on the wave number spectrum of oceanic mesoscale variability observed by the seasat altimeter variations of sea surface height measured by the seasat altimeter in nearly repeat orbits during the last 24 days of the mission are used to compute the wave number spectrum of mesoscale variability in various parts of the oceans the instrument noise level 150 cm2 cycles km has limited the resulting oceanic spectrum to wavelengths longer than 100 km we found that the characteristics of the oceanic spectrum are dependent on the energy level of the mesoscale variability in the high energy areas close to major current systems most of the energy is contained at wavelengths longer than 250 km at wavelengths shorter than 250 km the spectrum basically follows a k 5 k is wave number dependence in the low energy areas remote from major current systems the spectrum follows a k 1 dependence at wave lengths from 100 to 1000 km based on the assumption of horizontal isotropy of mesoscale variability scalar wave number spectra of sea surface height and geostrophic kinetic energy are also presented dynamical implications of these spectra are discussed the effects of residual geoid and atmospheric water vapor on the computed oceanic spectra have been rigorously examined it was found that the general characteristics of the oceanic spectra were not significantly affected by them

an evaluation of the barotropic and internal tides in a high resolution global ocean circulation model 1 global comparisons of barotropic and internal tides generated in an eddy resolving ocean circulation model are made with tidal estimates obtained from altimetric sea surface heights and an altimetry constrained tide model as far as we know our hybrid coordinate ocean model hycom simulations shown here and in an earlier paper are the only published high resolution global simulations to contain barotropic tides internal tides the general circulation and mesoscale eddies concurrently comparing the model barotropic tide with a global data assimilative shallow water tide model shows that the global tidal elevation differences are approximately evenly split between discrepancies in tidal amplitude and phase both the model and observations show strong generation of internal tides at a limited number of hot spot regions with propagation of beams of energy for thousands of kilometers away from the sources the model internal tidal amplitudes compare well with observations near these energetic tidal regions averaged over these regions the model and observation internal tide amplitude estimates agree to approximately 15 for the four largest semidiurnal constituents and 23 for the four largest diurnal constituents away from the hot spots the comparison between the model and altimetric amplitude is not as good due in part to two problems errors in the model barotropic tides and overestimation of the altimetric tides in regions of strong mesoscale eddy activity examining the general energy distribution of the simulated internal tide is an important first step in the evaluation of internal tides in hycom

global wavenumber spectrum with corrections for altimeter high frequency noise the altimetry wavenumber spectra of sea surface height ssh provide a unique dataset for testing of geostrophicturbulence whilesshspectralslopesofk 211 3 andk 25 areexpectedfromtheoriesandnumerical simulations the altimetry spectra from the original unfiltered and instrument noise corrected data often are too shallow falling between k 22 and k 23 in this study the possibility that the flattened spectral slopes are partly due to contamination by unresolved high frequency 10 days motions is tested a spatiotemporal filter based on empirical orthogonal function expansion eof is used to remove the temporally incoherent signals the resulting spectral slopes are much steeper than in the previous studies over 70 of the revised global spectral estimates excluding the tropics are above k 23 moreover in high energy regions like the gulf streamandkuroshio thespectralslopesare aboutk 25 whichis consistentwiththeclassicalquasigeostrophic qg turbulence the spectral slopes are validated with the eddy kinetic energy eke spectra from shipboard acoustic doppler current profiler adcp measurements in the high and low energy regions

calculation of beach change under interacting cross shore and longshore processes this paper presents a mathematical approach and numerical model that simulates beach and dune change in response to cross shore processes of dune growth by wind and dune erosion by storms and by gradients in longshore sand transport that will alter shoreline position sub aerial transport processes are represented whereas sub aqueous transport is neglected the system is tightly coupled morphologically with the berm playing a central role for example the potential for sand to be transported to the dune by wind depends on berm width and sand lost in erosion of the dune during storms can widen the berm morphologic equilibrium considerations are introduced to improve reliability of predictions and stability of the non linear model an analytical solution is given under simplification to illustrate properties of the model sensitivity tests with the numerical solution of the coupled equations demonstrate model performance with one test exploring beach and dune response to potential increase in storm wave height with global warming finally the numerical model is applied to examine the consequences of groin shortening at westhampton beach long island new york as an alternative for providing a sand supply to the down drift beach results indicate that the sand will be released over several decades as the shoreline and dune move landward in adjustment to the new equilibrium condition with the shortened groins

the influence of phase boundary deflection on velocity anomalies of stagnant slabs in the transition zone 1 although the behavior of subducted slabs in the mantle transition zone remains uncertain images from seismic tomography provide insight into a rather complex geodynamic evolution of slabs in this region using a numerical mantle convection model we consider in more detail the dynamics of subducted slabs around an endothermic phase change at 660 km depth the time dependent temperature fields from the flow simulation are used to derive perturbations from a radially stratified seismic velocity model we find that the positive velocity anomalies of the cold descending slabs may be significantly decreased at the phase change owing to the slab induced downward phase boundary deflection and associated velocity discontinuity across the boundary the slab may be completely or partially rendered seismically undetectable depending on the amount of phase boundary deflection the results have implications for the seismic interpretation of the dynamics of subducted slabs interacting with a phase transition

temporal and spatial variations of surf zone currents and suspended sediment concentration temporal and spatial variations of surf zone currents and suspended sediment concentrations were investigated at the u s army engineer research and development center s large scale sediment transport facility lstf a longshore uniform fine sand beach 35 m alongshore 20 m cross shore and 25 cm thick was placed in the facility for these experiments two unidirectional long crested irregular wave conditions were examined one resulted in predominantly spilling breakers and one in plunging breakers waves and currents and sediment concentrations were measured at 20 and 16 hz respectively at various longshore and cross shore locations and throughout the water column both currents and sediment concentrations exhibit great temporal and spatial variations in the surf zone the variation patterns however of the longshore current cross shore current and sediment concentration are substantially different caution should be exercised when averaging these parameters over time and space for the two wave cases examined the temporal variations of longshore current including those at principal incident wave frequencies were relatively small across most of the surf zone over 70 of the variations are within approximately f60 of the mean value the wave motion with a strong peak at principal incident wave frequencies dominated the temporal variations of cross shore current temporal variations of suspended sediment concentration under the irregular waves were episodic characterized by occasional large values induced by suspension events or due to horizontal advection the variance of the concentration at the peak incident wave frequency was not significant except very near the bed time averaged longshore current profiles over the predominantly rippled sand bed were logarithmic in shape below the wave trough depth averaged longshore current excluding the portion of water column above wave trough matched well with the current measured at an elevation of 1 3 of the water depth from the bed time averaged cross shore current profiles were characterized by an onshore mass flux near the surface and a balancing offshore flow below the wave trough level undertow sediment concentration decreased very rapidly upward through the water column across most of the surf zone except at the plunging breaker line where relatively homogeneous concentration was measured throughout much of the water column above 4 cm from the bed depth averaged sediment concentration over the range from 1 cm above the bed to the bottom of wave trough roughly equaled the concentration measured at an elevation from the bed equal to 20 of the still water depth

mass flux and undertow in a surf zone abstract the mass of water carried shoreward by the breaking waves in a surf zone will in a two dimensional situation be compensated by a seaward return flow the undertow it is shown that the undertow is driven by the local difference between radiation stress and the set up pressure gradient which only balance each other in average over the depth turbulent shear stresses are required to maintain a steady situation comparison with measurements confirms the theoretical results

fragmentation processes and xenolith transport in a proterozoic minette dyke grenville province quebec the mesoproterozoic rivard minette dyke provides a case example of dyke parallel fracturing induced by propagation of low viscosity melts at deep crustal levels the dyke constitutes a xenolith choked intrusion breccia and provides samples of an extensive section of the lithosphere underlying the southwestern grenville province of quebec at 1 08 ga the xenoliths occupy approximately 50 of the volume of the breccia they are extremely diverse and include pyroxenites and mafic granulites from the upper mantle and lower crust and grenvillian gabbroids gneisses and quartzites wall rock fragments are detached to various extents along dyke parallel fractures and apophyses the host lamprophyre magma has a calculated viscosity of ca 40 pa s rapid ascent of magma and turbulence are suggested by the presence of large dense fragments and the brittle to ductile deformation at the margins of some xenoliths a minimum ascent velocity of ca 50 cm s 1 is estimated from the settling velocity of a 40 cm long pyroxenite xenolith the progressive addition of xenoliths increased the effective viscosity of the liquid solid mixture to 103 pa s during emplacement this favoured bingham behaviour and laminar flow of the magma and xenolith suspension field evidence suggests that xenoliths were formed through 1 early fracturing of wall rock by inelastic deformation during dyke propagation and 2 continuous delamination of wall rock by intrusion of magma along the dyke parallel fractures this led to removal of chilled margins and to fluid infiltration partial melting and microbrecciation in the wall rock pre existing discontinuities played a minor role in the fracturing process xenoliths may thus be abundant in alkaline magmas not only because these magmas ascend rapidly and can transport xenoliths but possibly also because their low viscosities promote intense fracturing of wall rock

phase equilibrium constraints on the viscosity of silicic magmas 1 volcanic plutonic comparison by using recently determined experimental phase equilibria we show that the viscosity of granitic magmas emplaced at upper crustal levels is approximately constant at 104 5 pa s irrespective of their temperature and level of emplacement magmas crystallizing as granitic plutons are not water poor and thus not more viscous than their extrusive equivalents instead comparison between pre eruption magma viscosities of extrusive silicic intermediate and intrusive granitic magmas shows that the former are on average slightly more viscous given the typical strain rates in silicic magma chambers magma rheological behavior is expected to be dominantly newtonian bubbles having a minor rheological influence at depth although exceptions can exist thus whether a silicic intermediate magma is erupted or frozen at depth depends primarily on the rheological properties of surrounding terranes or on external tectonic factors but not on the rheology of the magma itself however preemptive viscosities of extrusive magmas rarely exceed 106 pa s which suggests that crystal melt mushes with higher viscosities cannot leave the magma storage regions beneath volcanoes the narrow range of viscosities displayed by silicic intermediate magmas results from both the strong control that pressure exerts on volatile solubilities in silicate melts and thermal limitations required to produce acid magmas considerations of the relationships between magma crystallinities bulk sio2 and preemptive melt h2o contents show that the higher the melt h2o content is the higher the maximum crystallinity that a given magma will be while still being potentially erupted an empirical correlation is proposed that enables us to estimate preemptive melt h2o contents of erupted magmas by knowing their crystallinity and bulk sio2

nonlinear and 3d effects in leaky infragravity waves abstract in this paper infragravity ig waves forced by normally and obliquely incident wave groups are studied using the quasi 3d q3d nearshore circulation model shorecirc van dongeren a r i a svendsen 1997b quasi 3 d modeling of nearshore hydrodynamics research report cacr 97 04 center for applied coastal research university of delaware newark 243 pp which includes the q3d effects the governing equations that form the basis of the model as well as the numerical model and the boundary conditions are described the model is applied to the case of leaky ig waves it is shown that the q3d terms have a significant effect on the cross shore variation of the surface elevation envelope especially around the breakpoint and in the inner surf zone the effect of wave groupiness on the temporal and spatial variation of all q3d terms is shown after which their contribution to the momentum equations is analyzed this reveals that only those q3d coefficients which appear in combination with the largest horizontal velocity shears make a significant contribution to the momentum equations as a result of the calculation of the q3d coefficients the ig wave velocity profiles can be determined this shows that in the surf zone the velocity profiles exhibit a large curvature and time variation in the cross shore direction and a small but essential depth variation in the longshore direction

wavenumber spectrum in the gulf stream from shipboard adcp observations and comparison with altimetry measurements the wavenumber spectra for velocity and temperature in the gulf stream region are calculated from a decade 1994 2004 of shipboard acoustic doppler current profiler adcp measurements taken as part of the oleander project the velocity and temperature spectra have comparable magnitude in terms of the kinetic and potential energy and both indicate a k 23 slope in the mesoscales in contrast the corresponding velocity spectrum determined from satellite altimetry sea surface heights yields a significantly higher energy level and a k 22 slope the discrepancy between altimeter derived and directly measured velocity spectra suggests that altimetric velocity probably is contaminated by noise in sea surface height measurement also the k 23 slope which appears to be in agreement with two dimensional quasigeostrophic turbulence theory does not support the contemporary surface quasigeostrophic theory these results highlight large gaps in the current understanding of the nature of surface geostrophic turbulence

an analytical model to predict dune erosion due to wave impact an analytical model is developed to calculate recession distance and eroded volume for coastal dunes during severe storms the transport relationship used in the model is based on wave impact theory where individual swash waves hitting the dune face induce the erosion combining this relationship with the sediment volume conservation equation describes the response of the dune to high waves and water levels four different data sets on dune erosion originating from the laboratory and the field were employed to validate the model and to determine the value of an empirical transport coefficient appearing in the analytical solutions the time evolution of dune recession observed in the different data sets was well described by the model but the empirical coefficient showed some variation between cases especially for the field data in practical applications of the model it is recommended to use a range of coefficient values to include an uncertainty estimate of calculated quantities such as recession distance and eroded volume

hydrodynamics and sediment transport in the swash zone a review and perspectives the dominant hydrodynamic forcing and resulting sediment transport mechanisms in the swash zone are reviewed combined with a discussion of future measurement and modelling requirements the importance of swash zone processes in the overall behaviour of the nearshore littoral zone are identified with the paper subsequently focusing on aspects that directly relate to sediment transport on beaches the review considers analytical and numerical modelling work and both field and laboratory data the hydrodynamics of the swash zone are first discussed with reference to the surf zone boundary swash characteristics forcing mechanisms and shoreline oscillations subsequent sections consider more micro scale processes such as the internal flow kinematics turbulence the bed boundary layer and infiltration exfiltration through permeable beds the second part of the paper outlines the fundamental mechanics of sediment transport in the swash zone followed by a more detailed discussion of sediment transport modes induced by the dominant hydrodynamic conditions modelling concepts are reviewed and the strengths and weaknesses of different approaches identified a final summary and future modelling perspectives conclude the paper

swash zone sediment transport and foreshore evolution field experiments and mathematical modeling data from field experiments carried out in the swash zone on two pacific beaches in japan were analyzed to determine net sediment transport rates and the resulting foreshore response the experiments involved artificial modification of the foreshore slope with a bulldozer either making the slope steeper or milder after which a wide range of measurements were performed as the slope evolved back towards its equilibrium value under the action of the incident waves a sediment transport formula was developed to predict the net transport rate over many swash cycles and compared with the derived transport rates from the surveys of the foreshore this formula was then combined with the conservation equation for sediment volume to yield a mathematical model for simulating the foreshore evolution under varying waves and water level predictions by the model were compared to measurements yielding satisfactory agreement although the optimum values on the main calibration coefficient displayed some variation between experiments further analysis of a limited number of cases indicated that this coefficient may be dependent upon the ratio between the incident wave period and the swash period which characterizes the interaction between individual waves in the swash zone a simple analytical solution was also derived for a schematized foreshore shape to estimate the typical time scale of the morphological response

modelling storm impacts on beaches dunes and barrier islands a new nearshore numerical model approach to assess the natural coastal response during time varying storm and hurricane conditions including dune erosion overwash and breaching is validated with a series of analytical laboratory and field test cases innovations include a non stationary wave driver with directional spreading to account for wave group generated surf and swash motions and an avalanching mechanism providing a smooth and robust solution for slumping of sand during dune erosion the model performs well in different situations including dune erosion overwash and breaching with specific emphasis on swash dynamics avalanching and 2dh effects these situations are all modelled using a standard set of parameter settings the results show the importance of infragravity waves in extending the reach of the resolved processes to the dune front the simple approach to account for slumping of the dune face by avalanching makes the model easily applicable in two dimensions and applying the same settings good results are obtained both for dune erosion and breaching

modeling the alongshore current on barred beaches mean alongshore currents observed on two barred beaches are compared with predictions based on the one dimensional time and depth averaged alongshore momentum balance between forcing by breaking waves wind and 10 100 km scale alongshore surface slopes bottom stress and lateral mixing the observations span 500 hours at egmond netherlands and 1000 hours at duck north carolina and include a wide range of conditions with maximum mean currents of 1 4 m s including rollers in the wave forcing results in improved predictions of the observed alongshore current structure by shifting the predicted velocity maxima shoreward and increasing the velocity in the bar trough compared with model predictions without rollers for these data wave forcing balances the bottom stress within the surfzone with the other terms of secondary importance the good agreement between observations and predictions implies that the one dimensional assumption holds for the range of conditions examined despite the presence of small alongshore bathymetric nonuniformities with stronger bathymetric variations the model skill deteriorates particularly in the bar trough consistent with earlier modeling and laboratory studies

a note on alongshore sediment transport on weakly curvilinear coasts and its implications abstract this paper presents a simple approximation for assessment of the alongshore sediment transport rate on dissipative weakly curvilinear coasts the approximation considers spatial variations in the wave angle and energy sediment size beach slope and type of wave breaking inside the surf zone similar approaches were employed in the past for coasts forced by high oblique waves where shoreline undulations frequently develop with our approach we can analyze more realistic situations i e alongshore relations between the sediment size and the beach slope the general expression for alongshore sediment transport is made explicit using a simple model for wave propagation the solution is used to examine the implications of the behavior of alongshore sediment transport on shoreline evolution after the analysis of the effects of variations in the wave conditions the alongshore beach slope distribution and the shoreline geometry three different shoreline tendencies were obtained for undulating shorelines migration for changes in deep water wave angle amplitude growth for increases in wave height or period and changes in shoreline geometry and wavelength changes and asymmetries for coasts with alongshore changes in beach slope our results also indicate that wave setup may enhance the formation of undulating shoreline features

impact of sediment supply on decadal scale dune evolution analysis and modelling of the kennemer dunes in the netherlands abstract this study investigates the impact of beach sediment supply on dune volume evolution through data analysis and model simulations of the kennemer dunes in the netherlands a cross shore sediment transport model the cs model is applied with local time averaged longshore sediment transport gradients derived from bathymetric and topographic observations the model is used to study the relative importance of different transport processes on dune volume evolution assuming that aeolian transport from the beach to the dune is supply limited the wave driven longshore transport gradients are found to explain a large part of the observed variation in the dune evolution within the study area in accreting parts of the coast dunes are growing due to sediment supply from longshore transport whereas in eroding parts dune growth depends on supply from artificial nourishments seasonal constructions on the beach and vegetation removal from the dunes partly impede dune growth along the considered stretch of coast the model performance is satisfactory being able to reproduce a considerable part of the large variation in the alongshore dune response observed in the study area overall the results are a promising contribution to the capability of simulating decadal scale dune evolution which is important for long term flood risk assessments and safe designs of nature based solutions

performance of a numerical short wave model abstract a numerical short wave model system based on the boussinesq equations is verified against analytical as well as experimental results for shoaling refraction diffraction and partial reflection processes it is shown that engineers can confidently and responsibly apply such a model system to the study of wave disturbance in coastal regions

impact of horizontal resolution 1 12 to 1 50 on gulf stream separation penetration and variability abstractthe impact of horizontal resolution 1 12 to 1 50 6 to 1 5 km at midlatitudes on gulf stream separation penetration and variability is quantified in a series of identical north atlantic experiments the questions the authors seek to address are twofold 1 is the realism of the modeled solution increased as resolution is increased 2 how robust is the modeled mesoscale and submesoscale eddy activity as a function of grid spacing and how representative is it of interior quasigeostrophic qg or surface quasigeostrophic sqg turbulence this study shows that i the representation of gulf stream penetration and associated recirculating gyres shifts from unrealistic to realistic when the resolution is increased to 1 50 and when the nonlinear effects of the submesoscale eddies intensifies the midlatitude jet and increases its penetration eastward ii the penetration into the deep ocean drastically increases with resolution and closely resembles the observations and iii surface power spec

interpreting energy and tracer spectra of upper ocean turbulence in the submesoscale range 1 200 km submesoscale 1 200km wavenumber spectra of kinetic and potential energy and tracer variance are obtained from in situ observations in the gulf stream region and in the eastern subtropical north pacific in the gulf stream region steep kinetic energy spectra at scales between 200 and 20km are consistent with predictions of interior quasigeostrophic turbulence theory both in the mixed layer and in the thermocline at scales below 20km the spectra flatten out consistent with a growing contribution of internal wave energy at small scales in the subtropical north pacific theenergyspectraareflatterand inconsistentwith predictionsofinteriorquasigeostrophic turbulence theory the observed spectra and their dependence on depth are also inconsistent with predictions of surface quasigeostrophic turbulencetheoryfortheobservedoceanstratification itappearsthatunbalancedmotions most likely internal tides at large scales and the internal wave continuum at small scales dominate the energy spectrum throughout the submesoscale range spectra of temperature variance along density surfaces which are not affected by internal tides are also inconsistent with predictions of geostrophic turbulence theories reasons for this inconsistency could be the injection of energy in the submesoscale range by small scale baroclinic instabilities or modifications of the spectra by coupling between surface and interior dynamics or by ageostrophic frontal effects

transition zone width and implications for modeling surfzone hydrodynamics the surfzone associated with a wave breaking on a plane slope may be subdivided into three regions the transition zone the inner zone and the swash zone the transition zone is the region just shoreward of the point of wave breaking and is characterised by rapid wave decay and also by constant wave setdown and thus constant radiation stress in this paper an empirical expression for the width of this zone is developed from monochromatic wave data two techniques are proposed for the consideration of this phenomenon in the numerical modelling of surfzone hydrodynamics for random waves the implications of a zone of nearly constant radiation stress inside the breakpoint are examined with respect to wave induced current generation both cross shore and longshore and sediment transport prediction comparisons are made to both field and laboratory data from plane and undulating profiles

spatial scales of mesoscale variability in the north atlantic as deduced from geosat data two years of geosat data were used to systematically investigate the mesoscale variability and spatial scales of the north atlantic we first calculated sea surface height variability and eddy kinetic energy these compare well with the eddy kinetic energy obtained with surface drifters then the spatial scales of mesoscale variability were characterized in 10 latitude 10 longitude areas by their wave number spectra and autocorrelation functions comparison with existing in situ data shows good agreement and it is believed that the total error budget is globally below that of the oceanic signal the wave number spectra show significant differences as a function of latitude and longitude and these can be related to different types of forcing instability of a mean current or fluctuating wind scales typically decrease from west to east and south to north simple proportionality with respect to the first internal rossby radii does not apply everywhere

surface manifestation of internal tides generated near hawaii analysis of topex poseidon satellite altimetry reveals short wavelength fluctuations in the ocean surface tide that are attributable to internal tides a significant fraction of the semidiurnal internal tide generated at the hawaiian ridge is evidently phase locked to the astronomical potential and can modulate the amplitude of the surface tide by 5 cm the internal tide is thus easily mapped along satellite groundtracks and it is found to be spatially coherent over great distances with waves propagating well over 1000 km from the hawaiian ridge before decaying below noise level both first and second baroclinic modes are observed in both the m 2 lunar and s 2 solar tides the high space time coherence is in sharp contrast to what is often inferred from current meter observations but it confirms recent speculations from an acoustic experiment north of hawaii

thermohaline variability in the upper ocean the main goal of this exploratory study is to determine how the temperature salinity relationship changes with horizontal length scale and depth in the ocean temperature and salinity were measured on a range of scales from 4 m to 1000 km towing a seasoar along isobars and isopycnals in the subtropical gyre of the north pacific during the winter of 1997 the wavelet transform technique is used to compute the horizontal density ratio and thermohaline variability as a function of scale and location measurements along an isobar in the mixed layer show that the horizontal density ratio is 1 at all scales observed that is horizontal temperature and salinity gradients tend to cancel each other in their effect on density thermohaline variability at small scales is intermittent and clusters around large scale thermohaline anomalies below the base of the mixed layer horizontal gradients of temperature are only partially opposed by salinity and the density ratio is close to 2 in the thermocline the distribution of thermohaline variability is uniform along isobars but intermittent and colocated at different scales along isopycnals density compensated variability ubiquitous in the mixed layer is reduced along deeper isopycnals compensation of horizontal temperature and salinity gradients supports recent theoretical ideas that mixing in the winter mixed layer depends on horizontal density gradients

cross shore distribution of longshore sediment transport comparison between predictive formulas and field measurements abstract the skill of six well known formulas developed for calculating the longshore sediment transport rate was evaluated in the present study formulas proposed by bijker bijker e w 1967 some considerations about scales for coastal models with movable bed delft hydraulics laboratory publication 50 delft the netherlands journal of the waterways harbors and coastal engineering division 97 4 1971 687 engelund hansen engelund f hansen e 1967 a monograph on sediment transport in alluvial streams teknisk forlag copenhagen denmark ackers white journal of hydraulics division 99 1 1973 2041 bailard inman journal of geophysical research 86 c3 1981 2035 van rijn journal of hydraulic division 110 10 1984 1431 110 11 1984 1613 110 12 1984 1733 and watanabe watanabe a 1992 total rate and distribution of longshore sand transport proceedings of the 23rd coastal engineering conference asce 2528 2541 were investigated because they are commonly employed in engineering studies to calculate the time averaged net sediment transport rate in the surf zone the predictive capability of these six formulas was examined by comparison to detailed high quality data on hydrodynamics and sediment transport from duck nc collected during the duck85 superduck and sandyduck field data collection projects measured hydrodynamics were employed as much as possible to reduce uncertainties in the calculations and all formulas were applied with standard coefficient values without calibration to the data sets overall the van rijn formula was found to yield the most reliable predictions over the range of swell and storm conditions covered by the field data set the engelund hansen formula worked reasonably well although with large scatter for the storm cases whereas the bailard inman formula systematically overestimated the swell cases and underestimated the storm cases the formulas by watanabe and ackers white produced satisfactory results for most cases although the former overestimated the transport rates for swell cases and the latter yielded considerable scatter for storm cases finally the bijker formula systematically overestimated the transport rates for all cases it should be pointed out that the coefficient values in most of the employed formulas were based primarily on data from the laboratory or from the river environment thus re calibration of the coefficient values by reference to field data from the surf zone is expected to improve their predictive capability although the limited amount of high quality field data available at present makes it difficult to obtain values that would be applicable to a wide range of wave and beach conditions

comparison of sediment transport formulae for the coastal environment most existing sediment transport formulae to estimate transport rate in the coastal environment have a restricted range of applicability and are often used beyond this range the aim of this paper is to investigate the limits of five of these formulae the bijker bailard van rijn dibajnia and watanabe and ribberink formulae the sensitivity of these formulae to wave orbital velocity wave period wave asymmetry sediment grain size and steady current has been studied and tested against data for large velocities where significant errors can appear the formulae behave in very different ways if one of the main parameters is slightly modified particularly when fine sediments are present and phase lag effect appears but important discrepancies between formulae can also be observed for medium sand at last the wave related sediment transport due to wave asymmetry has great importance for the morphodynamic and is only accounted for in the bailard dibajnia and watanabe and ribberink formulae

wave height variation across beaches of arbitrary profile an intuitive expression for the spatial change in energy flux associated with waves breaking in the surf zone is developed using shallow water linear wave theory analytical solutions for wave height transformation due to shoaling and breaking on a flat shelf a plane slope and an equilibrium beach profile are derived and then compared to laboratory data with favorable results the effect of beach slope on wave decay is included explicitly while wave steepness effects are included implicitly by specification of the incipient conditions set down set up in the mean water level bottom friction losses and bottom profiles of arbitrary shape are introduced and solutions are obtained numerically the model is calibrated and verified using laboratory data with very good results for the wave decay but not so favorable results for set up a test run on a prototype scale profile containing two bar and trough systems demonstrates the model s ability to describe the shoaling breaking and wave re forming process commonly observed in nature bottom friction is found to play a negligible role in wave decay in the surf zone when compared to shoaling and breaking

surf zone dynamics simulated by a boussinesq type model part ii surf beat and swash oscillations for wave groups and irregular waves abstract this is the second of three papers on the modelling of various types of surf zone phenomena in the first paper the general model was described and it was applied to study cross shore motion of regular waves in the surf zone in this paper part ii we consider the cross shore motion of wave groups and irregular waves with emphasis on shoaling breaking and runup as well as the generation of surf beats these phenomena are investigated numerically by using a time domain boussinesq type model which resolves the primary wave motion as well as the long waves as compared with the classical boussinesq equations the equations adopted here allow for improved linear dispersion characteristics and wave breaking is modelled by using a roller concept for spilling breakers the swash zone is included by incorporating a moving shoreline boundary condition and radiation of short and long period waves from the offshore boundary is allowed by the use of absorbing sponge layers mutual interaction between short waves and long waves is inherent in the model this allows for example for a general exchange of energy between triads rather than a simple one way forcing of bound waves and for a substantial modification of bore celerities in the swash zone due to the presence of long waves the model study is based mainly on incident bichromatic wave groups considering a range of mean frequencies group frequencies modulation rates sea bed slopes and surf similarity parameters additionally two cases of incident irregular waves are studied the model results presented include transformation of surface elevations during shoaling breaking and runup and the resulting shoreline oscillations the low frequency motion induced by the primary wave groups is determined at the shoreline and outside the surf zone by low pass filtering and subsequent division into incident bound and free components and reflected free components the model results are compared with laboratory experiments from the literature and the agreement is generally found to be very good finally the paper includes special details from the breaker model time and space trajectories of surface rollers revealing the breakpoint oscillation and the speed of bores envelopes of low pass filtered radiation stress and surface elevation sensitivity of surf beat to group frequency modulation rate and bottom slope is investigated part iii of this work sorensen et al 1998 presents nearshore circulations induced by the breaking of unidirectional and multi directional waves

a laboratory study of longshore currents over barred and non barred beaches abstract a detailed description is given of the results of laboratory experiments on wave driven longshore currents on both barred and non barred beaches the objective is to examine the cross shore distribution of the longshore current velocities for purely wave driven currents with emphasis on the position of maximum current velocity with respect to areas where wave energy is dissipated unidirectional obliquely incident waves both regular and random were used the measurements were performed in a large wave basin with a pump recirculation system to create spatially homogeneous longshore currents the experiments yielded information on wave transformation set up of the mean water level and the cross shore distribution of wave driven longshore current velocity a number of cases are presented and compared with each other the measurements show that in the case of purely wave driven longshore currents the maximum current velocities occur close to areas where wave breaking is most intense the effect of mixing bottom friction and wave rollers on the longshore current velocity profile are examined in more detail with help of numerical modelling existing model equations based on the assumption of alongshore uniformity are used the results for the mean longshore current profile on a barred beach are in close agreement with the measurements

examination of the influence of several factors on longshore current computation with random waves abstract influence of various factors affecting the longshore currents induced by obliquely incident random waves is examined through numerical calculation seven numerical models for random wave breaking process are found to yield large differences in the wave heights in the surf zone and longshore current velocities the turbulent eddy viscosity formulation by larson and kraus larson m and kraus n c 1991 numerical model of longshore current for bar and trough beaches j waterway port coastal and ocean eng asce 117 4 pp 326 347 functions almost equal to that by battjes battjes j a 1975 modeling of turbulence in the surf zone proc symp modeling techniques pp 1050 1061 but the formulation by longuet higgins longuet higgins m s 1970 longshore current generated by obliquely incident sea waves 1 and 2 j geophys res 75 33 pp 6779 6801 produces excessive diffusion of longshore currents into the offshore zone the generation and decay process of the surface roller is indispensable in the longshore current analysis the random wave transformation model called pegbis parabolic equation with gradational breaker index for spectral waves by goda goda y 2004 a 2 d random wave transformation model with gradational breaker index coastal engineering journal jsce and world scientific 46 1 pp 1 38 produced good agreement with several laboratory and field data of longshore currents

non stationary internal tides observed with satellite altimetry 1 temporal variability of the internal tide is inferred from a 17 year combined record of topex poseidon and jason satellite altimeters a global sampling of along track sea surface height wavenumber spectra finds that non stationary variance is generally 25 or less of the average variance at wavenumbers characteristic of mode 1 tidal internal waves with some exceptions the non stationary variance does not exceed 0 25 cm2 the mode 2 signal where detectable contains a larger fraction of non stationary variance typically 50 or more temporal subsetting of the data reveals interannual variability barely significant compared with tidal estimation error from 3 year records comparison of summer vs winter conditions shows only one region of noteworthy seasonal changes the northern south china sea implications for the anticipated swot altimeter mission are briefly discussed

mesoscale to submesoscale transition in the california current system part i flow structure eddy flux and observational tests in computational simulations of an idealized subtropical eastern boundary upwelling current system similar to the california current a submesoscale transition occurs in the eddy variability as the horizontal grid scale is reduced to o 1 km this first paper in a series of three describes the transition in terms of the emergent flow structure and the associated time averaged eddy fluxes in addition to the mesoscale eddies that arise from a primary instability of the alongshore wind driven currents significant energy is transferred into submesoscale fronts and vortices in the upper ocean the submesoscale arises through surface frontogenesis growing off upwelled cold filaments that are pulled offshore and strained in between the mesoscale eddy centers in turn some submesoscale fronts become unstable and develop submesoscale meanders and fragment into roll up vortices associated with this phenomenon are a large vertical vorticity and rossby number a large vertical velocity relatively flat horizontal spectra contrary to the prevailing view of mesoscale dynamics a large vertical buoyancy flux acting to restratify the upper ocean a submesoscale energy conversion from potential to kinetic a significant spatial and temporal intermittency in the upper ocean and material exchanges between the surface boundary layer and pycnocline comparison with available observations indicates that submesoscale fronts and instabilities occur widely in the upper ocean with characteristics similar to the simulations

ssh wavenumber spectra in the north pacific from a high resolution realistic simulation abstractfollowing recent studies based on altimetric data this paper analyses the spectral characteristics of the sea surface height ssh using a new realistic simulation of the north pacific ocean with high resolution in the horizontal and 100 vertical levels this simulation resolves smaller scales down to 10 km than altimetric data limited to 70 km because of the noise level in high eddy kinetic energy eke regions as in the western part ssh spectral slope almost follows a k 4 with k the wavenumber or slightly steeper law in agreement with altimeter studies the new result is that unlike altimeter studies such a k 4 slope is also observed in low eke regions as in the eastern part in these regions this slope mostly concerns scales not well resolved by altimetric data such k 4 ssh spectral slopes are weaker from what is expected from quasigeostrophic turbulence theory but closer to surface quasigeostrophic sqg turbulence theory the consequence is that the small scales concerned

simulating cross shore material exchange at decadal scale model application a model developed to describe long term cross shore cs exchange of sand and resulting profile evolution at regional scale was employed to simulate the evolution at three different sites the model consists of modules for calculating dune erosion and overwash bar berm material exchange and dune build up by wind blown sand transport as described in detail in a companion paper larson et al 2016 selected study sites represent coastal stretches influenced by beach nourishment barra in portugal overwash and breaching macaneta spit in mozambique and dune development angelholm in sweden the model applications showed overall good performance and the results of the simulations are promising due to limitations in data availability in angelholm and macaneta values on calibration parameters were mainly determined based on previous studies for barra where more field measurements were available the application showed good agreement between the simulated results and observations the cs model proved to be a useful tool to predict long term evolution of beach dune systems in a time perspective from years to decades however additional efforts should be directed towards improving the schematized model profile so that it can better represent other beach shapes such as a sloping berm or a barrier shape

rheometry of a dacitic melt experimental results and tests of empirical models for viscosity estimation this paper reports on experimental measurements of the viscosity of a dacitic melt by means of the technique of of concentric cylinder rheometry the measurements were done in a temperature range of 1000 to 1150 degrees c and at different shear rates the results were compared with empirical models which are commonly used to estimate the viscosity of single phase melts of silicates this data is of great use to the study of magma transport

do altimeter wavenumber spectra agree with the interior or surface quasigeostrophic theory in high eddy energy regions it is generally assumed that sea level wavenumber spectra compare well with quasigeostrophic qg turbulence models and that spectral slopes are close to the expected k 5 law this issue is revisited here sea level wavenumber spectra in the gulf stream kuroshio and agulhas regions are estimated using the most recent altimeter datasets the ocean topography experiment topex poseidon jason 1 the environmental satellite envisat and the geosat follow on the authors show that spectral slopes in the mesoscale band are significantly different from a k 5 law in disagreement with the qg turbulence theory however they very closely follow a k 11 3 slope which indicates that the surface quasigeostrophic theory sqg is a much better dynamical framework than the qg turbulence theory to describe the ocean surface dynamics because of the specific properties of the sqg theory these results offer new perspectives for the analysis and interpretation of satellite data

a new form of the boussinesq equations with improved linear dispersion characteristics part 2 a slowly varying bathymetry abstract a new form of the boussinesq equations applicable to irregular wave propagation on a slowly varying bathymetry from deep to shallow water is introduced the equations incorporate excellent linear dispersion characteristics and are formulated and solved in two horizontal dimensions in an earlier paper we concentrated on wave propagation and diffraction on a horizontal bottom in deep water in this paper these principles are generalized and the boussinesq equations are extended to include terms proportional to the bottom slope which are essential for the shoaling properties of the equations the paper contains a linear shoaling analysis of the new equations and a verification of the numerical model with respect to shoaling and refraction diffraction in deep and shallow water

surf zone longshore currents and random waves field data and models abstract analytic and numerical models for longshore currents generated by obliquely incident random waves am compared with field observations five days of observations were selected during which the waves were narrow banded in both frequency and direction in keeping with model assumptions the extensive measurements included radiation stress and wave directional spectra in 9 m depth and a closely spaced array of current and pressure sensors on a line perpendicular to shore the longshore current models are based on balancing the gradient of the radiation stress with the alongshore bed shear and reynold s stresses assuming stationary wave conditions and straight and parallel bottom contours the spatial variation of wave height required to determine the gradient of the radiation stress is modeled using linear random wave theory given hrms in 9 m depth the model predicts hrms at shoreward locations with an average error of less than 9 using a nonlinear bottom shear stress formulation and the meas

inferring dynamics from the wavenumber spectra of an eddying global ocean model with embedded tides 1 the slopes of the wavenumber spectra of sea surface height ssh and kinetic energy ke have been used to infer interior or surface quasi geostrophic qg or sqg dynamics of the ocean however inspection of spectral slopes for altimeter ssh in the mesoscale band of 70 to 250 km shows much flatter slopes than the qg or sqg predictions over most of the ocean comparison of altimeter wavenumber spectra with spectra from an eddy resolving global ocean circulation model the hybrid coordinate ocean model hycom at 1 12 5 equatorial resolution which has embedded tides suggests that the flatter slopes of the altimeter ssh may arise from three possible sources 1 presence of strong internal tides 2 shift of the inertial sub range to smaller scales and 3 altimeter noise artificially adding noise to the model tends to flatten the spectra for low ke regions near internal tide generating regions spectral slopes in the presence of internal waves are much flatter than qg or sqg predictions separating the variability into high and low frequency around periods of 2 days then a different pattern emerges with a flat high frequency wavenumber spectrum and a steeper low frequency wavenumber spectrum for low mesoscale ke the inertial sub range defined by the nearly flat enstrophy band moves to smaller scales and the mesoscale band of 70 to 250 km no longer represents the inertial sub range the model wavenumber spectra are consistent with qg and sqg theory when internal waves and inertial sub range shifts are taken into consideration

establishing uniform longshore currents in a large scale sediment transport facility a large scale laboratory facility for conducting research on surf zone sediment transport processes has been constructed at the u s army engineer research and development center successful execution of sediment transport experiments which attempt to replicate some of the important coastal processes found on long straight beaches requires a method for establishing the proper longshore current an active pumping and recirculation system comprised of 20 independent pumps and pipelines is used to control the cross shore distribution of the mean longshore current pumping rates are adjusted in an iterative manner to converge toward the proper settings based on measurements along the beach two recirculation criteria proposed by visser coastal eng 15 1991 563 were also used and they provided additional evidence that the proper total longshore flow rate in the surf zone was obtained the success of the external recirculation system and its operational procedure and the degree of longshore uniformity achieved along the beach are the subjects of this paper to evaluate the performance of the recirculation system and as a precursor to sediment transport experiments two comprehensive test series were conducted on a concrete beach with straight and parallel contours 1 30 slope one using regular waves and the other using irregular waves in the regular wave case the wave period was 2 5 s and the average wave height at breaking was approximately 0 25 m in the irregular wave case the peak wave period was 2 5 s and the significant breaking wave height was approximately 0 21 m the longshore current recirculation system proved to be very effective in establishing uniform mean longshore currents along the beach in both cases this facility and the data presented here are unique for the following reasons 1 the high cross shore resolution of the recirculation system and the ease with which changes can be made to the longshore current distribution 2 the degree of longshore uniformity achieved as a percentage of the length of the basin even near the downdrift boundary 3 the scale of the wave conditions generated and 4 the relatively gentle beach slope used in the experiments compared to previous laboratory studies of the longshore current measured data are provided in an appendix for use in theoretical studies and numerical model development and validation

the effects of altimeter instrument noise on the estimation of the wavenumber spectrum of sea surface height the wavenumber spectrum of sea surface height ssh observed by satellite altimetry was analyzed by xu and fu the spectral shape in the wavelength range of 70 250 km was approximated by a power law representing a regime governed by geostrophic turbulence theories the effects of altimeter instrument noise were assumed insignificant at wavelengths longer than 70 km the authors reexamined the assumption in the study using nearly simultaneous observations made by jason 1 and jason 2 during their cross calibration phase this study found that the white noise level of altimetry measurement was best estimated from the spectral values at wavelengths from 25 to 35 km after removing a white noise level based on such estimate from the ssh spectrum the spectral slope values changed significantly over most of the oceans a keyfinding is that the spectral slopes are generally steeper than k 22 k is wavenumber poleward of the 208 latitudes where flatter spectral slopes in some regions have previously caused problems for dynamic interpretations the new results indicate that the spectral slopes in the core regions of the major ocean current systems have values between the original geostrophic turbulence theory and the surface quasigeostrophic theory the near k 24 spectrum suggests that the sea surface height variability at these wavelengths in the high eddy energy regions might be governed by frontogenesis

simulating cross shore material exchange at decadal scale theory and model component validation a model is developed to simulate the cross shore cs exchange of sand and the resulting profile response at decadal scale to be used in regional coastal evolution models the cs model consists of modules for calculating dune erosion and overwash wind blown sand transport and bar berm material exchange the sand transport equations included in these modules are formulated based on relevant physics in combination with empirical observations and then validated towards laboratory and field data in order to couple the transport equations to the evolution of key morphological features describing the profile a set of sand volume conservation equations are employed and solved together with the transport equations the features that are modeled include dune height from dune foot to crest the locations of the landward dune foot seaward dune foot berm crest and shoreline as well as the longshore bar volume the cs model is employed and tested at three different field sites in a companion paper palalane et al 2016 whereas in the present paper the properties of the model are demonstrated by simulating the evolution of the dune berm and shoreline in connection with accretion and erosion of sand in a groin compartment this case derives from a study at westhampton beach that focused on shortening the length of a number of groins in order to release accumulated sand in the groin field to eroding downdrift beaches

global variability of the wavenumber spectrum of oceanic mesoscale turbulence abstractthe wavenumber spectra of sea surface height from satellite altimeter observations have revealed complex spatial variability that cannot be explained by a universal theory of mesoscale turbulence near the edge of the core regions of high eddy energy agreement is observed with the prediction of the surface quasigeostrophic sqg turbulence theory which has fundamental differences from that of the traditional quasigeostrophic qg turbulence theory in the core regions of high eddy energy the spectra are consistent with frontogenesis that is not fully accounted for by the sqg theory however the observations in the vast ocean interior of low eddy energy exhibit substantial differences from the predictions of existing theories of oceanic mesoscale turbulence the spectra in these regions may reflect the ocean s response to short scale atmospheric forcing and air sea interaction the observations presented in this paper serve as a test bed for new theories and ocean general circulation models

validating satellite altimeter measurements of internal tides with long term tao triton buoy observations at 2 s 156 e satellite altimetry is regularly used to map the global distribution of mode 1 internal tides validating altimeter measurements of internal tides with in situ data is difficult as the mooring observations typically are too short compared with the altimetry here taking advantage of the long term since 1999 tropical atmosphere ocean triangle trans ocean buoy network tao triton buoy observations at 2 s 156 e located at a topex poseidon crossover in a region of strong internal tides direct comparisons are made between altimeter and in situ measurements over a common 15 year period the hourly buoy data are decimated every 9 9 day to emulate altimeter measurements the altimeter and decimated buoy data are highly coherent at the aliased semidiurnal period 60 day and they agree well for the stationary semidiurnal internal tide for the nonstationary internal tide which consists of a significant annual cycle the demodulated amplitude from the altimeter appears to be contaminated by nontidal signals the demodulated amplitude from the decimated buoy data on the other hand is capable of resolving the temporal variability this suggests the potential of mapping nonstationary internal tides from satellites

numerical modeling of infragravity wave response during delilah 1 the nearshore circulation model shorecirc is applied to simulate the infragravity wave conditions at two intervals during the 1990 delilah campaign at duck n c the model has been extended to solve the energy equation for random short waves on the timescale of the wave groups which acts as a wave driver for the long wave model to simulate the wave conditions an algorithm has been derived which synthesizes a directional offshore wavefield from measured data including the bound directional low frequency components the model data comparison shows that the mean short wave transformation and mean longshore current are predicted well the structure of the infragravity spectrum as measured in the nearshore array is correctly represented albeit that the energy levels are underpredicted in most locations the 2 d frequency longshore wavenumber spectra show that the infragravity wave energy consists mostly of edge waves and that the computations qualitatively resemble the measurements it is shown that for 1 day bar trapped edge waves are present the model is also used to show that the influence of the longshore variability is small for this particular beach and that the directional spreading in the offshore wave field is critical in predicting the nearshore infragravity wave conditions correctly edge waves which propagate against the current are generated by the directionally broad short wave forcing and to a lesser extent by back scattering the nonlinear terms are relatively unimportant for the prediction of the infragravity wave climate the cross shore gradient of the onshore directed radiation stress is the most important of the forcing terms

a numerical model of nearshore waves currents and sediment transport a two dimensional numerical model of nearshore waves currents and sediment transport was developed the multi directional random wave transformation model formulated by mase mase h 2001 multidirectional random wave transformation model based on energy balance equation coastal engineering jounnal 43 4 317 337 based on an energy balance equation was employed with an improved description of the energy dissipation due to breaking in order to describe surface roller effects on the momentum transport an energy balance equation for the roller was included following dally and brown dally w r brown c a 1995 a modeling investigation of the breaking wave roller with application to cross shore currents journal of geophysical research 100 c12 24873 24883 nearshore currents and mean water elevation were modeled using the continuity equation together with the depth averaged momentum equations sediment transport rates in the offshore and surf zone were computed using the sediment transport formulation proposed by camenen and larson camenen b larson m 2005 a general formula for non cohesive bed load sediment transport estuarine coastal and shelf science 63 249 260 camenen b larson m 2007 a unified sediment transport formulation for coastal inlet application technical report erdc chl cr 07 1 us army engineer research and development center vicksburg ms camenen b larson m 2008 a general formula for non cohesive suspended sediment transport journal of coastal research 24 3 615 627 together with the advection diffusion equation whereas the swash zone transport rate was obtained from the formulas derived by larson and wamsley larson m wamsley ty 2007 a formula for longshore sediment transport in the swash proceedings coastal sediments 07 asce new orleans pp 1924 1937 three high quality data sets from the lstf experimental facility at the coastal and hydraulics laboratory in vicksburg usa were used to evaluate the predictive capability of the model good agreement between computations and measurements was obtained with regard to the cross shore variation in waves currents mean water elevation and sediment transport in the nearshore and swash zone the present model will form the basis for predicting morphological evolution in the nearshore due to waves and currents with special focus on coastal structures c 2009 elsevier b v all rights reserved less