Search

A 2D hydrodynamic model is employed to study the characteristics of tidal wave propagation in the Persian Gulf (PG). The study indicates that tidal waves propagate from the Arabian Sea and the Gulf of Oman into the PG through the Strait of Hormuz. The numerical model is first validated using the measured water levels and current speeds around the PG and the principal tidal constituents of Admiralty tide tables. Considering the intermediate width of the PG, in comparison to Rossby deformation radius, the tidal wave propagates like a Kelvin wave on the boundaries. Whereas the continental shelf oscillation resonance of the basin is close to the period of diurnal constituents, the results show that the tide is mixed mainly semidiurnal. A series of numerical tests is also developed to study the various effects of geometry and bathymetry of the PG, Coriolis force, and bed friction on tidal wave deformation. Numerical tests reveal that the Coriolis force, combined with the geometry of the gulf, results in generation of different amphidromic systems of diurnal and semidiurnal constituents. The configuration of the bathymetry of the PG, with a shallow zone at the closed end of the basin that extends along its longitudinal axis in the southern half (asymmetrical cross section), results in the deformations of incoming and returning tidal Kelvin waves and consequently the shifts of amphidromic points (APs). The bed friction also results in the movements of the APs from the centerline to the south border of the gulf.

The effects of sea-level rise on the future morphological functioning of estuaries are largely unknown because tidal amplitudes will change due to combined deepening of the estuary mouth and shifting amphidromic points at sea. Fluvial sediment supply is also globally decreasing, which hampers infilling necessary to maintain elevation relative to sea level. Here we model 36 estuaries worldwide with varying sizes, shapes and hydrodynamic characteristics, and find that small shallow estuaries and large deep estuaries respond in opposite ways to sea-level rise. Large estuaries are threatened by sediment starvation and therefore loss of intertidal area, particularly if tidal amplitude decreases at the mouth. In contrast, small estuaries face enhanced flood risks and are more sensitive to tidal amplification on sea-level-rise-induced deepening. Estuary widening can partly mitigate adverse effects. In large estuaries, expanded intertidal areas increase tidal prism and available erodible sediment for adaptation, whereas it slightly reduces tidal amplification in small estuaries. Small shallow estuaries face enhanced flood risk under climate change because of sea-level-rise-induced tidal amplification. In contrast, large deep estuaries are threatened by sediment starvation and therefore a loss of intertidal area. Both cases can potentially be mitigated by estuary widening.

Direct numerical simulations are performed to investigate the generation of internal waves by tide-topography interaction in a lab-scale model. The bottom topography is a triangular ridge with two critical slopes. With increasing tidal forcing, subhar-monic instabilities are identified, which cause internal wave beams to become unstable and turbulent. Kinetic energy densities in the upward going beams from the ridge top are stronger than those from the ridge bottom, whereas the reverse is true for the energy flux. This disparity between energy and energy flux is due to the existence of strong pressure disturbances near the ridge bottom. On each side of the critical ridge, there exists an amphidromic point, from which internal wave beams are emitted in opposite directions. The calculated energy conversion rate scales linearly with the square of the forcing amplitude and agrees within 13% of theoretical prediction, even when turbulence occurs. The fraction of radiated baroclinic energy becomes saturated in the range of low excursion parameter considered, which agrees with the behavior in large-scale systems wherein mixing parameterizations must be used. The present work enriches the studies on the generation of internal waves over a critical triangular ridge.

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.

In this theoretical study, we use linear stability analysis to investigate the cause of parietal vortex shedding in Taylor–Culick flow, which is representative of the flow in solid rocket motors. We focus on the effects of the lateral-injection Reynolds number and the length-to-radius ratio of the combustion chamber. Through a comparison with pipe flow, we find that flow turning is a major contributor to parietal vortex shedding. We explore the role of amphidromic points and find that they can divide the flow field into two distinct regions, an outer region with strong perturbations and an inner region with weak perturbations. In the outer region, we find that the velocity perturbations develop advection patterns with axial (streamwise) periodicity, while the pressure perturbations induce flow gradients that enhance shear stresses. Collectively, these effects are thought to combine to induce parietal vortex shedding in solid rocket motors.

The location of the amphidromic point of the M2 tide in Hudson Bay roughly coincides with Belcher Islands, a region where the surface mixed layer stays relatively fresh throughout summer and winter due to significant ice melt and river discharge. High-resolution satellite radar imagery for the ice-free season revealed that the coastal region in the south-east Belcher Islands is a hot spot for short-period internal wave activity. For a first investigation of tidal dynamics in the region, we took advantage of the sea ice platform to deploy an ice-tethered mooring consisting of nine conductivity and temperature sensors and an acoustic Doppler current profiler. The mooring was deployed at 65 m depth in January–March 2014 in a narrow channel between Broomfield and O′Leary islands located in the south-east tip of the Belcher Islands group in Hudson Bay (56°20′N, 79°30′W), northeast Canada. The surface mixed layer under the land-fast ice in this area stays relatively fresh through winter presumably because of significant winter river discharge in nearby James Bay. The mooring recorded oscillations of temperature and salinity throughout the whole water column, which were attributed to vertical displacement caused by internal tidal waves. The tidal harmonic analysis performed for the M2 tidal constituent showed the dominance of the baroclinic tide with maximum velocity amplitudes at the surface and decreasing with depth. Vertical displacements of water parcels derived from both temperature and salinity were statistically similar and displayed the maximum values of 11.9 m at 35 m (instrument depth). The combination of winter hydrographic data and summer satellite observations confirmed that the observed internal waves were generated by the interaction of strong tides, typical for Hudson Bay, with highly variable bottom topography south-east of the Belcher Islands archipelago.

Longterm hourly data from 28 tide gauges were used to examine the main features of tides in the Black Sea. The tides in this basin are directly caused by tide-generating forces and the semidiurnal tides prevail over diurnal tides. Based on the Princeton Ocean Model (POM), a numerical model of tides in the Black Sea and adjacent Sea of Azov was developed and found to be in good agreement with tide gauge observations. Detailed tidal charts for amplitudes and phase lags of the major tidal harmonics in these two seas were constructed. The results of the numerical modelling and observations reveal for the semidiurnal tides the presence of an amphidromy with clockwise rotation and another one with counterclockwise rotation for the diurnal tides, both located in the central part of the sea near the Crimean Peninsula. Therefore, for this part of the sea the amplitudes of harmonics M2 and K1 are less than 0.1 cm. Relatively larger M2 amplitudes are observed on the east and west coasts of the sea (2–3 cm). The maximum amplitude of the harmonic M2 was found at Karkinit Bay—up to 4.5 cm—while the maximum tidal range varies from 1 cm near the Crimean Peninsula to 18–19 cm in the Dnieper–Bug Estuary and Karkinit Bay. Radiational tides, initiated mainly by sea breezes, make an important contribution to the formation of tidal oscillations in the Dnieper–Bug Estuary.

Marine renewable energy deployment involves site resource assessment as strategic support for installation and optimization. This part of the design needs to be based on best available measurement technologies and deployment methods, minimizing the investments. The siting and design of a kinetic energy converter (like a Tidal Energy Converter ones) require characterization of the variability of the flow velocity acting on the energy capture area in space and time, in order to assess the hydrodynamic forces, to design the structural loading and power capacity of the TEC, helping investment decisions and project financing. In this work, a site assessment procedures for emplacement of TEC machines are shown, comparing sites with different hydrogeological characteristics using the same design approach. In order to define the best conditions for siting, three case studies have been carried out, two for sea and last for river installation. The strait of Messina (Italy), a marine channel with an amphidromic point for the tides, has its minimum depth at 72 m, between Ganzirri and Punta Pezzo, deepening to 1000 m to the North East and down to 2000 m to the South. The Cook Inlet (Alaska), a large subarctic estuary in South-central Alaska which extends about 250 km from Anchorage bay to the Pacific Ocean. Tidally dominated currents control the hydrographic regime, meanwhile water levels and currents are influenced by tides coming from the Gulf of Alaska, which are significantly amplified as approaching Anchorage bay. The Pearl River Estuary and its adjacent coastal waters (China) have a length of about 70 km, a width of about 15 km and an average depth of about 4.8 m, but it has a depth of more than 20 m in its eastern part.

A new data set of observations by six cruises of ship-mounted acoustic doppler current profiler (SADCP) and three 40 d long bottom-mounted ADCPs (BADCPs) is employed to reveal the spatiotemporal variability of tidal and subtidal currents in the western Taiwan Strait (TWS) during winter season. The results confirm the existence of intense cotidal lines for M2 tidal current, which is located north of 25°N. In this case, no existence of an amphidromic point can be identified. It is also revealed that the counter-wind current (CWC) can extend through the whole western TWS and even occupy the entire water column during winter monsoon relaxation. However, this CWC is observed to be thoroughly overwhelmed by the downwind China coastal current (CCC) during the two big monsoon bloom events in the winter of 2007, and the CCC consequently extends southward throughout the western TWS instead. Most importantly, the variation of the spatial extent for the CWC and the CCC in the western TWS is found to be well explained by the first two modes of the vector empirical orthogonal function (VEOF) analysis, that is, it is mainly controlled by a wind-driven quasi barotropic current as the first mode and slightly modulated by a relatively weak background current with a first-order baroclinic structure as the second mode.

Contiguous mudflats exist along the coast zone of the Bohai Bay in the western part of the Bohai Sea of China. They are generally suitable for land reclamation, which can ease the contradiction between land resource shortage and the demand for development, because mudflats are important geomorphological systems which provide land resources. The shoreline at the Bohai Bay has experienced significant changes since 2003 due to high intensity reclamation. Environmental impacts of reclamation at different stages, especially on the tidal wave system, have attracted worldwide attention. However, there is still a lack of understanding on the cumulative response process of the tidal wave system and its response mechanism to high intensity development of mudflats. In this study, six periods were selected as representative reclamation stages in the Bohai Bay: 2003, 2006, 2012, future planning, and 0 m and −5 m reclamation stages. A two-dimensional tidal wave mathematical model was developed to analyze the cumulative changing process and dominant mechanism of the change of the tidal wave system by comparing effects of reclamation of the entire bay and cumulative effects of sequential reclamation projects, as well as studying the relations between the tidal wave change and tidal range on the shore segment where the reclamation project is located. Based on the analysis results, the influence of reclamation in the Bohai Bay on the M2 constituent tide was much greater than that on the K1 constituent tide, especially on the M2 constituent tide amphidromic point outside of the Yellow River mouth. The movement distance of the M2 constituent tide amphidromic point outside the Yellow River mouth for the aforementioned reclamation stages compared to its location in 2003 was about 1, 10, 22.5, 27.3, and 83.8 km, respectively. In contrast, the maximum movement distance of the other M2 constituent tide amphidromic point outside Qinhuangdao and the unique K1 constituent tide amphidromic point in the Bohai Sea for the aforementioned reclamation stages compared to their conditions in 2003 were about 5.9 and 6.3 km, respectively. With the increase of the reclamation scale, the M2 constituent tide amphidromic point outside of the Yellow River mouth first moved southeastward, and then moved northeastward, and the tidal range of the western Bohai Bay first increased and then decreased, while the speed of tidal wave propagation first accelerated and then stabilized during the 0 m reclamation stage. During the −5 m reclamation stage, the tidal wave system experienced obvious changes, however, the tidal properties inside the bay remained the same. The average tidal current velocity of the bay decreased with the increase of the reclamation scale, and the tidal current velocity of 2003, 2012, future planning and −5 m reclamation stages were 0.33–0.37, 0.3–0.34, 0.29–0.31, and 0.16–0.17 m/s, respectively. When reclamation projects were performed one by one counterclockwise from Caofeidian (future planning) in the north to south until all the future planned reclamation projects were completed, the M2 constituent tide amphidromic point first moved southwestward, and then moved southeastward. In semi-closed bays influenced by rotational tidal wave, the impact intensity of reclamation projects to the tidal wave system depends mostly on the tidal range of the coast where the reclamation projects are located. The greater the tidal range, the more obvious the effects of the reclamation projects will be on the tidal wave system. Continuous reclamation will increase flooding risks and tendency of siltation in the bay, weaken the water exchange rate in the bay, affect scouring and silting, as well as impact the design and defense standards of coastal engineering projects near the Yellow River mouth.

Tidal current is one of the main driving forces for shaping the topography of marginal seas. A globally unique radial sand ridge field exists in the South Yellow Sea off the central Jiangsu coast, China. Its formation is related to the distinctive ‘radial tidal current’ pattern at that location. A generally accepted hypothesis is that the ‘radial tidal current’ is a consequence of the interaction between the northern amphidromic tidal wave system and the southern incoming tidal wave. In this study, we adopted a schematized numerical tidal model to directly investigate the tidal current system and the factors of influence in the South Yellow Sea. We first introduce the tidal Current Amphidromic Point (CAP) and the tidal current inclination angle for illustration of a tidal current system. By conducting series of numerical experiments, we found that the overall basin aspect ratio and the cross-basin phase differences of the tidal wave are two aspects of influence on the emergence of the ‘radial tidal current’. The ‘radial tidal current’ has opportunities to emerge in a basin where the basin length (L) is larger than width (B), and a lateral depth difference exists (or the offshore incoming tidal wave has an oblique angle). The Yellow Sea is featured by these aforementioned prerequisites favouring the formation of the ‘radial tidal current’. Further results analyses indicate that the CAP system (i.e., the co-inclination lines, the CAPs and the tidal ellipticity) can get deeper insights into the dynamic structure of a tidal current system than the tidal ellipse field and therefore it deserves more attention in future study.

The Head Bay of Bengal is highly vulnerable to flooding events caused due to monsoons, cyclones and sea-level rise, owing to its funnel-like shape, high tidal range, presence of numerous river drainage systems, low-lying topography, and shallow bathymetry. Tides dominate the hydrodynamic behaviour and coastal processes in this region and its propagation is quite distinct. The present study uses ADCIRC hydrodynamic model customized for the Head Bay of Bengal, discretized using unstructured finite elements and validated against limited available observations in this data sparse region. The water-level elevations derived from ADCIRC simulation was used to understand the pattern of non-linear tidal propagation with respect to complex coastal geomorphology prevalent in this region. The study finds a marginal amplification of diurnal tide, nearly double amplification of semi-diurnal components, and existence of a degenerate amphidromic point near Meghna delta consistent with previous studies. The spatial and temporal variability of tidal spectral components were examined by applying the techniques of wavelet, harmonic, and time-series analysis at various locations. Maximum amplification of tides occurs at the head of the bay, along a zone enclosing the mouth of tidal inlets; and for regions northward, the tides decay with progressively increasing phase lags. The study signifies dominance of a forced fortnightly tide and tidal asymmetry leading to flood-dominance in the rivers Hooghly, Meghna, and Tetulia. The non-linear properties of tides have been elucidated, and their origin and spatio-temporal variability in these riverine systems were further investigated. Shallow depth and sharp depth gradients were discerned to be the important conditions for the origin of non-linear components. It has been deduced that non-linear tides are generated in regions where propagating tides are accumulated, and amplified in regions where they are funneled. A study of tidal energetics show that maximum rate of tidal energy dissipation is deep inside the rivers at head of the bay. The spatial variability analysis of tidal form factor shows an overall semi-diurnal dominance in the Head Bay.

Standard methods of tidal inference should be revised to account for a known resonance that occurs mostly within the K1 tidal group in the diurnal band. The resonance arises from a free rotational mode of Earth caused by the fluid core. In a set of 110 bottom-pressure tide stations, the amplitude of the P1 tidal constituent is shown to be suppressed relative to K1, which is in good agreement with the resonance theory. Standard formulas for the K1 nodal modulation remain essentially unaffected. Two examples are given of applications of the refined inference methodology: one with monthly tide gauge data and one with satellite altimetry. For some altimeter-constrained tide models, an inferred P1 constituent is found to be more accurate than a directly determined one.

The general framework for identifying tidal duration asymmetry proposed by Song et al. (2011) is extended to express fortnightly variability in duration asymmetry. The extended metrics are verified and studied using observed sea-level data at 481 stations worldwide. The results reveal that fortnightly variability is universal and that duration asymmetry can be stronger during neap tide than during spring tide. The fortnightly variability in duration asymmetry is primarily induced by three types of tidal interactions: interactions within the principal tidal constituents, interactions between high-frequency and principal tidal constituents, and interactions between long-period and principal tidal constituents. Among these interactions, the first type is most important at most of the stations and is related to the form number F. The contributions of different interactions can be quantified using their frequencies, amplitudes and phases. Global patterns of the fortnightly variation are illustrated using TOPEX/Poseidon altimetry data. The findings show that remarkable fortnightly variation in the tidal duration asymmetry occurs in most open oceans and is significant around an amphidromic point. The metrics derived in this study can be used to examine any time-varying characteristics in tidal asymmetry (not limited to duration asymmetry) by selecting a suitable frequency threshold. This article is protected by copyright. All rights reserved.

In epicontinental seas, as well as in oceans, amphidromic systems control tidal movement, acting on coastal dynamics and, therefore, influencing the depositional record. Inland seas were common in Pangea during the Permian. However, estimating the conditions that governed the tide in these seas is highly complex. Although Permian marine deposits are well documented on a regional scale, the tidal behavior in the epicontinental sea has not been analyzed yet. In this work, we present a theoretical perspective on the behavior of tides in the epicontinental sea of the Parana Basin during the Early Permian (Guata Sea), covering an area of ~1200,000 km2. Mathematical models were applied to test the existence of amphidromic points in the basin (determined from the Rossby radius of deformation) as well as to verify the possibility of resonance. Since paleodepth is unknown and the basin tectonism is still under discussion, an estimated bathymetry from 20 to 500 m was used to cover even some unlikely scenarios. We also tested, using mathematical models, the amplification of the tide inside two paleovalleys. The obtained results were compared to Hudson Bay, considered here to be a modern analog of the Guata Sea. According to the paleogeography, paleolatitude (Southern Hemisphere), and depositional records, the Guata Sea had clockwise-rotation amphidromic systems. However, resonant effects may also have affected circulation, especially at sea depth below 100 m. In the simulated scenarios, the tide amplification in both valleys was variable but concentrated between micro to mesotidal amplitudes. This study presents the first contribution to the understanding of the tidal behavior of the Early Permian epicontinental sea of the Parana Basin in the basinal context of the Gondwanan paleocontinent. Recognition of amphidromic circulation in an inland sea is important because it may help to explain the general behavior of tidal deposits recorded in the basin, which were built and reworked under the influence of this system.

Ice induced variability of tides in the Canadian Arctic Archipelago, including Baffin Bay and Hudson Strait/Hudson Bay system, was studied by means of a new high resolution tidal model. Here we show that the seasonal variations of the tidal constants are significant in the major part of the domain. Month to month changes of the tidal phases can reach 180 degrees due to changes in the number and positions of the amphidromic points, whereas the amplitude variations are especially large in the near resonant basins. We also show that the tidal seasonality has undergone dramatic changes in the past decades due the decaying extent of the Arctic sea ice. These seasonal/decadal scale changes not only vary tidal dissipation on the shelf, but also impact tides in the adjacent open ocean and, therefore, cannot be neglected.

Zhou, C.Y.; Zheng, J.H.; Dong, P.; Zhang, J.S.; Zhu, Y.L., and Zhang, Z.H., 2016. Tidal evolution in the Yellow and East China Sea during Holocene. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 785–789. Coconut Creek (Florida), ISSN 0749-0208. The impact of the sea level (SL) change on the propagation of tides in the Bohai Sea, Yellow Sea and East China Sea (BYECS) during Holocene was investigated by a 3D numerical model with SL of −60, −30, −15, 0 and +2 m, respectively. Same amplitude and phase of tidal constituents M2, S2, K1 and O1 were applied along the open boundaries in all the cases. The results showed that the number of amphidromic points of M2 increased from 2 to 4 while that of K1 increased from 1 to 2 as the SL rising. Both M2 and K1 co-phase lines rotated anti-clockwise as sea-level rising. S2 shared similar evolution patte...

Enhanced M2 tidal amplitude in the Taiwan Strait (TS) and asymmetric M2 tidal amplitude in the cross-strait direction have been found and reproduced in numerical simulations. In this study, Finite Volume Coastal Ocean Model (FVCOM) is applied to investigate the mechanisms behind these features. Model results show that the linear interaction of waves from the East China Sea (ECS) and the Luzon Strait (LS) can explain the formation of the co-amplitude and co-phase lines of the M2 tide in the nodal point area, while the waves from the ECS dominate the tidal motion in the TS according to a basic linear wave superposition. Model simulation also show that wave reflection and transition occur when the M2 tidal waves from the ECS propagate through the TS and encounter an sharply deepened topography. The interaction of these induced reflection waves and the incident waves from the ECS is the main cause for the enhanced M2 tidal amplitude in the TS. The distribution of the sharply deepened topography, rather than the Coriolis effect, is the main reason for the asymmetry of the M2 tidal amplitude in the cross-strait direction in the TS. These findings provide some references for tidal dynamics in other areas, especially where long waves propagate through the shallow water to the deep sea.

Tide is one of the most important hydrodynamic driving forces and has unique features in the Yangtze Estuary (YE) due to the complex geometry of third-order bifurcations and four outlets. This paper characterizes the tidal oscillations, tidal dampening, tidal asymmetry, and tidal wave propagation, which provides insights into the response of the estuary to tides during the dry season. The structural components of tidal oscillations are initially attained by tidal analysis. The increasingly richer spectrum inside the estuary shows an energy transfer corresponding to the generation and development of nonlinear overtides and compound tides. A 2-D numerical model is further set up to reproduce tidal dynamics in the estuary. The results show that the estuary is a strongly dissipative estuary with a strong nonlinear phenomenon. Three amplifications are presented in the evolution process of tidal ranges due to the channel convergence. Tidal asymmetry is spatiotemporally characterized by the M4/M2 amplitude ratio, the 2M2-M4 phase difference, and the flood-ebb duration-asymmetry parameter, and the estuary tends to be flood-dominant. There exists mimic standing waves with the phase difference of the horizontal and vertical tide close to 90° when tidal wave propagates into the estuary, especially during the neap tide. In addition, the differences in tidal distortion, tidal ranges, and tidal waves along the two routes in the South Branch (S-B) suggest the branched system behaves differently from a single system.

We adopt a parameterized internal tide dissipation term to the two-dimensional (2-D) shallow water equations, and develop the corresponding adjoint model to investigate tidal dynamics in the South China Sea (SCS). The harmonic constants derived from 63 tidal gauge stations and 24 TOPEX/Poseidon (T/P) satellite altimeter crossover points are assimilated into the adjoint model to minimize the deviations of the simulated results and observations by optimizing the bottom friction coefficient and the internal tide dissipation coefficient. Tidal constituents M 2 , S 2 , K 1 and O 1 are simulated simultaneously. The numerical results (assimilating only tidal gauge data) agree well with T/P data showing that the model results are reliable. The co-tidal charts of M 2 , S 2 , K 1 and O 1 are obtained, which reflect the characteristics of tides in the SCS. The tidal energy flux is analyzed based on numerical results. The strongest tidal energy flux appears in the Luzon Strait (LS) for both semi-diurnal and diurnal tidal constituents. The analysis of tidal energy dissipation indicates that the bottom friction dissipation occurs mainly in shallow water area, meanwhile the internal tide dissipation is mainly concentrated in the LS and the deep basin of the SCS. The tidal energetics in the LS is examined showing that the tidal energy input closely balances the tidal energy dissipation.

To obtain internal tidal currents and full-depth tidal currents from limited mooring observations, a method is put forward combining harmonic analysis and modal decomposition. Harmonic analysis is used to separate tidal currents of different constituents, and modal decomposition is used to calculate full-depth tidal currents of each mode. By adding the barotropic tidal currents to all the baroclinic ones, the full-depth tidal currents of each constituent are reconstructed. The feasibility and accuracy of the proposed method is tested by twin experiments. Then, the method is used to extract tidal currents of each mode and to reconstruct full-depth tidal currents for M2 and K1 from a 3-month-long time series of acoustic Doppler current data observed at a station in the northern South China Sea. Results indicate that the total kinetic energy (KE) of M2 is 25% larger than that of K1. For M2, the first baroclinic mode is the dominant one, followed by the barotropic one, and the sum of these modes accounts for more than 90% of the total M2 KE. Tidal constituent K1 is dominated by the barotropic mode, which accounts for more than 90% of the total K1 KE.

Topography around the Yellow River mouth has changed greatly in recent years, but studies on the current state of marine dynamics off the Yellow River mouth are relatively scarce. This paper uses a two-dimension numerical model (MIKE 21) to reveal the tidal and wave dynamics in 2012, and conducts comparative analysis of the changes from 1996 to 2012. The results show that M2 amphidromic point moved southeastward by 11 km. It further reveals that the tides around the Yellow River mouth are relatively stable due to the small variations in the tidal constituents. Over the study period, there is no noticeable change in the distribution of tidal types and tidal range, and the mean tidal range off the river mouth during the period studied is 0.5–1.1 m. However, the tidal currents changed greatly due to large change in topography. It is observed that the area with strong tidal currents shifted from the old river mouth (1976–1996) to the modern river mouth (1996–present). While the tidal current speeds decreased continually off the old river mouth, they increased off the modern river mouth. The Maximum Tidal Current Speed (MTCS) reached 1.4 m s−1, and the maximum current speed of 50-year return period reached 2.8 m s−1. Waves also changed greatly due to change in topography. The significant wave height (H 1/3) of 50-year return period changed proportionately with the water depth, and the ratio of H1/3 to depth being 0.4–0.6. (H 1/3) of the 50-year return period in erosion zone increased continually with increasing water depth, and the rate of change varied between 0.06 and 0.07 m yr−1. Based on the results of this study, we infer that in the future, the modern river mouth will protrude gradually northward, while the erosion zone, comprising the old river mouth and area between the modern river mouth and the old river mouth (Intermediate region) will continue to erode. As the modern river mouth protrudes towards the sea, there will be a gradual increase in the current speed and decrease in wave height. Conversely, the old river mouth will retreat, with gradual decrease in current speed and increase in wave height. As more coastal constructions spring up around the Yellow River mouth in the future, we recommend that variation in hydrodynamics over time should be taken into consideration when designing such coastal constructions.

We investigate the effect of the future sea level rise (SLR) on the propagation of tides in the Patagonian Shelf by means of numerical simulations. Using a barotropic implementation of the MARS model, we obtain solutions for scenarios which represent the present condition and for potential future SLRs of 1, 2 and 10 m. The effect of flooding of low-lying land areas is studied, and its influence on the propagation of tides in the region is discussed. Due to the coastal morphological features and the sense of propagation of the tidal wave in the Southern Hemisphere, inundation does not significantly modify the solution in the Patagonian Shelf; nevertheless, results are substantially changed in the much lower Northern Argentinean Shelf, north of 40º S, where dissipation is increased. The amplitude of M2 responds to SLR in a spatially non uniform manner. The response is non linear, particularly in the regions close to the amphidromic points. Tidal dissipation by bottom friction increases by 16% for the more extreme scenario consistently with a generalized increment of tidal amplitudes, and therefore currents, over the Patagonian Shelf. The changes in the extension and position of the tidal fronts are also explored. Results suggest that changes will be significant, with a reduction of the mixed areas in Cabo Blanco and San Sebastián and an increment of them in the vicinity of Península Valdés. The physical mechanisms which explain the observed modifications in the tidal regime are the changes with SLR of the speed of the tidal wave, the Rossby radius of deformation, the energy dissipation by bottom friction and the resonant properties of the basin. Similarly to numerical studies performed for other coastal areas of the world ocean, results indicate that important changes in the characteristics of the tides can occur if the SLR is large. Fil: Luz Clara Tejedor, Moira. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina Fil: Simionato, Claudia Gloria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina Fil: D'onofrio, Enrique Eduardo. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; Argentina Fil: Moreira, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; Argentina

The tidal response of Titan′s two largest northern seas, Ligeia Mare and Kraken Mare, is studied by means of a two-dimensional, depth-averaged, shallow water model, SLIM (http://www.climate.be/slim). Kraken Mare is formed of two basins, the northern one being assumed to be linked by a single strait, Trevize Fretum, to Ligeia Mare. The tidal motions tend to be independent of each other in each basin (i.e., Ligeia Mare, Kraken 1 and Kraken 2) which results in sharp transitions in the straits. Our results are overall rather similar to those of Tokano et al. (2014), suggesting that a 2D model such as SLIM is adequate for modelling Titan′s tides and, since it is (presumably) less computationally demanding, may be better for sensitivity studies. For instance, the maximum tidal range in Kraken and Ligeia Maria respectively are 0.29 m and 0.14 m, which is within the range predicted by Lorenz et al. (2014) although smaller by 0.07 m and larger by 0.04 m than the estimates of Tokano et al. (2014) (but it occurs at the same location). The tidal currents are faster (by about one order of magnitude) in the straits linking those Maria than in the basins themselves (with a maximum of 0.36 m/s in the strait linking Kraken 1 and Kraken 2, Seldon Fretum). A decomposition of the tidal history into different harmonic components is carried out. Except in specific areas such as the straits and the amphidromic point(s), the main tidal component has a period of 1 Titan Day. We also briefly studied the eigenmodes of the northern seas whose period is close to the tidal period: such modes are very local. Indeed, their magnitude is significant (with respect to the magnitude of the modes elsewhere in the seas) in small bay(s) or near the islands of Kraken 2 and Ligeia Mare. They are not excited by the tides as they do not appear in the tidal motion. A sensitivity analysis to poorly constrained parameters (bottom friction coefficient, depth of Trevize Fretum and attenuation factor – the latter is briefly discussed with respect to the values of the Love numbers found in the literature) is also conducted. The model parameters are seen to have a significant impact on the liquid exchanges between the basins and, consequently, on the tidal range and phase, fluid velocity and location of amphidromic point(s).

Huang, J.; Xu, J.; Gao, S.; Lian, X., and Li, J., 2015. Analysis of influence on the Bohai Sea tidal system induced by coastline modification. Four identical hydrodynamic simulation experiments for the Bohai Sea have been implemented respectively with MIKE31 model based on four different coastlines of 2000, 2008, 2010, and 2012, when the intensive usage of the Bohai Sea was carried on. The comparison of these four experiments is used to present the influence on the Bohai Sea tidal system caused by coastline modification. The analysis shows that the semi-diurnal amphidromic point near the Yellow River estuary moves towards south-east gradually as the coastline changes, which makes the semi-diurnal amplitude in Bohai Bay increase and the phase rotate anticlockwise. Meanwhile, the semi-diurnal amplitude in Laizhou Bay becomes smaller and the phase rotates clockwise. Besides, the semi-diurnal amphidromic point near Qinhuang Island moves gradually to southwest. The location of diurnal amphidromic poin...

In this work, a two-dimensional numerical model based on Delft3D modelling system was setup to study the tidal characteristics of the Red Sea. Besides that, analyses of available observed time series of surface elevations were carried out. Sensitivity analyses of the numerical model were carried out by testing different model parameters aiming at selecting optimal settings. The model performance was evaluated against available time series of surface elevation observations. RMS error was found to vary from 0.03 to 0.1 meter, while the ADM values range from 0.02 to 0.05 meter. On the whole, the model is able to reproduce the tidal wave in the Red Sea, reflecting a consistent level of agreement with the observations and previous works. The model results suggest that the semidiurnal tidal waves play a major role in the region except in the central part of the Red Sea where amphidromic system exists. Major semidiurnal and diurnal tidal constituents were computed to generate co-charts and form factor. The results have revealed that the distribution of the co-charts of the major semidiurnal constituents M2, N2, and S2 show the existence of anticlockwise amphidromic system in the central part of the Red Sea at about 19.5°N, north of the Strait of Bab el Mandeb at 13.5°N and in the Gulf of Suez. The chart of the diurnal tidal constituent K1 showed a single counterclockwise system in the southern part of the Red Sea centred around 15.5°N. The form factor chart shows the appearance of diurnal character in the central part of the basin and the northern end of the strait. The hydrodynamics patterns under spring and neap tidal conditions were also analysed (during flood and ebb conditions). Model results showed that currents generally are weak and strongest currents are present in the strait of Bab el Mandeb and Gulf of Suez.

Nearly a decade ago, it was recognized that “amphidrome” is not a tide-only feature. Although more than a dozen annual amphidromes have been reported for several oceanic/atmospheric variables, little has been done so far to identify nontidal amphidromes under the sea surface. In this study, analysis of annual phase properties of sea temperature at different depths has been conducted using Argo data. As a result, four annual amphidromic columns of sea temperature (AACST) with different thicknesses have been identified across the tropical oceans. The concept of “amphidromic column” is defined for the first time as the water column where an amphidromic point extends vertically for a given depth in the ocean. Given the fact that it is coupled with the lower limit of the oceanic mixed layer and provides a direct measure of the solar penetration, the determination of AACST has many potential implications ranging from a more precise monitoring of the interannual to multidecadal temperature changes under global warming, to a better understanding of the thermal-dynamical, biological, and fishery processes in the tropical oceans.

Barotropic to baroclinic tidal conversion rates and baroclinic tidal energy fluxes are derived from a high resolution ocean circulation and tide model (STORMTIDE) simulation. Two semi-diurnal ( M 2 and S 2 ) and two diurnal ( K 1 and O 1 ) tidal constituents are considered in the present study. The model resolves mesoscale eddies and internal tides and it is forced by a climatological forcing. It is estimated that 1.7 TW of tidal energy is converted from barotropic tides into baroclinic motions. About 32% (50%) of this energy conversion occurs in shallow waters with ocean depths shallower than 1000 m (2000 m). The spatial patterns of tidal energy conversion and the global net conversion are consistent with previous analytical and numerical model studies and it shows that most of the energy is converted in the West Pacific. An important result from the present study is that about 30% (0.11 TW) of diurnal tidal energy is converted poleward of the critical latitudes, and presumably transfered locally to turbulent mixing processes with a high efficiency. Further, a modulation function is derived from the full lunisolar tidal potential described by ephemerides, in order to allow the internal tide generation to be modulated on monthly to bi-decadal timescales. This function reproduces the modulation of the tidal constituents in real-time. The coupling of this function with the spatial conversion rates depicts the regional and temporal dependence of tidal energy conversion. In some regions the nodal cycles of semi-diurnal and diurnal tides interfere destructively (e.g. North Atlantic and South Pacific) and in others the strong diurnal nodal cycle is dominant and modulates the tidal energy conversion by 10–20% (North West Pacific and Southern Ocean). In sight of climate bi-decadal variability this approach shows that the consideration of tidal mixing parameterizations in climate models should acknowledge the spatial and temporal dependence of internal tide generation.

In recent decades, the reclamation of tidal flat carried out by the authorities around the Bohai Sea, Yellow Sea, and East China Sea (BYECS) has reached new heights as a consequence of significant economic expansion in the coastal areas. We are concerned that the tidal flat reclamation may have not only local but also far-field effects on tidal dynamics in the entire BYECS. Numerical study shows different tidal patterns due to tidal energy redistribution when tidal flats around the BYECS are removed, in which the tidal range and phase are changed, and the amphidromic points are displaced. Tidal flats provide storage and dissipation for tidal energy; the former is much more significant than the latter. Loss of these functions caused by tidal flat reclamation will induce a redistribution of the extra tidal energy. Furthermore, we show that far-field effects on tidal dynamics would be observed on the west coast of Korea following significant reclamation on the Chinese Jiangsu coast. In turn, reclamation on the west coast of Korea may generate the far-field effects on the Chinese coast. Reclamation in the BYECS can result in rise of tidal amplitude and onshore sediment transport. The former may enhance the coastal hazards such as storm surge, and the latter may result in severe siltation. Therefore, careful consideration must always be given to any proposed artificial changes to tidal flat, given the effects of these on both the local environment and further afield.

It has been suggested in recent papers that even moderate sea-level rise (SLR) may have significant and unexpected effects on the tidal dynamics of the European Shelf. The response of the tidal amplitudes varied significantly between the studies, however. Here, it is shown that the way SLR is implemented in the tidal models used for the investigations causes significant differences between the results. When vertical walls are added at the present coastline, the changes are due to (subtly) changed properties of the propagating wave as the water depth is altered, whereas when flooding of existing land is allowed, the response is controlled by the newly introduced dissipation in the new cells. For example, the response of the Irish Sea is controlled by the flooding of estuaries, increasing the tidal amplitudes through the increased dissipation in the newly formed cells as explained by the dampened harmonic oscillator, whereas the North Sea is dominated by the flooding of the Dutch coast which shifts the areas of tidal energy dissipation from the present coastline to the new cells and thus moves the amphidromic points towards the coast. This is further supported by semi-analytical solutions to the Taylor problem. Identifying the processes which control the responses of shelf sea tides to SLR not only increase our knowledge about tidal systems, but also aids predictions of how other shelf sea systems will respond to future climate change.

This paper provides an explanation of an automated solution for correctly interpolating phase-lags across abrupt boundaries. Although an automated solution to this problem has existed for several years, this is not commonly known and so many researchers continue to perform corrections manually. Interpolation errors commonly occur when tidal propagation surfaces are generated for regimes with amphidromic points. General correction methods are manual, clunky and prone to operator error. The problem can be solved by applying a simple method to scalarize the phase-lag vectors pre-interpolation. This approach successfully and automatically generates correct tidal phase-lag interpolation values and may be applied to any surface mapping software used to interpolate phase-lags.

In the southeast coastal zone of Yellow Sea, the tide characteristics showing ebb-dominant tide and tidal flow were confirmed by analysis of observed tide and tidal currents. Physical factors generating asymmetric tide were reviewed. Influence of bottom shear stress, tidal flat, and nonlinear terms in shallow water equations was investigated by two-dimensional tide modeling. The model results gave good agreements with observed tides, but the amplitude of simulated tide was less than that of observed tide. The tidal flats existing in the study area widely have great effect on the generation of nonlinear tide. The M4 tide is mainly generated near the tidal flats. The deletion of tidal flats prevents the production of the M4 tide. We can conclude that the wide tidal flats is a primary cause of tide asymmetry in the study area.

The German North Sea coast is not only recently characterized by different geomorphological, hydrographical and geological situations that have to be taken into account when working with sea-level data. Today’s sea-level research asks for high resolution and accuracy. The question arises whether this can be achieved by the field data being available and whether potential sea-level fluctuations are masked or not by the error ranges to be assumed (cf. Gehrels 1999). This holds for any coastal region around the North Sea, the Irish Sea and the English Channel. The present German North Sea coast may be subdivided into different landscapes such as estuaries, barrier islands, embayments and marshlands. These landscapes all have their own specific sedimentation processes in terms of changing rates of accommodation space to sediment supply and also flood basin effects. These in turn influence sedimentation and sedentation rates. Therefore, progradation and retrogradation of the coastline are not necessarily connected to sea-level changes alone. Also, the tidal situation along the German North Sea coast at present varies from approximately microtidal in the North at the island Sylt to macrotidal conditions in the Jade Bay. The mean high water level differs up to more than 1 m along the German North Sea coast, which is caused by the present palaeogeographical setting in relation to the amphidromic point in the North Sea. The construction heights of the local dwelling mounds on the marshland islands in the North of the German Bight differ up to 0.75 m due to differences in the storm wave surges in that area. Furthermore, regionally different glacio-isostatic movements during the Holocene due to the position to the collapsing glacial forebulge have to be regarded. Following the most recent geophysical models, the differences in isostatic subsidence along the German North Sea coast during the Holocene are in the order of several metres (i.e. Busschers et al. 2007). Therefore, comparing data from regions with different tidal situations and glacio-isostatic movements by amalgamation of data of the entire German North Sea coast in one single curve without quoted vertical error may lead to data artefacts showing fluctuations in a decimetre scale up to more than 1 m within 200–500 years as in the curve published by Behre (2003, 2007). Baeteman et al. (2011) examined the sea-level index points of the dataset used by Behre (2003, 2007) by setting them in their stratigraphic and also geographical context. These re-evaluated data show a range of age and altitude not supporting any interpretation of fluctuations any more. Consequently, several coastal sections have to be defined to reduce the error resulting from the above-mentioned influences and to reduce the probability of upscaling local effects. In our publication in 2010 (Bungenstock 2010), we present five coastal sections (Fig. 1) as a ‘‘first approach’’ and as ‘‘... a first step to show that several curves are needed to demonstrate the Holocene sea-level history of such a big area as the entire German North Sea coast ...’’. The suggestion we made in our 2010 paper is to construct several new regional sea-level curves for the German North Sea coast based on the assumption that the vertical error ranges to be adopted may be reduced when collecting data from smaller defined areas mirroring the F. Bungenstock (&) Lower Saxony Institute for Historical Coastal Research, Wilhelmshaven, Germany e-mail: bungenstock@nihk.de

Finite element grid system using h-refinement on the Yellow Sea was constructed based on previous study (Suh, 1999b) from 14 K to 210 K and special attention was concentrated on refining the coastal zone. In grid generation, depth change between adjacent points and non-dimensional tidal wave length ratio were considered. As a result approximately a quarter of the total nodes are located nearby 5 m of shallow area. Accurate bathymetry data using 30`s and ETOPO1 with open boundary conditions of 8 major tidal constituents extracted automatically from FES2004 have been applied. In tidal simulation a 3-dimensional nonlinear harmonic model was setup and tidal amplification due to changes in vertical turbulent and bottom friction were simulated. In this study not only 8 major tidal constituents but also nonlinear shallow tides , and long period , were reproduced. It is found that implication of spatial variation of friction coefficient plays a very important role in reproduction of astronomical and shallow tides which are computed by iterative computation of nonlinear terms. Also it should be considered differently with respect to tidal periods. To understand the distribution of tidal asymmetry, amplitude ratio of and phase differences were calculated. Tidal distortion ratio marks up to 0.2 on the west coast showing shallow coastal characteristics and somewhat wide range of ebb-dominances in front of Mokpo area are reproduced.

Based on pressure tide-gauge observations, sea-level records are derived for ten sites along the coast of West Greenland. The ocean tidal signal is extracted by a harmonic tidal analysis. The accuracy of the determined tidal constants is discussed in detail. The tides account for 85% of the observed sea-level standard deviation. The tide gauge records reveal significant shallow-water tidal effects, in particular compound and overtide amplitudes reaching 5 cm. The propagation of the tidal waves into the fjords depends strongly on local conditions and is in some cases accompanied by an amplification of the tidal amplitudes. The observed tidal signals are compared to the predictions of the global ocean tide model FES2004. At the outer coast, a good agreement is found. Inside the fjords, however, the model performs worse and tide gauge observations may still be indispensable when accurate tidal signals are required.

Tidal currents and surface amplitudes are calculated globally for the dominating diurnal and semidiurnal constituents using an established tidal model under a range of altered bathymetry. The purpose is to evaluate if the well-known amplification of the global tides during the Last Glacial Maximum (LGM) is related to changed propagation properties for the tidal wave or to changed damping due to removal of shelf seas. The response of the tides and tidal dissipation to future sea-level rise is also discussed. The tides in the present and LGM oceans were simulated first, followed by runs where the present day bathymetry was used but the shelf seas removed by the introduction of vertical walls or where sea level is allowed to rise. Previously reported results regarding tidal amplitudes and dissipation rates are reproduced in the control runs. The runs without shelf seas show significantly enhanced tidal amplitudes in the North Atlantic, whereas sea-level rise of 5 m above present levels show a significant shift in the amphidromic points on a local and regional scale but had a limited effect on the open ocean tides. Simulations with very large sea-level rise show a significantly decreased global tidal dissipation, whereas experiments without friction in present-day shallow water display results similar to those with no shelf seas. The results all point towards changing damping properties due to the removal of shelf seas as being the mechanism behind the LGM amplification, and they imply the importance of implementing future sea-level changes properly in tidal simulations.