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Surface current velocity from high-frequency radar data are used to study tidal currents in the Mid-Atlantic Bight, which represent an average 32% of the total kinetic energy of the surface circulation. Average annual and seasonal tidal current characteristics and the associated variance of the semi-major axis are computed. The M2 constituent dominates the tide, representing a maximum of 72.26% and an average of 51.63% of the total studied tidal signal. Its semi-major axis reaches a maximum of 10 cm s−1 around mid-shelf and its phase sweeps from north to south. Local maxima of the same order of magnitude are found near the mouths of estuaries (Long Island Sound, Hudson River, Delaware Bay, Chesapeake Bay) and an absolute maximum of 50 cm s−1 is found in Nantucket Shoals. These regions of localized elevated tidal amplitude are associated with high interannual and intra-annual variability due to seasonal stratification, internal waves, and sand waves. Seasonal tidal changes are large in some of these regions; thus, should not be neglected in making tidal predictions. Lastly, the authors position this paper as an updated alternative to the Moody tidal atlas as the source for tidal current values in the Mid-Atlantic Bight.

The Arctic Ocean is a challenging region for tidal modelling. The accuracy of the global tidal models decreases by several centimeters in the Polar Regions, which has a large impact on the quality of the satellite altimeter sea surface heights and the altimetry-derived products. NOVELTIS, DTU Space and LEGOS have developed Arctide2017, a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of an extension of the CryoSat Plus for Ocean (CP4O) ESA STSE (Support to Science Element) project. In particular, this atlas benefits from the assimilation of the most complete satellite altimetry dataset ever used in this region, including Envisat data up to 82°N and CryoSat-2 data between 82°N and 88°N. The combination of these satellite altimetry missions gives the best possible coverage of altimetry-derived tidal constituents. The available tide gauge data were also used for data assimilation and validation. This paper presents the implementation methodology and the performance of this new regional tidal model in the Arctic Ocean, compared to the existing global and regional tidal models.

Previous tidal energy studies in Puget Sound have focused on major deep channels such as Admiralty Inlet that have a larger power potential. This paper focuses on the possibility of extracting tidal energy from minor tidal channels of Puget Sound by using a hydrodynamic model to quantify the power potential and the associated impact on tidal circulation. The study site is a multi-inlet bay system connected by two narrow inlets, Agate Pass and Rich Passage, to the Main Basin of Puget Sound. A three-dimensional hydrodynamic model was applied to the study site and validated for tidal elevations and currents. We examined three energy extraction scenarios in which turbines were deployed in each of the two passages and concurrently in both. Extracted power rates and associated changes in tidal elevation, current, tidal flux, and residence time were examined. Maximum instantaneous power rates reached 250 kW, 1550 kW, and 1800 kW, respectively, for the three energy extraction scenarios. Model results suggest that with the level of energy extraction in the three energy extraction scenarios, the impact on tidal circulation is very small. It is worth investigating the feasibility of harnessing tidal energy from minor tidal channels of Puget Sound.

The tidal stream energy sector is now at the stage of deploying the world's first pre-commercial arrays of multiple turbines. It is time to study the environmental effects of much larger full-size arrays, to scale and site them appropriately. A theoretical array of tidal stream turbines was designed for the Pentland Firth (UK), a strait between Scotland and the Orkney Islands, which has very fast tidal currents. The practical power resource of a large array spanning the Pentland Firth was estimated to be 1.64 GW on average. The ocean response to this amount of energy extraction was simulated by an unstructured grid three-dimensional FVCOM (Finite Volume Community Ocean Model) and analysed on both short-term and seasonal timescales. Tidal elevation mainly increases upstream of the tidal array, while a decrease is observed downstream, along the UK east coast. Tidal and residual flows are also affected: they can slow down due to the turbines action or speed up due to flow diversion and blockage processes, on both a local and regional scale. The strongest signal in tidal velocities is an overall reduction, which can in turn decrease the energy of tidal mixing and perturb the seasonal stratification on the NW European Shelf.

The Taiwan Strait has recently been proposed as a promising site for dynamic tidal power systems because of its shallow depth and strong tides. Dynamic tidal power is a new concept for extracting tidal potential energy in which a coast-perpendicular dike is used to create water head and generate electricity via turbines inserted in the dike. Before starting such a project, the potential power output and hydrodynamic impacts of the dike must be assessed. In this study, a two-dimensional numerical model based on the Delft3D-FLOW module is established to simulate tides in China. A dike module is developed to account for turbine processes and estimate power output by integrating a special algorithm into the model. The domain decomposition technique is used to divide the computational zone into two subdomains with grid refinement near the dike. The hydrodynamic processes predicted by the model, both with and without the proposed construction, are examined in detail, including tidal currents and tidal energy flux. The predicted time-averaged power yields with various opening ratios are presented. The results show that time-averaged power yield peaks at an 8% opening ratio. For semidiurnal tides, the flow velocity increases in front of the head of the dike and decreases on either side. For diurnal tides, these changes are complicated by the oblique incidence of tidal currents with respect to the dike as well as by bathymetric features. The dike itself blocks the propagation of tidal energy flux.

This paper deals with an energy characterization method of tidal sites. This method is illustrated by the study of a typical tidal site close to the Ouessant (Ushant) Island of the Bretagne region in France. The main objective of this study is to find the optimal location of a tidal turbine including the effect of using or not a yaw drive system. After presenting the different data used in this work, the marine current velocity is first evaluated at different specific locations and times of the studied zone. Afterwords, the tidal energy is evaluated for different systems (tidal turbine with a yaw and bidirectional tidal turbine with fixed axis) and presented in terms of energy distribution maps.

A method of tidal stream energy resource assessment around the Ushant Island in the Iroise Sea, using surface velocity time series from High Frequency radars (HFR) and ADCP measurements, is presented. Remotely sensed velocities provided by the radars allow to augment the industry standard approach of 3D numerical modeling and in-situ ADCP surveying to make a large-scale quantification of tidal stream resource. They capture the real ocean dynamics and thus provide context on the complex spatial variability of tidal currents that are so often feature at potential tidal energy sites. The observations show current velocities of 4 m/s northwest of the Island and in the Fromveur Strait, with 1 m/s value exceeded 60% and 70% of time respectively. Emphasis is given to the peculiarities in tidal flow asymmetry and to the study of the variation of vertical velocity profiles during different tidal stages. Radar derived velocities reveal a pronounced asymmetry between the flood and ebb flow around the Ushant Island, quantified by dimensionless number a - velocity asymmetry. The largest range of asymmetry variation, from 0.5 to 2.5, is observed in the Fromveur Strait. Harmonic analysis demonstrated that a joint variation of phase of the principal semi-diurnal (M2) and quarter-diurnal (M4) tidal velocity component accounts for flow asymmetry variation in the strait. Asymmetry in current direction is also quantified. ADCP measurements show that the vertical velocity profiles follow a 1/α power law with a power law exponent mostly depending on geographic location than on tidal stage. It was demonstrated that, in the Fromveur Strait, the 1/7 power law is appropriate to characterize the velocity profile. The combination of two sources of data enables characterization of the velocity variations in three spatial dimensions and in time thus increasing accuracy of the hydrokinetic resource assessment from HF radar observations. The estimation shows that the mean technical resource is 50% smaller in the lower half than in the upper half of the water column. The theoretical resource on average is three times higher than the technical resource and appears to be more sensitive to variations in the shape of the velocity profile in the lower layer.

The eco-geomorphological development of tidal marshes, from initially low-elevated bare tidal flats up to a high-elevated marsh and its typical network of channels and creeks, induces long-term changes in tidal hydrodynamics in a marsh, which will have feedback effects on the marsh development. We use a two-dimensional hydrodynamic model of the Saeftinghe marsh (Netherlands) to study tidal hydrodynamics, and tidal asymmetry in particular, for model scenarios with different input bathymetries and vegetation coverages that represent different stages of eco-geomorphological marsh development, from a low elevation stage with low vegetation coverage to a high and fully vegetated marsh platform. Tidal asymmetry is quantified along a 4 km marsh channel by (1) the difference in peak flood and peak ebb velocities, (2) the ratio between duration of the rising tide and the falling tide and (3) the time-integrated dimensionless bed shear stress during flood and ebb. Although spatial variations in tidal asymmetry are large and the different indicators for tidal asymmetry do not always respond similarly to eco-geomorphological changes, some general trends can be obtained. Flood-dominance prevails during the initial bare stage of a low-lying tidal flat. Vegetation establishment and platform expansion lead to marsh-scale flow concentration to the bare channels, causing an increase in tidal prism in the channels along with a less flood-dominant asymmetry of the horizontal tide. The decrease in flood-dominance continues as the platform grows vertically and the sediment-demand of the platform decreases. However, when the platform elevation gets sufficiently high in the tidal frame and part of the spring-neap cycle is confined to the channels, the discharge in the channels decreases and tidal asymmetry becomes more flood-dominant again, indicating an infilling of the marsh channels. Furthermore, model results suggest that hydro-morphodynamic feedbacks based on tidal prism to channel cross-sectional area relationships keep the marsh channels from filling in completely by enhancing ebb-dominance as long as the tidal volume and flow velocities remain sufficiently high. Overall, this study increases insight into the hydro-morphodynamic interactions between tidal flow and marsh geomorphology during various stages of eco-geomorphological development of marshes and marsh channels in particular.

In recent years, the application of large-scale beach nourishments has been discussed, with the Sand Motor in the Netherlands as the first real-world example. Such protruding beach nourishments have an impact on tidal currents, potentially leading to tidal flow separation and the generation of tidal eddies of length scales larger than the nourishment itself. The present study examines the characteristics of the tidal flow field around protruding beach nourishments under varying nourishment geometry and tidal conditions, based on extensive field observations and numerical flow simulations. Observations of the flow field around the Sand Motor, obtained with a ship-mounted current profiler and a set of fixed current profilers, show that a tidal eddy develops along the northern edge of the mega-nourishment every flood period. The eddy is generated around peak tidal flow and gradually gains size and strength, growing much larger than the cross-shore dimension of the coastline perturbation. Based on a 3 week measurement period, it is shown that the intensity of the eddy modulates with the spring-neap tidal cycle. Depth-averaged tidal currents around coastline perturbations are simulated and compared to the field observations. The occurrence and behavior of tidal eddies is derived for a large set of simulations with varying nourishment size and shape. Results show that several different types of behavior exist, characterized by different combinations of the nourishment aspect ratio, the size of the nourishment relative to the tidal excursion length, and the influence of bed friction.

The finite volume community ocean model (FVCOM) has been applied to the Ganges-Brahmaputra-Meghna (GBM) delta in the northern part of the Bay of Bengal in order to simulate tidal hydrodynamics and freshwater flow in a complex river system. The delta region is data-poor in observations of both bathymetry and water level; making it a challenge for accurate hydrodynamic models be configured for and validated in this area. This is the first 3D baroclinic model covering the whole GBM delta from deep water beyond the shelf break to 250 km inland, the limit of tidal penetration. This paper examines what controls tidal penetration from the open coast into an intricate system of river channels. A modelling approach is used to improve understanding of the hydrodynamics of the GBM delta system. Tidal penetration is controlled by a combination of bathymetry, channel geometry, bottom friction, and river flow. The simulated tides must be validated before this delta model is used further to investigate baroclinic processes, river salinity and future change in this area. The performance of FVCOM tidal model configuration is evaluated at a range of sites in order to assess its ability to capture water levels which vary over both a tidal and seasonal cycle. FVCOM is seen to capture the leading tidal constituents well at coastal tide gauge stations, with small root-mean-squared errors of 10 cm on average. Inland, the model compares favourably with twice daily observed water levels at thirteen stations where it is able to capture both tidal and annual timescales in the estuarine system. When the river discharge is particularly strong, the tidal range can be reduced as the tide and river are in direct competition. The bathymetry is found to be the most influential control on water levels within the delta, though tidal penetration can be significantly affected by the model's bottom roughness, and the inclusion of large river discharge. We discuss the generic problem of implementing a model in a data-poor region and the challenge of validating a hydrodynamic model from the open coast to narrow river channels.

In this study, the bottom tracking observation in the tidal entrance within Mokpo coast is performed using ADCP in order to estimate net flux of water mass and tidal prism. First of all, observed rawdata was conducted coordinate rotation considering rotation of the cross-section in order to derive the predominant velocity component. And observed rawdata is converted into Sigma coordinate with normalization and blank zone data near the water surface and bottom is interpolated using von-Karman equation. Net flux of water mass is calculated quantitively from the interpolated data, calculated results show that these represent well characteristic of ebb superiority at Mokpo coast as well as change of net flux of water mass with tide. Also, by complementing the definition of tidal prism proposed in past studies, the definition of tidal prism including tidal condition was re-established. Based on the new definition, tidal prism at a tidal entrance using bottom tracking data with ADCP is estimated quantitively for the first time domestically. The results are compared with those for results of previous study, calculated results were in good agreement with previous studies.

The cause of abnormal tidal residuals was examined by analyzing sea levels, sea surface atmospheric pressures, winds at ten tide stations, and current, measured at the coast of the Yellow Sea from the night of November to the morning of the in 2013, along with weather chart. Additionally, the cross-correlations among the measured data were also examined. The `abnormal tidal residuals` mentioned in this study refer to differences between maximum and minium tidal residuals. The largest abnormal tidal residual was identified to be a difference of 176 cm occurring over 4 hours and 1 minute at YeongJongDo (YJD) with a maximum tidal residual of 111 cm and minimum of -65 cm. The smallest abnormal tidal residual was 68 cm at MoSeulPo (MSP) during 8 hours 52 minutes. The cause of these abnormal tidal residuals was not a meteo-tsunami generated by an atmospheric pressure jump but wind generated by the pressure patterns. The flow speed due to these abnormal tidal residuals as measured at ten tide stations was not negligible, representing 16 ~ 41 % of the annual average ebb current speed. From the cross correlation among the tidal residuals, winds, and tidal residual currents, we learned the northern flow, due to southerly winds, raised the sea level at Incheon when a low pressure center located on the left side of the Korean Peninsula. After passing the Korean Peninsula, a southern flow due to northerly winds decreased the sea level.

The present tidal correction of sea level records of Satellite with ARgoes and ALtimeter (SARAL) is based on the finite element solution (FES) of global tide model FES2012 tidal solution. In this study, we examined the validity of the tidal corrections in the coastal oceans around India using tide gauge measurements and a regional tidal model. Our regional model is based on the barotropic version of the Princeton Ocean Model that is forced by the time-varying tidal levels at the open ocean end based on the global FES99 tidal solution. Tide charts prepared from the simulated tidal levels are very similar to the FES tidal solutions. Comparison with the tide gauge measurement shows close agreement with the regional tidal solutions. On the other hand, the agreement with the FES tide models differ significantly in the Gulf of Khambhat and the Gulf of Kutch on the northwest, and in the Hooghly estuary on the northeast continental shelf. However, the agreement is exceptional in other parts of the study d...

International audience; Downscaling physical processes from a large scale to a regional scale 3D model is a recurrent issue in coastal processes studies. The choice of boundary conditions will often greatly influence the solution within the 3D circulation model. In some regions, tides play a key role in coastal dynamics and must be accurately represented. The Bay of Biscay is one of these regions, with highly energetic tides influencing coastal circulation and river plume dynamics. In this study, three strategies are tested to force with barotropic tides a 3D circulation model with a variable horizontal resolution. The tidal forcings, as well as the tidal elevations and currents resulting from the 3D simulations, are compared to tidal harmonics extracted from satellite altimetry and tidal gauges, and tidal currents harmonics obtained from ADCP data. The results show a strong improvement of the M2 solution within the 3D model with a "tailored" tidal forcing generated on the same grid and bathymetry as the 3D configuration, compared to a global tidal atlas forcing. Tidal harmonics obtained from satellite altimetry data are particularly valuable to assess the performance of each simulation. Comparisons between sea surface height time series, a sea surface salinity database, and daily averaged 2D currents also show a better agreement with this tailored forcing.

Potential energy extraction from tidal currents is investigated in this work. Recordings on the streams' velocity and the sea level in the Euripus' strait in Evia, Greece are used to calculate the energy yield. Data on sea level measurements were used to extract information for the current velocity profile through harmonic analysis method. Requirements, limitations and possible new designs that will improve the energy extraction from the low velocity tidal current of the area are discussed. Also, exploitation of tidal energy in cooperation with RES microgrid is proposed for areas where the abundance of sun, wind, island communities and coast areas such as the Mediterranean.

National efforts to reduce energy dependency on fossil fuels have prompted examination of macrotidal nearshore sites around the United Kingdom (UK) for potential tidal stream resource development. A number of prospective tidal energy sites have been identified, but the local hydrodynamics of these sites are often poorly understood. Tidal energy developers rely on detailed characterisation of tidal energy sites prior to device installation and field trials. Although first-order appraisals may make macrotidal tidal straits appear attractive for development, detailed, site-specific hydrodynamic and bathymetric surveys are important for determining site suitability for tidal stream turbine (TST) installation. Understanding the ways in which coastal features affect tidal velocities at potential TST development sites will improve identification and analysis of physical constraints on tidal energy development. This paper presents and examines tidal velocity data measured in Ramsey Sound (Pembrokeshire, Wales, UK), an energetic macrotidal strait, which will soon host Wales' first TST demonstration project. While maximum tidal velocities in the strait during peak spring flood exceed 3 m s−1, the northern portion of Ramsey Sound exhibits a marked flood-dominated tidal asymmetry. Furthermore, local bathymetric features affect flow fields that are spatially heterogeneous in three dimensions, patterns that depth-averaged velocity data (measured and modelled) tend to mask. Depth-averaging can therefore have a significant effect on power estimations. Analysis of physical and hydrodynamic characteristics in Ramsey Sound, including tidal velocities across the swept area of the pilot TST, variations in the stream flow with depth, estimated power output, water depth and bed slope, suggests that the spatial and temporal variability in the flow field may render much of Ramsey Sound unsuitable for tidal power extraction. Although the resource potential depends on velocity and bathymetric conditions that are fundamentally local, many prospective tidal energy sites are subject to similar physical and hydrodynamic constraints. Results of this study can help inform site selection in these complicated, highly dynamic macrotidal environments. In order to fully characterise the structure of the tidal currents, these data should be supplemented with 3-D modelling, particularly in areas subject to a highly irregular bathymetry and complicated tidal regime.

Tidal rivers are intrinsically complex because tidal propagation is influenced by river discharge. This study aims to examine the seasonal variation of tidal prism and energy variance in the tidal river of the Changjiang (Yangtze) River estuary in China. In order to quantify the behaviour of river and tide, we use numerical modelling that has been validated using measured data. We conduct our analysis by quantifying the discharge and energy variance in separate components for both the river and the tide, during wet and dry seasons. We note various definitions of tidal prism and explore the difference between tidal discharge on the flood and ebb and tidal storage volume. The results show that the river discharge attenuates the tidal motion and reduces the tidal flood discharge but the tidal storage volume is approximately constant with different riverine discharge since part of the fresh water discharge is intercepted and captured in the estuary due to the backwater effect. It appears that the tidal discharge adjusts according to the variation of river discharge to keep a constant tidal storage volume. An analysis of the hydraulics shows that the transition from tidal dominance (at the mouth) to river dominance (upstream) depends on the location of tidal current reversal which varies from wet season to dry season. Duringthe wet season, the Changjiang River estuary is totally dominated by energy from fresh water discharge.

The radial tidal current field accounts for the formation of the radial sand ridges in the South Yellow Sea. Understanding the formation and evolution of this radial tidal current field is vital to assessing the morphodynamic features in the area. A semi-enclosed rectangular basin with and without a coastal barrier was schematized from the topography of the Bohai Sea and Yellow Sea. The 2D tidal current field in this basin was simulated using the DELFT3D-FLOW model. The concept of tidal wave refraction, which highlights the effect of the sloped or stepped submarine topography on the propagation of the tidal waves, was introduced to explain the formation of the radial tidal current field. Under the effect of tidal wave refraction, co-phase lines of the counterclockwise rotating tidal wave and incident tidal wave are transformed into clockwise and counterclockwise deflections, respectively, leading to the convergence and divergence of the flow field. Regardless of whether a coastal barrier exists or not, the outer radial tidal current field might emerge over certain topography. The responses of the radial tidal current field in this basin to the environmental variations such as coastline changes and bottom erosions were discussed. Results show that local protrusion near the focal point of the radial tidal current field will have limited effects on the location of the tidal system. However, a remarkable shift of the amphidromic point toward the entrance and central axis of this basin and a movement of the focal point of the radial tidal current field toward the entrance could be caused by the significant seaward coastline advance and submarine slope erosion.

The formation and dynamics of tidal bores in funnel-shaped estuaries is investigated from both a global tidal wave scaling analysis and new quantitative field observations. We show that tidal bore occurrence in convergent estuaries can be estimated from a dimensionless scaling parameter characterizing the relative intensity of nonlinear friction versus local inertia in the momentum equation. A detailed analysis of tidal bore formation and secondary wave structure is presented from a unique long-term database (observations of more than 200 tides) acquired during four campaigns in the two main French tidal-bore estuaries: the Seine and Gironde/Garonne estuaries. We describe the effect of freshwater discharge on the global tidal wave transformation at the estuarine scale and on local tidal bore occurrence in the upper estuary. Our field data suggest that the tidal bore intensity is mainly governed by the dimensionless tidal range, which characterizes the local tidal wave nonlinearity. We also show that the secondary wavefield associated with tidal bore propagating in natural estuaries differs significantly from those associated to undular bores in rectangular channels. In particular, we observe an abrupt decrease of the whelp steepness when the Froude number goes below 1.1. This secondary field transition can explain why tidal bore occurrence in worldwide estuaries is certainly underestimated.

Tidal stream energy is a reliable and predictable low-carbon energy source. Over the next few years the first arrays of multiple tidal stream turbines will be deployed mostly in UK, French and Canadian waters. The potential environmental effects should first be examined, in order to scale and site them appropriately. Large theoretical arrays of tidal stream turbines were designed for Scottish Waters (UK), to quantify the available power and the ocean response to its extraction. A comprehensive assessment of the tidal energy resource realistically available for electricity generation and the study of the potential environmental impacts associated with its extraction in Scottish Waters, can then lead the way to further development in different countries with potential tidal stream energy sources. In order to examine both local ( 100 km) spatial scales, the Scottish Shelf Model, an unstructured grid three-dimensional FVCOM (Finite Volume Community Ocean Model) implementation, is a useful tool, since it covers the entire NW European Shelf, but with a high resolution where the tidal stream energy is extracted. The arrays of tidal stream turbines were implemented in the model using the momentum sink approach, in which a momentum sink term represents the loss of momentum due to tidal energy extraction. A typical annual cycle of the NW European Shelf hydrodynamics was reproduced by the SSM model and compared with the same period perturbed by tidal stream energy extraction. The power extracted by the tidal stream arrays was estimated, taking into account the tidal stream energy extraction feedbacks on the flow and considering the realistic operation of a generic tidal stream turbine, which is limited to operate in a range of flow velocities due to technological constraints. The ocean response to tidal stream power extraction was then analysed at the temporal scale of a spring-neap tidal cycle and, for the first time, on longer term seasonal timescales. It is shown that the very large tidal stream arrays can introduce detectable changes to the tidal elevation, marine currents and ocean stratification patterns. Tidal elevation mainly increases upstream of the tidal farms locations (considering the direction of propagation of the tidal wave), while a decrease in the mean spring tidal range is observed downstream, along the UK East Coast and also in the Irish Sea. Marine currents, both tidal and residual flows, are also affected. They can slow down due to the turbines' action or speed up due to flow diversion and blockage processes, on both a local and regional scale. The strongest signal in tidal velocities is an overall reduction, which can in turn decrease the energy of tidal mixing and perturb the seasonal stratification on the NW European Shelf. Although the strength of summer stratification has been found to slightly increase, the extent of the stratified region does not greatly change, thus suggesting the enhanced biological and pelagic biodiversity hotspots, e.g. tidal mixing front locations, are not displaced. Such large-scale tidal stream energy extraction is unlikely to occur in the near future, since very large numbers of devices are required, but such potential changes should be considered when planning future tidal energy exploitation. It is likely that large scale developments around the NW European shelf will interact and could, for example, intensify or weaken the changes predicted here, or even be used as mitigation measures (e.g. coastal defence) for other changes, e.g. effects of climate change.

The Pará River estuary is a complex and special system in amazon continental shelf, with micro and mesoscale physical processes generated by forces of different sources (e.g., astronomical tides and river discharge). In this study, the main semidiurnal (M2) and the overtide (M4) components were analyzed by quantifying distortions degrees and identifying tidal asymmetries in the Pará River estuary. Two submersible tidal gauges were moored to measure the water level. One on the right margin (point #RG) and another on the left margin (#LF) recorded measurements 6 months (from September 2014 to March 2015). Furthermore, we used harmonic charts from Marine Studies Foundation (FEMAR, Fundação de Estudos do Mar). Lateral variations were also identified between #RG and #LF points from the amplitude and phase cotidal charts, with about 10 minutes delay and variation of 2 cm in tidal amplitude. We verified that the tidal wave enters in system by the right margin (#RF). The results show distortion degrees higher than 10% and positive asymmetry of the tidal wave in the Pará River, and the tidal attenuation in the estuary may be greater than 400 km upstream along the drainage basin.Keywords: Tidal distortion, Tidal asymmetry, Tidal components, Lateral variations.

The Sofala Bank, a wide shelf located along the central coast of Mozambique, hosts tides with high amplitudes. The Regional Ocean Modelling System (ROMS) was used to analyse the tidal currents on the bank and to investigate their effects on the stratification and generation of tidal fronts. During spring tides, barotropic tidal currents with maximum values ranging from 40 cm s–1 to 70 cm s–1 are found on the central bank. The major axis of the tidal ellipses for M2 and S2 follow a cross-shelf direction with mainly anticlockwise rotation. Similar to observations, three distinct regimes occur: (i) a warm well-mixed region on the inner shelf where the depths are 30 m. The shelf edge of the bank is important for internal tide generation. Two frontal structures result, one offshore between cooler mixed waters and warmer stratified waters and the other in shallow inshore waters, between cooler mixed waters and solar heated mixed waters.Keywords: barotropic tidal currents, ROMS, sea surface temperature, shallow seas, tidal front

International audience; The influence of the 18.6-year nodal tidal cycle on estuarine accretion, and indirectly on channel migration patterns, in Mont-Saint-Michel Bay, a UNESCO World Heritage Site famous for its monastery, is explored over three tidal cycles from a 68-year dataset that combines aerial photographs (1947–2007), one DGPS survey (1997), and nine LiDAR Digital Elevation Models (2002–2015). Sand-flat elevation and sediment-budget changes in this megatidal environment were further determined over the last nodal cycle using DGPS and LiDAR surveys. We infer that the changes observed are linked to variations in tidal prism and current velocities in this shallow, large tide-range setting. Increasing (rising tidal range) or decreasing (falling tidal range) flood-dominated asymmetry are deemed to lead, respectively, to waxing and waning of sediment import, in the form of large sand banks, into the bay over the 18.6-year nodal tidal cycle that, in turn, force channel migration. Coriolis acceleration and centrifugal forces are also considered to contribute to the observed channel migration.

Successful deployment of tidal energy converters relies on access to accurate and high resolution numerical assessments of available tidal stream power. However, since suitable tidal stream sites are located in relatively shallow waters of the continental shelf where tidal currents are enhanced, tidal energy converters may experience effects of wind-generated surface-gravity waves. Waves may thus influence tidal currents, and associated kinetic energy, through two non-linear processes: the interaction of wave and current bottom boundary layers, and the generation of wave-induced currents. Here, we develop a three-dimensional tidal circulation model coupled with a phase-averaged wave model to quantify the impact of the waves on the tidal kinetic energy resource of the Fromveur Strait (western Brittany) - a region that has been identified with strong potential for tidal array development. Numerical results are compared with in situ observations of wave parameters (significant wave height, peak period and mean wave direction) and current amplitude and direction 10 m above the seabed (the assumed technology hub height for this region). The introduction of waves is found to improve predictions of tidal stream power at 10 m above the seabed at the measurement site in the Strait, reducing kinetic energy by up to 9% during storm conditions. Synoptic effects of wave radiation stresses and enhanced bottom friction are more specifically identified at the scale of the Strait. Waves contribute to a slight increase in the spatial gradient of available mean tidal stream potential between the north-western area and the south-eastern part of the Strait. At the scale of the region within the Strait that has been identified for tidal stream array development, the available mean spring tidal stream potential is furthermore reduced by 12% during extreme waves conditions. Isolated effects of wave radiation stresses and enhanced bottom friction lead to a reduction in spring tidal potential of 7.8% and 5.3%, respectively. It is therefore suggested that models used for tidal resource assessment consider the effect of waves in appropriately wave-exposed regions.

The astronomical tide was numerically simulated by the MOHID model for the South-Central Region of Espírito Santo State (Brazil), between latitudes 19.8ºS and 21.2ºS. The grid nesting technique was used to transpose the boundary conditions from the larger domain to a more refined local domain (spatial resolution around 450 m), with tidal harmonics provided by the TPXO tide inverse model as boundary conditions for the larger domain. Results from the numerical model were compared with both the pre-existing tide harmonics and the harmonics calculated from measured data. From the maps of phase, amplitude, tidal ellipses and residual currents the main tidal kinematic characteristics in the study area were described. On the continental shelf, the results showed that the physiography and bathymetry of the region play an important role in the distribution of tidal co-phases, co-amplitudes, ellipses and residual currents. The MOHID model was able to reproduce satisfactorily the astronomical tide and thus can be used to study the behaviour of the tidal propagation in continental shelf areas. Resumo A maré astronômica foi simulada numericamente pelo modelo MOHID para a região Centro-Sul do Estado do Espírito Santo (Brasil), entre as latitudes 19.8ºS e 21.2ºS. A técnica de aninhamento de grades foi utilizada para transpor as condições de contorno do maior domínio para um domínio local mais refinado (resolução espacial de cerca de 450 m), sendo as componentes harmônicas disponibilizadas pelo modelo TPXO utilizadas como condições de contorno para o domínio maior (resolução espacial de cerca de 11,25 km). Os resultados do modelo numérico foram comparados com componentes de maré pré-existentes e com harmônicos calculados a partir de dados medidos. Mapas de fase, amplitude, elipses de maré e correntes residuais foram utilizados para descrever as principais características cinemáticas da maré na área de estudo. Os resultados mostram que a fisiografia e a batimetria da região desempenham um importante papel na distribuição da fase, amplitude, elipses e correntes residuais da maré. O modelo foi capaz de reproduzir satisfatoriamente a maré astronômica, podendo ser utilizado para descrever esse processo em plataforma continental.

A baroclinic three-dimensional numerical model for the entire Wadden Sea of the German Bight in the southern North Sea is first assessed by comparison to field data for surface elevation, current velocity, temperature, and salinity at selected stations and then used to calculate fluxes of volume and salt inside the Wadden Sea and the exchange between the Wadden Sea and the adjacent North Sea through the major tidal inlets. The model is simulating the reference years 2009–2011. An overview of tidal prisms and residual volume fluxes of the main inlets and their variability is given. In addition, data from an intensive observational campaign in a tidal channel south of the island of Spiekeroog as well as satellite images and observations of sea surface properties from a ship of opportunity are used for the skill assessment. Finally, the intensity of estuarine overturning circulation and its variability in the tidal gullies are quantified and analyzed as function of gravitational and wind straining using various estimates including Total Exchange Flow (TEF). Regional differences between the gullies are assessed and drivers of the estuarine circulation are identified. For some inlets, the longitudinal buoyancy gradient dominates the exchange flow, for some others wind straining is more important. Also the intensity of tidal straining (scaled covariance of eddy viscosity and vertical shear) depends on buoyancy gradient and wind forcing in different ways, depending on local topography, orientation toward the main wind direction, and influence by freshwater run off inside or outside the tidal basin.

The tidal energy potential of low current tidal and marine currents is investigated in this work. Existing data on the current velocity and sea level at the Euripus' strait in Evia, Greece, is used to compute the energy yield based on contemporary turbine designs. Requirements, limitations and opportunities concerning the exploitation of low velocity tidal streams are discussed.

Tidal current power generation system extracts energy by transferring the kinetic energy of tidal movement to the motion of power turbines. The long coastline of China contains abundant tidal energy, but not all coastal area worth exploiting. It is generally considered that a mean spring peak tidal current of at least 2 m/s is required for tidal current power exploitation. Thus we choose to evaluate the tidal kinetic energy of East China Sea coastal area where 95 waterways contained, accounting for 78.6% of China's tidal kinetic energy. Considering the interaction between the Yangtze Estuary and Hangzhou Bay, a high resolution model with unstructured 3D grid system FVCOM (finite volume coastal ocean model) has been applied to simulate tidal motion in the Yangtze Estuary-Hangzhou Bay. The numerical results of the refined model has been validated with: (a) measured tidal currents data after harmonic analysis; (b) measured tide level hydrograph and velocity which were observed by China's coastal physical oceanography and marine meteorological special investigation on the East China Sea during August, 2014. It is also noticed that the area where power density larger than 10 kW/m2 are mainly distributed over North Port of Yangtze Estuary and north of Hangzhou Bay, and the maximal value of the possible maximum velocity of the tidal current reaches 3.0–3.5 m/s at Hangzhou Bay.

A regional 2DH hydrodynamic model is used to estimate the tidal stream resource of a site located in a macrotidal environment with extreme tidal velocities. The study site is the Alderney Race (Raz Blanchard in French) which is a straight located in the English Channel between the Alderney Island and La Hague cape (France). The estimation of the resource is used to build two realistic tidal energy extraction scenarios consisting in placing a 290 MW tidal turbine array in two different areas. Then, we analyze the impact of turbines on the hydrodynamics and the sediment transport. The hydrodynamic perturbation is restricted to the vicinity of the array where the mean current velocity reduction reaches 0.3 m/s locally (corresponding to 15% of the baseline velocity). Focusing on the variable driving the bedload (the critical erosion threshold exceedance), we confirm that tidal energy extraction tends to reduce the bedload rate and to deflect the sediment fluxes. Our simulations with a simple model for the suspended sediment transport suggest that tidal energy extraction has a significant effect on the area of deposition of the particles transiting through the tidal farm. For the baseline, the sediment particles transiting through the tidal farm deposit mostly in the eastern part of the English Channel. Depending on the location of the tidal farm, the sediment mass balance between the eastern and the western part of the English Channel changes drastically.

International audience; A refined assessment of tidal currents variability is a prerequisite for successful turbine deployment in the marine environment. However, the numerical evaluation of the tidal kinetic energy resource relies, most of the time, on integrated parameters, such as the averaged or maximum stream powers. Predictions from a high resolution three-dimensional model are exploited here to characterize the asymmetry and misalignment between the flood and ebb tidal currents in the " Raz de Sein " , a strait off western Brittany (France) with strong potential for array development. A series of parameters is considered to assess resource variability and refine the cartography of local potential tidal stream energy sites. The strait is characterized by strong tidal flow divergence with currents' asymmetry liable to vary output power by 60% over a tidal cycle. Pronounced misalignments over 20 • are furthermore identified in a great part of energetic locations, and this may account for a deficit of the monthly averaged extractable energy by more than 12%. As sea space is limited for turbines, it is finally suggested to aggregate flood and ebb-dominant stream powers on both parts of the strait to output energy with reduced asymmetry.

To investigate the near-field and far-field hydrodynamic conditions along the Jiangsu Coast in large scale, a two-dimensional tidal wave model which covers the Bohai Sea, the Yellow Sea and the East China Sea is developed and validated. After a brief review of previous models, some influencing factors, such as tide generating force, river discharges as well as shoreline changes due to land reclamation, are examined in this study. We suggest that whether these factors should be considered in the model depends on the different purposes and geographical regions of interest. Then, a series of experiments are designed to further investigate the previously proposed important factors of influence [i.e. local bathymetry and the role of Shandong Peninsula (SDP)] on the tidal motions in the Yellow Sea. The numerical experimental results show that the interaction between the tidal wave system in the northern Yellow Sea and the incoming tidal wave plays a main role on the formation of the rotating tidal wave system in the southern Yellow Sea, whereas the role of geometric position of the SDP is secondary. With respect to the tidal current, it is found that the radial shape of it is independent of the local bathymetry, but may be generated by the convergent tidal wave formed by the meeting of the rotating tidal wave in the southern Yellow Sea and the incoming tidal wave from the East China Sea. Furthermore, a certain water depth is crucial for the intensity of current velocity to generate the special topography of radial sand ridges.