Strong Tides Research Articles

Real-Time and Long-Term Monitoring of Coastal Water Turbidity Using an Ocean Buoy Equipped with an ADCP

In this study, an acoustic Doppler current profiler (ADCP) operating at 600 kHz was installed on an ocean data buoy in the Qigu waters, Taiwan, to gather real-time sound echo intensity data. These data were then correlated with turbidity measurements obtained by a turbidimeter mounted on the buoy’s mooring line at a water depth of 13 m. The data buoy operated from 6 June to 16 August 2017. During this period, turbidity measurements were recorded from 6 to 21 June 2017. This study established a calibration between the sound echo intensity measured by the ADCP and the turbidity measured using the turbidimeter; a strong linear correlation was discovered between these two variables. This correlation enabled the conversion of echo intensity data into a continuous time series of turbidity measurements, facilitating real-time and long-term monitoring of coastal water turbidity through the deployment of a buoy equipped with an ADCP. The relationships between turbidity and environmental factors such as rainfall, tides, current speeds, and wave activity over an extended period were then investigated. The results revealed that stronger tides and currents in the Qigu waters often lead to higher turbidity, suggesting that these two factors are the primary driving forces for sediment transport in the Qigu waters. Additionally, sampling of water in the Qigu area revealed sediment particles of size ranging from 2 to 120 μm.

The Feasibility of Asynchronous Rotation via Thermal Tides for Diverse Atmospheric Compositions

The equilibrium rotation rate of a planet is determined by the sum of torques acting on its solid body. For planets with atmospheres, the dominant torques are usually the gravitational tide, which acts to slow the planet’s rotation rate, and the atmospheric thermal tide, which acts to spin up the planet. Previous work demonstrated that rocky planets with thick atmospheres may produce strong enough thermal tides to avoid tidal locking, but a study of how the strength of the thermal tide depends on atmospheric properties has not been done. In this work, we use a combination of simulations from a global climate model and analytic theory to explore how the thermal tide depends on the shortwave and longwave optical depth of the atmosphere, the surface pressure, and the absorbed stellar radiation. We find that for planets in the habitable zones of M stars only high-pressure but low-opacity atmospheres permit asynchronous rotation owing to the weakening of the thermal tide at high longwave and shortwave optical depths. We conclude that asynchronous rotation may be very unlikely around low-mass stars, which may limit the potential habitability of planets around M stars.

Spurious numerical mixing under strong tidal forcing: a case study in the south-east Asian seas using the Symphonie model (v3.1.2)

Abstract. The role of mixing between layers of different densities is key to how the ocean works and interacts with other components of the Earth's system. Correctly accounting for its effect in numerical simulations is therefore of utmost importance. However, numerical models are still plagued with spurious sources of mixing, originating mostly from the vertical advection schemes in the case of fixed-coordinate models. As the number of phenomena explicitly resolved by models increases, so does the amplitude of resolved vertical motions and the amount of spurious numerical mixing, and regional models are no exception to this. This paper provides a clear illustration of this phenomenon in the context of simulating the south-east Asian (SEA) seas along with a simple way to reduce its impact. This region is known for its particularly strong internal tides and the fundamental role they play in the dynamic of the region. Using the Symphonie ocean model, simulations including and excluding tides and using a pseudo-third-order upwind advection scheme on the vertical are compared to several reference datasets, and the impact on water masses is assessed. The high diffusivity of this advection scheme is demonstrated along with the importance of accounting for tidal mixing for a correct representation of water masses. Simultaneously, we present an improvement in this advection scheme to make it more suitable for use in the vertical. Simulations with the new formulation are added for comparison. We conclude that the use of a higher-order numerical diffusion operator greatly improves the overall performance of the model.

Triton’s Captured Youth: Tidal Heating Kept Triton Warm and Active for Billions of Years

Neptune’s moon Triton has two remarkable attributes: its retrograde orbit suggests that it was captured from the Kuiper Belt, and Triton has one of the youngest surfaces of all the icy satellites in the solar system. Soon after capture, Triton experienced strong diurnal tides raised by Neptune, which caused intense deformation, heating, and melting of its ice shell as its highly eccentric initial orbit was circularized. While previous studies have suggested that Triton’s orbit would have circularized early in solar system history, we show that internal feedbacks between tidal heating and ice shell melting significantly reduce the orbital evolution rate, causing strong tidal heating to persist for billions of years. We simulate Triton’s post-capture evolution over a range of initial semimajor axes and ice shell properties. We find that Triton’s ice shell would have been extremely thin (1–10 km) for a period of 1–4 billion years, with tidal stresses strong enough to fracture the entire ice shell down to the subsurface ocean. A final phase of intense geologic activity may have occurred after tidal dissipation waned, in which late-stage ice shell thickening caused ocean pressurization potentially sufficient to refracture the ice shell and push water to the surface. Such overpressurization could have caused recent massive cryovolcanic resurfacing, perhaps explaining Triton’s geologically young surface. It is therefore possible that Triton’s youthful surface and its origin as a captured satellite may in fact be related. A long-lived subsurface ocean and extended thin ice shell period also greatly increase Triton’s astrobiological potential.

Geochemical characteristics of the modern Yellow River Delta sediments and their response to evolution of the sedimentary environment

IntroductionSedimentary evolution and river channel changes of large river delta (e.g. Huang River, Changjiang River) in response to environmental changes have been one of the key issues in global change research.MethodsThis study reconstructed sedimentary environment changes in the modern Yellow River Delta (YRD), based on grain size and elemental chemical analysis of two short cores (YDC and YDG) from the southern region of the Qing 8 course delta of the modern YRD. ResultsThe results indicated that the cores YDC and YDG sediment were dominated by silt (58.47% and 67.6%, respectively) with varied grain-size variations and poor sediment sorting. The cores YDC and YDG sediments are both predominantly composed of the major element SiO2, and have an average content of 55.53% and 58.45%, respectively. The R-mode factor analysis showed the content of chemical substances of core sediments was controlled by three factors: grain size, sedimentary provenance, and marine sedimentary dynamics. DiscussionBefore the diversion of the Yellow River to the Qing 8 course in 1996, the two cores sediment were mainly sources from the Yellow River, and both cores were in the delta-front sedimentary environment under weak hydrodynamic conditions. After the Yellow River was diverted to the Qing 8 course, the cores YDC and YDG experienced significant erosion under the nearshore strong waves and tides. And then the sedimentary environment of the YRD changed from siltation to erosion. The results of the study would be helps to further our understanding of the changes in sediment grain size and geochemical element characteristics in the Yellow River estuary, and reveal the evolution of its sedimentary environment.

Influences of sudden stratospheric warmings on the ionosphere above Okinawa

Abstract. We analyzed the ionosonde observations from Okinawa (26.7° N, 128.1° E; magnetic latitude: 17.0° N) for the years from 1972 to 2023. Okinawa is in the northern low-latitude ionosphere, where the influences of sudden stratospheric warmings (SSWs) on the ionosphere are expected to be stronger than in the mid- and high-latitude ionospheres. We divided the dataset into winters with major SSWs in the Northern Hemisphere (SSW years) and winters without major SSWs (no-SSW years). During the SSW years, the daily cycle of the F2-region electron density maximum (NmF2) is stronger than in the no-SSW years. The relative NmF2 amplitudes of solar and lunar tidal components (S2, O1, M2, MK3) are stronger by 3 % to 8 % in the SSW years than in the no-SSW years. The semidiurnal amplitude, averaged across 29 SSW events, has a significant peak at the central date of the SSW (epoch time 0 of the composite analysis). The SSW influence is not strong: the semidiurnal amplitude is about 38.2 % in the SSW years and about 34.0 % in the no-SSW years (relative to the NmF2 of the background ionosphere). However, there is a sharp decrease in the amplitude of about 10 % after the SSW peak is reached. The amplitude of the diurnal component does not show a single peak at the central date of the SSW. We present the maximal semidiurnal amplitudes of the SSWs since 1972. The SSW of 31 December 1984 has the strongest amplitude (162 %) in the ionosphere above Okinawa (with a high geomagnetic activity, Ap, of 37 nT). The most surprising finding of the study is the strong lunar tides with relative amplitudes of about 10 % and the discovery of a terdiurnal lunar tide (5 %) in the NmF2 during the SSW years. The periods of the ionospheric lunar tides align with the periods of ocean tides and lunisolar variations in the atmosphere.

Ocean internal tides suppress tropical cyclones in the South China Sea

Tropical Cyclones (TCs) are devastating natural disasters. Analyzing four decades of global TC data, here we find that among all global TC-active basins, the South China Sea (SCS) stands out as particularly difficult ocean for TCs to intensify, despite favorable atmosphere and ocean conditions. Over the SCS, TC intensification rate and its probability for a rapid intensification (intensification by ≥ 15.4 m s−1 day−1) are only 1/2 and 1/3, respectively, of those for the rest of the world ocean. Originating from complex interplays between astronomic tides and the SCS topography, gigantic ocean internal tides interact with TC-generated oceanic near-inertial waves and induce a strong ocean cooling effect, suppressing the TC intensification. Inclusion of this interaction between internal tides and TC in operational weather prediction systems is expected to improve forecast of TC intensity in the SCS and in other regions where strong internal tides are present.

Distributed Optical Fibre Sensing for High Space‐Time Resolution Ocean Velocity Observations: A Case Study From a Macrotidal Channel

AbstractDespite significant recent technological advances, oceanographic observations on horizontal scales of meters to a few kilometres prove challenging. Exploiting legacy seafloor cables presents a disruptive prospect to address this gap, as it may provide low‐cost sustained observations with high space‐time resolution, enabled through novel opto‐electronic interrogation of optical fibers within the cables. Here, we demonstrate this approach in a renewable tidal energy cable embedded within a region with a strong barotropic tide. By making remote measurements continuously over 12 hr, we obtain the distributed differential strain experienced by 2 km of offshore cable from a diverse range of oceanic flow processes, with an along‐cable resolution of 2.04 m. We successfully identify: (a) nearshore wave breaking and its modulation by changes in water depth; (b) along‐cable tidal velocity, shown to be linearly related to the differential strain; and (c) high‐frequency motions consistent with 3‐dimensional turbulent processes, either of natural origin or from flow‐cable interaction. These inferences are supported by nearby conventional measurements of water depth and velocity.

Study of the effect of spur dikes on beach protection based on physical model experiment

The Qiantang River is a typical strong tide estuary, the world-famous tidal bore have huge turbulent energy and causes damage to the sea wall. Spur dike is an important engineering to prevent the seawall foundation from tidal bore. But the tidal bore occurs at the low tide level, strong turbulence, high flow velocity, water level rises sharply. The spur dike height, length, inclination angle need to be determined by physical model according to the specific bore dynamic conditions. In the tests, the fixed-bed model was used to study the tidal current velocity reduction rate and region, the falling current circulation characteristics in dike field. The movable-bed model test is used to study the effect of each test on protecting the beach. This physical model study reveals the rule of spur dike influence on tidal bore dynamics so the effect of spur dike on protecting the beach is clear.

A Multiscale 1D-2D Coupled Model Of The Scheldt Estuary Rivers And The European Continental Shelf

This study presents a model for simulating the interaction of river influxes with tidal propagation in region of varying complexity for the Scheldt basin (river, tributaries and estuary) and the European continental shelf. While the domain for inland rivers is one-dimensional and extends until the limit of tidal influence, the estuary and shelf region are dealt by means of two-dimensional equations. Within this region, there exists a hydraulic structure in one of the Scheldt tributaries (Dyle River), that is implemented to simulate the bidirectional flow of the tide. In this model a tidal forcing at the shelf break, metrological forcing at the free water surface and hourly discharges for the rivers and tributaries at the upstream boundaries are applied. Using this, the coupled model was firstly calibrated for the Manning coefficient for a relatively quiet period. Then it is extensively validated using available measurements for simulations in the month of January (2021), which is generally marked by strong tides. Moreover, the shelf region of the model was evaluated with the existing literature for the harmonic analysis of the dominant M2 tide. The simulated results show good agreement with a RMSE under 0.3 meters for the measured water levels.

Impacts of extreme river discharge on coastal dynamics and environment: Insights from high-resolution modeling in the German Bight

The intricate relationship between extreme river discharge and its consequential effects on coastal basins’ environment and dynamics remains a subject of profound significance. The impact of extreme river discharge on coastal basin dynamics and environment is a complex phenomenon, particularly relevant in the context of the German Bight. The inflow of freshwater from rivers into the German Bight plays a crucial role in driving the complex thermohaline circulation. Addressing the challenges posed by local hydro-meteorological extremes, compounded by strong wind waves, currents and tides is vital for comprehensive impact assessment. Utilizing the Geesthacht Coupled cOAstal model SysTem (GCOAST) with high-resolution configuration, we investigate the sensitivity of the thermohaline properties to the river forcings. By incorporating river discharge as lateral land forcing in a coupled hydrodynamic and wave model, we conducted five sensitivity experiments. Our findings reveal that the simulated temperatures closely match measurements in all experiments. The salinity, however, is remarkably sensitive to the variation of freshwater from the rivers Elbe and Ems in the German Bight, causing the haline stratification. The statistical evaluation, as demonstrated by the Taylor diagram at the Marnet DB station, underscores the skill of the Mesoscale Hydrologic Model (mHM) in generating the freshwater discharge that drives the thermohaline characteristics of the German Bight, especially during events like the June 2013 flooding. Significantly, the use of climatological runoff proves to be ineffective in simulating stratification during extreme flooding events. In essence, this investigation enhances our understanding of the pivotal role played by high-frequency river freshwater buoyancy. It emerges as a driving force behind salinity fluctuations during extreme floods, providing valuable insights into coastal dynamics within the German Bight.

A Global View on Internal Tides

This is a review paper on generation of internal tides in the global ocean based on literature data and publications of the author. Energy fluxes of semidiurnal internal tide generation over submarine ridges were estimated based on modeling and measurements on moorings in many regions of the ocean. Data from 4000 moorings during a period of 50 years are considered. Regions of intense generation of internal tides are indicated. They are related to several underwater oceanic ridges. Energy fluxes from submarine ridges greatly exceed those from the continental slopes because generally the currents of the barotropic tide are parallel to the coastline. If the barotropic tide currents are normal to the ridge, they generate strong internal tides. They account approximately for one fourth of the energy losses of the barotropic tide. Decay of internal tide during propagation was estimated based on the data from lines of moorings located normal to the ridges. Model simulations and moored measurements result in a global map of semidiurnal internal tide amplitudes

The Macroeconomic Effect of Oil Sector Crisis in Libya

This paper analyses and investigates the impact of the oil sector crisis on the Libyan economy from 2012 Q4 to 2022 Q3, using the Bai-Perron model and a structural vector autoregressive model (SVAR). The findings demonstrate that the multiple structural breaks test statistics approved that nearly all of the study's variables had a structural break at years around political division and political agreement. In contrast to inflation, the results of the impulse response functions (IRFs) indicate that the shock to oil revenue had a considerable negative impact on the money supply and exchange rate. Furthermore, the study reveals that, with the exception of claims on the government with the central bank, shocks to oil revenue are the major contributors to variance decomposition for all variables. The results reveal that oil revenue, in particular, accounts for roughly 16%, 13%, and 16% of the variance decomposition of the money supply, exchange rate, and inflation rate, respectively. As a result, the oil sector crisis is a controlling factor in the explanation of variations in these variables. The study concluded that oil sector revenues have a sensitive impact on the Libyan economy and that the latter has a strong tide with a secure environment and political stability.

Estuarine Exchange Flow in the Salish Sea

AbstractThe Salish Sea is a large, fjordal estuarine system opening onto the northeast Pacific Ocean. It develops a strong estuarine exchange flow that draws in nutrients from the ocean and flushes the system on timescales of several months. It is difficult to apply existing dynamical theories of estuarine circulation there because of the extreme bathymetric complexity. A realistic numerical model of the system was manipulated to have stronger and weaker tides to explore the sensitivity of the exchange flow to tides. This sensitivity was explored over two timescales: annual means and the spring‐neap. Two theories for the estuarine exchange flow are: (a) “gravitational circulation” where exchange is driven by the baroclinic pressure gradient due to along‐channel salinity variation, and (b) “tidal pumping” where tidal advection combined with flow separation forces the exchange. Past observations suggested gravitational circulation was of leading importance in the Salish Sea. We find here that the exchange flow increases with stronger tides, particularly in annual averages, suggesting it is controlled by tidal pumping. However, the landward salt transport due to the exchange flow decreases with stronger tides because greater mixing decreases the salinity difference between incoming and outgoing water. These results may be characteristic of estuarine systems that have rough topography and strong tides.

Spatial patterns of sediment contamination and their influence on benthic infaunal communities in a highly tidal and industrial estuary in Atlantic Canada

Sediment contamination can be elevated in ports, harbours, and estuaries with legacies of exploitation, negatively impacting infaunal invertebrate communities. Saint John Harbour (45.25° N, 66.05° W), New Brunswick, Canada, is an active harbour with strong tides and a long history of human activity. To examine spatial patterns of sediment contamination, samples were collected between 2011 and 2021 from subtidal sites near potential contaminant sources. Invertebrate data from the same samples were used to investigate potential effects on biological communities. Contaminant concentrations in the inner parts of the harbour were elevated compared to reference sites, but generally did not reach levels comparable to other highly contaminated harbours in the region. Effects on invertebrates were detectable, particularly at sites with higher contamination, although physical factors (depth, sediment grain size) were more important. Dynamic tidal conditions in the harbour may reduce the accumulation of contaminants in subtidal sediments and their impacts on infaunal communities.

Reflection and Scattering of Low-Mode Internal Tides on the Continental Slope of the South China Sea

Abstract It is well known that strong low-mode internal tides generated in Luzon Strait propagate westward to impinge continental slopes in the northeastern South China Sea (SCS). The reflection and scattering of these internal tides including diurnal and semidiurnal components on the slopes are quantitatively investigated using two sets of mooring data and a linear internal tide model with realistic topography and stratification. Flux reflections computed from mooring data collected on the continental slopes are consistent with the linear model. Based on the results of the observations and simulations, a map of low-mode internal tide reflection and scattering coefficients along the continental margin in the northeastern SCS is revealed. On average, diurnal internal tides lose 38% of their energy to high modes (≥mode 4) that are assumed to dissipate on the slopes, transmit 28% onto the continental shelf, and reflect 31% back to the deep ocean. On the contrary, most of the semidiurnal energy (89%) transmits onto the continental shelf, and only 11% is scattered to high modes (7%) and reflected back to the deep ocean (4%). For diurnal internal tides, a large fraction of energy that is scattered to high modes and reflected back to the deep sea can be attributed to the critical–supercritical slopes, while the weak reflection for the semidiurnal energy is due to the subcritical slopes. These quantitative descriptions for evolutions of low-mode internal tides incident to the slopes provide an energy budget map on the continental slopes in the northeastern SCS.

Strait of Kara Gates: A Region of Strong Internal Tides in the Arctic Seas

This is a review paper about measurements of internal tides in the Kara Gates Strait. Kara Gates is one of the straits where intense internal tides are generated by tidal currents overflowing the transversal sill of the strait. Tidal currents are superimposed on a constant current from the Barents to the Kara Sea. Field studies of internal waves in the strait were carried out in 1997, 2007, 2015, and 2016. Analysis of measurements on moorings and towed CTD in scanning mode is presented. Field studies are supported by model simulations of generation and propagation of internal tides.

Fatigue condition assessment of subsea pipelines under vortex induced vibration and cyclical lateral displacement

ABSTRACT Subsea pipeline may suffer from vortex-induced vibration (VIV) and cyclical lateral displacement (CLD), which can result in fatigue failure of subsea pipeline. This paper presents a fatigue damage assessment of subsea pipelines under VIV and CLD. A finite element model of pipeline considering the pipe–soil coupling action is developed, and dynamic response of subsea pipeline under VIV and CLD is implemented to obtain time history of equivalent stress. The integrated fatigue damage of subsea pipeline under VIV and CLD is estimated using Palmgren–Miner linearly cumulative fatigue damage theory. The effect of pipe diameter, span length, pipe length and tidal period on fatigue damage of subsea pipelines under CLD is analyzed. A case study of a subsea pipeline in the strong tide area is performed. The results show the fatigue life of pipeline under VIV and CLD is 14.1 years, which is 2.3 years lower than the pipeline under VIV alone. The study can support more accurate estimation of fatigue life of subsea pipelines.

Spatial and Temporal Variability of the Thermohaline Structure of Waters in the Antarctic Sound

The sea straits of the Antarctic Peninsula region are characterized by intense currents, the presence of sea ice and large icebergs, strong tides, and many other factors that form the thermohaline structure of the waters in this region and its temporal variability. The existence of local ecological communities depends on the thermohaline properties of the waters in the straits that determines the relevance of this work. From this point of view, the Antarctic Sound, which connects the Bransfield Strait with the western part of the Weddell Sea, stands out in particular. Based on new field data, a description of the thermohaline structure of this strait is given. Unique data from autonomous sensors installed on marine mammals were used for the first time and made it possible to track changes in the waters throughout the year. The transitional seasons, as well as the general boundaries of the thermohaline characteristics of the waters in the strait, have been determined. The spatial, seasonal and interannual variability of the thermohaline structure of the waters in the strait was studied on the basis of data over the last 40 years.

Oceanic and ecological response to native Typhoons Cempaka and Lupit (2021) along the northern South China Sea continental shelf: comparison and evaluation of global and regional Operational Oceanography Forecasting Systems

The Global Operational Oceanography Forecasting System from the Mercator Ocean (MO) and the regional South China Sea Operational Oceanography Forecasting System (SCSOFSv2) were compared and evaluated using in situ and satellite observations, with a focus on the oceanic and ecological response to two consecutive native typhoons, Cempaka and Lupit, that occurred in July–August 2021. Results revealed a better simulation of the chlorophyll a (Chla) structure by SCSOFSv2 and a better simulation of the temperature profile by MO in the Pearl River Estuary. In addition, SCSOFSv2 sea surface temperature (SST) and MO Chla variations corresponded well with observations along the northern SCS shelf. Simulated maximum SST cooling was larger and 2–3 days earlier than those observations. Maximum Chla was stronger and led the climatological average by 2 days after the typhoon passage. Typhoon-induced vertical variations of Chla and NO3 indicated that different Chla bloom processes from coastal waters to the continental shelf. Discharge brought extra nutrients to stimulate Chla bloom in coastal waters, and model results revealed that its impact could extend to the continental shelf 50–150 km from the coastline. However, bottom nutrients were uplifted to contribute to Chla enhancement in the upper and middle layers of the shelf. Nutrients transported from the open sea along the continental slope with the bottom cold water could trigger Chla enhancement in the Taiwan Bank. This study suggests considering strong tides and waves as well as regional dynamics to improve model skills in the future.