Tidal Constituents Research Articles

Tidal regime deformation due to sea level rise in the Malacca Strait: its impact on tidal bore generation in macro-tidal estuaries

The significance of this research lies in its contribution to understanding the changes in tidal characteristics in the Malacca Strait due to sea level rise (SLR) and the subsequent impacts on tidal bore generation in macro-tidal estuaries. As sea levels continue to rise, the semidiurnal tidal constituents (M2) in the southern Malacca Strait have shown a notably sensitive response, with an increased amplitude of ∼2 cm and a decreased phase shift of 2 ° over 33 years of field observations. Under future SLR scenarios, models predict that the amplitudes of tidal constituents will further increase by about 6–16% by the year 2100, while the phase will slightly decrease by around 10 ° , leading to a more accelerated tidal cycle. Of particular concern is the fact that the peak water level in the Malacca Strait is expected to rise more rapidly than the SLR itself due to the ‘double’ effect of SLR, which is becoming increasingly pronounced over time. This will lead to a significant rise in tidal bore height by ∼100 cm, with turbulent velocities during bore passages ranging from 1.1 to 1.5 m/s. Such changes increase the risk of local flooding and shoreline erosion. To address the long-term effects of SLR in the study area, it is crucial to regulate the proximity of settlements to riverbanks, manage land use effectively, and construct shoreline protection structures.

Tidal-Driven Water Residence Time in the Bohai and Yellow Seas: The Roles of Different Tidal Constituents

Tidal-Driven Water Residence Time in the Bohai and Yellow Seas: The Roles of Different Tidal Constituents

Development of an Ellipsoid Based Chart Datum Around the China Seas

Establishing a continuous chart datum (CD) surface is essential for marine navigation and geodetic applications. In China, the theoretical lowest tide (TLT) surface is adopted as the CD, calculated using 13 specific tidal constituents. This study outlines a comprehensive methodology for constructing a continuous TLT surface referenced to the Chinese Geodetic Coordinate System 2000 (CGCS2000) ellipsoid around the China Seas. A high-precision hybrid tide model was developed by integrating global tide models with satellite altimetry data to ensure a reliable CD. Accuracy evaluations of four global tide models, based on 72 tide gauge observations, identified EOT20 as the optimal model. The hybrid tide model incorporates eleven short-period constituents from EOT20 and FES2014, and two long-period constituents empirically derived from along-track satellite data. Using this hybrid tide model, we first constructed a mean sea surface (MSS) based TLT model. By integrating the HYBRID2023MSS model, this study further established a CGCS2000-based TLT model. Validation against measurements from the 72 tide gauge stations revealed that the ellipsoid based TLT model produces ellipsoid heights ranging from −53.44 to 74.50 m, exhibiting significant spatial variation. The MSS based TLT model achieved a standard deviation of 14.68 cm, confirming its high accuracy and reliability for practical applications.

Estimating tidal constituents in shallow waters from satellite altimetry using a 2D hydrodynamic model with nonlinear tide-surge interactions

Tidal models that incorporate satellite altimeter data have historically shown discrepancies in accuracy between shallow and deep marine environments. A recent study suggests that these differences may partly stem from neglecting the nonlinear tide-surge interactions in tidal analyses. In this study, we introduce a novel method for estimating tidal constituents from satellite altimeter data in shallow waters, leveraging a 2D hydrodynamic model that accounts for these nonlinear interactions. This approach substantially reduces the variance of unaccounted water level variability, thereby benefiting the estimation. A distinctive feature of our method is the treatment of prior model tidal constituents as stochastic, which helps manage the low temporal resolution of altimeter data by ensuring that unresolved tidal constituents are not updated. We tested our method in the data-rich northwest European continental shelf region, using the high-resolution 2D Dutch Continental Shelf Model version 7 (DCSM). Results show a substantial reduction in the standard deviations of residual water level time series in the shallow waters around Great Britain and in the German Bight, from 11 cm to 5 cm. In deep waters (>200 m), the median standard deviation decreased from 6.8 cm to 6.2 cm. When compared to state-of-the-art ocean tide and surge corrections from publicly available models, our method outperformed them in shallow waters (median standard deviation of 6.0 cm versus 7.5 cm), though the alternative products performed better in deep waters (median standard deviation of 5.5 cm versus 6.2 cm). An estimate of the accuracy at satellite crossovers resulted in an estimated total tidal error of about 1.5 cm (RSS VD). We acknowledge that comparisons in shallow waters are complicated, as alternative products do not account for nonlinear tide-surge interactions. Overall, the demonstration along-track tidal product developed in this study shows potential for improving the tidal representation in the DCSM model. In data-poor regions, the number of tidal constituents that can be reliably estimated using the method may be limited, and alternative strategies might be needed to evaluate the model’s uncertainty in representing tides.

Depth modernization by integrating mean sea surface model, ocean tide model, and precise ship positioning

This paper presents a study on depth modernization, paralleling height modernization for land elevations. Depth modernization integrates mean sea surface (MSS) models, ocean tide models, and precise ship positioning to achieve accurate seafloor depth measurements. Conventional methods rely on tidal corrections and chart datum from temporary tide gauges, which can be challenging in regions with complex tidal patterns and inconsistent chart datums. For depth modernization, we developed (1) a hybrid MSS model using satellite altimeter data, tide gauge records, and a regional geoid model, and (2) a hydrodynamic-driven ocean model with 26 tidal constituents to determine separations between the hybrid MSS and five tidal surfaces, resulting in five ellipsoid-based surfaces analogous to a geoid model for height modernization. Precise ship positioning is demonstrated using GNSS data collected by the Legend research ship in the Pacific Ocean east of Taiwan and the Canadian spatial reference system precise point positioning toolbox. We used measurements in the Taiwan Strait to show how modern depth is implemented. Comparisons of depths in four regions from the conventional and modern methods show small (a few cm) to moderate (a few dm) differences with some variability depending on the region and equipment. Discontinuities in depths from the conventional method are analyzed. Depth modernization has significantly benefited rapid and accurate bathymetric mapping for electronic navigation charts. Future work in MSS and ocean tide models and the availability of PPP tools for depth modernization are discussed. For mapping agencies worldwide, depth modernization should be prioritized alongside height modernization to ensure rapid and accurate depth data provision.

Optimized gravity field retrieval for the MAGIC mission concept using background model uncertainty information

Errors in ocean tide and non-tidal atmospheric and oceanic models are among the largest error sources in gravity field recovery from space. We co-estimate corrections to these background models subject to uncertainty constraints during the adjustment procedure of gravity field spherical harmonic coefficients. Simulations are performed for the Mass-Change and Geoscience International Constellation to evaluate the effect of such a constrained procedure on monthly gravity field retrievals for the planned ESA-NASA double-pair mission. The influence of co-estimating background model corrections subject to known uncertainty information is evaluated separately for both types of background models and is then combined and used to retrieve monthly gravity fields over one year. Retrieval errors are compared to those obtained with the standard recovery procedure, which neglects these corrections. It is shown that gravity field retrieval errors are reduced by up to 36%. In addition, the one-year simulation is used to estimate residual corrections for eight major tidal constituents in order to improve ocean tide background modelling. Adding these residual corrections to the applied a priori ocean tide model shows that ocean tide errors are decreased by up to 27%.

Constraining the parameters of the Andrade rheology in Earth's mantle with Love numbers of 12 tidal constituents

Constraining the parameters of the Andrade rheology in Earth's mantle with Love numbers of 12 tidal constituents

ANALYSIS FROM 1980 TO 2018 OF TIDAL OBSERVATION DATA FOR ASSESSING THE STABILITY OF TIDAL CONSTANTS FOR PRIMARY PORT

Tidal analysis involves the computation of tidal constants (phase lag (g) and amplitude (H)) of tidal constituents at a location. This study focuses on the assessment of the stability of g and H for the Bonny port which is the only standard tidal port in Nigeria. Monthly analysis of tidal observations was carried out with 1980, 1994 and 2018 year’s data using Least Squares Method (LSM) of Harmonic Analysis with MATLAB programming codes. The observation equation technique of LSM is adopted; the dimension of the Normal (N) matrix equations obtained for the monthly analysis is 72 56 i.e. 72 rows, and 56 columns. The N matrix is inverted and gave results for mean sea level (MSL) and g and H of 28 primary constituents of tide. Four major constituents of tide (M2, S2, K1 and O1) remain stable throughout the analysis. The mean of g and H obtained for each year was observed to be almost equal to the mean obtained from the three-year data. The maximum residuals and spreads of the computed g and H over the period of study show that g and H at Bonny are stable and that results from accurately analyze one-month data observation can be employed for tidal prediction for several years. Therefore, it can be concluded that the g and H for M2, S2, K1 and O1 are stable and that the type of tide (F) at Bonny port is semidiurnal since the computed F is 0.16 which is 0.25.

Investigation of Coastal Effects of Current-Wave Coupling during a Typhoon Event using Delft3D-FM

In this study, the effects of current-wave coupling on coastal hydrodynamics during a typhoon event were investigated using the Delft3D-FM (Flexible Mesh) model. This model is advantageous for simulating flows and waves without the need for nesting, transitioning from the deep seas of the far offshore area, which have coarse resolution, to the shallow waters of the coastal area, which require high resolution. As a result, its computational time is relatively shorter compared to other unstructured grid-based numerical models. This study focused on Typhoon Maysak, which caused significant damage along the coast of Busan, a metropolitan city located on the southeastern coast of Korea. The flow module of the model was forced at the offshore boundaries with the main 13 tidal constituents extracted from the TPXO 8.0 Global Tidal Model database. Boundary conditions and wind forcing for the wave simulations were provided by the ERA5 reanalysis wave data. The flow and wave modules were coupled to simulate the storm surge during the typhoon event. The simulation results showed good agreement with the measured water level and wave data. The results also indicated that the coupling effects tend to increase the storm surge in the inner parts of the bays and raise current speeds in the nearshore.

Modelling Sand Wave Evolution and Migration in North Sea Using ROMS

Sand waves are large and transverse bed features, typically with lengths and heights of about 100-500 m and 2-10 m, respectively. The height can grow up to 30% of the average water depth, especially in shallow water conditions. Sand waves can migrate up to around 10 m/year and may profoundly impact subsea infrastructure, such as offshore pipelines and cables, key elements of offshore energy development. In this study, the evolution and migration of sand waves in the Dutch shoreface, North Sea 1986, was investigated using the Regional Oceanographic Modeling System (ROMS) and validated with DELFT3D and survey results from 2000. ROMS is an open-source oceanographic model available for free, created by the United States Geological Survey (USGS) to simulate ocean circulation, sediment transport, and seabed morphodynamics. Calibration of ROMS model conducted by modelling velocity profile in different location and free surface compared to field data. Validation ROMS and DELFT3D result was conducted by comparison the sandwave profile plotting in same graph. ROMS' simulation results agree with DELFT3D's results regarding horizontal grid size; vertical grid level; stretching parameters; time step; sediment diameter; M2 tide velocity which is the most dominant tidal constituent, representing the principal lunar semi-diurnal tide that has a period of approximately 12.42 hours and is caused by the gravitational pull of the Moon; M4 tide velocity which is the overtide of M2, generated by nonlinear interactions, especially in shallow water regions, a harmonic of M2 and has a period of approximately 6.21 hours (half the period of M2); net current in tidal; water depth; and waves. It can be concluded that horizontal grid size and stretching parameters are weakly sensitive to the results. In contrast, sediment diameter, M2 tide velocity, M4 tide velocity, net current in tidal, water depth, and waves may affect the migration significantly. Even though vertical grid level and time step parameters impact the results, these parameters need to be defined with a certain value following the Courant-Friedrichs-Lewy (CFL) condition.

Full-grid bathymetry estimation in the numerical simulation of 8 tidal constituents using an ensemble adjustment Kalman filter-smoothing scheme

The spatially varying geographic-parameters introduce significant uncertainty into the ocean model. Due to the impracticality of manually tuning spatial varying parameters, data assimilation methods are widely used for geographic-parameter optimization (GPO). Practically, the limited observations do not contain enough information to perform GPO directly on the entire grid. Therefore, techniques are required to reduce the complexity of the parameters. A full-grid GPO scheme based on the ensemble adjustment Kalman filter (EAKF) is developed. Via smoothing the spatial distribution of posterior parameter members, the EAKF-smoothing (EAKF-S) introduces additional spatial correlations among parameters. Meanwhile, the small-scale correlation between the state and the parameters, which exhibit strong pseudo-correlations, is filtered out. A tide model of the Bohai Sea and Yellow Sea, considering 8 principal tidal constituents. is constructed using the Princeton Ocean Model with the generalized coordinate system (POMgcs). The EAKF-S is employed for optimizing the full-grid bathymetry. In twin experiment, based on idealized water level observations, EAKF-S effectively reduced model errors and approximately inverted the “true” bathymetry. After GPO, the lowest mean absolute error of the parameter ensemble is 0.83 m. A series of practical GPO experiments based on synthetic water level observations calculated from NAO.99Jb data are performed. First, the improvement of EAKF-S in accuracy and efficiency over standard EAKF is proven using an M2 tide model. After that, a practical experiment on an 8 constituents tide model is performed. The results show that the forecasting performance of all 8 constituents is improved after GPO, indicating the efficacy of EAKF-S.

Magnetic signals from oceanic tides: new satellite observations and applications.

The tidal flow of seawater across the Earth's magnetic field induces electric currents and magnetic fields within the ocean and solid Earth. The amplitude and phase of the induced fields depend on the electrical properties of both seawater and the solid Earth, and thus can be used as proxies to study the seabed properties or potentially for monitoring long-term trends in the global ocean climatology. This article presents new global oceanic tidal magnetic field models and their uncertainties for four tidal constituents, including [Formula: see text] and even [Formula: see text], which was not reliably retrieved previously. Models are obtained through a robust least-squares analysis of magnetic field observations from the Swarm and CHAMP satellites using a specially designed data selection scheme. We compare the retrieved magnetic signals with several alternative models reported in the literature. Additionally, we validate them using a series of high-resolution global three-dimensional (3D) electromagnetic simulations and place constraints on the conductivity of the sub-oceanic mantle for all tidal constituents, revealing an excellent agreement between all tidal constituents and the oceanic upper mantle structure.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.

Physical oceanographic factors controlling the ocean circulation-induced magnetic field.

Oceanic tidal constituents and depth-integrated electrical conductivity (ocean conductivity content, or OCC) extracted from electromagnetic (EM) field data are known to have a strong potential for monitoring ocean heat content, which reflects the Earth's energy imbalance. In comparison to ocean tide models, realistic ocean general circulation models have a greater need to be baroclinic; therefore, both OCC and depth-integrated conductivity-weighted velocity ([Formula: see text]) data are required to calculate the ocean circulation-induced magnetic field (OCIMF). Owing to a lack of [Formula: see text] observations, we calculate the OCIMF using an ocean state estimate. There are significant trends in the OCIMF primarily owing to responses in the velocities to external forcings and the warming influence on OCC between 1993 and 2017, particularly in the Southern Ocean. Despite being depth-integrated quantities, OCC and [Formula: see text] (which primarily determine the OCIMF in an idealized EM model) can provide a strong constraint on the baroclinic velocities and ocean mixing parameters when assimilated into an ocean state estimation framework. A hypothetical fleet of full-depth EM-capable floats would therefore help improve the accuracy of the OCIMF computed with an ocean state estimate, which could potentially provide valuable guidance on how to extract the OCIMF from satellite magnetometry observations.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.

Accuracy assessment of recent global ocean tide models in coastal waters of the European North West Shelf

Accuracy assessment of recent global ocean tide models in coastal waters of the European North West Shelf

Dissipation Scaled Internal Wave Drag in a Global Heterogeneously Coupled Internal/External Mode Total Water Level Model

AbstractThis study showcases a global, heterogeneously coupled total water level system wherein salinity and temperature outputs from a coarser‐resolution (12 km) ocean general circulation model are used to calculate density‐driven terms within a global, higher‐resolution (2.5 km) depth‐averaged total water level model. We demonstrate that the inclusion of baroclinic forcing in the barotropic model requires modification of the internal wave drag term to prevent excess degradation of tidal results compared to the barotropic model. By scaling the internal tide dissipation by an easy to calculate dissipation ratio, the resulting heterogeneously coupled model has complex root mean square errors (RMSE) of 2.27 cm in the deep ocean and 12.16 cm in shallow waters for the tidal constituent. While this represents a 10%–20% deterioration as compared to the barotropic model, the improvements in total water level prediction more than offset this degradation. Global median RMSE compared to observations of total water levels, 30‐day sea levels, and non‐tidal residuals improve by 1.86 (18.5%), 2.55 (42.5%), and 0.36 (5.3%) cm respectively. The drastic improvement in model performance highlights the importance of including density‐driven effects within global hydrodynamic models and will help to improve the results of both hindcasts and forecasts in modeling extreme and nuisance flooding. With only an 11% increase in model run time compared to the fully barotropic total water level model, this approach paves the way for high resolution coastal water level and flood models to be used alongside climate models, improving operational forecasting of total water levels.

Behavior and Energy of the M2 Internal Tide in the Madagascar–Mascarene Region

Internal tides serve as essential intermediate steps in the cascading of oceanic energy, playing a crucial role in oceanic mixing. M2 internal tides are the dominant tidal constituent in many oceanic regions, significantly influencing ocean dynamics. The Madagascar–Mascarene Region has high-energy internal tides, but due to a lack of observational studies, their propagation remains underexplored and warrants further investigation. In this study, we used satellite altimetry data to capture the sea surface manifestation of the first-mode M2 internal tides in the region. The results show that the Mascarene Plateau plays a key role in shaping the region’s uneven internal tide distribution. The Mascarene Strait is the most intense generation area, with an east-west energy flux of 1.42 GW. Using the internal tidal energy concentration index, we decomposed the internal tidal beams, finding the primary beam oriented at 148°. These beams propagate outward for over 800 km, with a maximum distance exceeding 1000 km. Geostrophic currents intensify the northward refraction of westward-propagating internal tides in the Mascarene Basin, particularly between 15°S and 20°S.

Disentangling hydrodynamic drivers of the Southern Venice (Italy) coastal aquifer via frequency decomposition analysis: Insights, challenges, and limitations

Disentangling hydrodynamic drivers of the Southern Venice (Italy) coastal aquifer via frequency decomposition analysis: Insights, challenges, and limitations

Benefits of tidal admittance functions for refining GNSS-observed solar and lunisolar tidal constituents

Benefits of tidal admittance functions for refining GNSS-observed solar and lunisolar tidal constituents

Assessing hydrodynamic impacts of tidal range energy impoundments in UK coastal waters

Assessing hydrodynamic impacts of tidal range energy impoundments in UK coastal waters

PREDIKSI PASANG SURUT PERAIRAN SEKITAR KOTA BITUNG DENGAN PENAMBAHAN KONSTANTA HARMONIK PERAIRAN DANGKAL

Bitung is a city with the most intensive marine space utilization activities in North Sulawesi Province. Therefore, information regarding oceanographic conditions is very important in relation to development in this city. One of the important information regarding oceanographic conditions is tides. This study was conducted with the aim of assessing the accuracy of tidal prediction with the addition of shallow water harmonic constituents and examining the amplitude fluctuations of the main harmonic component due to the addition of the shallow water constituents. The least squares method was used to calculate the amplitude and phase of tidal harmonic constituents, followed by data prediction. The data used is the measurement data of BMKG Bitung City tidal station in January, February and March 2024. The results obtained are the addition of shallow water harmonic constituents to the tidal analysis around Bitung City increases the accuracy of the prediction data. The best RMSE value for January data is 3.8323 cm; February 4.1902 cm; and March 4.2558 cm. The correlation coefficient increases and the percentage of predicted data with differences < 3 cm and < 6 cm with the observation data becomes larger. It is also found that when processing with few harmonic constituents, the amplitudes of constants M2, S2, K1, and O1 fluctuate. The addition of harmonic constituents in the analysis results in more constant amplitudes of constituents M2, S2, K1, and O1.