be attributed to the barotropic forcing with the semi-annual cycle caused by the modulation of diurnal P 1 and K 1 . Highlights: Long-term mooring data are first used to investigate the ITs in the southern SCS. ITs in this region are dominated by mode-1 diurnal motions. The diurnal ITs displayed an evident seasonal change. The enhanced semi-annual cycle of diurnal ITs was due to modulation of P 1 and K 1 .