numerical assessment of infragravity swash response to offshore wave frequency spread variability this work has been funded under 1 the retos investigacion 2014 grant bia2014 59718 r program of the spanish ministry of economy and competitiveness and 2 the neptune 2 project l r 7 2007 by regione autonoma della sardegna

infragravity swash parameterization on beaches the role of the profile shape and the morphodynamic beach state abstract a field campaign was undertaken at somo beach in northern spain with the aim of understanding the processes involved in the generation of low frequency swash taking the parameterization presented in earlier studies as a starting point a novel empirical model was defined based on a database which included datasets from somo beach and from 9 other experiments this new parameterization was obtained by relating the horizontal cross shore component of the infragravity swash to the foreshore slope and the morphodynamic beach state through the non dimensional fall velocity parameter the role of previous sea states when determining the morphodynamic beach state was also assessed a strong correlation between low frequency oscillations and the morphology of the beach was verified resulting in a substantial improvement over existing infragravity swash predictions proposed in the literature

laboratory model of a planetary eastward jet the concentration of eastward planetary currents into strong wavy jets is a major feature of the atmospheric general circulation for example the jet stream and of oceanic currents for example the gulf stream east of cape hatteras these strongly nonlinear jets are however not well understood here we describe experiments in which we have produced similar jets in a rotating annulus with mechanical forcing the coriolis force acting on fluid pumped radially inward from a ring of sources to a ring of sinks results in a strong eastward jet for a wide range of parameters the jet has a robust wavy shape as shown in fig 1 the wave velocity and wavelength of these rossby waves are accounted for by simple scaling arguments experiments with dye injected into the fluid show that the jet acts as a barrier to tracer transport see fig 1e much as the southern polar night jet may act as a barrier to the transport of ozone from lower latitudes into the polar region1 our observations are insensitive to the details of the arrangement of the sinks and sources

rugged crater ejecta as a guide to megaregolith thickness in the southern nearside of the moon the southern highlands of the moon comprise superposed ejecta layers individually as thick as a few kilometers from the major basins smaller 1 16 km diameter impact craters that penetrate this layered megaregolith and excavate material from depth have radar properties that provide insight into the variability of megaregolith thickness above a postulated basement of large crustal blocks we observe a significant difference in the population of radar bright craters 1 16 km and larger in diameter between regions of the southeastern near side highlands north and south of lat 48 s there are about one third more radar bright craters north of this line than to the south broadly coincident with the mapped boundary between southern deposits mapped as pre nectarian age and those of nectarian imbrian age to the north the radar bright crater population is consistent with a megaregolith thickness of 1 5 km in the north and 2 5 km in the south a difference we attribute to south pole aitken basin ejecta

modeling the provenance of the apollo 16 regolith 1 the regolith at the apollo 16 landing site the only apollo landing site in the central lunar highlands contains material derived from a number of sources a model that accounts for the introduction of basin ejecta and mixing of the megaregolith is used to estimate the abundance of basin material in the apollo 16 regolith megaregolith mixing model estimates of the abundance of primary ejecta from the imbrium serenitatis and nectaris basins are found to be present in roughly equal 8 10 proportions additionally the presence of mare derived material in the apollo 16 regolith suggests that a significant component of the regolith 15 23 is derived from lateral transport there are inherent difficulties in directly comparing model results with ground truth at apollo 16 results suggest shallower mixing during ejecta emplacement than predicted by oberbeck et al 1975

simulating wave setup and runup during storm conditions on a complex barred beach abstract the purpose of this study is to assess the ability of the swash model to reproduce wave setup and runup in highly dissipative stormy conditions to proceed we use data collected during the ecors truc vert 08 experiment especially during the johanna storm in the winter of 2007 008 wave setup under hs 8 2 m and tp 18 3 s and runup under 6 4 m and peak period up to 16 4 s we test different model settings 1d and 2d mode and model forcing spectral and parametric to reproduce sensor measured wave setup at several locations in the nearshore area and video measured runup on two beach profiles for the whole tested configurations the wave setup is reproduced accurately results considering all the sensor locations in the near shore area in 1d and 2d are significantly correlated to the observations with respectively 0 66 and 0 81 rmse 0 13 m and 0 08 m without any significant bias observations and simulations of runup are investigated in terms of spectra and statistic component 1d simulations produces an overall overestimation and no significant improvement is obtained by modifying the breaking parameters the results for 2d simulations are fairly satisfactory reproducing significant swash height s but are significantly improved with spectral forcing than parametric with respectively 0 73 and 0 71 rmse 0 19 m and 0 43 m generally the model reproduces accurately the infragravity component but tends to overestimate the incident component leading to an overestimation of the energy density for moderate wave conditions and more accurate results for higher energy wave conditions results in 2d with spectral forcing show a saturation of the infragravity component with a threshold around hs 4 to 5 m which is comparable to the observations collected at truc vert beach as regards the conventional statistical parameter for runup estimation r2 three methods are applied to derive the 2 exceedence value for runup from observed and simulated shoreline vertical elevation time series when r2 is based on the sum of wave setup and half of the significant swash height results provided by the model are close or even better than estimations provided by empirical formulas from the bibliography defining r2 as the exceeded 2 values of the time derived considering the cumulative distribution function of the entire water level time series also provide fairly good results results using only runup maxima time series are less satisfactory in the two last cases r2 is slightly underestimated for moderate wave conditions hs

experimental study of runup for sandy beaches under waves and tide abstract this paper describes an experimental investigation of runup for intermediate sandy beaches from a physical modelling in a wave flume with tide simulation shoreline elevation measurements are acquired over a wide range of conditions using an optical method simultaneous morphological and hydrodynamic changes are considered to determine the best parameters to predict the maximum wave runup the tidal level significantly affects the breaking conditions position height and type and the slopes of the beach present data show that the surf zone slope and the wave breaking height should be used to estimate the maximum runup the results are compared with previous formulations issued from the literature a new formula is proposed for the runup estimation for intermediate beaches

global distribution of lunar impact melt flows abstract in this study we analyzed the distribution and properties of 146 craters with impact melt deposits exterior to their rims many of these craters were only recently discovered due to their unusual radar properties in the near global mini rf data set we find that most craters with exterior deposits of impact melt are small 20 km and that the smallest craters have the longest melt flows relative to their size in addition exterior deposits of impact melt are more common in the highlands than the mare this may be the result of differing target properties in the highlands and mare the difference in titanium content or the greater variation of topography in the highlands we find that 80 of complex craters and 60 of simple craters have melt directions that are coincident or nearly coincident with the lowest point in their rim implying that pre existing topography plays a dominant role in melt emplacement this is likely due to movement during crater modification complex craters or breached crater rims simple craters we also find that impact melt flows have very high circular polarization ratios compared to other features on the moon this suggests that their surfaces are some of the roughest material on the moon at the centimeter to decimeter scale even though they appear smooth at the meter scale

monsoon surges trigger oceanic eddy formation and propagation in the lee of the philippine islands 1 two winter monsoon surge events northerly and easterly of january 2005 are captured in a one way coupled atmosphere 8 km resolution and ocean 3 km resolution simulation of the philippines region intensified wind jets and wakes in the lee of mindoro and luzon islands induce the generation and migration of a pair of counter rotating oceanic eddies in the model with propagation direction related to the orientation of the winds during each of the surges features shared by the eddies include size 100 200 km depth 300 m and propagation speed 0 1 0 15 m s 1 for cyclones mean wintertime model wind stress positive negative curl coincides with the climatological cyclone anticyclone distribution from a prior 8 year altimetry based census of eddies in the southeast quadrant of the south china sea during the winter monsoon moreover the simulation results agree with contemporaneous satellite and historical in situ data characterizing regional oceanic eddy and atmospheric surface jet properties

advances in swash zone research small scale hydrodynamic and sediment transport processes abstract extensive research efforts in the last decade have improved knowledge of swash zone processes this paper reviews and synthesizes from 2004 onward the research advances of small scale hydrodynamics and sediment transport processes considering field laboratory and numerical modeling efforts swash zone hydrodynamics are examined by means of shoreline motions fluid velocities pressure gradients flow structure bed shear stress friction coefficients and turbulence subsequently advances related to sediment transport mechanisms and morphological changes are described detailed descriptions of measuring techniques novel findings and the strengths and weaknesses of the different approaches are discussed the review also acknowledges the major advances in the development of instrumentation to collect highly resolved flow and sediment concentration measurements in direct proximity of the bed and the experimental framework for analyzing local dynamics on a wave by wave time scale e g dam break

lithification mechanisms for planetary regoliths the glue that binds it is understood how rocks are made on earth however on the moon mercury and to a lesser extent mars and venus there are distinct rock forming processes that we do not fully comprehend the surfaces and crusts of the inner planetary bodies may retain a history of disruption by hypervelocity impact resulting in the generation of disaggregated materials to several kilometers depth the uppermost component of this is called regolith typically 20 m thick on the moon which is part of a more extensive megaregolith that is up to tens of kilometers thick and which in places may pervade the entire crust of a planetary body it is from these pulverized materials that new rocks are reaggregated to form so called breccias this work reviews regolith and megaregolith structure for the inner planetary bodies and investigates how extraterrestrial breccias are produced three principal formation mechanisms are explored thermal sintering shock sintering and the dynamic interaction of impact generated melt w

swash oscillations on a natural beach run up swash oscillations were measured on a gently sloping beach face for a variety of incident wave conditions run up energy spectra at wind wave frequencies show an 3 dependence and energy levels that are independent of incident wave height this suggests saturation in contrast run up energy at surf beat periods increase approximately linearly with increasing incident wave energy thus in the inner surf zone where wave breaking limits the energy at wind wave frequencies the principal manifestation of large incident wind waves is energetic surf beat

infragravity wave generation on shore platforms bound long wave versus breakpoint forcing abstract shore platforms are ubiquitous morphological features along rocky coastlines and display a spectrum of forms from gently sloping to sub horizontal with a low tide cliff they generally front eroding coastal cliffs and play an important natural coastal protection role by dissipating wave energy especially during energetic wave conditions sea swell wave energy dissipates during wave breaking but the transfer of incident wave energy to lower frequencies resulting in infragravity waves can enable significant amounts of wave energy to persist up to the shoreline this residual wave motion at the shoreline can carry out geomorphic work for example by directly impacting the cliff face but also for removing cliff toe debris there are two main mechanisms for generating infragravity wave motion group bound long waves and breakpoint forcing and it is not known which of these mechanisms operate on shore platforms here we show using field data collected at a sloping platform in england and a sub horizontal platform in new zealand and supported by numerical modelling that the group bound long wave mechanism is most important on sloping platforms whereas breakpoint forcing dominates on sub horizontal platforms our results also suggest that the infragravity wave motion on the sloping platform is somewhat more energetic than that on the sub horizontal platform implying that the latter type of platform may provide better protection to coastal cliffs however site specific factors especially platform elevation with respect to tidal level and platform gradient play a key role in wave transformation processes on shore platforms and more field data and modelling efforts are required to enhance our understanding of these processes especially collected under extreme wave conditions hs 5 m

wave reflection and saturation on natural beaches the role of the morphodynamic beach state in incident swash abstract in this work we present an analysis of the effect of the processes related to beach morphodynamic state on high frequency incident band swash oscillations the effect of wave reflection and saturation on swash oscillations was assessed based on new field data measured under different morphodynamic conditions on the northern coast of spain data measured under more reflective conditions indicated the occurrence of a cross shore partial standing structure a process which was observed earlier using laboratory and numerical data part of the dataset data showed saturation in accordance to limits between reflection and saturation established in previous works the new measured data was added to a large database compiled from previous works and assuming the hypothesis that the reflection and saturation processes are related to the beach state a new parameterization was established to calculate the incident swash under different morphodynamic conditions our results indicate that the role of the foreshore slope and wave steepness varies according to the morphodynamic beach state the proposed formula showed a reasonable correlation with measured data 2 0 56 and rmse 0 41 m and improvements in s i n c predictions were observed for all beach types when compared to existing formulas

swash on steep and shallow beaches extensive field observations of swash on natural beaches are used to relate the magnitudes of swash oscillations to incident wave conditions and the beach slope swash fluctuations at wind wave frequencies defined here as f 05 hz appear to be saturated as in laboratory experiments with monochromatic waves wave breaking prevents the magnitudes of swash oscillations at incident wave frequencies from increasing past a certain level which depends on the beach slope all data sets considered support this conclusion in contrast the magnitude of swash oscillations at surf beat frequencies defined as f 05 hz varies between data sets possible reasons for the discrepancy are discussed despite their differences all data sets show that motions at surf beat frequencies dominate the swash spectrum on dissipative beaches as in previous studies the frequencies of spectral hills and valleys in the spectra of surf zone sensors suggests that a significant fraction of the surf beat energy is contained in motions which are standing in the cross shore direction preliminary analysis indicates that shoreward propagating surf beat is coupled to incident wave groups

the dynamics of infragravity wave transformation over a fringing reef a 3 week field study was conducted to investigate the dynamics of low frequency infragravity wave motions over a fringing reef at ningaloo reef western australia short period wave motions 0 04 0 2 hz were observed to dissipate on the reef crest beyond which infragravity wave motions 0 004 0 04 hz gradually dominated toward the lagoon however both the short waves and the infragravity waves were relatively small both 0 3 m on the reef flat owing to the shallow water depth 2 m the results revealed that the surf zone generation of free infragravity wave motions on the steep 1 20 fore reef slope was dominated by breakpoint forcing as opposed to shoaling bound waves which was also supported by detailed numerical simulations of the generation process this is consistent with theory suggesting the efficiency of the breakpoint forcing mechanism should be high in this steep slope regime shoreward propagating infragravity waves traveled across the reef but were damped by bottom friction dissipation however this was at a rate much smaller than experienced by the residual short waves with these rates of frictional dissipation also strongly dependent on the water depth over the reef the infragravity wave heights increased at higher water levels and hence were strongly modulated by the tide due to the strong dissipation of infragravity waves over this wide and shallow reef that is hydraulically rough any seaward propagating infragravity waves that reflected at the shoreline were small leading to the dominance of progressive shoreward propagating infragravity wave motions throughout the reef and lagoon

extreme value statistics for wave run up on a natural beach abstract statistics of wave run up maxima have been calculated for 149 35 minutes data runs from a natural beach during the experiment incident wave height varied from 0 4 to 4 0 m incident wave period from 6 to 16 s and beach face slope from 0 07 to 0 20 four extreme statistics were calculated the maximum run up height during each run the 2 exceedence level of shoreline elevation the 2 exceedence height for individual run up peaks and the 2 exceedence level for swash height as determined by the zero upcrossing method these statistics were best parameterized when normalized by the incident significant wave height and plotted against the iribarren number h l 0 1 2 the swash data with set up removed showed less scatter than total run up with set up included for iribarren number greater than 1 5 the run up was dominated by the incident frequencies for lower iribarren number longer period motions dominated the swash a reasonable value of wave steepness for a fully developed storm sea is 0 025 so that a storm iribarren number can be estimated as 6 3 times the beach slope using this and an offshore design wave height the included graphs may provide guidance in determining a design run up height

chaotic transport of mass and potential vorticity for an island recirculation the method of lobe analysis is used and extended to analyze a time dependent boundary trapped recirculation the recirculation gyre occurs in a numerical model of wind driven flow around an island but the underlying geometry of the gyre is similar to persistent eddies such as the alboran gyre and the great whirl even in the steady weak forcing limit the gyre leaks fluid due to the fact that the surface ekman pumping above it is directed downward the authors show that this leakage is rapidly superseded by chaotic transport into and out of the gyre when time dependence sets in variations of the traditional turnstile approach to transport are used to study the dynamics of the gyre a lagrangian recirculation boundary consisting of pieces of stable and unstable manifolds joined by a gate allows straightforward calculation and visualization of potential vorticity flux

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

observations and predictions of run up for a significant range of offshore wave conditions and foreshore slopes run up observations are compared to semiempirical formulations and predictions of an existing numerical model based on the depth averaged one dimensional nonlinear shallow water equations with bore like breaking wave dissipation and quadratic bottom friction the numerical model is initialized with time series of sea surface elevation and cross shore velocity observed in 80 cm mean water depth approximately 50 m offshore of the mean shoreline on a gently sloping beach and in 175 cm water depth 100 m offshore of the shoreline on a steep concave beach run up was measured with a stack of resistance wires at elevations 5 10 15 20 and 25 cm above and parallel to the beach face at sea swell frequencies nominally 0 05 f 0 18 hz run up energy is limited by surf zone dissipation of shoreward propagating waves so that increasing the offshore wave height above a threshold value does not substantially increase the predicted or observed sea swell run up excursions e g run up is saturated existing semiempirical saturation formulations are most consistent with the observations and numerical model predictions of run up excursions nearest the bed in contrast at infragravity frequencies 0 004 f 0 05 hz where surf zone dissipation is relatively weak and reflection from the beach face is strong e g saturation formulas are not applicable the run up excursions increase approximately linearly with increasing offshore wave height the numerical model also accurately predicts that the tongue like shape of the run up results in sensitivity of run up measurements to wire elevation for instance run up excursions and mean vertical superelevation above the offshore still water level increase with decreasing wire elevation and continuous thinning of the run up tongue during the wave uprush can result in large phase differences between run up excursions measured at different wire elevations numerical model simulations suggest that run up measured more than a few centimeters above the bed cannot be used to infer even the sign of the fluid velocities in the run up tongue

grain size variability on a rip channeled beach abstract grain size is an important variable when predicting beach morphodynamics beaches to the eye seem relatively uniform in grain size and morphodynamic modeling efforts usually assume a single mean grain size for an entire beach environment therefore estimating grain size is traditionally done by collecting only a few samples and averaging to characterize the mean grain size of the whole beach however some studies have shown that even small variations in grain size can have a significant effect on model results when predicting beach morphology changes here a mobile digital imaging system dis has been developed for surveying spatial and temporal variation in grain size across a beach following the ideas of rubin 2004 using an off the shelf camera and underwater housing macro photographs are taken of sand across a beach which produce estimates of mean grain size that are highly correlated with estimates from sieves r2 0 92 high resolution maps of mean surface grain size are produced using the dis with 1000 images over a 300 500 m area which suggest that large variations in grain size exist 0 2 0 7 mm over tens of meters with accuracies of 0 03 mm and that there is a correlation between spatial grain size variations and morphological variability

focused 70 cm wavelength radar mapping of the moon we describe new 70 cm wavelength radar images of the lunar near side and limb regions obtained via a synthetic aperture radar patch focusing reduction technique the data are obtained by transmitting a circularly polarized pulsed waveform from the arecibo telescope in puerto rico and receiving the echo in both senses of circular polarization with the robert c byrd green bank telescope in west virginia the resultant images in both polarizations have a spatial resolution as fine as 320 m 450 m near the lunar limb the patch focusing technique is a computationally efficient method for compensating for range migration and doppler azimuth smearing over long coherence times i e 983 s which is needed to achieve the required doppler resolution three to nine looks are averaged for speckle reduction and to improve the signal to noise ratio at this long wavelength the radar signal penetrates up to several tens of meters into the dry lunar surface materials thus revealing details of the bulk loss properties and decimeter scale rock abundance not evident in multispectral and other remote sensing data application of the new radar images to the analysis of basalt flow complexes in mare serenitatis shows that the long wavelength radar data are sensitive to differences in both flow age and composition and may be particularly useful for studies of smaller deposits that do not have robust crater statistics the new 70 cm lunar radar data are archived at the national aeronautics and space administration planetary data system

wave runup over steep rocky cliffs wave runup is known to depend on offshore wave conditions and coastal morphology while most field studies on wave runup have focused on low to mild sloping sandy beaches runup measurements on steep and irregular rocky cliff profiles are still very scarce here we investigate the physical processes controlling wave runup in such environments and the range of applicability of empirical runup formula this study focuses on the steep rocky cliffs 0 1 tani i 0 4 of banneg island a small island located in the molene archipelago brittany france occasionally flooded during extreme water level events a statistical parameter for extreme runup is derived from the measurements of pressure sensors deployed in the intertidal zone deep water wave parameters are used to force a high resolution wave model and nearshore wave parameters and high resolution topographic data are analyzed concurrently with runup time series in order to assess the dependence of the runup on hydrodynamic conditions and morphological parameters the wave runup is shown to be strongly related to the square root of the offshore significant wave height times the offshore wavelength the measurements also reveal the depth dependence of the runup which is mainly attributed to the curvature of the foreshore profile in comparison to empirical relation obtained for a mild sloping beach the present data show a significant reduction in normalized wave runup that is attributed to enhanced bottom friction over the rocky bottom

observations of wave energy fluxes and swash motions on a low sloping dissipative beach 1 field observations of swash and ocean waves show that runup saturation at infragravity frequencies 0 025 0 035 hz infragravity waves where typically less than 5 of the linear energy flux was reflected from the beach and where similar to the sea swell band the swash energy was independent of offshore wave energy the infragravity frequency range of saturation was determined by the tide with saturation extending to lower frequencies at low tide when the local beach face slope over the concave shaped profile was gentler runup was strongly dominated by infragravity frequencies which accounted on average for 96 of the runup variance and its energy levels were entirely consistent with strong infragravity wave dissipation observed in the surfzone particularly when including the nonlinear contributions to the wave energy fluxes the infragravity wave dissipation was strongly associated with breaking of sea swell waves which abruptly decreased nonlinear transfers to infragravity frequencies and made infragravity dissipation prevail over forcing within the breaking region our observations show evidence of nonlinear interactions involving infragravity and high frequency harmonic waves and suggest that these harmonics could play a role in the wave energy balance near the shoreline on low sloping dissipative beaches

beach response to a sequence of extreme storms abstract a sequence of daily beach surveys acquired over one month covering an area larger than 100 000 m 2 was analyzed to study morphological changes resulting from a cluster of storms the beach response was highly variable in both the cross and alongshore a cumulative storm effect was not observed despite one storm being characterized by a 10 year return period that had significant wave height h s of 8 1 m and a peak wave period t p of 17 s instead storms that can potentially cause significant erosion in terms of h s had a limited effect on the morphology because the large wave height was coupled to either neap tides normally incident short waves f 0 04 hz or low levels of infragravity 0 004 f

field experiments of beach scarp erosion during oblique wave stormy conditions normandy france abstract a field based experimental study of beach scarp morphodynamic evolution was conducted on the shoreface of a macrotidal sandy beach subject to storms combined with spring tide events luc sur mer france both video and in situ measurements on an artificial berm are used to understand beach scarp evolution over one tide during stormy conditions image time stacks are used to analyze the swash action on the beach scarp and topographical data of the scarp are recorded with a terrestrial scanner laser to quantify the morphodynamic response of the beach scarp to wave action this work provides a new and unique dataset about beach scarp changes and berm morphology in particular under rising tide and oblique wind wave conditions during one stormy event the berm was completely destroyed however contrasting alongshore changes were measured during the erosive phase with different crest and foot scarp retreats and eroded volumes between the west and the east side of the berm the beach in front of the scarp also shows a contrasting residual evolution indicating an evident longshore sediment transport on the study area as a consequence of incident oblique wave conditions a strong connection between beach evolution and beach scarp changes is clearly identified the scarp erosion increases on the west side of the berm when the beach level is lowered and reduces when the beach surface rises on the east side the beach slope and foreshore elevation as a result of a longshore sediment transport between east and west profiles influence swash activity overall water depth and swash activity became progressively different along the scarp during the experiment swash measurements indicate that the presence of the beach scarp strongly influences the swash motion at high tide the reflection of the uprush on the scarp front induces a collision between the reflected backwash and the following uprush dynamic these collisions reduce and sometimes stop the motion of the following uprush reducing the incoming swash excursion consequently the scarp presence modifies the swash interaction that normally appears on a planar beach surface with a beach scarp the swash energy level is substantially attenuated and its spectrum is characterized by a large band the number of uprush impacts on the scarp front calculated from video images reaches about 25 per 5 min in spite of the swash energy attenuation due to swash swash interactions these impacts provoke the berm destruction in about two hours however the onshore migration of the swash zone induced by the rising tide appears to be important to explain scarp destruction compensating the attenuated swash activity due to backwash uprush interactions

video observations of beach cusp morphodynamics beach cusps are a common feature of steep reflective and intermediate beaches although many observations of beach cusp spacing exist there are few observations quantifying the incipient formation evolution and eventual destruction of these features beach cusp morphodynamics were analyzed using a 3 year dataset of video images collected at tairua beach new zealand twenty four beach cusp episodes were selected to monitor the cycle of beach face changes from planar to the appearance of the cusp patterns and back to planar again observations show that beach cusp disappearance can be ascribed not only to the erosive influence of storms but also to the persistence of accretionary conditions leading to the infilling of beach cusp bays and the development of an alongshore continuous berm we also report observations of changes in beach cusp spacing over time which can be attributed to the merging of adjacent cusps within the cusp field with the overall cusp spacing re adjusting to accommodate the disappearance of a horn although the self organization theory provides a better fit to the data and theory we were unable to conclusively refute any of the mechanisms causing beach cusp formation since both existing theories subharmonic standing edge wave and self organization can predict the trend in the observed beach cusp spacing these observations show that initial beach cusp formation primarily occurs around 70 of the episodes analyzed under mildly accretionary conditions and when accretion persists the pattern disappearance is likely to occur as a result of bay infilling to form a featureless berm

optimisation of focused wave group runup on a plane beach abstract insight is provided into focused wave group runup on a plane beach by means of laboratory wave flume experiments and numerical simulations a focused wave group is presented as an alternative to an empirical description of the wave conditions leading to extreme runup second order correction to the laboratory wavemaker generation signal is observed to remove about 60 of the sub harmonic error wave that would otherwise contaminate coastal response experiments laboratory measurements of the wave runup time history are obtained using inclined resistance type wires and copper strips attached to the beach surface the numerical wave runup model is based on hybrid boussinesq nonlinear shallow water equations empirical parameters for wave breaking and bed friction and a wetting and drying algorithm after calibration against experimental runup data the numerical model reproduces satisfactorily the propagation shoaling and runup of focused wave groups over the entire length of the wave flume results from a comprehensive parametric study show that both measured and predicted maximum runup elevations exhibit strong dependence on the linear focus amplitude of the wave group linked to its probability of occurrence the focus location and the phase of the wave group at focus the results also demonstrate that extreme runup events owing to focused wave incidence cannot be characterised using spectral parameters alone the optimal band of focus locations shifts onshore as linear focus amplitude of the incident wave group increases optimisation of phase and focus location leads to a maximum runup elevation at each linear amplitude and when generated using second order corrected paddle signals the maximum runup appears to approach saturation at very large focused wave amplitudes this study therefore moves beyond simple wave focusing and presents a focused wave group as a tool for investigating the relationship between extremes within an incident wave field and extreme wave runup

empirical wave run up formula for wave storm surge and berm width abstract an empirical model to predict wave run up on beaches considering storm wave and surge conditions and berm widths dry beach has been derived through a synthetic data set generated from a one dimensional boussinesq wave model the new run up equation is expressed as a function of a new iribarren number composed of three regions the foreshore the berm or dry beach width and the dune the dissipative effect of the berm is included as a reduction factor expressed as a function of the berm width normalized by the offshore wavelength the equation is relatively simple but is shown to be applicable for a fairly wide variety of berm widths and storm wave conditions associated with extreme events such as hurricanes and it is shown to be an improvement over existing empirical run up models that do not consider the berm width explicitly in addition the new parameterization of the iribarren number considering the three regions and the berm width reduction factor are shown to improve other empirical models

importance of infragravity waves for the generation of washover deposits abstract washover deposits are among the most remarkable sedimentary signatures of dune breaching and coastal inundation overwash of the barrier leading to washover development can be related either to storms or tsunamis but the distinction between these two processes based on the depositional record is still a matter of debate hence studying recent well documented washover deposits combining sedimentological and hydrodynamic investigations is a key approach to identify the processes governing the washover deposition and to analyze their sediment record within the washover during the winter of 2013 2014 the coasts of the bay of biscay experienced an exceptional wave climate leading to dune breaching and washover deposition at many locations including the gatseau spit south of oleron island france field observations aerial photographs topographic measurements gpr investigations trenches and cores grain size analysis and magnetic fabric measurements were carried out and complemented with hydrodynamic modeling of tides storm surges short waves and infra gravity waves in order to compute maximum runup during the winter of 2013 2014 such an interdisciplinary approach led to propose that 1 large overwash events occurring during the winter of 2013 2014 were mainly driven by infra gravity ig waves combined with high tides 2 the washover elongated outer shape was strongly controlled by the antecedent morphology of the back barrier area 3 one overwash flow driven by one ig wave is recorded by one normally graded lamina composed of quartz sand at base and heavy minerals enriched sand at top 4 dominant settling of the particles from a suspension during sedimentation occurred in the end of each overwash flow in response to flow velocity decrease 5 laminae can be grouped in laminasets generally composed of thinning upward laminae related to overwash flow depth decrease during falling tide and to erosion of basal laminae by highest overwash flows occurring more likely around the high tide 6 the number of laminasets in a proximal position is in the same order of magnitude as the number of modeled highest runup events offering an almost complete record of overwash events that occurred during the winter 2013 2014

the role of beach state and the timing of pre storm surveys in determining the accuracy of storm impact assessments abstract dune erosion principally occurs when water level exceeds the elevation of the beach and predicting erosion is progressively becoming more important for management as coastal populations increase sea level rises and storms become more powerful this study assesses storm impacts using a simple model from stockdon et al 2007 configured with oceanographic information from the adcirc swan model and frequently collected beach profiles we applied that model to barrier islands in north carolina including core banks with a more dissipative beach morphology and shackleford banks and onslow beach with intermediate beach morphologies the study periods captured 10 events where wave collision with the dunes and or overwash were either predicted or observed including large multiple day events caused by hurricanes and smaller events caused by onshore winds and high tide comparing model output with a time series of beach photographs shows the predictive power and sensitivity of the model was consistently high at the core banks site with its wide and low gradient beach high elevation dunes 2 58 m and high resistance to overwash model predictive power and sensitivity was lowest at the shackleford banks site because frequent and large changes to beach slope and intermediate dune elevation 0 54 1 25 m caused small variations of modeled total water level to either overpredict or underpredict storm impacts in addition storm impacts were always overpredicted during hurricanes at the shackleford banks site which was likely due to storm waves decreasing the beach slope from what was measured prior to the event and used as model input like shackleford banks the beach slope of the onslow beach site was steep and variable but the low elevation dunes 0 24 0 28 m made resistance to overwash low and the predictive power and sensitivity of the model higher than at the shackleford banks site results suggest that storm impacts and the associated potential for dune erosion is predicted more accurately at beaches where the threshold for overwash is high or low because total water level during most events will commonly fall short of or exceed the overwash threshold respectively the accuracy of predicting the storm impact regime is sensitive to beach slope the slope of intermediate beaches is more variable than dissipative beaches and requires frequent measurement if it is to be represented accurately in the model but this can be impractical and costly even using the latest drone surveying methods to maximize the accuracy of predicting storm impacts intermediate beach morphology should be constrained by surveying at seasonal or yearly time scales and used as input to numerical models that estimate beach slope over short time scales hours during an event or daily configured with the latest wave and water level forecasts

observations of swash under highly dissipative conditions video measurements of swash were made at the low sloping beach of the multiple bar system at terschelling netherlands the majority of the measurements were conducted under highly dissipative conditions with iribarren numbers 0 the ratio of beach slope to the square root of offshore wave steepness less than 0 2 infragravity 0 004 0 05 hz waves dominated the swash with an average ratio of infragravity and total swash height rig r of 0 85 using linear regression we investigated the dependence of swash parameters on environmental conditions such as short wave height period and local beach slope on average rig was about 30 of the offshore wave height h0 the slope in the linear h0 dependence of rig amounted to only 0 18 considerably smaller than that observed on steeper beaches the data set shows evidence for saturation of the higher infragravity frequencies for 0 less than roughly 0 27 in our opinion this saturation caused the constant of proportionality in the linear relationship between rig h0 and 0 to be significantly larger than that observed under higher iribarren number regimes the saturated tails of the swash spectra had an approximate f 3 roll off where f is frequency whereas in general the nonsaturated parts were white this lack of significant peaks casts doubt on the causality between infragravity waves and nearshore bars

radar probing of planetary regoliths an example from the northern rim of imbrium basin 1 imaging radar measurements at long wavelengths e g 30 cm allow deep up to tens of meters probing of the physical structure and dielectric properties of planetary regoliths we illustrate a potential application for a mars orbital synthetic aperture radar sar using new earth based 70 cm wavelength radar data for the moon the terrae on the northern margin of mare imbrium the montes jura region have diffuse radar backscatter echoes that are 2 4 times weaker at 3 8 cm 70 cm and 7 5 m wavelengths than most other lunar nearside terrae possible geologic explanations are 1 a pyroclastic deposit associated with sinuous rilles in this region 2 buried mare basalt or a zone of mixed highland basaltic debris cryptomaria or 3 layers of ejecta associated with the iridum and plato impacts that have fewer meter sized rocks than typical highlands regolith while radar data at 3 8 cm to 7 5 m wavelengths suggest significant differences between the montes jura region and typical highlands the surface geochemistry and rock abundance inferred from clementine uv vis data and eclipse thermal images are consistent with other lunar terrae there is no evidence for enhanced iron abundance expected for basaltic pyroclastic deposits near the source vents of the sinuous rilles radial to plato the regions of low 70 cm radar return are consistent with overlapping concentric haloes about iridum and plato and do not occur preferentially in topographically low areas as is observed for radar mapped cryptomaria thus we suggest that the extensive radar dark area associated with the montes jura region is due to overlapping rock poor ejecta deposits from iridum and plato craters comparison of the radial extent of low radar return crater haloes with a model for ejecta thickness shows that these rock poor layers are detected by 70 cm radar where they are on the order of 10 m and thicker a sar in orbit about mars could use similar deep probing to reveal the nature of crater and basin related deposits

swash groundwater dynamics in a sandy beach laboratory experiment abstract experiments are carried out in a wave basin in order to study the swash groundwater interaction a set of wave gages and pressure sensors are used to monitor the free surface and groundwater dynamics the study is based on the comparison of two selected cases which differ by the gravity and infragravity forcing conditions the features of wave breaking in the surf zone the presence of a standing wave attached to the beach face and the wave setup at the shoreline significant differences are observed in the response of the swash groundwater system the water table overheight appears to be controlled by the amount of infragravity energy available at the shore cyclic beach drainage processes can be observed when the water table is low significant time averaged and time resolved flows are observed into the sand depending on the swash hydrodynamics the presence of a gravity standing wave modulation attached to the shore is shown to affect swash and groundwater dynamics most of the pressure gradients observed under the swash zone are related to infiltration flows and are thus related to moderate increase of the sediment relative weight

chaotic advection in an archipelago abstract techniques from dynamical systems theory have been applied to study horizontal stirring of fluid in the philippine archipelago the authors analysis is based on velocity fields produced by two high resolution 3 and 6 km numerical models particular attention is paid to identifying robust surface flow patterns and associating them with dominant lagrangian coherent structures lcss a recurrent wind driven dipole in the lee of the coastline is considered in detail the associated lcss form a template for stirring exchange and biological transport in and around the dipole chaotic advection is argued to provide a relevant framework for interpreting mesoscale horizontal stirring processes in an archipelago as a whole implications for the formation of filaments the production of tracer variance and the scale at which stirring leads to mixing are discussed in connection with an observed temperature record

the role of tides in beach cusp development 1 field measurements of morphology and swash flow during three episodes of beach cusp development indicate that tides modulate the height and cross shore position of beach cusps during rising tide beach cusp height decreases as embayments accrete more than horns and the cross shore extent of beach cusps decreases during falling tide beach cusp height increases as embayments erode more than horns and cross shore extent increases a numerical model for beach cusp formation based on self organization extended to include the effects of morphological smoothing seaward of the swash front and infiltration into the beach reproduces the observed spacing position and tidal modulation during rising tide water particles simulating swash infiltrate preferentially in embayments causing enhanced deposition during falling tide exfiltration of water particles combined with diversion of swash from horns causes enhanced erosion in embayments smoothing of beach morphology in the swash zone seaward of the swash front and in the shallow surf zone accounts for most of the observed tidal modulation even in the absence of infiltration and exfiltration despite the qualitative and in some cases quantitative agreement of the model and measurements the model fails to reproduce observed large deviations of horn orientation from shore normal some aspects of beach cusp shape and deviations from the basic tidal modulation possibly because of the simplified parameterization of cross shore sediment transport and the neglect of the effects of sea surface gradients on flow index terms 4546 oceanography physical nearshore processes 4255 oceanography general numerical modeling 3220 mathematical geophysics nonlinear dynamics keywords beach cusp tides infiltration exfiltration erosion

wave runup and overwash on a prototype scale sand barrier abstract accurate methods to predict wave runup are of critical importance to coastal engineers extreme runup during storm conditions can present a danger to coastal infrastructure and lead to dune overtopping and erosion overwash of barrier beaches and is an essential design parameter for certain coastal protection works this paper uses data obtained during the unique bardex ii prototype scale laboratory experiment on a reflective sand barrier to investigate wave runup and overwash runup measurements were acquired using ultrasonic altimeters 2d scanning lidar and camera systems under controlled wave and water level conditions it was found that extreme runup r 2 scaled well with the deepwater irribarren number where the beach slope was taken to be the beach face gradient the lower limit of the swash zone defined by the 2 wave rundown limit was also found to be a function of the irribarren number and was consistently below the swl in all tests the high resolution free surface measurements obtained using the ultrasonic altimeters and lidar enabled an analysis of the dynamics of individual swash events it was found that the vertical runup excursion of each swash correlated strongly with the height of the bore at collapse and could be predicted based on the assumption of a conversion of potential to kinetic energy at bore collapse

swell dominated sediment re suspension in a silty coastal seabed abstract waves are fundamentally important for sediment re suspension in estuary and coastal areas especially for silty sediments which can be easily suspended by waves but the differential effects of swell and wind waves are still unclear integrated field observations were made from november 2012 to march 2013 including waves currents and suspending sediments on the offshore seabed of the huanghe delta to explore the mechanism of sediment re suspension in silty coastal zones during the five months of observation there were more than 30 winter wind events that affected the study area and induced sediment re suspension with varying suspended sediment concentration the observed wave composition was separated into swell and wind waves using a bandpass filter results show that large swell with significant height 1 0 m coming from the offshore direction ne in our study area dominated sediment resuspension in the coastal seabed due to the fact that this wind direction had the longest average fetch winds from the onshore direction usually had smaller swell due to their short fetches and caused limited sediment re suspension the residual currents caused by ne winds also transport larger sediment an individual ne wind event could transport sediment 8 13 6 t m2 and 5 1 8 2 t m2 in directions parallel and perpendicular respectively to the isobaths which is much higher than the sediment transportation during an individual nw wind event which could transport 1 5 4 t m2 and 0 6 5 t m2 parallel and perpendicular respectively to the isobaths our research shows that large swell and the accompanying residual currents caused by ne winds from offshore direction are a vital driving force for sediment resuspension and transportation in the offshore zone

osmium isotope and highly siderophile element systematics of the lunar crust abstract coupled 187os 188os and highly siderophile element hse os ir ru pt pd and re abundance data are reported for pristine lunar crustal rocks 60025 62255 65315 ferroan anorthosites fan and 76535 78235 77215 and a norite clast in 15455 magnesian suite rocks mgs osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks previously identified as pristine contain meteorite derived hse low hse abundances in fan and mgs rocks are consistent with derivation from a strongly hse depleted lunar mantle at the time of formation the lunar floatation crust represented by fan had 1 4 0 3 pg g 1 os 1 5 0 6 pg g 1 ir 6 8 2 7 pg g 1 ru 16 15 pg g 1 pt 33 30 pg g 1 pd and 0 29 0 10 pg g 1 re 0 00002 ci and re os ratios that were modestly elevated 187re 188os 0 6 to 1 7 relative to ci chondrites mgs samples are on average characterised by more elevated hse abundances 0 00007 ci compared with fan this either reflects contrasting mantle source hse characteristics of fan and mgs rocks or different mantle crust hse fractionation behaviour during production of these lithologies previous studies of lunar impact melt rocks have identified possible elevated ru and pd in lunar crustal target rocks the new results provide no supporting evidence for such enrichments if maximum estimates for hse in the lunar mantle are compared with fan and mgs averages crust mantle concentration ratios d values must be 0 3 such d values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle with the notable exception of re given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust the potential similarities in crust mantle hse partitioning for the earth and moon are somewhat surprising low hse abundances in the lunar crust coupled with estimates of hse concentrations in the lunar mantle implies there may be a missing component of late accreted materials as much as 95 to the moon if the earth moon mass flux estimates are correct and terrestrial mantle hse abundances were established by late accretion

effect of wave frequency and directional spread on shoreline runup 1 wave breaking across the surf zone elevates the mean water level at the shoreline setup and drives fluctuations about the mean runup runup often is divided into sea swell 0 04 0 3 hz and lower frequency infragravity 0 00 0 04 hz components with energetic incident waves runup is dominated by infragravity frequencies and total water levels combined setup and runup can exceed 3 m significantly contributing to coastal flooding and erosion setup and runup observations on sandy beaches are scattered about empirical parameterizations based on near shoreline beach slope and deep water wave height and wavelength accurate parameterizations are needed to determine flooding and erosion risk to coastal ecosystems and communities here numerical simulations with the boussinesq wave model funwavec are shown to statistically reproduce typical empirical setup and runup parameterizations furthermore the model infragravity runuprs ig strongly depends on the incident wave directional and frequency spread about the mean direction and peak frequency realistic directional spread variations change rs ig equivalent to a factor of two variation in incident wave height the modeled rs ig is shown to vary systematically with a new non dimensional spreading parameter that involves peak frequency frequency spread and directional spread this suggests a new parameterization forrs ig potentially useful to predict coastal flooding and erosion

earth based radar data reveal extended deposits of the moon s orientale basin we present new earth based radar observations of ejecta associated with the lunar orientale impact basin we can distinguish 1 a block poor ejecta facies composing a concentric halo of mantling material 10 m or greater in thickness that extends more than 1000 km from the basin center and 2 a melt rich deposit that forms a discontinuous but areally extensive stratigraphic marker across the southern highlands the melt rich component likely extends well into the south pole aitken basin a key target for future landed and sample return missions the observation of these two ejecta facies and their distribution across the southern nearside yields new insight into the types and distribution of material contributed by large basin forming impacts to the highlands megaregolith

double bar beach dynamics on the high energy meso macrotidal french aquitanian coast a review the french aquitanian coast is an approximately 250 km long straight low coast exposed to high energy conditions in a mesomacrotidal setting offshore wave conditions are seasonally modulated predominantly with a wnw incidence with offshore significant wave height likely to reach 10 m during winter truc vert beach representative of most of the aquitanian coast beaches commonly exhibitstwodistinctsandbarsystems theinnerbarcangothroughallthestateswithintheintermediateclassificationandusuallyexhibitsa tansversebarandripmorphology afterafewweeksoflowerenergyconditionsduringsummer theinnerbarcommonlybecomesalow tideterracewithameanwavelengthof400mandameansoutherlymigrationrateofabout2 3m day crescenticbarshavebeenreported in the literature in nontidal to microtidal settings long term persistent crescentic patterns are however exhibited at a narrow range of wavelength mean of 700m by the outer bar at the meso macrotidal truc vert beach most of the time the outer bar is inactive and stagnates as offshore waves ofhsn3 m are required to induce a significant morphological change the crescent shape varies from a symmetric shape to a strongly asymmetric shape likely to be the result of a long period of nw wave conditions a strong and rarely observed elsewhere morphological coupling between the inner and outer bars can sometimes be observed and may be the result of the combined effectsof the initial presence of a well developed outer crescentic bar and a long period of shore normal low energy conditions a synthesis of all the data available on the area combined with observations on other environments leads to a truc vert beach state model ranging from a modal double bar configuration to an occasional triple bar configuration this work also identifies knowledge gaps to be explored by further numerical and field studies in tidal double sandbar environments 2007 elsevier b v all rights reserved

observations of surf beat forcing and dissipation 1 we used a simple energy balance equation and estimates of the cross shore energy flux carried by progressive surf beat to calculate the rate of net surf beat forcing or dissipation on a beach near duck north carolina far inside the surf zone surf beat dissipation exceeded forcing outside the surf zone surf beat forcing exceeded dissipation when incident waves were large surf beat dissipation inside the surf zone and forcing just outside the surf zone were both very strong the surf beat energy dissipated in the surf zone in a single beat period was of the same order as the total amount of surf beat energy stored in the surf zone during storms shoreward propagation of surf beat maintained surf beat energy in the surf zone net surf beat dissipation in the surf zone scaled as predicted by a simple bottom stress parameterization the inferred dissipation factor for surf beat was 0 08 within the range of wave dissipation factors usually observed in the field and 27 80 times larger than drag coefficients appropriate for the mean longshore current the observed rapid forcing rapid dissipation and shoreward propagation of surf beat are not simulated by existing models of surf beat dynamics

beach steepness effects on nonlinear infragravity wave interactions a numerical study the numerical model swash is used to investigate nonlinear energy transfers between waves for a diverse set of beach profiles and wave conditions with a specific focus on infragravity waves we use bispectral analysis to study the nonlinear triad interactions and estimate energy transfers to determine energy flows within the spectra the energy transfers are divided into four types of triad interactions with triads including either one two or three infragravity frequency components and triad interactions solely between sea swell wave frequencies the swash model is validated with a high resolution laboratory data set on a gently sloping beach which shows that swash is capable of modeling the detailed nonlinear interactions from the simulations we observe that especially the beach slope affects nonlinear infragravity wave interactions on a low sloping beach infragravity wave energy dominates the water motion close to shore here infragravity infragravity interactions dominate and generate higher harmonics that lead to the steepening of the infragravity wave and eventually breaking causing large infragravity energy dissipation on the contrary on a steep sloping beach sea swell wave energy dominates the water motion everywhere here infragravity frequencies interact with the spectral peak and spread energy to a wide range of higher frequencies with relatively less infragravity energy dissipation although both beach types have different nonlinear interaction patterns during infragravity wave dissipation the amount of infragravity wave reflection can be estimated by a single parameter the normalized bed slope

numerical modeling of wave runup on steep and mildly sloping natural beaches abstract runup on ocean beaches includes steady wave setup and oscillating swash often decomposed into wind generated sea swell ss and lower frequency infragravity ig waves we show that the numerically fast open source numerical model 1d swash predicts accurately the bulk properties of runup observed on two natural beaches one steep and one shallow sloped for a range of incident wave conditions the runup tongue shape was measured with a scanning lidar and the waterline location was defined in both the observations and model with a 10 cm depth threshold runup is reasonably accurately predicted with energetic e g 5 m significant height incident waves even though the assumption of 1d bound waves significantly overpredicts infragravity energy at the offshore boundary in 10 m depth the model data comparisons are limited by statistical chatter often larger in runup than offshore because runup energy is concentrated in the relatively narrow infragravity ig band with low effective degrees of freedom

earth based observations of radar dark crater haloes on the moon implications for regolith properties 1 earth based radar can be used in conjunction with other data sets collected remotely or in situ to characterize the physical and chemical properties of the lunar regolith we use previously existing and newly acquired earth based radar measurements at 70 cm wavelength to investigate the properties of distinctive low return haloes surrounding 39 nearside impact craters these haloes are distinct from the well known optically dark haloes associated with volcanic craters or with impacts into cryptomare deposits we examine two possible mechanisms for formation of radar dark haloes 1 excavation of high tio2 high loss tangent basalt and 2 deposition of a mantling layer produced in the impact process that is depleted in meter sized blocks comparison of the radar data with apollo and lunar orbiter images indicates a general spatial correspondence between radar dark crater haloes and radial ridged ejecta facies distal to the radar bright crater rims comparison with clementine uv vis multispectral data indicates no apparent spatial correlation between regions of enhanced tio2 content and radar dark haloes though variations in tio2 content may play a role for some mare craters they are insufficient to account for the observed offsets in radar echo power we conclude that the radar dark haloes result from a block poor ejecta deposit that disappears over time with meteoroid bombardment a more detailed and comprehensive analysis of ejecta degradation processes and rates following acquisition of additional high resolution radar data could lead to a refinement of the lunar geologic timescale

cross shore decay of cliff top ground motions driven by local ocean swell and infragravity waves 1 ground motions at the frequencies between 0 01 and 0 1 hz of ocean infragravity and swell waves were observed on a cross shore transect extending landward from the edge of a southern california coastal cliff cliff top ground motions are coherent and in phase with water level fluctuations at the cliff base vertical ground motions at infragravity and single frequencies decay rapidly with inland distance from the cliff edge e folding scale is about 12 m and at the edge decrease by several orders of magnitude between high tide when waves reach the cliff base and low tide when the waterline is about 50 m from the cliff base the observed cross shore decay scales are qualitatively consistent with gravitational loading and attraction of water waves at tidally modulated distances from the cliff base at approximately constant distance from the waterline ground motions vary roughly linearly with nearshore swell wave energy in contrast to these locally forced ground motions double frequency band 0 1 0 2 hz cliff top vertical ground motions are remotely generated with spatially uniform magnitudes approximately equal to those observed 14 km inland near the cliff edge ground tilt dominates the observed large relative to vertical cross shore acceleration at infragravity frequencies contributes significantly to cross shore acceleration at swell frequencies and is a small fraction of cross shore acceleration at higher frequencies

ejecta megaregolith accumulation on planetesimals and large asteroids megaregolith accumulation can have important thermal consequences for bodies that lose heat by conduction as vacuous porosity of the kind observed in the lunar megaregolith lowers thermal conductivity by a factor of 10 i have modeled global average ejecta accumulation as a function of the largest impact size with no explicit modeling of time in conjunction with an assumed cratering size distribution exponent b the largest crater constrains the sizes of all other craters that significantly contribute to a megaregolith the largest impactor mass ratio is a major fraction of the catastrophic disruption mass ratio and in general the largest crater s diameter is close to the target s diameter total accumulation is roughly 1 5 of and proportional to the target s radius global accumulations estimated by this approach are higher than in the classic housen et al 1979 study by a factor of roughly 10 this revision is caused mainly by higher typical largest crater size for b 2 the single largest crater typically contributes close to 50 of the total of new nonrecycled ejecta megaregolith can be destroyed by sintering a process whose pressure sensitivity makes it effective at lower temperature on larger bodies planetesimals 100 km in diameter may be surprisingly well suited about as well suited as bodies two to three times larger in diameter for attaining temperatures conducive to widespread melting a water rich composition may be a significant disadvantage in terms of planetesimal heating as the shallow interior may be densified by aqueous metamorphism and will have a low sintering temperature

response of wave dominated and mixed energy barriers to storms wave dominated and mixed energy barriers are extremely dynamic landforms responding to processes operating over a spectrum of time scales ranging from daily to monthly fluctuations related to storm and post storm conditions to century to millennium scale evolution driven by relative sea level change two types of storms are of particular relevance warm core tropical and cold core extratropical cyclones both are responsible for generating very large waves highly energetic surf zone dynamics and sediment transport elevated inshore water levels and extensive morphological responses all cyclones are affected by climate change which governs their frequency intensity and tracks barrier storm response is primarily governed by maximum storm runup and barrier morphology as conceptualised in abby sallenger s storm impact scale model sallenger 2000 this model defines four storm impact regimes and includes erosive as well as accretionary responses on the erosion side the swash regime drives bar and berm flattening the collision regime is marked by dune scarping and beach lowe the overwash regime leads to dune scouring and channel incision and the inundation regime may result in barrier destruction on the deposition side storm berms and beach ridges may form and accrete in the swash and collision regimes localised vertical beach and barrier accretion are associated with the collision and overwash regimes and washover deposition takes place in the overwash and inundation regimes site specific factors play a key role in moderating the morphological response and include storm characteristics type duration and track longshore sediment supply upwelling downwelling currents coastal setting and inner shelf topography the response of a barrier to a tropical or extratropical cyclone can however not be considered in isolation and has to be appreciated in a longer temporal context involving morphological preconditioning due to antecedent wave and water level conditions additionally a simple process response approach of the cause and effect type is inappropriate and a more complex conceptual framework involving thresholds feedbacks resilience and vulnerability will need to be adopted a useful way to visualise and conceptualise more complex storm behaviours and the longer term vulnerability of barriers is the resilience trajectory which maps out the changes in barrier geometry elevation and width over various time scales from weeks to years or even longer and under varying forcing conditions including changes in storminess and sea level rise an increased understanding of barrier response to storms and sequences of storms is required to better quantify long term barrier response to climate change high resolution and comprehensive decadal records of barrier response to storms are a prerequisite to achieve this ambition linking site specific coastal settings hydrodynamic drivers and morphological responses and allowing the recognition of recovery and impact dominated phases the enhanced insights in barrier response to extreme events must then be incorporated into improved coastal response models to help predict the impacts of future climate change on wave dominated and mixed energy barriers around the world 2013 elsevier b v

spectral signatures for swash on reflective intermediate and dissipative beaches in this paper we synthesise a large data set gathered from a wide variety of field deployments and integrate it with previously published results to identify the spectral signatures of swash from contrasting beach types the field data set includes the full range of micro tidal beach types reflective intermediate and dissipative with beach gradients ranging from approximately 1 6 to 1 60 exposed to offshore significant wave heights of 0 5 3 0 m the ratio of swash energy in the short wave f 0 05 hz to long wave f 0 05 hz frequency bands is found to be significantly different between the three beach types swash energy at short wave frequencies is dominant on reflective and intermediate beaches and swash at long wave frequencies is dominant on dissipative beaches consistent with previously reported spectral signatures for the surf zone on these beach types the available swash spectra were classified using an automated algorithm clara into five different classes the ordered classes represent an evolution in the spectrum shape described by a frequency downshifting of the energy peak from the short wave into the long wave frequency band and an increase in the long wave swash energy level compared to a relatively minor variation in the short wave swash energy level a universally common feature of spectra from all beach states was an f 4energy roll off in the short wave frequency band in contrast to the broadly uniform appearance of the short wave frequency band the appearance of the long wave frequency band was highly variable across the beach states we incorporate the results presented here and previously published observations into the morphodynamic beach state model and propose an ordered sequence of swash spectra under increasing and decreasing incident wave energy level this extension of the beach state model to include the swash zone leads to the following propositions for morphodynamic controls on the nature of the swash spectrum 1 the short wave part of the swash spectrum is relatively constant in form across all beach states f 4 energy roll off and the energy density per unit frequency is controlled by the beach face gradient alone 2 the spectral bandwidth of the energy roll off varies directly with offshore wave energy level and inversely with beach face gradient or beach state in a manner consistent with the non linear wave breaking criterion 3 the infragravity part of the swash spectrum is highly variable in form across all beach states and the energy level is related to the offshore wave energy level and surf zone morphology

radar mapping of lunar cryptomaria east of orientale basin 1 lunar cryptomare deposits represent early basaltic volcanic material that has been mantled by or incorporated into highland rich ejecta from basin or crater forming impacts mapping these buried basalts is important for understanding regional stratigraphy and the history and extent of lunar volcanism we use new 70 cm wavelength radar images collected using arecibo observatory and the green bank telescope and clementine data to study cryptomaria east of orientale basin earlier multispectral analyses showed that mare material is mixed with the highland terrain along the western margin of oceanus procellarum leading to a detectable increase in the feo and tio2 abundance of the regolith surface the highland margin of western procellarum is also characterized by low 70 cm radar returns consistent with an increased regolith loss tangent due to ilmenite in the mare derived material the low 70 cm radar echo however persists well to the west of the mixed zone evident in multispectral data and includes the region surrounding cruger crater it is likely that mare basalt or a mixed zone of mare and highland material exists at depth across the region and only reaches the visible surface near the western procellarum margin the plausible depth to this mixed zone is dependent upon the loss tangent of the overlying pure highland ejecta if orientale ejecta is primarily low loss anorthosite then the mixed zone could lie at depths of up to several tens of meters we propose that pre orientale mare deposits flooded the region between cruger grimaldi and oceanus procellarum and also patches west and northwest of humorum basin the total area of these deposits represents 178 103 km2 or an additional 0 5 of the lunar surface covered by mare basalts

how well can wave runup be predicted comment on laudier et al 2011 and stockdon et al 2006 abstract laudier et al 2011 suggested that there may be a systematic bias error in runup predictions using a model developed by stockdon et al 2006 laudier et al tested cases that sampled beach and wave conditions that differed from those used to develop the stockdon et al model based on our re analysis we found that in two of the three laudier et al cases observed overtopping was actually consistent with the stockdon et al predictions in these cases the revised predictions indicated substantial overtopping with in one case a freeboard deficit of 1 m in the third case the revised prediction had a low likelihood of overtopping which reflected a large uncertainty due to wave conditions that included a broad and bi modal frequency distribution the discrepancy between laudier et al results and our re analysis appear to be due in part to simplifications made by laudier et al when they implemented a reduced version of the stockdon et al model

transport in an idealized three gyre system with application to the adriatic sea abstract motivated by observations of surface drifters in the adriatic sea transport in a three gyre system is studied with the aid of dynamical systems techniques particular attention is paid to the issue of intergyre transport the velocity field is assumed to be two dimensional and incompressible and composed of a steady three gyre background flow on which a time dependent perturbation is superimposed two systems of this type are considered 1 an observationally motivated analytically prescribed model consisting of a steady background on which a multiperiodic time dependent perturbation is superimposed and 2 an observationally based model of the adriatic sea consisting of the mean surface circulation derived from surface drifter trajectories on which a time dependent altimetry based perturbation velocity field is superimposed it is shown that for a small perturbation to the steady three gyre background two of the gyres exchange no fluid with the third gyre when the perturbation strength excee

why does the deep western boundary current leak around flemish cap abstractthe southward flowing deep limb of the atlantic meridional overturning circulation is comprised of both the deep western boundary current dwbc and interior pathways the latter are fed by

wave runup video motion detection using the radon transform abstract a new method of runup detection from video imagery is introduced and validated at an energetic dissipative beach the instantaneous waterline is detected from uprush and backwash by using the radon transform rt the method is compared to conventional color contrast method from rgb images and lidar measurements in our observations the rt shows better detection skill even for adverse conditions such as those present on flat dissipative swash zones where contrast is reduced because the rt is a proxy of deeper waterline 0 1 m it is less sensitive to lack of contrast due to sand saturation moreover since it is based on motion detection it is less sensitive to changes in lighting conditions overall the rt offers an attractive alternative for long term automated detection of the runup

intertidal beach profile estimation from reflected wave measurements abstract the intertidal beach profile provides coastal engineers and managers with a good indication of the current state of a sandy coastline however regular beach profile measurements are time consuming and expensive to obtain using conventional surveying methods the potential to reconstruct the intertidal beach profile from measurements of reflected waves is tested here using three field datasets covering a different range of hydro morphological conditions from dissipative to reflective the swash is found to behave as a low pass filter on reflected waves with a cut off frequency that primarily depends on the swash slope an agreement is found between video derived swash spectrum saturation tail and the shortest reflected waves computed from deep water directional wave measurements by integrating this swash slope over a tidal cycle the shape of the intertidal beach profile can be reconstructed our results clearly show the potential of such method to estimate complex intertidal beach profile such as double slope beaches

swash zone sediment suspension and transport and the importance of bore generated turbulence a study of swash zone sediment transport was conducted at gleneden beach oregon during february 25 28 1994 the data collected included suspended sediment concentration ssc sea surface elevation and velocity initially 4 and 8 cm above the bed at three cross shore locations within the swash zone spanning high tides ensemble averages of 6 9 and 12 s duration swash events showed that the uprush suspension was high concentrated in the leading edge and nearly vertically uniform above the lower 1 2 cm of the water column shortly after the sensors were inundated by run up the sediment rapidly settled out of the water during flow reversal the ssc was small but increased again in the backwash backwash vertical profiles were markedly different from uprush profiles with much of the suspension being confined to very near the bed where strong vertical gradients in ssc existed these marked differences show that the backwash is not simply the reverse of the uprush implying significant differences in the underlying fluid dynamics and sediment transport mechanisms backwash sediment suspension increased with flow duration however ensemble averaged ssc profiles of varying duration showed that the backwash concentrations were not consistent at the same temporal phases which suggests that water depth in addition to flow duration may be a controlling factor strong cross shore gradients in ssc suggest that bore derived turbulence may affect local sediment transport specifically our data show this bore generated turbulence turbulent kinetic energy directly influences local sediment suspension hence standard bed shear bagnold type sediment transport models may no longer be valid in the vicinity of the bore in the vicinity of the bore a higher correlation between bore generated turbulence and suspended sediment transport was found than between a bagnold type formulation and suspended sediment transport

observations of nonlinear internal wave run up to the surfzone abstractthe cross shore evolution of nonlinear internal waves nliws from 8 m depth to shore was observed by a dense thermistor array and adcp isotherm oscillations spanned much of the water column at a variety of periods at times nliws propagated into the surfzone decreasing temperature by 1 c in 5 min when stratification was strong temperature variability was strong and coherent from 18 to 6 m depth at semidiurnal and harmonic periods when stratification weakened temperature variability decreased and was incoherent between 18 and 6 m depth at all frequencies at 8 m depth onshore coherently propagating nliw events had associated rapid temperature drops t up to 1 7 c front velocity between 1 4 and 7 4 cm s 1 and incidence angles between 5 and 23 front position t and two layer equivalent height ziw of four events were tracked upslope until propagation terminated front position was quadratic in time and normalized t and ziw both decreased collapsing as a linearly decaying funct

cross shore sand transport by infragravity waves as a function of beach steepness two field data sets of near bed velocity pressure and sediment concentration are analyzed to study the influence of infragravity waves on sand suspension and cross shore transport on the moderately sloping sand motor beach 1 35 the local ratio of infragravity wave height to sea swell wave height is relatively small hig hsw 0 4 most sand is suspended during negative infragravity velocities and qig is offshore directed the infragravity contribution to the total sand flux is considerably larger and reaches up to 60 during energetic conditions on the whole hig hsw is a good indicator for the infragravity related sand suspension mechanism and the resulting infragravity sand transport direction and relative importance

wave run up on a high energy dissipative beach 1 because of highly dissipative conditions and strong alongshore gradients in foreshore beach morphology wave run up data collected along the central oregon coast during february 1996 stand in contrast to run up data currently available in the literature during a single data run lasting approximately 90 min the significant vertical run up elevation varied by a factor of 2 along the 1 6 km study site ranging from 26 to 61 of the offshore significant wave height and was found to be linearly dependent on the local foreshore beach slope that varied by a factor of 5 run up motions on this high energy dissipative beach were dominated by infragravity low frequency energy with peak periods of approximately 230 s incident band energy levels were 2 5 to 3 orders of magnitude lower than the low frequency spectral peaks and typically 96 of the run up variance was in the infragravity band a broad region of the run up spectra exhibited an f 4 roll off typical of saturation extending to frequencies lower than observed in previous studies the run up spectra were dependent on beach slope with spectra for steeper foreshore slopes shifted toward higher frequencies than spectra for shallower foreshore slopes at infragravity frequencies run up motions were coherent over alongshore length scales in excess of 1 km significantly greater than decorrelation length scales on moderate to reflective beaches

observations of runup and energy flux on a low slope beach with high energy long period ocean swell the transformation of surface gravity waves from 11 m depth to runup was observed on the low sloped 1 80 agate beach oregon with a cross shore transect of current meters pressure sensors and a scanning lidar offshore wave heights h0 ranged from calm 0 5 m to energetic 7 m runup measured with pressure sensors and a scanning lidar increases linearly with h0l0 1 2 with l0 the deep water wavelength of the spectral peak runup saturation in which runup oscillations plateau despite further increases in h0l0 1 2 is not observed infragravity wave shoaling and nonlinear energy exchanges with short waves are included in an infragravity wave energy balance this balance closes for high infragravity frequencies 0 025 0 04 hz but not lower frequencies 0 003 0 025 hz possibly owing to unmodeled infragravity energy losses of wave breaking and or bottom friction dissipative processes limit but do not entirely damp increases in runup excursions in response to increased incident wave forcing

setup and swash on a natural beach wave setup and swash statistics were calculated from 154 runup time series measured on a moderately steep beach under incident waves varying from 0 4 to 4 0 m significant wave height when scaled by the incident wave height setup swash height and total runup the sum of setup and half the swash height were found to vary linearly with the surf zone similarity parameter 0 h0 l0 1 2 the foreshore slope appeared the appropriate value for the calculation of 0 although the setup data showed some influence of an offshore bar at low tide for low irribaren numbers the swash height in the incident frequency band becomes saturated while for high irribaren numbers no such signs of saturations were seen thus the infragravity band appears to become dominant in the swash below some value of 0 for these data that value is approximately 1 75 although there is considerable scatter associated with that estimate

wave runup during extreme storm conditions 1 video measurements of wave runup were collected during extreme storm conditions characterized by energetic long swells peak period of 16 4 s and offshore height up to 6 4 m impinging on steep foreshore beach slopes 0 05 0 08 these conditions induced highly dissipative and saturated conditions over the low sloping surf zone while the swash zone was associated with moderately reflective conditions iribarren parameters up to 0 87 our data support previous observations on highly dissipative beaches showing that runup elevation estimated from the variance of the energy spectrum can be scaled using offshore wave height alone the data is consistent with the hypothesis of runup saturation at low frequencies down to 0 035 hz and a hyperbolic tangent fit provides the best statistical predictor of runup elevations

surviving the heavy bombardment ancient material at the surface of south pole aitken basin 1 the oldest deepest and largest basin recognized on the lunar surface is the south pole aitken spa basin in the time since its formation several processes have modified the original interior of the basin including the introduction of foreign material by impact basins during the period of heavy bombardment these later basins redistributed material ballistically across the lunar surface forming a mixed and crushed zone on the scale of about one kilometer deep models of crater excavation ejected material transport and mixing during emplacement are used to estimate the amount of foreign material from each basin event introduced into spa and the degree to which that material mixes with the surface of the interior of spa we varied the size of the transient craters for all basins the degree of mixing between foreign and local material and the number of basins considered in our evaluation our modeling results indicate that materials derived from the original spa melt breccia comprise at least 15 of the present regolith the most realistic combinations of model parameters predict a spa melt breccia component that ranges from 50 80 of the current surface regolith the compositional character of the spa interior has apparently not been obliterated by aeons of subsequent basin forming events

evidence for impact melt sheets in lunar highland smooth plains and implications for polar landing sites abstract smooth plains units attributed to fluidized basin ejecta occur over much of the lunar highlands we examined 4 20 km diameter imbrian and eratosthenian period craters in the southern highlands that have high 12 6 cm wavelength radar backscatter and circular polarization ratios associated with their interior walls but not with their proximal ejecta of these craters about 70 occur on or very near deposits of imbrian highland plains we propose that melt rich ejecta from basin forming impact events near the top of the stratigraphic section supplies fragmental material that is exposed in the interior wall regolith of these small craters these results support previous interpretations of 70 cm radar data which provide insight on the near surface morphology and rock provenance in proposed smooth plains landing sites such as that of chandrayaan 2

swash on a gently sloping beach waves observed in the inner surf and swash zones of a fine grained gently sloping beach are modeled accurately with the nonlinear shallow water equations the model is initialized with observations from pressure and current sensors collocated about 50 m from the mean shoreline in about i m depth and model predictions are compared to pressure fluctuations measured at five shoreward locations and to run up run up was measured with a vertical stack of five wires supported parallel to and above the beach face at elevations of 5 10 15 20 and 25 cm each 60 m long run up wire yields time series of the most shoreward location where the water depth exceeds the wire elevation as noted previously run up measurements are sensitive to the wire elevation owing to thin run up tongues not measured by the more elevated wires as the wire elevation increases the measured mean run up location moves seaward low frequency infragravity energy decreases and higher frequency sea swell energy increases these trends as well as the variation of wave spectra and shapes e g wave skewhess across the inner surf zone are well predicted by the numerical model

the production and dissipation of compensated thermohaline variance by mesoscale stirring abstract temperature salinity profiles from the region studied in the north atlantic tracer release experiment natre show large isopycnal excursions at depths just below the thermocline it is proposed here that these thermohaline filaments result from the mesoscale stirring of large scale temperature and salinity gradients by geostrophic turbulence resulting in a direct cascade of thermohaline variance to small scales this hypothesis is investigated as follows measurements from natre are used to generate mean temperature salinity and shear profiles the mean stratification and shear are used as the background state in a high resolution horizontally homogeneous quasigeostrophic model the mean state is baroclinically unstable and the model produces a vigorous eddy field temperature and salinity are stirred laterally in each density layer by the geostrophic velocity and vertical advection is by the ageostrophic velocity the simulated temperature salinity diagram exhibits fluctuations at depths ju

investigation of scattering in lunar seismic coda 1 we investigate the intrinsic attenuation and scattering properties of the moon by parameterizing the coda decay of 369 higher quality lunar seismograms from 72 events via their characteristic rise and decay times we investigate any dependence of the decay times on source type frequency and epicentral distance intrinsic attenuation scattering and possible focusing of energy in a near surface low velocity layer all contribute to the coda decay although it is not possible to quantify the exact contribution of each of these effects in the seismograms results suggest that scattering in a near surface global layer dominates the records of shallow events 0 200 km depth particularly at frequencies above 2 hz and for increasing epicentral distance we propose that the scattering layer is the megaregolith and that energy from shallow sources encounters more scatterers as it travels longer distances in the layer increasing the coda decay times a size distribution of ejecta blocks that has more small scale than large scale scatterers intensifies this effect for increasing frequencies deep moonquakes 700 1100 km depth exhibit no dependence of the decay time on epicentral distance we suggest that because of their large depths and small amplitudes deep moonquakes from any distance sample a similar region near a given receiver near station structure and geology may also control the decay times of local events as evidenced by two natural impact records this study provides constraints and testable hypotheses for waveform modeling of the lunar interior that includes the effects of intense scattering and shallow low velocity layers

morphodynamic response of a meso to macro tidal intermediate beach based on a long term data set article four years of bi monthly topographic surveys have been conducted on a 350 m stretch of the meso to macro tidal truc vert beach france herewe study the dynamics of boththe inner bar and the upper partof the beach where a berm can develop in the presence of fair weather conditions for the inner bar the occurrences of the different states within the intermediate classification following thatof wright and short wright l d short a d 1984 morphodynamic variability of surf zones and beaches a synthesis marine geology 56 93 118 arepresentedandcomparedtoothersitesinbothmicro andmeso tidalenvironments theresultsshowasimilar frequencyofoccurrenceofthetransversebarandrip tbr state whilethemoredissipativestates rhythmicbar and beach rbb and longshore bar and trough lbt are less regularly observed despite the high wave energy levels the lbt and rbb states are also observed in the presence of fair weather conditions and the tbr state can persist during very energetic events similar results are also observed with the upper beach dynamics veryenergeticeventsarenotnecessarilyassociatedwitherosionwhileandlow energyeventsarenotnecessarily

lagrangian motion and fluid exchange in a barotropic meandering jet kinematic models predict that a coherent structure such as a jet or an eddy in an unsteady flow can exchange fluid with its surroundings the authors consider the significance of this effect for a fully nonlinear dynamically consistent barotropic model of a meandering jet the calculated volume transport associated with this fluid exchange is comparable to that of fluid crossing the gulf stream through the detachment of rings although the model is barotropic and idealized in other ways the transport calculations suggest that this exchange mechanism may be important in lateral transport or potential vorticity budget analyses for the gulf stream and other oceanic jets the numerically simulated meandering jet is obtained by allowing a small amplitude unstable meander to grow until a saturated state occurs the resulting flow is characterized by finite amplitude meanders propagating with nearly constant speed and the results clearly illustrate the stretching and stirring of fluid particles along the edges of the recirculation regions south of the meander crests and north of the troughs the fluid exchange and resulting transport across boundaries separating regions of predominantly prograde retrograde and recirculating motion is quantified using a dynamical systems analysis the geometrical structures that result from the analysis are shown to be closely correlated with regions of the flow that are susceptible to high potential vorticity dissipation moreover in a related study this analysis has been used to effectively predict the entrainment and detrainment of particles to and from the jet