a subtropical oceanic ring of magnitude storm in the eastern north atlantic physical chemical and biological properties a subtropical oceanic ring of magnitude storm that budded from the azores current was studied in the eastern north atlantic ocean in april 1999 the cyclonic eddy called leticia was centred at 32 4 n 28 7 w and extended across more than 200 km in an east west direction leticia had been previously detected by means of topex poseidon altimetry data and further intensively investigated using expendable bathythermograph and conductivity temperature depth stations the altimeter surface signature of the eddy revealed a 20 cm sea level depression an upward displacement of the 16 c isotherm of 125 m was linked to the eddy centre and geostrophic transport of the amount of water swirling cyclonically was 7 sv the temperature nitrate and oxygen anomalies on the 0 26 5 isopycnal surface inside leticia were 0 4 c 1 mol l 1 and 0 3 ml l 1 respectively with respect to surrounding waters shallowing 50 m of the deep chlorophyll maximum 0 3 mg m 3 was observed at the eddy centre associated with vertical displacements of the isotherms 100 m within the photic layer vertical excursions of the isopycnals and the deep chlorophyll maximum of more than 30 m were observed over temporal scales of a few 3 6 h integrated nitrate concentration over the photic layer was 4 fold higher inside leticia than outside however primary production rates were only slightly higher eddy diffusive fluxes across the nitracline located 30 m below the deep chlorophyll maximum ranged from 0 02 to 0 10 mmol no3 m 2 d 1 and explained 25 of the nitrate required to sustain the estimated new production 0 24 0 48 mmol no3 m 2 d 1

static bay beach concept for scientists and engineers a review abstract headland bay beach hbb is one of the most prominent physiographic features on the oceanic margin of many countries in the world under the influence of a predominant swell its curved periphery in natural environment may reach static equilibrium and remains stable without sediment supply from updrift and or a riverain source within its own embayment coastal scientists and engineers have attempted to develop mathematical expressions to quantify this ideal bay shape since the 1940s as the scenario with depleting sediment supply has become a common reality on many parts of the world coastline in more recent time some coastal engineers have advocated a rational approach to mimicking the static bay shape found in nature in order to mitigate beach erosion as well as for coastal management nowadays many useful applications have emerged since the publication of the parabolic bay shape equation pbse developed for static equilibrium planform sep in late 1980s the advance in modern computer technologies and international collaboration has further facilitated the exchange of knowledge and applications of this static bay beach concept sbbc this paper reviews the progress on the research in hbb made by geographers and geologists since the 1940s together with the involvement of coastal engineers working on shore protection and management from the 1960s aided by software mepbay developed in 2003 for the pbse several practical examples are demonstrated in this paper for the stability verification of natural and man made bay beaches shore protection mitigating downdrift erosion of a harbour design of recreational bay beach as well as for environmental impact assessment limitations on and clarifications for engineering applications based on the sbbc are also discussed in this paper

role of geological inheritance in australian beach morphodynamics the australian coast contains 10 685 beaches which occupy 49 of the 30 000 km coast and average 1 37 km in length their relatively short length is largely due to the presence of bedrock calcarenite and laterite which form boundaries to many of the beaches as well as occurring as rocks reefs and islands along and off the beaches this geological inheritance plays a major role in australian beach systems determining their length and through wave refraction and attenuation influencing beach location shape type morphodynamics and circulation which in turn influence sediment transport and the backing dune and barrier systems this paper uses a database covering every australian beach to review the role of headlands rocks and reefs on australian beaches major effects are the short average beach length reduction in breaker height resulting in lower energy beach types wave refraction resulting in increased beach curvature the presence of topographic rips on moderate and higher energy beaches and megarips during high wave conditions and the interruption of and or trapping of longshore sand transport leading to beach rotation

wave energy distribution and morphological development in and around the shadow zone of an embayed beach abstract background the curved shoreline shape of embayed beaches is one of its most notable characteristics and can be described using the parabolic bay shape equation pbse wave diffraction in and around the shadow zone is often regarded as the primary forcing mechanism leading to the prominent curvature of the shoreline however wave climate variables wave direction directional spreading and wave height are shown to be influential in redistributing wave energy throughout the bay and in the shadow zone methods in this study a process based morphological model delft3d is used for hydrodynamic and morphodynamic simulations of a schematic embayed beach wave forcing conditions are systematically varied between a mixture of time invariant and time varying cases results the role of diffraction is shown to be dominant only when the wave conditions are both narrow banded 30 otherwise as little as 6 variation in wave direction within a 90 range can account for the shoreline curvature in and around the shadow zone conclusion the degree to which wave direction and directional spreading vary through time therefore has a large effect on the equilibrium orientation and shoreline planform of the bay

surface circulation in the gulf of cadiz 2 inflow outflow coupling and the gulf of cadiz slope current 1 a study of the upper slope circulation in the gulf of cadiz is presented observations both original and revisited and realistic numerical modeling are used together to describe the structure and variability of the slope current system above the mediterranean outflow it is shown that the mediterranean inflow outflow coupling plays a stronger role than that of the atmospheric forcing in driving the upper slope currents the mediteranean outflow forces a surface open ocean current toward the strait of gibraltar part of it is entrained into the outflow and the remaining flows into the mediterranean this latter component does not suffice for the observed transport of the atlantic inflow into the mediterranean a secondary contribution to the inflow is therefore needed to complement the transport this contribution comes from a persistent equatorward current along the upper slope between cape st vincent and the strait of gibraltar the jet is 20 30 km wide and significant in the upper 200 m attaining subinertial maxima as much as 0 3 0 4 m s and monthly means in the order of 0 1 0 15 m s this current shows a strong variability at time scales in the order of 2 8 days and displays a significant vertical shear the response of the upper slope current to synoptic and seasonal atmospheric variability is analyzed very low correlation was detected at synoptic scales and the response of the system to seasonal forcing is unclear a cycle of intensification in june july and a decrease in winter is apparent in the measurements but is weak in the model results it is speculated that the cycle in the observed currents is associated with variability in the inflow outflow coupling system rather than driven by seasonally changing wind forcing

a spatial temporal analysis of the development of a log spiral shaped embayment with the use of semi annual data collected from may 1985 to may 1995 this study assesses the evolution of a log spiral shaped embayment at the northeast beach located at canada s southernmost promontory the emplacement of stone breakwaters initiated scour of the shoreline and the embayment which developed thereafter adjusted to reflect changes in lake levels and naturally occurring variance in wave and sediment dynamics each of the 21 recorded measurements of the embayment configuration is assessed for characteristics of log spiral morphology the results demonstrate that logarithmic spiral curves fit the 21 recorded embayment configurations very closely the significant parameters and statistics associated with each log spiral curve show that no heteroschedacity of variance is present among the residuals and only one significant autocorrelation is observed the appropriateness of the log spiral fits is verified by the coefficients of determination which with the exception of the november 1988 dataset are all over the required value of 0 98 both the spiral angle and the radius show decreasing trends through time and the graphical plots illustrate only minor fluctuations after may 1991 these results suggest that the embayment may have shifted from some form of quasi equilibrium condition to approach a state of dynamic equilibrium the persistence of the logarithmic spiral configuration through time supports the findings of other investigators who claim that the log spiral planform represents the equilibrium embayment shape that might be expected on the flank of a breakwater system 1997 john wiley sons ltd

exploring the sensitivities of crenulate bay shorelines to wave climates using a new vector based one line model we use a new exploratory model that simulates the evolution of sandy coastlines over decadal to centennial timescales to examine the behavior of crenulate shaped bays forced by differing directional wave climates the model represents the coastline as a vector in a cartesian reference frame and the shoreface evolves relative to its local orientation allowing simulation of coasts with high planform curvature shoreline change is driven by gradients in alongshore transport following newly developed algorithms that facilitate dealing with high planform curvature coastlines we simulated the evolution of bays from a straight coast between two fixed headlands with no external sediment inputs to an equilibrium condition zero net alongshore sediment flux under an ensemble of directional wave climate conditions we find that planform bay relief increases with obliquity of the mean wave direction and decreases with the spread of wave directions varying bay size over 2 orders of magnitude 0 1 16 km the model predicts bay shape to be independent of bay size the time taken for modeled bays to attain equilibrium was found to scale with the square of the distance between headlands so that all else being equal small bays are likely to respond to and recover from perturbations more rapidly over just a few years compared to large bays hundreds of years empirical expressions predicting bay shape may be misleading if used to predict their behavior over planning timescales

the southern oscillation index wave climate and beach rotation short embayed beaches bounded by headlands are a common feature along the southern and central coastline of new south wales australia many of these embayed beaches have experienced severe erosion at their southern end over the last decade previous studies have suggested that this erosion may be the result of an oscillatory medium term phenomenon known as beach rotation the present study was undertaken with the objectives of 1 establishing definitive links between the southern oscillation index soi wave climate and beach rotation and 2 determining the physical processes governing beach rotation data from two similar new south wales beaches were analysed using time series analysis techniques and image processing techniques using argus video images in this study the results indicate that the northern end of this type of beach accretes during el nino phases while the southern end erodes resulting in a net clockwise rotation of the beach the opposite occurs during la nina phases resulting in a net anti clockwise rotation of the beach the beach response at the northern and southern ends lags soi trend shifts by 3 and 17 months respectively waves are predominantly incident from the southeast during both el nino and la nina phases offshore wave height is positively correlated with the soi while offshore wave direction is negatively correlated with the soi on average the number of storms per year doubles from el nino to la nina based on these links between beach width fluctuations soi and incident wave conditions a conceptual model of beach rotation is presented the model describes the combinations of cross shore and longshore sediment transport and hydrodynamic processes that are expected to result in the observed clockwise and anti clockwise beach rotation during el nino and la nina phases respectively

extreme erosion on high energy embayed beaches influence of megarips and storm grouping abstract megarips have long been recognised as an important yet poorly documented mechanism of beach erosion on high energy embayed beaches the persistence and cumulative effect of megarips during storm groups are described from three embayed beaches arrifana mt clerigo and amoreira exposed to high energy wave conditions in the mesotidal bedrock dominated southwestern coast of portugal morphological changes determined by topographic monitoring and supplemented by interpretation of digital imagery over two years revealed the development of storm induced megarips which exerted a major influence on beach erosion differences in megarip influence within and between beaches are related to embayment geometry and orientation which significantly influence the nearshore wave field rip location is topographically controlled being determined by alongshore variations in breaking wave height and obliquity along with interaction of wave driven circulation patterns and embayment nearshore topography moderate beach sand loss during individual storms was linked to the development of megarips with associated rip neck and feeder channels extreme erosion however occurred when megarips and feeder channels persisted during successive storms promoting continued erosion and seaward sediment export observations show that once initiated megarip channels persist for several months and continue to act as conduits for offshore sediment transport under non storm conditions the maintenance of such rip circulation systems driven by morphodynamic feedback reduces beach recovery ability until the rip neck and feeder channels are infilled

circulation patterns and transport of the azores front current system in this paper different types of new data sets hydrography lagrangian and eulerian current measurements and quasi geostrophic model results obtained after altimetric data assimilation are used to study the structure and variability of the azores current and frontal system the azores current was observed to transport between 11 0 and 18 0 sv eastwards and the associated counter current some 2 0 10 0 sv to the west resulting in a net value of about 8 9 sv furthermore both data and model results revealed a meandering azores current where some freely rotating eddies were also identified these hydrographic and lagrangian results exhibit space and time scales that agree fairly well with the dynamics shaped by baroclinic instability current meters moored across the azores current system delineated a mean counter current flowing westwards with a maximum subsurface core of about 2 0 cm s at a mean depth of 800 dbar this is in excellent agreement with previous studies which explains this azores counter current as the rectification process of the geostrophic turbulence occurring north of the main azores current stream a new scheme is proposed for the formation mechanism of the freely rotating cyclonic eddies observed south of the azores it is shown that the north south contrast thickness of the 17 19 c water layer across the azores front decreases downstream this will create in turn a downstream increase of the most unstable wavelength in a non linear baroclinic instability context as a consequence both large cyclonic and anticyclonic features are able to form at the eastern side of the azores current around 19 w while at the western side around 35 w only large anticyclones will survive western generated cyclones will be small enough to be quickly dissipated this means that the eastern cyclones of the azores current may live longer than the shorter western ones however because longer lived cyclonic eddies propagate westwards with a mean speed of 2 5 km day they may be observed south of azores and of the main stream several months later although they were not formed there

shore and bar cross shore migration rotation and breathing processes at an embayed beach a principal component analysis pca is used to decompose data on the coupled morphodynamics of the shoreline and nearshore sandbar of a typical single barred embayed beach tairua beach new zealand dynamic patterns are classified into simultaneous modes where the bar and shoreline move at the same time and non simultaneous modes where the shore moves independently from the bar and vice versa two simultaneous modes accounting for 65 of the variance of the shoreline and barline dominate the system one mode describes inverse shoreline and sandbar cross shore migrations alongshore averaged occurring with simultaneous rotations in the same direction the other mode accounts for migration in the same direction accompanied by variations of the barline curvature similar to breathing modes previously described in embayed beach shoreline modelling studies two non simultaneous modes of lesser importance account separately for independent shoreline and barline rotations 10 to 15 of the variance explained a pca applied to the shore and sandbar behaviours modelled by four standard equilibrium models simulating shore and sandbar cross shore migrations and rotations show that these are interrelated because of a correlation between wave energy and direction shore and bar rotations are coupled partially because the shape of the bay induces a correlation of their respective drivers the wave angle of incidence and the alongshore gradient of wave energy however this correlation depends on the wave energy this in combination with different shore and sandbar response times quantified using the models also explains the independent rotations reflected by the non simultaneous modes

variability of shore and shoreline evolution shore and shoreline evolution both due to natural and human induced causes or factors can be variable over a wide range of different temporal and or spatial scales our capability to understand and especially predict this variability is still limited this can lead to misinterpretation of coastal change information which hampers informed decision making and the subsequent design and implementation of soft engineering interventions collecting and describing example observations of shore and shoreline variability is one way to support and improve such human intervention this paper describes causes and factors for the variability and the resulting possible evolutions of wave dominated shores and shorelines which are illustrated by a number of case studies the new element of this work is that the variability is described in terms of a range of different time and space scales which helps to structure such analysis however it is difficult to generalise the results for arbitrary situations especially on decadal time scales scientific and engineering improvements require more quantitative insight into the physical mechanisms behind the free and forced shore behaviour responsible for the variability

a probabilistic description of the mesoscale eddy field in the ocean global and regional probability density functions and higher statistical moments are analyzed for anomalies of the surface geostrophic velocity components inferred from the 3 year jason 1 topex poseidon tandem mission and for sea level anomalies sla observed through the topex poseidon jason 1 and jason 2 altimetric missions together covering a 19 year period results are compared with those obtained from the aviso 19 year 1 3 gridded sla space time objective analysis and associated geostrophic velocity anomalies the study reveals that eddy variability appears to be gaussian over most parts of the ocean outside the influence of energetic current systems and that specific flow regimes in the ocean can be identified through higher statistical moments of the flow field and sla observations however the moment ratio diagrams of skewness and kurtosis reveal that in energetic boundary currents the ocean does not follow gaussian statistics but rather behaves like an exponential distribution higher statistical moments of sla and velocity anomalies do vary seasonally and thereby provide valuable information about the seasonal changes of the oceans flow field

an equilibrium model to predict shoreline rotation of pocket beaches a novel and simple beach evolution model for estimating shoreline rotation at sandy pocket beaches is presented the model is based on the assumption that the instantaneous changes to the planview shape of the shoreline depend on the long term equilibrium planview shape two years of shoreline observations extracted from video images of three artificially embayed beaches of barcelona and hourly wave timeseries are used to validate the model numerical model results and field observations show an excellent agreement with an rmse less than 1 5 m the model successfully reproduced the shoreline response over a range of scales months and years because of its simplicity and its computational efficiency the model provides a powerful tool to understand the dynamics regulating the evolution of pocket beaches and predict temporal patterns in beach rotation

evidence of time mean cyclonic cell southwest of iberian peninsula the mediterranean outflow driven β plume 1 first observational evidence of time mean cyclonic recirculation southwest of iberia is presented data sets of hydrography satellite altimetry and surface drifters velocities are analyzed jointly in order to obtain an accurate time averaged circulation in the mid latitude northeast atlantic off the gulf of cadiz a cyclonic recirculation cell with characteristics similar to those predicted by theoretical and modeling studies is detected in all computed velocity fields the cell in the upper 1000 m layer exhibits transports of 3 to 4 sv that are only slightly smaller than the model transports the cell is centered at approximately 36 n 10 w is elongated zonally and extends to 15 w westwards wind driven sverdrup transport and plume dynamics are both suggested to play a role in the generation of the cyclonic cell but the relative contribution of these effects is yet to be clarified the core of the recirculation appears compact and the magnitude of the cell fades westwards much faster than predicted by the theoretical and modeling studies considered

hydrodynamics of a headland bay beach nearshore current circulation this paper is devoted to the analysis of the hydrodynamic equilibrium of a headland or semi elliptic shaped beach it is shown that the state of equilibrium depends not only on the in and outgoing sediment but also on the accommodation of the sediment within the embayment the shape and relative depth of shoals or settling zones also directly affect the wave and current patterns inside the bay within which the resultant breaker line almost stops wave induced currents at some locations whereas the magnitude of current increases at other locations several numerical tests are analytically conducted in a semi elliptic beach with two symmetrical shoals of varying relative depth where circulatory current systems are detected and analyzed numerical modelling for wave climate and wave induced current estimation is also presented in order to corroborate results and provide a tool for complicated and or physical domains the results lead to a redefinition of the concept of equilibrium for headland bay beaches taking into account not only the net sediment transport but also the role of the formation and disappearance of settling zones as well as sediment interchanges between the beach and shoals

large scale dune erosion tests to study the influence of wave periods article i nfo large scale physical model tests were performed to quantify the effects of the wave period on dune erosion attention was focussed on 2d cross shore effects in a situation with sandy dunes and extreme water levels and wave conditions besides profile measurements detailed measurements in time and space of water pressure flow velocities and sediment concentrations were performed in the near near shore area it was concluded that a longer wave period leads to a larger dune erosion volume and to a larger landward retreat of the dune face tests with double peaked wave spectra showed that the influence of the spectral shape on dune erosion was best represented by the tm 1 0 spectral mean wave period better than the peak wave period tp the effect of the wave period on dune erosion was implemented in a dune erosion prediction method that estimates erosion volumes during normative storm conditions for the dutch coast more details of the measurements and additional analyses of physical processes are described in an accompanying paper by van thiel de vries et al van thiel de vries j s m van gent m r a reniers a j h m and walstra d j r submitted for publication analysis of dune erosion processes in large scale flume experiments in this volume of coastal engineering

seasonal scale nearshore morphological evolution field observations and numerical modeling abstract a coupled waves currents bathymetric evolution model delft 3d is compared with field measurements to test hypotheses regarding the processes responsible for alongshore varying nearshore morphological changes at seasonal time scales a 2001 field experiment along the beaches adjacent to grays harbor washington usa captured the transition between the high energy erosive conditions of winter and the low energy beach building conditions typical of summer the experiment documented shoreline progradation on the order of 10 20 m and on average approximately 70 m of onshore sandbar migration during a four month period significant alongshore variability was observed in the morphological response of the sandbar over a 4 km reach of coast with sandbar movement ranging from 20 m of offshore migration to over 175 m of onshore bar migration the largest seasonal scale onshore migration event observed in a natural setting both observations and model results suggest that in the case investigated here alongshore variations in initial bathymetry are primarily responsible for the observed alongshore variable morphological changes alongshore varying incident hydrodynamic forcing occasionally significant in this region due to a tidal inlet and associated ebb tidal delta was relatively minor during the study period and appears to play an insignificant role in the observed alongshore variability in sandbar behavior at kilometer scale the role of fully three dimensional cell circulation patterns in explaining the observed morphological variability also appears to be minor at least in the case investigated here

numerical modeling of crenulate bay shapes a numerical model is developed to compute the shoreline planform in a crenulate bay beach the new model combines polar and cartesian coordinates and can be used effectively to compute a hooked zone shoreline in the lee of upcoast headland the model is calibrated using laboratory data with an incident wave angle ranging from 25 to 60 the results of calibration and verification suggest that the ratio of the sediment transport parameters by wave and longshore current in this model is close to unity and the computed shoreline planforms for the hooked and unhooked zones are in good agreement with the ones measured especially when a bay is close to static equilibrium in addition the bay shape calculated by the present model is similar to that given by the well known empirical parabolic equation for a bay in static equilibrium the process of bay shape development from a straight beach to a static equilibrium bay is studied using laboratory experiments and the present numerical model the temporal variations in the computed longshore sediment transport at different locations within a bay beach are analyzed from this the decrease in the sediment transport becomes apparent while a bay beach changes its shape from straight toward a state of equilibrium based on this experience it may be concluded that the present numerical model can produce a temporal change in the shoreline planform of a crenulate bay beach from a transition state to static equilibrium subject to seasonal wave action

controls of local geology and cross shore longshore processes on embayed beach shoreline variability 10 shoreline variability along the 3 6 km long narrabeen beach embayment in se australia is 11 investigated over a 5 year period we apply the one line shoreline change model lx shore 12 which couples longshore and cross shore processes and can handle complex shoreline 13 planforms non erodible emerged headlands and submerged rocky features the model 14 skilfully reproduces the three dominant modes of shoreline variability which are by 15 decreasing order of variance cross shore migration rotation and a third mode possibly 16 related to breathing model results confirm previous observations that longshore processes 17 primarily contribute to the rotation and third modes on the timescales of months to seasons 18 while cross shore processes control the shoreline migration on shorter timescales from hours 19 storms to months additional simulations simplifying progressively the bathymetry show 20 how the inherent geology strongly modulates the spatial modes of shoreline variability the 21 offshore central rocky outcrop is found to limit the rotation in contrast the submerged rocky 22 platforms that extend from the headlands enhance the shoreline rotation mode and increase 23 alongshore variability of the cross shore migration mode owing to increased alongshore 24 variability in wave exposure offshore wave transformation across large scale submerged 25 rocky features and headland shape are therefore critical to contemporary shoreline dynamics 26 2

u pb ages of apatite in the western tauern window eastern alps tracing the onset of collision related exhumation in the european plate we performed single spot u pb analyses of zircons and apatites from eighteen samples distributed along three sections crossing the western tauern window eastern alps zircon analyses yield concordant ages of similar to 295 ma dating the variscan emplacement of the zentralgneiss batholith common pb corrected apatite u pb ages show two age groups the first is characterized by apparent pb 206 u 238 ages scattering between similar to 300 and 40 ma and a second having a relatively uniform cluster of age values around 30 ma we applied an age extractor algorithm tuffzirc isoplot to all apatite analyses of each sample to calculate median ages from the younger age cluster and asymmetric 2 sigma errors as their uncertainties which are mostly in the range of similar to 10 these median ages are interpreted to date cooling below similar to 450 500 degrees c during alpine orogeny after the thermal climax of barrovian metamorphism in the western tauern window cooling ages give a consistent pattern over the study area of similar to 31 29 ma along each section younger cooling ages were obtained in the center compared to its margins the eastern section shows older cooling ages of similar to 36 34 ma whereas the western section younger cooling ages of similar to 26 25 ma the reliability of both age trends 1 younging towards the centers of the sections and 2 younging towards the west across all three sections were verified by six independent two sample student s t tests spatially the cooling age pattern resembles those observed from geochronometers having lower closure temperatures similar to 375 110 degrees c that are largely related to doming of the tauern window cooling rates of five samples where additional fission track ages are available yielded uniform results and were averaged to 15 3 1 9 k myr 2 sigma linear extrapolation using the specific cooling rates and the estimated maximum temperature t max indicates a time range of similar to 37 34 ma interpreted to date the thermal climax of barrovian metamorphism in the western tauern window

a reevaluation of coastal embayment rotation the dominance of cross shore versus alongshore sediment transport processes collaroy narrabeen beach southeast australia 1 over 30 years of wave and beach survey data at collaroy narrabeen beach in southeast australia are analyzed to investigate the extent to which shoreline variability within this coastal embayment is dominated by shoreline oscillations due to cross shore sediment exchange or shoreline rotations due to alongshore exchange between the beach s extremities offshore wave data are derived from both buoy measurements and era 40 reanalysis data eof analysis of the monthly shoreline data suggests that the dominant mode of shoreline variability 60 of variability is an onshore offshore sediment exchange that is greater at the more exposed northern end of the beach than at the predominantly sheltered southern end this mode is primarily associated with variability in wave energy storms which by the nature of the wave climate of this region chiefly occurs from the south southeast the secondary mode of shoreline variability 26 of variability is a rotational signal between either end of the beach which coincides with 24 of the offshore wave climate shifting between the south southeast and east as well as changes in the wave period and wave energy storms a distinct annual cycle is identified in this rotation signal it is concluded that alongshore sediment transport processes associated with embayment rotation is more subtle than previously thought and a refined conceptual model of coastal embayment variability in this region is presented highlighting the dominance of cross shore sediment exchange processes

synchronised patterns of erosion and deposition observed at two beaches abstract a similarity in the observed variability through time of two or more individual beaches here quantified by synchronous changes in shoreline position and subaerial sand volume can have significant implications to the increased focus worldwide on the need for expanded coastal monitoring if it can be established that one or a select few beach sites exhibit regionally representative behaviour in response to varying and or changing wave and other climatic forcing then this will assist to guide the extent and scope of the ongoing monitoring effort required in this study two beaches located on the southeast australian coastline of similar size and orientation but separated by 35 km were simultaneously monitored and compared for a period spanning 3 years intensive sub aerial surveys were conducted each month at both sites using atv mounted rtk gnss the purpose was to establish whether detailed embayment wide patterns of erosion and deposition quantified at either site were indicative of the behaviour observed at the other during the data collection period storm wave events caused substantial fluctuations in monthly sub aerial sand volumes in the range of 60 70 of mean volume including month to month changes at the berm and episodic foredune erosion and recovery principal component analysis of the two beaches revealed that both were dominated by oscillation corresponding north south behaviour rather than rotation contrasting north south behaviour over this three year period comparison of alongshore averaged volume time series between the two sites indicated a similar total range 68 m3 m and 78 m3 m and the average difference between the two sites 4 5 m3 m was found to be of the order of 50 of the average monthly change 9 7 m3 m and 10 2 m3 m corresponding spatial patterns in the occurrence of erosion accretion along the two sites were also compared and found to closely correspond five synchronised snap shot observations from historical aerial photogrammetry and surveys at both sites spanning the period 1974 to 2011 one per decade suggest coherence between the sites extends beyond the three year intensive monitoring period reported here

properties and pathways of mediterranean water eddies in the atlantic abstract data from ship vertical casts nodc data set argo profiling floats coriolis data set and rafos type neutral density floats woce data set are used to study characteristics of meddies in the northeast atlantic in total 241 mediterranean water eddies meddies and 236 parts of float trajectories within meddies are selected for detailed analysis the results suggest that the meddy generation rate at the southern and southwestern iberian peninsula portimao canyon cap st vincent estremadura promontory gorringe bank is 3 times that at the northwestern iberian peninsula porto aveiro canyons cape finisterre and galicia bank meddies generated south of estremadura promontory the southern meddies as compared to those generated north of it the northern meddies have smaller radii smaller vertical extension higher aspect ratio higher rossby number and higher stability stronger potential vorticity anomaly these latter properties result from the southern meddies higher relative vorticity and stronger buoyancy frequency anomaly away from the generation regions meddy drift concentrates along four main paths three quasi zonal paths northern central southern and a path following the african coast coastal the quasi zonal paths are aligned to the isolines of the ambient potential vorticity field several cross path exchanges identified in this work are aligned to topographic rises northward translation of the northern meddies within the north atlantic current to the subpolar gyre is detected within the first 600 km from the coast meddy merger is proved to be a common event this explains the observed difference in radii between the newly generated meddies and those away from the iberian margin the decay of the southern meddies proceeds mainly via the loss of their skirts and does not affect meddy cores until the latest stages the decay of the northern meddies goes in parallel with the decay of their cores in average meddy decay is achieved within 1 2 years although may take over 3 years collisions with the mid atlantic ridge and seamounts sensibly decrease meddy lifetimes meddy decay also speeds up when meddies meet the azores current or the north atlantic current a rapid drop in the number of meddies south of the azores current proves that it represents a dynamic barrier for weak meddies

shoreline evolution in an embayed beach adjacent to tidal inlet the impact of anthropogenic activities abstract embayed beaches are widely distributed around the world their shoreline evolution is controlled primarily by the upstream headland and prevailing wave conditions tidal inlets are also ubiquitous in sandy coasts they are quite dynamic and act as a sediment source or sink depending on the sediment transport pattern and budget an embayed beach may develop downstream of a tidal inlet if a protruding headland is formed at the inlet owing to either natural processes or human construction in this study gaolong bay located downstream of a tidal inlet qinglan inlet in wenchang city hainan island china is used as an example to examine the effects of an upstream tidal inlet on the evolution of an embayed beach emphasis is placed on the impact of anthropogenic activities such as landfilling and jetty construction historical remote sensing data were collected and the evolution of the shoreline from 1998 to 2018 was analyzed the shoreline change pattern in gaolong bay was identified with the empirical orthogonal function eof method and the mechanisms behind these changes were explored with a coupled current wave sediment transport modeling system our results indicate that the construction of an artificial peninsula and a jetty beside the inlet channel dramatically changed the evolution of the gaolong bay shoreline defying the classical expectation of shoreline retreat downdrift of a tidal inlet a clockwise shoreline rotation was prevalent in gaolong bay with the shadow zone accreting and the distal zone retreating along with an overall shoreline propagation translation the static equilibrium shoreline planform model model of equilibrium of bay beaches mepbay was further used to predict the future evolution of the shoreline this study demonstrates that an embayed beach downdrift of a tidal inlet can exhibit a complex response to human interventions at the inlet and highlights the necessity of considering adjacent shoreline changes when assessing the impact of inlet stabilization

on the morphological development of embayed beaches abstract the typically curved and stable planform shape of embayed beaches is often observed in the presence of rigid headlands the long term alongshore equilibrium shape is variable and is controlled by headland geometry cellular circulation patterns and wave obliquity at the shoreline we use a process based morphological model to simulate the development of embayed beaches depending on different environmental conditions and geological settings i e topography and geometry the embayment is allowed to develop from an initially straight beach to one which is curved under idealized wave forcing conditions and without external sediment input bay development can be approximated with an exponential function with coefficients representing rate of growth and bay size long term shoreline cutback is both uniform shoreline translation and non uniform shoreline rotation and is parameterized alongshore gradients in flow and transport patterns are related to long term non uniform shoreline cutback rotation of the beach ceases as the bay matures leading to a curved shoreline planform which is a remnant of decaying erosion processes

storm driven changes in rip channel patterns on an embayed beach this paper introduces a semi automatic computer algorithm designed to detect rip current channels in video imagery as a case study this method is applied to 3 3 years of video data from an embayed beach to demonstrate the link between antecedent surf zone morphology wave energy and up down transitions in beach state an objective measure of rip channel change was developed to define six significant rip reconfiguration events and relate these events to wave energy over the period of study no complete resets of the nearshore morphology occurred the analysis indicates that direct correlation of rip patterns with the instantaneous wave conditions is not a useful way to demonstrate how rips and waves interact the average wave energy over a period of ten days combined with storm duration were good indicators of rip channel change demonstrating that in general beach morphology responds with a time lag to changes in forcing rip channels with a short cross shore length and narrow alongshore spacing responded faster to changes in wave conditions than rips with a long cross shore length and wider alongshore spacing to force changes in the rip morphology longer rip channels required wave events of higher energy and or a longer duration offshore islands protect the beach under certain wave approach angles sometimes resulting in a dual width surf zone which was narrow at the sheltered end and wide at the exposed end of the beach the wider surf zone end was characterised by three dominant and persistent rip channels whereas the narrow surf zone section contained a number of smaller rips which evolved rapidly under wave forcing our observations demonstrate the importance of rip channel size in controlling the response time of nearshore morphology

the effects of wave chronology on medium and long term coastal morphology the sequencing or chronology of wave events plays an important role in determining how coastlines and nearshore regions evolve over medium and long timescales from weeks to decades however present day computer models of coastal morphology treat the input wave conditions in either a deterministic i e a single wave sequence or a probabilistic manner in neither method are the effects of the full range of possible future wave sequences for given overall statistical values calculated the methodology presented here addresses this problem by multiple model runs using different re orderings of a wave sequence a series of tests demonstrate different aspects of wave chronology and its importance in the prediction of seabed and beach levels the method provides a means both for understanding wave chronology effects and for predicting these effects in practical engineering problems involving medium and long timescale changes to coastal morphology

on the origin of the azores current the azores current south of the azores archipelago is part of the subtropical north atlantic gyre using an international hydrographic data set we analyze mean and seasonal geostrophic transport fields in the upper 800 m of the ocean in order to determine the origin of the azores current in the western basin and seasonal changes in the related flow geostrophic currents are obtained by using the method applied by stramma 1984 in the eastern basin the azores current is found to originate in the area of the southwest newfoundland rise figure 10 in winter an almost uniform current connects this region of origin with the azores current while a branching into two current bands is observed in summer with the southern band forming a marked cyclonic loop within the upper 800 m all of the transport in the northern band and about 70 of the transport in the southern band recirculates in the eastern basin additionally expendable bathythermograph data from the azores current region indicate an increase of eddy potential energy from winter to summer

faceted spurs at normal fault scarps insights from numerical modeling 1 we present a combined surface processes and tectonic model which allows us to determine the climatic and tectonic parameters that control the development of faceted spurs at normal fault scarps sensitivity tests to climatic parameter values are performed for a given precipitation rate when hillslope diffusion is high and channel bedrock is highly resistant to erosion the scarp is smooth and undissected when instead the bedrock is easily eroded and diffusion is limited numerous channels develop and the scarp becomes deeply incised between these two end member states diffusion and incision compete to produce a range of scarp morphologies including faceted spurs the sensitivity tests allow us to determine a dimensionless ratio of erosion f for which faceted spurs can develop this study evidences a strong dependence of facet slope angle on throw rate for throw rates between 0 4 and 0 7 mm a facet height is also shown to be a linear function of fault throw rate model performance is tested on the wasatch fault utah using topographic geologic and seismologic data a monte carlo inversion on the topography of a portion of the weber segment shows that the 5 ma long development of this scarp has been dominated by a low effective precipitation rate 1 1 m a and a moderate diffusion coefficient 0 13 m2 a results demonstrate the ability of our model to estimate normal fault throw rates from the height of triangular facets and to retrieve the average long term diffusion and incision parameters that prevailed during scarp evolution using an accurate 2 d misfit criterion

morphodynamics of structurally controlled headland bay beaches in southeastern brazil a review abstract this paper presents a comprehensive review on the interaction between hydrodynamic processes beach morphology and sedimentology at large scale coastal behaviour along the coastline of santa catarina between laguna and sao francisco island a microtidal east coast swell environment with headland and bay geomorphologies the parabolic bay shape equation has proven to be a convenient and practical tool for studying the stability of the headland bay beaches tombolos and salients in santa catarina the beaches exhibit different patterns of sediment removal as a function of the degree of beach curvature in highly curved beaches there is a well developed shadow zone and a range of morphodynamic conditions from a sheltered low energy beach adjacent to the downdrift headland to a high energy exposed beach on the straight end of the headland bay beach the less curved beaches instead tend to show more uniform behaviour since they are directly exposed to incident waves there is no obvious relationship between average wave height and mean grain size showing the importance of sediment source to characterize the sedimentary distribution patterns in the study area the analysis of beaches showed that beach morphodynamics and sequence profiles for a bay headland coast in a microtidal east coast environment is a function of geological inheritance e g distance between headlands and orientation nearshore and inner shelf morphology coastal plain morphology and sediment source and hydrodynamic factors wave conditions oceanic wave exposure and relative tidal range

hydrological and dynamical characterization of meddies in the azores region a paradigm for baroclinic vortex dynamics the structure des echanges mer atmosphere proprietes des heterogeneites oceaniques recherche experimentale semaphore oceanographic experiment surveyed a 500 500 km2 domain south of the azores from june to november 1993 and collected hydrological data float trajectories and current meter recordings this data exhibited three intrathermocline eddies of mediterranean water meddies two of them being repeatedly sampled their hydrological and dynamical properties are quantified here by an isopycnic analysis for the three meddies intense temperature and salinity anomalies up to 4 c and 1 1 practical salinity units psu are observed extending vertically over up to 1000 m and centered around 1000 m horizontally these anomalies spread out to radii of 50 60 km while the maximum azimuthal velocities 30 cm s 1 as computed by geostrophy lie only at 35 40 km from the central axis these meddies followed curved trajectories with drift velocities up to 7 5 cm s 1 under the influence of the neighboring mesoscale features cyclonic vortices or azores current meanders the three dimensional structure of potential vorticity in and around these features evidences their complex interactions northwest of the domain a meddy was coupled to a subsurface anticyclone forming an aligned vortex it later interacted with the azores current creating a large amplitude northward meander by vertical alignment of vorticity in the southeastern part of the domain another meddy was vertically aligned with an anticyclonic meander of the azores current and horizontally coupled with a cyclone of large vertical extent these two features as well as a small warm and salty fragment in their vicinity seem to result from the southward crossing of the meddy under the azores current these observations illustrate previous theoretical studies of baroclinic vortex dynamics

modelled channel patterns in a schematized tidal inlet abstract tidal inlets in the dutch wadden sea show typical morphological features i e westward oriented main inlet channel and ebb tidal delta the objective of this study is to find the governing physical processes of these morphological features the study uses a 2dh process based morphodynamic model delft3d on a schematized model domain with dimensions similar to the ameland inlet in the dutch wadden sea starting from a flat bed the models are forced by tides only short term simulations are made to explore the hydrodynamic characteristics and initial sedimentation and erosion patterns long term morphodynamic simulations are employed to investigate the governing parameters of the main inlet channel and the ebb tidal delta evolution sensitivity of the evolution is described in terms of initial inlet width 1 0 km and 3 5 km direction and asymmetry of tidal forcing m2 m4 transport formulations van rijn 1993 engelund and hansen 1967 and relative position of the tidal basin with respect to the inlet east existing middle and west the results tend to produce morphological features typical to the ameland inlet the direction of tidal forcing is the main governing parameter to the present orientation of the main inlet channel and the ebb tidal delta the model results generally prove the conceptual hypotheses that describe the orientation of the main inlet channel and the ebb tidal delta

the upper oceanic response to overflows a mechanism for the azores current abstract the oceanic response to overflows is explored using a two layer isopycnal model overflows enter the open ocean as dense gravity currents that flow along and down the continental slope while descending the slope overflows typically double their volume transport by entraining upper oceanic water the upper oceanic layer must balance this loss of mass and the resulting convergent flow produces significant vortex stretching overflows thus represent an intense and localized mass and vorticity forcing for the upper ocean in this study simulations show that the upper ocean responds to the overflow induced forcing by establishing topographic plumes that are aligned more or less along isobaths and that have a transport that is typically a few times larger than that of the overflows for the topographic plume driven by the mediterranean overflow the occurrence of eddies near cape st vincent portugal allows the topographic plume to flow across isobaths the modeled topographic plume circu