Effects of wave-current interaction on the waves, cold-water mass and transport of diluted water in the Beibu Gulf

Wave-current interaction and its effects on the hydrodynamic environment in the Beibu Gulf(BG) have been investigated via employing the Coupled Ocean–Atmosphere–Wave–Sediment Transport(COAWST) modeling system. The model could simulate reasonable hydrodynamics in the BG when validated by various observations.Vigorous tidal currents refract the waves efficiently and make the seas off the west coast of Hainan Island be the hot spot where currents modulate the significant wave height dramatically. During summer, wave-enhanced bottom stress could weaken the near-shore component of the gulf-scale cyclonic-circulation in the BG remarkably, inducing two major corresponding adjustments: Model results reveal that the deep-layer cold water from the southern BG makes critical contribution to maintaining the cold-water mass in the northern BG Basin.However, the weakened background circulation leads to less cold water transported from the southern gulf to the northern gulf, which finally triggers a 0.2℃ warming in the cold-water mass area;In the top areas of the BG, the suppressed background circulation reduces the transport of the diluted water to the central gulf. Therefore, more freshwater could be trapped locally, which then triggers lower sea surface salinity(SSS) in the near-field and higher SSS in the far-field.

Effects of tidal currents on winter wind waves in the Qiongzhou Strait:a numerical study

Effects of currents on winter wind waves in the tide-dominated Qiongzhou Strait(QS)were numerically evaluated via employing the coupled ocean-atmosphere-wave-sediment transport(COAWST)modeling system.Validations showed satisfactory model performance in simulating the intense tidal currents in the QS.Different effects of sea level variations and tidal currents on waves were examined under the maximum eastward(METC)and westward(MWTC)tidal currents.In the east entrance area of the QS,the positive sea levels under the MWTC deepened the water depth felt by waves,benefiting the further propagation of wave energy into the inner strait and causing increased wave height.The METC and the MWTC could both enhance the wave height in the east entrance area of the QS,mainly through current-induced convergence and wavenumber shift,respectively.By current-induced refraction,the METC(MWTC)triggered counterclockwise(clockwise)rotation in peak wave directions in the northern part of the QS while clockwise(counterclockwise)rotation in the southern part.

Upwelling off the west coast of Hainan Island: sensitivity to wave-mixing

The coupled ocean atmosphere wave sediment transport(COAWST)modeling system is employed to investigate the role of wave-mixing playing in the upwelling off the west coast of Hainan Island(WHU).Waves,tides and sea surface temperature(SST)are reproduced reasonably well by the model when validated by observations.Model results suggest the WHU is tidally driven.Further investigations indicate that inclusion of wave-mixing promotes the intensity of the WHU,making the simulated SST become more consistent with remote-sensed ones.Dynamically,wave-mixing facilitates the“outcrop”of more upwelled cold water,triggering stronger WHU and leading to a three-dimensional dynamical adjustment.From the perspective of time,wave-mixing contributes to establishing an earlier tidal mixing front strong enough to generate WHU and that is,WHU may occur earlier when taking wave-mixing into consideration.