Tidal Characteristics Research Articles

Arctic tidal characteristics at Eureka (80° N, 86° W) and Svalbard (78° N, 16° E) for 2006/07: seasonal and longitudinal variations, migrating and non-migrating tides

Abstract. Operation of a Meteor Radar at Eureka, Ellesmere Island (80° N, 86° W) began in February 2006. The first 12 months of wind data (82–97 km) are combined with winds from the Adventdalen, Svalbard Island (78° N, 16° E) Meteor Radar to provide the first contemporaneous longitudinally spaced observations of mean winds, tides and planetary waves at such high Arctic latitudes. Unique polar information on diurnal non-migrating tides (NMT) is provided, as well as complementary information to that existing for the Antarctic on the semidiurnal NMT. Zonal and meridional monthly mean winds differed significantly between Canada and Norway, indicating the influence of stationary planetary waves (SPW) in the Arctic mesopause region. Both diurnal (D) and semi-diurnal (SD) winds also demonstrated significantly different magnitudes at Eureka and Svalbard. Typically the D tide was larger at Eureka and the SD tide was larger at Svalbard. Tidal amplitudes in the Arctic were also generally larger than expected from extrapolation of high mid-latitude data. For example time-sequences from ~90 km showed D wind oscillations at Eureka of 30 m/s in February–March, and four day bursts of SD winds at Svalbard reached 40 m/s in June 2006. Fitting of wave numbers for the migrating and non-migrating tides (MT, NMT) successfully determines dominant tides for each month and height. For the diurnal tide, NMT with s=0, +2 (westward) dominate in non-summer months, while for the semi-diurnal tide NMT with s=+1, +3 occur most often during equinoctial or early summer months. These wave numbers are consistent with stationary planetary wave (SPW)-tidal interactions. Assessment of the global topographic forcing and atmospheric propagation of the SPW (S=1, 2) suggests these winter waves of the Northern Hemisphere are associated with the 78–80° N diurnal NMT, but that the SPW of the Southern Hemisphere winter have little influence on the summer Arctic tidal fields. In contrast the large SPW and NMT of the Arctic winter may be associated, consistent with Antarctic observations, with the observed occurrence of the semidiurnal NMT in the Antarctic summer.

Tidal characteristics in a coral reef system from the western Gulf of Mexico

This study shows the computed tidal harmonic results from a sea level time series performed to elucidate the temporal and spatial behavior of tides in the Veracruz Reef System (western Gulf of Mexico). Data from 11 pressure sensors moored from October to December 2004 revealed that the predominant harmonics within the coral reef system were the diurnal K1 and O1 components, followed by the semidiurnal M2 component. The fortnightly constituent showed an amplitude comparable to that of the M2 harmonic. Tidal amplitudes showed small differences throughout the area when compared with the phases. Phase lags among different stations were induced by bathymetric effects.

DEM and bathymetry estimation for mapping a tide‐coordinated shoreline from fine spatial resolution satellite sensor imagery

Fine spatial resolution remotely sensed imagery has considerable potential for mapping a shoreline. Although fine spatial resolution imagery typically allows the instantaneous shoreline to be mapped with high accuracy, interest is normally focused on a reference shoreline, defined on a stable vertical datum, which is generally not apparent in the imagery unless acquired at a time carefully coordinated with the tidal characteristics of the region. To map a tide‐coordinated shoreline, such as the mean sea level (MSL), information on terrain topography, bathymetry and tidal characteristics is required. In this study, IKONOS imagery was used to derive topographic and bathymetric information for an extract of the Malaysian coast and combined with a tide chart for the region to map the MSL. The digital elevation model (DEM) derived had a root mean square error (RMSE), calculated on independent control points, of ∼2.2 m while the bathymetric model had an RMSE of 0.87 m. The shoreline derived from the combination of the DEM, bathymetry and tidal information was mapped with an RMSE of 1.8 m.

静岡県馬込川河口域における非対称な流況場と堆砂特性

This paper investigates asymmetric current fields and resulting sedimentation characteristics observed around the Magome River mouth. Field survey was first conducted to obtain detailed bathymetry of the river mouth and to capture spatial current patterns by tracing wooden chips floated on the water surface. Image rectification technique was utilized to track the actual coordinates of wooden tracers. Time-varying water level and flow velocity near the bottom were also measured and, not only yielded time-varying tidal characteristics, did these data support the validity of estimated current patterns using wooden tracers. Circulation current patterns induced by broken waves were clearly observed in the area where the distance between two jetties was widened and local sedimentation was observed in the landward edge of this circulation current. This circulation current also caused asymmetric distributions of tidal current velocity across the narrow river mouth. Numerical analysis was finally conducted to investigate the influence of observed asymmetric current on the sand discharge rate at the river mouth.

Tidal ice drift and ice-generated changes in the tidal dynamics/energetics on the Siberian continental shelf

Tidal ice drift is regarded as an element of the 3D tidal dynamics on the Siberian continental shelf. Two cases are considered: (1) when sea ice is immobile (in a horizontal plane), so that ice-induced changes of tidal characteristics may be treated as if they are limiting, and (2) when sea ice is moveable and internal stresses in the ice cover are described by a viscous-elastic rheology. It is shown that sea ice does not lead to radical changes of the tidal and energetic regimes, although their quantitative changes may be quite significant. In general, the ice-induced influence on the tidal dynamics is less than that on the tidal energetics. Therefore, the commonly accepted assumption that this influence may be viewed as being negligible is justified only partially. We present model results for tidal ice drift parameters—its magnitude, direction, the amplitude of tidal variations of ice concentration and the pressure of ice compression—as well as for ice-induced changes of tidal characteristics and the residual tidal ice drift. Partial attention is given to revealing the zones of ice compression–rarefaction, that is of importance in Arctic navigation.

On the variability of tidal constants induced by the influence of one subsystem on another

It is stated that the seasonal variation of tidal constants may be generated through a mechanism related to the influence of one subsystem on another. This statement is verified on the basis of the three-dimensional nonlinear finite-element thermohydrodynamic model QUODDY-4, which is used to investigate the tidal dynamics of the wave M 2 in the system of the White and Barents seas. It is testified that the freezing of the White Sea and the resulting fixed ice cover change the tidal characteristics in the other subsystem—the nonfreezing Barents Sea. Here (especially, in the southern part of the Barents Sea, adjacent to the boundary of the White Sea), the relative variations in the amplitude of tidal sea surface level elevations and the maximum barotropic tidal velocity may constitute up to 75%, and the variation in phases of tidal sea surface level elevations may cover a few tens of degrees. It follows that the seasonal variability of tidal constants induced by the influence of one subsystem on another may in principal occur and there are no good grounds for its disregard, as has been done usually.

A numerical study of the tidal circulation and buoyancy effects in a Scottish fjord: Loch Torridon

The tidal and buoyancy‐driven circulation in Loch Torridon, a Scottish fjord, is investigated using a three‐dimensional, hydrostatic, primitive equation model. The predictions from the model have been quantitatively compared to available data gathered between 1998 and 2001. The model performed well in reproducing the tidal characteristics and density evolution of the fjord over the 3‐month simulation period. Results show that tidal currents are dominated by the constraint imposed on the flow by the shallow sill separating the upper and middle basins: the flow is strongly accelerated during flood and ebb tides, and significant residual currents are generated that may influence exchange and residence times of the middle basin. A strong baroclinic response to the flow over the sill is predicted throughout the fjord, with a propagating linear M2 tide displacing isopycnals vertically by up to 32 m. At the sill the formation of stationary lee waves on both flood and ebb tides is predicted, with the wave generated during flood tide being notably larger as the growth of the ebb wave is inhibited by deep dense water. This allows more energy to transfer into the seaward propagating internal tide. As the tidal flow weakens, the lee waves propagate over the sill and upstream. Estimates of the total vertical turbulent buoyancy flux in the fjord are made, and the distribution of mixing over a tidal cycle is shown; vertical mixing is seen to be highly spatially and temporally variable and strongly linked to the presence and dissipation of lee waves near the sill.

Tidal and Sub-tidal Current Characteristics in the Kangjin Bay, South Sea, Korea

This study analyzed the current meter records along with wind records for over 500 days obtained in the Kangjin Bay, South Sea, Korea spanning from March, 2003 to Nov. 2005. Various analyses include descriptive statistics, harmonic analysis of tidal constituents, spectra and coherence, the principal axis, progressive vector diagrams. These analyses can illustrate the response of residual current to the local wind resulting in the net drift with rotational motion. Current speed ranges from -28 to 33 (cm/sec), with standard deviations from 6.5 to 12.9 (cm/sec). The harmonic analyses of the tidal current show the average form number, 0.12 with semi-diurnal type and the recti-linear orientation of the major axis toward northeast. The magnitudes of the semi-major range from 12.7 to 17.7 (cm/sec) for M2 harmonics, while for S2 harmonics, they range from 6.3 to 10.4 (cm/sec), respectively. In the spectral and coherency analysis of residual current and wind, a periodicity of 13.6 (day) is found to be most important in both records and plays an important role in the net drift of residual current. The progressive vector diagrams of residual current and wind show two types of behaviors such as unidirectional drift and rotational motion. It was also found that 3 % rule holds approximately to drive 1 (cm/sec) drift current by 30 (cm/sec) wind speed based on the correlation of the semimajor axis of wind and residual current.

Effect of hydrodynamic properties of the sea bottom on the tidal dynamics in a rectangular basin

Expressions derived for the friction coefficient in an oscillatory rotating turbulent bottom boundary layer (BBL) over rough, incompletely rough (smoothly rough), and smooth underlying surfaces are incorporated as an individual module into a two-dimensional nonlinear tidal model, and the standard version of the model and its modified analogue are used to discuss the titular subject. It is established that the dynamics of tides in the Taylor basin can change noticeably under the effect of hydrodynamic properties of the sea bottom. Such changes occur mainly in the influence domains of amphidromies. In the remaining parts of the basin, relative changes in the amplitudes and phases of tidal sea-surface level elevations do not exceed ±10% and ±10°, respectively. The largest discrepancies of tidal characteristics take place in the cases of the incompletely rough and smooth sea bottoms; the smallest discrepancies, in the case of the rough sea bottom. Estimates for the changes in tidal characteristics that are caused by the usually neglected effects of rotation and phase difference between the bottom friction and the tidal velocity at the upper BBL boundary are presented as well.

Salt intrusion in multi-channel estuaries: a case study in the Mekong Delta, Vietnam

Abstract. There is a well-tested theory for the computation of salt intrusion in alluvial estuaries that is fully analytical and predictive. The theory uses analytical equations to predict the mixing behaviour of the estuary based on measurable quantities, such as channel topography, river discharge and tidal characteristics. It applies to single-channel topographies and estuaries that demonstrate moderate tidal damping. The Mekong delta is a multi-channel estuary where the tide is damped due to a relatively strong river discharge (in the order of 2000 m3/s), even during the dry season. As a result the Mekong is a strongly riverine estuary. This paper aims to test if the theory can be applied to such a riverine multi-channel estuary, and to see if possible adjustments or generalisations need to be made. The paper presents salt intrusion measurements that were done by moving boat in 2005, to which the salt intrusion model was calibrated. The theory has been expanded to cater for tidal damping. Subsequently the model has been validated with observations made at fixed locations over the years 1998 and 1999. Finally it has been tested whether the Mekong calibration fits the overall predictive equations derived in other estuaries. The test has been successful and led to a slight adjustment of the predictive equation to cater for estuaries that experience a sloping bottom.

Flood control areas as an opportunity to restore estuarine habitat

Intertidal areas in estuaries play a multi-functional role, from energy dissipation and mitigation of floods over provision of natural habitat to a contribution in the cycling and recycling of nutrients. Many of these intertidal areas have been claimed for urban, agricultural or industrial expansion. When considering restoration in a land-scarce environment, managed realignment is not always an option and thus other approaches need to be considered. In this paper we investigate the possibility to combine the concept of a flood control area (FCA) with nature development and the functions of intertidal areas, by use of simple sluice constructions to introduce a controlled reduced tide (CRT). Model results show the possibility to introduce acceptable tidal influence in FCAs. Nevertheless there are major differences with tidal characteristics of natural outer dike marshes: the spring-neap tidal range is strongly reduced, the tidal curve flattened. Also the relation between inundation time (IT) and inundation frequency (IF) shows strong distortion compared to the natural situation, with roughly doubled inundation times as compared with a natural outer dike marsh. This has important implications for nature and vegetation development. Further research and monitoring of test sites is necessary to conclude about the desirability of the implementation on larger scale of this concept.

Predicting the Effectiveness of Phragmites Control Measures using a Rhizome Growth Potential Bioassay

In the last century, Phragmites australis (common reed) has expanded from a minor component of the mid-Atlantic tidal wetlands to a dominant species in many locations. Expansion of Phragmites results in decreased plant diversity and alterations to the tidal characteristics of the marsh, resulting in decreased wetland value. Management efforts have used a variety of strategies in an attempt to control its expansion. We tested a greenhouse bioassay that provided insight into the rhizome vitality of six herbicide-treated sites in the Alloway Creek Watershed, NJ well in advance of the growing season. At three sites, rhizomes were exhumed and classified by depth (0–25 cm and 25–75 cm) and appearance (color and firmness). Concurrently, the same protocol was followed, but conducted on an areal basis at three additional sites. Material was grown in sand under greenhouse conditions void of nutrient supplements for 70 days, after which shoots were removed and the rhizomes replanted for 30 days. Effectiveness of control strategies was quantified by examining rhizome color, vitality, and shoot densities in the field. Color was indicative of quality of rhizome reserves. Less than 0.2% of the firm, brown rhizomes produced shoots upon initial planting and none produced shoots upon replanting, whereas 50.9% of white rhizomes produced shoots on initial planting. Rhizome vitality was quantified by examining shoot emergence and the morphology of the shoots. Coupling rhizome vitality with observed field densities resulted in a predictive capability, and shoot density and biomass predictions were compared to field measurements in July 2001. We tested and accurately predicted the relative shoot densities and shoot biomass of the three sites for which we collected rhizome material on an areal basis. The result is a rapid, valuable, and cost-effective monitoring tool that can quickly quantify the effects of past control methods and predict future growth potential.

Tidal circulation and energy dissipation in a shallow, sinuous estuary

The tidal dynamics in a pristine, mesotidal (>2 m range), marsh-dominated estuary are examined using moored and moving vessel field observations. Analysis focuses on the structure of the M 2 tide that accounts for approximately 80% of the observed tidal energy, and indicates a transition in character from a near standing wave on the continental shelf to a more progressive wave within the estuary. A slight maximum in water level (WL) occurs in the estuary 10–20 km from the mouth. M 2 WL amplitude decreases at 0.015 m/km landward of this point, implying head of tide approximately 75 km from the mouth. In contrast, tidal currents in the main channel 25 km inland are twice those at the estuary mouth. Analysis suggests the tidal character is consistent with a strongly convergent estuarine geometry controlling the tidal response in the estuary. First harmonic (M 4) current amplitude follows the M 2 WL distribution, peaking at mid-estuary, whereas M 4 WL is greatest farther inland. The major axis current amplitude is strongly influenced by local bathymetry and topography. On most bends a momentum core shifts from the inside to outside of the bend moving seaward, similar to that seen in unidirectional river flow but with point bars shifted seaward of the bends. Dissipation rate estimates, based on changes in energy flux, are 0.18–1.65 W m−2 or 40–175 μW kg–1. A strong (0.1 m/s), depth-averaged residual flow is produced at the bends, which resembles flow around headlands, forming counter-rotating eddies that meet at the apex of the bends. A large sub-basin in the estuary exhibits remarkably different tidal characteristics and may be resonant at a harmonic of the M 2 tide.

Model estimates for the interaction of wind waves and tides in the Pechora Basin-White Sea subsystem

The “weak-interaction” approximation is used to investigate the role of wind waves in tidal dynamics. The resulting expression for the drag coefficient in the wave-affected tidal flow is incorporated into the QUODDY-4 three-dimensional finite-element hydrothermodynamic model, and the thus modified model is used to calculate the K 1 diurnal tide in the Pechora Basin-White Sea subsystem. It is shown that, depending on a combination of local and nonlocal factors, wind waves can cause opposite variations in the amplitudes and phases of tidal oscillations of the level. Local factors control variations in the tidal regime nearly in the entire water area of the subsystem under consideration, apart from the eastern part of the Pechora Basin, the outlet from the White Sea Throat, and Dvina Bay. In the aforementioned areas, the tidal regime changes are due either to the displacement of the nearest amphidromy or to other nonlocal factors resulting from the reorganization of the fields of tidal characteristics. It is also shown that the variations in tidal characteristics induced by wind waves vary within a fairly wide range and that allowance for the interaction of wind waves and tides improves the agreement between calculated and observed values of the amplitudes and phases of tidal oscillations of the level.

Tidal resuspension of microphytobenthic chlorophyll a in a Nanaura mudflat, Saga, Ariake Sea, Japan: flood–ebb and spring–neap variations

The resuspension of microphytobenthic chlorophyll a (chl a) and suspended particulate matter (SPM) from the upper intertidal flat was studied at Nanaura, Ariake Sea, Japan, and a spatial comparison of chl a and SPM in the northern Ariake Sea is presented here. A 15 d time series of chl a and SPM records (measured at 15 cm above the bottom) revealed that resuspension was clearly asso- ciated with flood-ebb and spring-neap tidal characteristics, where significant resuspension was found during early flood, particularly in the high-energy period (viz. spring tide). The peaks of resus- pended chl a and SPM during 28 tidal periods were observed to consistently occur shortly after the current velocity reached a maximum and when the threshold current velocity was found to be ca. 15 cm s -1 . Much more highly fluctuating, irregular peaks of chl a and SPM were occasionally observed, these were attributable to high wind speeds, ≥3 m s -1 . Computation of chl a and SPM fluxes showed clear spring-neap variation, and time-integrated fluxes denoted predominant offshore residual transport during the observation period. Benthic chl a measured in the surficial sediment (top 0.5 cm) during 13 exposure periods showed a decreasing trend from spring to neap tide, similar to spring-neap variations of chl a in the water column during the semi-lunar tidal period. The daily mean percentage of resuspended chl a in the water column relative to the amount of benthic chl a was estimated to be ca. 10 to 70% (mean = 33%), implying that a certain portion of the microphyto- benthos is resuspended during high tide and partly contributes to the total biomass in the water column of the upper intertidal flat.

Effect of ice cover on the dynamics and energetics of surface and internal tides in the white sea: Model estimates

The effect of ice cover on the dynamics and energetics of surface and internal tides in the White Sea is investigated using the three-dimensional finite-element hudrothermodynamic model QUODDY-4. The sea ice is represented as a continuous and motionless ice cover that can move vertically but not horizontally. It is assumed that the resulting changes in the tidal regime are the maximum possible in reference to those occurring in real conditions when, in the cold season, a continuous and motionless ice cover is ubiquitous only in Kandalaksha, Dvina, and Onega bays, while drift ices prevail in all other areas of the White Sea. It is shown that the effect of sea ice does not lead to a qualitative restructuring of the tidal regime. However, its quantitative changes prove to be significant, which indicates that the ice-induced seasonal variation in tidal characteristics in the White Sea is important.

Verification studies for a z-coordinate primitive-equation model: Tidal conversion at a mid-ocean ridge

We document the accuracy and convergence of solutions for a z-coordinate primitive-equation model of internal tide generation and propagation. The model, which is based on MOM3 numerics, is linearized around a state of rest to facilitate comparison with analytic estimates of baroclinic generation at finite-amplitude topography in a channel forced by barotropic tidal flow at its boundaries. Unlike the analytical model, the numerical model includes mixing of both buoyancy and momentum, and several definitions of “baroclinic conversion” are possible. These are clarified by writing out the energetics of the linearized equations in terms of barotropic kinetic energy, baroclinic kinetic energy, and available potential energy. The tidal conversion computed from the model, defined as the rate of conversion of barotropic kinetic energy into available potential energy, agrees well with analytical predictions. A comparison of different treatments of bottom topography (full-cells, partial-cells, and ghost-cells) indicates that the partial-cell treatment is the most accurate in this application. Convergence studies of flow over a smooth supercritical ridge show that the dissipation along tidal characteristics is, apparently, an integrable singularity. When the ocean bottom is not smooth, the accuracy and convergence of the model depend on the power spectrum of the topography. A numerical experiment suggests that the power spectrum of the resolved topography must roll off faster than k −2 to obtain convergent results from a linear numerical model of this type.

Oxidative stress in gills of limpets from the Beagle Channel: comparison with limpets from the Antarctic

The aim of this work was to study the oxidative profile of gills of two limpet species ( Nacella (Patinigera) magellanica and Nacella (Patinigera) deaurata ) (Gmelin, 1971) exposed to different environmental conditions. Due to the tidal characteristics of the Beagle Channel, N. magellanica are exposed to air twice daily for 3 to 5 hours each time, whereas N. deaurata are exposed to air for 3 hours only during spring tides. The different regime of exposure includes extreme temperatures under 0oC during winter and more than 20°C in summer for N. magellanica , whereas N. deaurata are usually covered by more than 0.3 m of water at 4°C in winter and 11°C in summer. No significant differences were found between the two molluscs regarding the oxygen uptake, the content of ?-tocopherol and ?-carotene and the activities of the antioxidant enzymes catalase and superoxide dismutase. Lipid peroxidation in gills was estimated as the content of lipid radicals, assessed by electron paramagnetic resonance (EPR). Lipid radical content and total iron content were respectively 80.6 and 62% lower in N. magellanica than in N. deaurata . A typical EPR spectrum of ascorbyl radical in gills from both limpets was observed. Both the ascorbyl radical content and the ascorbyl radical content/ascorbate content ratio were significantly lower in N. magellanica than in N. deaurata . In the Antarctic Nacella concinna inhabits all levels of the littoral zone. Limpets at the highest level in the intertidal showed significantly increased activities of both catalase and superoxide dismutase as compared to their intertidal and subtidal relatives. Thus, it seems that Antarctic high intertidal conditions, involving regular exposure to air and presumably also thermal stress on sunny days during the Antarctic summer, cause a necessity for N. concinna to ward off higher oxygen radical species production by increasing its antioxidant defence. Taken as a whole, the data presented here indicate that coping with environmentally demanding conditions requires a complex adjustment of the physiological metabolic pathways to ensure survival by minimising intracellular damage.

Tidal characteristics of Maputo Bay, Mozambique

The tidal characteristics of Maputo Bay (a bay located in South part of Mozambique) were assessed in this work through the implementation of a numerical model (SIMSYS2D) and exploration of its numerical results, and by the analysis of observed time series of free surface elevations in Maputo Harbor. The calibration of the numerical model was carried out based on time series of tidal currents and free surface elevation, which were collected at Maputo Harbor, Baixo Ribeiro and Portuguese Island. By means of the model results, important harmonic constants of the tidal heights and currents, as well as the form factor, were computed. These results have revealed that there is a phase delay and an increase in amplitude of the major constituents as the tide propagates to the inshore zone. Based on these results, the tidal ellipses in whole Maputo Bay were also computed, which showed the pattern of the tidal currents. The hydrodynamics of the Maputo Bay under extreme tidal conditions were also analyzed (during the largest spring tide and smallest neap tide). The phase difference between tidal heights and currents revealed that there are no maximum fluxes of energy in most of Maputo Bay and that the mean tidal current (residual) may be different from zero in this system.

Latest Observational Results from the Superconducting Gravimeter at Station Wuhan and Investigation of Ocean Tide Models

Using observations of the superconducting gravimeter GWR-C032 at station Wuhan, the tidal gravity parameters reflecting the characteristics of the Earth's interior medium are obtained based on the harmonic analysis after variable preprocessing to the raw data. Meanwhile the gravity loading are calculated using the loading theory and a numerical integral convolution technique based on various global ocean tide models developed by methods of the altimetry technology and finite element with consideration of tidal gauge data as constraints. The loading corrections are carried out for tidal gravity parameters in diurnal and semidiurnal wave bands, respectively in order to investigate the adaptability of global ocean tide models. The numerical results show that the efficiencies of loading correction reach to 91% (O1, NAO99) and 92% (M2, ORI96) for instance. The average efficiencies of the loading corrections obtained with 11 oceanic models for four main constituents (O1, K1, M2 and S2) are 86%, 70%, 73% and 84%, respectively. And the discrepancies between amplitude factors and theoretical values decrease from (2.12%, 1.55%, 1.16% and 0.80%) to (0.31%, 0.39%, 0.34% and 0.08%), respectively. The comparison among various ocean models also shows that the loading correction efficiencies when using NAO99 and ORI96 models are higher than those when using other models. Additionally, other observations obtained with superconducting gravimeters at 7 stations in a network of the Global Geodynamic Project are also adopted to investigate the adaptability of the global ocean models. The results show that there exist obvious local tidal characteristics for different constituents in different ocean models and the earlier constructed SCW80 ocean model can still be used as an important reference in geodesy research.