Tidal Anomalies Research Articles

A Statistical review of the dates and patterns of volcanic activity of Lewotolo Volcano, East Nusa Tenggara, Indonesia

Lewotolo is a stratovolcano located on the Lembata Island, East Nusa Tenggara (Lesser Sunda Islands), Indonesia. The first geohistory of the Lewotolo volcanic eruption was recorded in 1660 (Volcanic Eruption Index (VEI) 3). Since November 11, 2020, Lewotolo has been included in the list of Indonesian volcanoes with the necessary precautions, comparable to the Anak Krakatau, Merapi, and Semeru volcanoes. We investigated Lewotolo volcanic activity by analyzing the height of the ash column data, maximum seismograph amplitude, and recorded seismic duration from November 29, 2020, to September 23, 2022, which are provided in magma.esdm.go.id. The results showed 191 records of eruption activity data, which formed three clusters for each variable using the Elbow Method in the Non-Hierarchical K-means clustering analysis. These data were plotted on the solar and Hijri lunar calendars. The data plot shows anomalies in the volcanic activity frequency and a significant pattern of activity at specific times. The data plot illustrates that the value of the activity frequency pattern tends to increase at Earth orbital events such as the December-January perihelion (up to 0.124) and June-July aphelion (up to 0.262) and at the new moon phases (up to 0.168). This phenomenon appears as solar and lunar tidal anomalies that commonly occur as gravitational sea tides. Along with the need for more comprehensive data, the results of this study may provide new perspectives for further research on the possible role of gravitational tide phenomena in volcanic activity, at least to explain the volcanic activity in Lewotolo.

Contributions of Different Sea‐Level Processes to High‐Tide Flooding Along the U.S. Coastline

AbstractCoastal communities across the United States (U.S.) are experiencing an increase in the frequency of high‐tide flooding (HTF). This increase is mainly due to sea‐level rise (SLR), but other factors such as intra‐ to inter‐annual mean sea level variability, tidal anomalies, and non‐tidal residuals also contribute to HTF events. Here we introduce a novel decomposition approach to develop and then analyze a new database of different sea‐level components. Those components represent processes that act on various timescales to contribute to HTF along the U.S. coastline. We find that the relative importance of components to HTF events strongly varies in space and time. Tidal anomalies contribute the most along the west and northeast coasts, where HTF events mostly occur in winter. Non‐tidal residuals are most important along the Gulf of Mexico and mid‐Atlantic coasts, where HTF events mostly occur in fall. We also quantify the minimum number of components that were required to cause HTF events in the past and how this number changed over time. The results highlight that at present, due to SLR, fewer components are needed to combine to push water levels above HTF thresholds, but tidal anomalies alone are still not sufficient to reach HTF thresholds in most locations. Finally, we explore how co‐variability between different components leads to compounding effects. In some places, positive correlation between sea‐level components leads to significantly more HTF events than would be expected if sea‐level components were uncorrelated, whereas in other places negative correlation leads to fewer HTF events.

Impact of Strong and Weak Stratospheric Polar Vortices on the Mesosphere and Lower Thermosphere

AbstractThe impact of strong and weak Northern Hemisphere stratospheric polar vortices on the zonal mean and atmospheric tides in the mesosphere and lower thermosphere (MLT) is investigated using Specified Dynamics Whole Atmosphere Community Climate Model (WACCM) with thermosphere‐ionosphere eXtension (SD‐WACCM‐X) simulations and Aura Microwave Limb Sounder observations. The observed and simulated zonal mean anomalies during strong and weak vortices are in good agreement. Zonal mean and tidal anomalies during weak polar vortex events are consistent with those known to occur during sudden stratospheric warmings. Generally opposite, though weaker, anomalies are found to occur when the stratospheric polar vortex is strong. The most notable impact in the MLT is a reduction in the migrating semidiurnal tide of ∼25%–35% during strong polar vortex times. The results demonstrate that, in addition to weak polar vortex events, a strong stratospheric polar vortex can also have an appreciable impact on the middle and upper atmosphere.

Forecasting and Evaluation of Impacts and Risk Due to Tidal Anomalies on a Coastal Island

Forecasting and Evaluation of Impacts and Risk Due to Tidal Anomalies on a Coastal Island

Long-Term Dataset of Tidal Residuals in New South Wales, Australia

Continuous water level records are required to detect long-term trends and analyse the climatological mechanisms responsible for extreme events. This paper compiles nine ocean water level records from gauges located along the New South Wales (NSW) coast of Australia. These gauges represent the longest and most complete records of hourly—and in five cases 15-min—water level data for this region. The datasets were adjusted to the vertical Australian Height Datum (AHD) and had the rainfall-related peaks removed from the records. The Unified Tidal Analysis and Prediction (Utide) model was subsequently used to predict tides for datasets with at least 25 years of records to obtain the associated tidal residuals. Finally, we provide a series of examples of how this dataset can be used to analyse trends in tidal anomalies as well as extreme events and their causal processes.

A CLIMATOLOGY BASED FORECAST TOOL FOR COASTAL FLOODING IN THE LOWCOUNTRY

AbstractCoastal nuisance flooding has increased by an order of magnitude over the past half century, but the National Weather Service has a limited suite of statistical tools to forecast them. Such a tool was developed using coastal flood events from 1996—2014 in Charleston, South Carolina, which were identified and classified by prevailing synoptic conditions based on composite mean sea level pressure anomalies. The synoptic climatology indicated low level northeasterly winds dominated the forcing in anticyclonic and cyclonic events, while a southeasterly surge was the main forcing component for frontal events. Tidal anomalies between flood events and previous low tides were used to create linear regression models for each composite classification studied for forecasting levels of coastal flood magnitude. Beta tests using data from 2018—2019 confirmed the effectiveness of the models with RMSE values less than 0.3 ft and MAE values less than 0.25 ft for each event type. The veracity of the methods was further verified by a multiple day case study from November 2018, where the model was tested against both statistically predicted heights and heights based on ETSS Model (v2.2). The RMSE and MAE for the statical model were 0.18 and 0.15 respectively, while the same values for the ETSS model were 0.28 and 0.23 respectively.

Multi‐Timescale Analysis of Tidal Variability in the Indian Ocean Using Ensemble Empirical Mode Decomposition

AbstractOcean tides have been observed to be changing worldwide for nonastronomical reasons, which can combine with rising mean sea level (MSL) to increase the long‐term impact to coastal regions. Tides can also exhibit variability at shorter timescales, which may be correlated with short‐term variability in MSL. This short‐term coupling may yield higher peak water levels and increased impacts of exceedance events that may be equally significant as long‐term sea level rise. Previous studies employed the tidal anomaly correlation (TAC) method to quantify the sensitivity of tides to MSL fluctuations at long‐period (>20 years) tide gauges in basin‐scale surveys of the Pacific and Atlantic Ocean, finding that TACs exist at most locations. The Indian Ocean also experiences significant sea level rise and tidal variability yet has been less studied due to a sparse network of tide gauges. However, since the beginning of the 21st century, more tide gauges have been established in a wider geographical range, bringing the possibility of better estimates of tidal and MSL variability. Here, we improve the TAC approach, using the ensemble empirical mode decomposition (EEMD) method to analyze tidal amplitudes and sea level at multiple frequency bands, allowing a more effective use of shorter record tide gauges and better understanding of multiple timescales of tidal variability. We apply this approach to 73 tide gauges in the Indian Ocean to better quantify tidal variability in these under‐studied regions, finding that the majority of locations exhibit significant correlations of tides and MSL.

Long-Term Observations of Beach Variability at Hasaki, Japan

Long-term beach observation data for several decades are essential to validate beach morphodynamic models that are used to predict coastal responses to sea-level rise and wave climate changes. At the Hasaki coast, Japan, the beach profile has been measured for 34 years at a daily to weekly time interval. This beach morphological dataset is one of the longest and most high-frequency measurements of the beach morphological change worldwide. The profile data, with more than 6800 records, reflect short- to long-term beach morphological change, showing coastal dune development, foreshore morphological change and longshore bar movement. We investigated the temporal beach variability from the decadal and monthly variations in elevation. Extremely high waves and tidal anomalies from an extratropical cyclone caused a significant change in the long-term bar behavior and foreshore slope. The berm and bar variability were also affected by seasonal wave and water level variations. The variabilities identified here from the long-term observations contribute to our understanding of various coastal phenomena.

Tidal variability in the Hong Kong region

Abstract. Mean sea level (MSL) is rising worldwide, and correlated changes in ocean tides are also occurring. This combination may influence future extreme sea levels, possibly increasing coastal inundation and nuisance flooding events in sensitive regions. Analyses of a set of tide gauges in Hong Kong reveal complex tidal behavior. Most prominent in the results are strong correlations of MSL variability to tidal variability over the 31-year period of 1986–2016; these tidal anomaly correlations (TACs) express the sensitivity of tidal amplitudes and phases (M2, S2, K1, O1) to MSL fluctuations and are widely observed across the Hong Kong region. At a few important harbor locations, time series of approximations of the parameter δ-HAT, computed from combinations of the major tidal constituents, are found to be highly sensitive to MSL variability, which may further increase local flood levels under future MSL rise. Other open-water locations in Hong Kong only show TACs for some individual tidal constituents but not for combined tidal amplitudes, suggesting that the dynamics in enclosed harbor areas may be partially frequency dependent and related to resonance or frictional changes. We also observe positive correlations of the fluctuations of diurnal (D1) tides to semidiurnal (D2) tides at most locations in the region, which may lead to further amplified tidal ranges under MSL. It is demonstrated here that tidal changes in the Hong Kong coastal waters may be important in combination with MSL rise in impacting future total water levels.

Extended Spectral Analysis of Tidal Variability in the North Atlantic Ocean

AbstractOcean tides have experienced large‐scale changes over the past century, in concert with regionally variable global mean sea level (MSL) rise. Additionally, there can be coherencies between MSL and tidal fluctuations that are active at shorter time scales. This combination of water level variabilities may enhance the probabilities of exceeding flood levels under high‐tide events, leading to increased frequency of short‐term coastal inundation and nuisance flooding. Previous studies have established the tidal anomaly correlation (TAC) method to analyze covariability of individual tidal components and MSL in the Pacific Ocean, as well as their combination as a proxy for the change in the highest astronomical tide (δ‐HAT). Here we extend this methodology to new regions and perform analyses of 170 tide gauges in the North Atlantic Ocean, considering the eight largest gravitational tides and seven overtides. Results indicate that nearly all gauges (95%) exhibit strong individual TACs in one or more tidal constituents, and over half show significant δ‐HATs, with a near‐equal occurrence of positive and negative tendencies. The most coherent connections of tides and MSL were found on the U.S. East Coast and in the marginal waters of Europe. At some locations, all tidal variabilities act in the same direction, which may amplify possible flood level. At other locations major parts of the tidal spectrum may counteract the MSL rise and partially mitigate extreme water levels due to tidal evolution. In either case, an understanding of regional tidal changes correlated to MSL changes can be instructive in guiding future coastal development efforts.

Southern California Coastal Response to the 2015–2016 El Niño

AbstractWidespread erosion associated with energetic waves of the strong 2015–2016 El Niño on the U.S. West Coast has been reported widely. However, Southern California was often sheltered from the northerly approach direction of the offshore waves. The few large swells that reached Southern California were not synchronous with the highest tides. Although west coast‐wide tidal anomalies were relatively large in 2015–2016, in Southern California, total water levels (sum of tides, anomalies, and wave superelevation) were lower than during the 1997–1998 Niño, and comparable to the 2009–2010 Niño. Airborne lidar surveys spanning 300 km of Southern California coast show the beach response varied from considerable erosion to accretion. On average, the shoreline moved landward 10 m, similar to the 2009–2010 El Niño. Some San Diego county beaches were narrower in the 1997–1998 El Niño than in 2015–2016, consistent with the higher erosion potential in 1997–1998. Beach retreat exceeded 80 m at a few locations. However, 27% of the shoreline accreted, often in pocket beaches, or near jetties. While adjacent beaches eroded, estuary mouths accreted slightly, and several estuaries remained or became closed during the study period. Only 12% of cliffs eroded (mostly at the base), and the average cliff face retreat was markedly less than historical values. Only two cliff‐top areas retreated significantly. Although some areas experienced significant change, the potential for coastal erosion and damage in Southern California was reduced compared to the 1997–1998 El Niño, because of low rainfall, a northerly swell approach, and relatively limited total high‐water levels.

Tidal Variability Related to Sea Level Variability in the Pacific Ocean

AbstractOcean tides are changing worldwide for reasons unrelated to astronomical forcing. Changes in tidal properties coupled with altered mean sea level (MSL) may yield higher peak water levels and increased occurrence of short‐term exceedance events, such as storm surge and nuisance flooding. Here we investigate the hypothesis that changes in relative sea level are correlated with alterations in tidal amplitudes. Our approach focuses on the correlation between short‐term (monthly to interannual) fluctuations in sea level with changes in tidal properties of major ocean tides (M2, and K1; S2 and O1) at 152 gauges. Results suggest that sea level variability is correlated to interannual tidal variability at most (92%) of tide gauges in the Pacific, with statistically significant rates between ±10 and ±500 mm per meter sea level rise observed. These tidal anomalies, while influenced by basin‐scale climate processes and sea level changes, appear to be locally forced (in part) and not coherent over amphidromic or basin‐wide scales. Overall, the Western Pacific shows a greater concentration of tide/sea level correlations at interannual time scales than the Eastern Pacific; 44% and 46% of gauges are significant in K1 and O1 in the west compared to 29% and 30% in the east, and 63% and 53% of gauges in the west are significant in M2 and S2 versus 47% and 32% in the east. Seasonal variation in tidal properties is less apparent in the empirical record, with statistically significant seasonal variations observed at only 35% of all gauges, with the largest concentrations in Southeast Asia.

Time, Tides, and Wandering Poles

Models of Neptune’s moon Triton reveal curious behavior in how tidal forces and mass anomalies cause the poles to reorient their location.

Combined Effects of Projected Sea Level Rise, Storm Surge, and Peak River Flows on Water Levels in the Skagit Floodplain

Abstract Current understanding of the combined effects of sea level rise (SLR), storm surge, and changes in river flooding on near-coastal environments is very limited. This project uses a suite of numerical models to examine the combined effects of projected future climate change on flooding in the Skagit floodplain and estuary. Statistically and dynamically downscaled global climate model scenarios from the ECHAM-5 GCM were used as the climate forcings. Unregulated daily river flows were simulated using the VIC hydrology model, and regulated river flows were simulated using the SkagitSim reservoir operations model. Daily tidal anomalies (TA) were calculated using a regression approach based on ENSO and atmospheric pressure forcing simulated by the WRF regional climate model. A 2-D hydrodynamic model was used to estimate water surface elevations in the Skagit floodplain using resampled hourly hydrographs keyed to regulated daily flood flows produced by the reservoir simulation model, and tide predictions...

Can tidal perturbations associated with sea level variations in the western Pacific Ocean be used to understand future effects of tidal evolution?

This study examines connections between mean sea level (MSL) variability and diurnal and semidiurnal tidal constituent variations at 17 open-ocean and 9 continental shelf tide gauges in the western tropical Pacific Ocean, a region showing anomalous rise in MSL over the last 20 years and strong interannual variability. Detrended MSL fluctuations are correlated with detrended tidal amplitude and phase fluctuations, defined as tidal anomaly trends (TATs), to quantify the response of tidal properties to MSL variation. About 20 significant amplitude and phase TATs are found for each of the two strongest tidal constituents, K1 (diurnal) and M2 (semidiurnal). Lesser constituents (O1 and S2) show trends at nearly half of all gauges. Fluctuations in MSL shift amplitudes and phases; both positive and negative responses occur. Changing overtides suggest that TATs are influenced by changing shallow water friction over the equatorial Western Pacific and the eastern coast of Australia (especially near the Great Barrier Reef). There is a strong connection between semidiurnal TATs at stations around the Solomon Islands and changes in thermocline depth, overtide generation, and the El Nino Southern Oscillation (ENSO). TATs for O1, K1, and M2 are related to each other in a manner that suggests transfer of energy from M2 to the two diurnals via resonant triad interactions; these cause major tidal variability on sub-decadal time scales, especially for M2. The response of tides to MSL variability is not only spatially complex, it is frequency dependent; therefore, short-term responses may not predict long-term behavior.

Shoreline Energy and Sea Level Dynamics in Lower Chesapeake Bay: History and Patterns

A long-term (1948–2010) shoreward energy history of upper tidal shorelines in lower Chesapeake Bay was developed using a simple calculation of kinetic energy from corresponding wind and tide data. These data were primarily used to determine the likelihood of shoreline energy increases coincident with local sea level rise. Total annual shoreward energy ranged from 620 kJ/m of shoreline in 1950 to 17,785 kJ/m of shoreline in 2009. No clear linear trends are apparent, but mean annual energy shows an increase from 2,732 kJ/m before 1982 to 6,414 kJ/m since then. This increase in mean energy was accompanied by more numerous spikes of comparatively higher annual energy. Shoreward energy delivered to lower Chesapeake Bay’s upper tidal shorelines was enabled by an increasing amount of time per year that tidal height exceeds mean high water, accompanied by increasing heights of tidal anomalies. An index termed the Hydrologic Burden was developed that incorporates the combination of time and tidal height that demonstrates this increasing trend. Although opportunities for greater shoreward energy increased as the Hydrologic Burden increased, and even though there is evidence that greater energy was delivered to the shorelines during the latter time series, energy per hour delivery was shown not to have increased, and may have decreased, due to a steady reduction in average wind speed in lower Chesapeake Bay since the mid-1980s. Energy delivery in lower Chesapeake Bay was primarily from the northeast, and energy delivery over the time series is shown to organize symmetrically around a point between the northeast and north–northeast directions. This is evidence of a self-organizational phenomenon that transcends changes in local wind and tide dynamics.

Statistical simulation of wave climate and extreme beach erosion

Recent developments in extreme values modelling have been used to develop a framework for determining the coastal erosion hazard on sandy coastlines. This framework quantitatively reproduced the extreme beach erosion volumes obtained from field measurements at Narrabeen Beach, Australia. This encouraging finding was achieved using Kriebel and Dean's [Kriebel, D.L. and Dean, R.G., 1993. Convolution method for time-dependent beach profile response. Journal of Waterway, Port, Coastal and Ocean Engineering, 119(2): 204–226.] simple beach erosion and accretion model. The method includes allowances for joint probability between all basic erosion variates including; wave height, period and direction, event duration, tidal anomalies and event spacing. A new formulation for the dependency between wave height and period has been developed. It includes the physical wave steepness limitation. Event grouping, where significantly more erosion can occur from two closely spaced storms is handled by temporally simulating the synthetic wave climate and the resulting beach erosion and accretion.

Observation of Luni-Solar Tides by the Long Base Laser Interferometer

Results of observations of tidal strains of the crust in the tectonically active region of the Northern Caucasus (the Elbrus mountain area) carried out with the use of the Baksan laser interferometer strainmeter over the period from 2003 through 2006 are presented. Harmonic analysis is performed with the help of the ETERNA software package. Statistically significant time variations in the amplitudes of the main tidal waves M2 and O1 are revealed. The influence of the Baksan canyon topography on tidal strains is estimated at 22% (an increase in the measured strain values). The reduced amplitude factors of the main diurnal O1 and semidiurnal M2 waves are underestimated. Numerical modeling of tidal anomalies produced by regional heterogeneous inclusions is performed in a 2–D approximation. The observed anomaly of the M2 wave (12%) is shown to be due to the influence of the main magmacontrolling fault associated with the deep magma source of the Elbrus dormant volcano.

Observations of crustal tide strains in the Elbrus area

Results of observations of tidal strains of the crust in the tectonically active Elbrus area of the Northern Caucasus carried out with the use of the Baksan SSAI laser interferometer strainmeter over the period from 2003 through 2006 are presented. Harmonic analysis is performed with the help of the ETERNA software package. Statistically significant time variations in the amplitudes of the main tidal waves M 2 and O 1 are revealed. The influence of the topography on tidal strains in the Baksan gorge is estimated at 22% (an increase in the measured strain values). The reduced amplitude factors of the main diurnal (O 1) and semidiurnal (M 2) waves are underestimated. Numerical modeling of tidal anomalies produced by regional heterogeneous inclusions is performed in a 2-D approximation. The observed anomaly of the M 2 wave (12%) is shown to be due to the influence of the main magma-controlling fault associated with the deep magma source of the Elbrus dormant volcano.

Tidal wave anomalies of geoelectrical field before remote earthquakes

In this paper, geoelectrical field anomalies at Changli and Xingji station in Hebei Province were analyzed before five remote earthquakes. It was found that the anomalies mainly occurred two or three months before earthquakes, which is of importance to short-term and impendent earthquake prediction. There exhibited different characteristics in geoelectrical field anomalies, but they were closely related to tidal waves, for example, the increasing in amplitude at semidiurnal and semimonthly periods of tidal waves; the decreasing or disappearing in amplitude of tidal waves that should have been recorded normally at that time; while there accompanied incremental signals with high frequency, such as jump variations. It was thought that the formation mechanism of the geoelectrical anomalies before strong earthquakes resulted from stress-strain resonance effects when rock was weakened during the preparation process in seismic area, and then signals of electric field propagated to remote stations in free space or crust, and superposed on the geoelectric field tidal waves recorded at the stations, leading to increasing or decreaseing in amplitude of geoelectrical tidal waves. The high frequency signals may be related to the variation of rock porosity, permeability and so on beneath the stations, as a result of the dynamic effects of remote earthquakes.