Numerical study of the circulation and water transport in Beibu Gulf: A short communication

The Beibu Gulf, located in the northwestern South China Sea, is rich in oceanic energy and biological resources. Based on the FVCOM model, a three-dimensional numerical model was adopted in the study, which was validated with the observation data. The results show that Beibu Gulf is a typical diurnal tidal area. The K1 and O1 tide have an amphidromic point near Hue, Vietnam, forming a rotary tidal system. From the amphidromic point, the amplitudes increase gradually, eventually reaching more than 80 cm and 100 cm, respectively. The maximum amplitudes of M2 and S2 tide are about 70 cm and 10 cm, respectively. Meanwhile the tidal current presents a typical rectilinear flow in Beibu Gulf, with strong the diurnal tidal currents. Seasonal changes in the circulation structure of Beibu Gulf are obvious. The Beibu Gulf is generally controlled by a non-closed anticlockwise circulation in winter. In summer, there are two counterclockwise eddies. The tidal residual current flowing through Qiongzhou Strait goes west all year round, with the largest average flow flux of 0.07 Sv in winter. Based on DYE module from FVCOM, pollutants from the Pearl River Estuary pass through Qiongzhou Strait, and reach Weizhou Island after 109 days. This is of great significance to the monitoring and control of red tide, and the protection of marine ecological environment in Beibu Gulf.

Study of the tidal dynamics of the Korea Strait using the extended Taylor method

The Korea Strait (KS) is a major navigation passage linking the Japan Sea (JS) to the East China Sea and Yellow Sea. Almost all existing studies of the tides in the KS employed either data analysis or numerical modelling methods; thus, theoretical research is lacking. In this paper, we idealize the KS–JS basin as four connected uniform-depth rectangular areas and establish a theoretical model for the tides in the KS and JS using the extended Taylor method. The model-produced K1 and M2 tides are consistent with the satellite altimeter and tidal gauge observations, especially for the locations of the amphidromic points in the KS. The model solution provides the following insights into the tidal dynamics. The tidal system in each area can be decomposed into two oppositely travelling Kelvin waves and two families of Poincaré modes, with Kelvin waves dominating the tidal system. The incident Kelvin wave can be reflected at the connecting cross section, where abrupt increases in water depth and basin width occur from the KS to JS. At the connecting cross section, the reflected wave has a phase-lag increase relative to the incident wave of less than 180∘, causing the formation of amphidromic points in the KS. The above phase-lag increase depends on the angular velocity of the wave and becomes smaller as the angular velocity decreases. This dependence explains why the K1 amphidromic point is located farther away from the connecting cross section in comparison to the M2 amphidromic point.

Study on the Tidal Dynamics of the Korea Strait Using the Extended Taylor Method

The Korea Strait (KS) is a major navigation passage linking the Japan Sea (JS) to the East China Sea and Yellow Sea. Almost all existing studies on the tides in the KS employed either data analysis or numerical modelling methods; thus, theoretical research is lacking. In this paper, we idealize the KS-JS basin as three connected uniform-depth rectangular areas and establish a theoretical model for the tides in the KS and JS using the extended Taylor method. The model-produced K1 and M2 tides are consistent with the satellite altimeter and tidal gauge observations, especially for the locations of the amphidromic points in the KS. The model solution provides the following insights into the tidal dynamics. The tidal system in each area can be decomposed into two oppositely travelling Kelvin waves and two families of Poincaré modes, with Kelvin waves dominating the tidal system. The incident Kelvin wave can be reflected at the connecting cross-section, where abrupt increases in water depth and basin width occur from the KS to JS. At the connecting cross-section, the reflected wave has a phase-lag increase relative to the incident wave by less than 180°, causing the formation of amphidromic points in the KS. The above phase-lag increase depends on the angular frequency of the wave and becomes smaller as the angular frequency decreases. This dependence explains why the K1 amphidromic point is located farther away from the connecting cross-section in comparison to the M2 amphidromic point.

Tidal Movement Characteristics Outside the Pearl River Estuary and Its Influence on the Mouths

The hydrology of the Pearl River Estuary is controlled both by river discharge and tide, where water and sediment move through eight outlets (mouths) into the sea. Using numerical modeling, this paper examines the characteristics of tidal movement in Pearl River Estuary. Results showed an amphidromic point near Modaomen mouth, and river runoff flows down. From marine dynamics point of view, Modaomen mouth is the main channel for water and sediment transportation of Pearl River. Using the tidal energy, we discuss the change of the sediment near the several entrances during the flood and dry seasons.

Use of the Acoustic Doppler Current Profiler (ADCP) in the study of the circulation of the Adriatic Sea

The results of basin-wide vessel-mounted ADCP measurements carried out from May 1995 through February 1996 in the Adriatic Sea are analysed in order to characterise the tidal flow, the steady current field and some specific sub-basin scale features. The M2 tide shows the amphidromic point close to the location predicted from theory. The K1 presents an almost constant phase structure that increases in the northern part from east to west during summer. The circulation in the Italian coastal shelf area is highly variable, due to the local wind forcing and pulses of the Po River discharge. The propagation of the signal associated with the latter, can be described in terms of hybrid internal Kelvin waves, revealed also from the upwelling events. It is also shown that the bottom density-driven current draining the bottom layer of the northern Adriatic is, to a large extent, a time-dependent feature with a temporal scale on the order of days.Key words. Oceanography: general (descriptive and regional oceanography; marginal and semi-enclosed seas) Oceanography: physical (currents)

Non-linear model of the tides in the Gulf of Carpentaria

A non-linear barotropic model was used to evaluate the tidal regime in the Gulf of Carpentaria. The model was forced by open boundary conditions specified on a line joining Wessel Islands to False Cape and a volume flow through Torres Strait estimated from tidal constants on each side of the Strait. The model gives results in agreement with the available observations and in particular predicts mixed tides in the northern half of the Gulf and diurnal tides in the south-east corner of the Gulf. The diurnal tide consists of a Kelvin wave entering the Gulf in the north-west and propagating clockwise around the Gulf with one amphidromic point. The higher frequencies of the semidiurnal tides allow the generation of a first-mqde Poincare wave and the trapping of energy in the northern half of the Gulf. Amphidromes near Mornington Island and Groote Eylandt are also predicted, as is a region of low amplitude and rapid phase variations in the centre of the Gulf.

Numerical modal of the tides in the Gulf of Carpentaria and the Arafura Sea

A numerical model of the tides in the Gulf of Carpentaria and the Arafura Sea is described and its results presented. The model is linear. time-independent and uses curved boundaries. The results show that the diurnal tide has an amphidromic point near the centre of the Gulf of Carpentaria and that the semidiurnal tide has two amphidromic points-one in the north of the Arafura Sea and a second, virtual one, at Mornington Island. The model also shows that both frictional and resonant effects are important in determining the tides of the region.