Tidal distortion caused by the resonance of sexta‐diurnal tides in a micromesotidal embayment

Abstract

Double high water and double‐peak flood current were observed in Daya Bay (DYB), China, which is a shallow, mixed, mainly semidiurnal‐tide dominated bay with a micro to mesotidal range. Harmonic analysis reveals that the quarter and especially the sexta‐diurnal constituents are getting much stronger as tides propagating into the bay. The astronomical tides‐induced tidal asymmetry is yet dominant at the bay entrance but overtaken by the sexta‐diurnal tides at the end of the bay. Both the M4 and M6 tide meet the requirement proposed in previous studies but still unable to produce a double high water alone. Therefore, the conditions to produce a double high water between a fundamental tide and its higher harmonics need to be revisited. Analytical solutions were obtained in this paper, which fit the numerical solutions very well. Modeling result indicates M6 alone with M2 can produce the double high water in DYB but limited in some regions, while the combination of M2, M4, and M6 tides would enhance the capability. The amplification of sexta‐diurnal tides in DYB is dominated by resonance and followed by shoaling effect. Bottom friction damped M6 a lot and largely confined its amplification. However, the quadratic friction and other nonlinear processes are just responsible for about 10% of the total M6 increase.

Impacts of human activities on tidal dynamics in a sexta-diurnal tidal resonant bay

“…No winds or rivers are given as only tidal dynamics are studied. The model for 2014 (hereinafter R14) has been fully described in Song et al (2016). The model configurations for 1989 (hereinafter R89) are the same as those in 2014, including the open boundary forcing, bottom friction coefficient, and other model settings (except the coastline and bathymetry).…”

“…The robust T_TIDE harmonic analysis program (Pawlowicz et al 2002;Leffler and Jay 2009) is adopted. As in Song et al (2016), tidal constituents P 1 and K 2 are inferred from K 1 and S 2 , respectively, using the amplitude factors and phase offsets obtained from a 1 year data set with 1 h intervals at the DW station ( Fig. 1) read from tidal tables.…”

“…There are more than 50 islands, but no major rivers discharge into the bay. It is a tidally dominated bay but has a poor water exchange rate (Song et al 2016). DYB has rich biological resources (Song et al 2004;Wu et al 2009), but it is suffering due to intensive human activities in recent years (Li et al 2015).…”

“…This paper aims to study the changes of tidal dynamics associated with development of the coastline of DYB. The bay is one of two with sexta-diurnal tidal resonance along the South China coast (Song et al 2016). It is interesting to learn how human activities affect the shallow-water tidal resonance, and it is of great significance to the protection of local marine environment.…”

Tidal Distortions Related to Extreme Atmospheric Forcing Over the Inner Shelf

“…Distortions of tidal waves, also known as overtides and compound tides (e.g., Le Provost, ), have been documented since the late 1800s (Craik, ). Their control on water, sediment, and nutrient transport in estuaries has motivated extensive study through combinations of theory and observations (Friedrichs & Aubrey, ; Grenier et al, ; Inoue & Garrett, ; Le Provost, ; Song et al, ; Stanev et al, ). Recent efforts have focused on power extraction (Neill et al, ), eco‐morphological evolution (Stark et al, ), and morphodynamic variability (Guo et al, ).…”