on the stochastic theory of solute transport by unsteady and steady groundwater flow in heterogeneous aquifers abstract in this study the exact and approximate deterministic partial differential equations of the time space evolution of mean solute concentration of solute concentration two point moment and of solute concentration n point moment for conservative solute transport by unsteady and steady groundwater flow in a heterogeneous aquifer were developed in the real time space domain under second order cumulant expansion these derivations were performed by means of the cumulant expansion method combined with the calculus for the time ordered exponential and with the calculus for lie operator the mean solute transport equations which describe the time space evolution of mean conservative solute concentration under transport by unsteady and steady groundwater flows in a heterogeneous aquifer have convective dispersive forms whose convective and dispersive coefficients are defined precisely in terms of the mean and covariance functions of the pore flow velocity random field however owing to the spatial nonuniformity of groundwater flow in heterogeneous porous media a new convective coefficient besides the standard mean velocity vector appeared in the derived mean solute transport equations in the case of steady flows in the case of transport by unsteady groundwater flow in a heterogeneous aquifer the new convective coefficient besides the standard mean velocity vector is due to the non zero divergence of the pore flow velocity the fundamental reason for the convective dispersive form of the mean transport equations is the second order truncation of the formal cumulant expansion in the derived mean solute transport equations the macroscopic dispersion coefficient emerges as the time integral of the covariance function of the pore flow velocity however both in the case of transport by unsteady groundwater flow and in the case of transport by steady spatially nonstationary nonuniform groundwater flow the macroscopic dispersion coefficients and convective coefficients vary with spatial locations within the porous medium only in the case of transport by steady spatially stationary nonuniform flow are both the macroscopic dispersion coefficient and the convective coefficient constant with respect to spatial location within the heterogenous aquifer therefore only in the case of conservative solute transport by steady spatially stationary nonuniform groundwater flow in a heterogeneous aquifer does the mean transport equation apply to all spatial locations within the aquifer with the same parameter values at each time instant

tsunami in coastal zone due to meteorite impact the impact of a meteorite into the ocean surface is a rare phenomenon however it can be catastrophic especially for the coastal area the aim of the paper is to describe the evolution of the tsunami impulse due to meteorite impact in shallow water including energy dissipation due to bottom friction and wave breaking as the exact nonlinear solutions for tsunami transformation with energy loss due to wave breaking are not known the linearised equations of motion are used and energy loss is parameterised accordingly to describe the evolution of tsunami impulse in shallow water the hilbert transform technique was introduced it facilitates considerably the evaluation of the tsunami impulse transformation its run up and coast inundation range examples are included to illustrate the applicability of the theoretical derivations

heat and fresh water transport by eddies into the gulf of alaska abstract anticyclonic mesoscale eddies form in winter along the continental margin of canada and southeast alaska between the latitudes of 51n and 60n and drift westward into the gulf of alaska carrying warmer fresher water away from the continental margin detailed measurements of temperature and salinity between 1995 and 2001 were examined to determine the amount of heat and fresh water transported seaward by several eddies that formed west of the queen charlotte islands eddies formed in a typical winter carry about 30 10 18 j of heat into the gulf which is about 35 to 60 of the heat transported northward each winter along the continental margin toward this region the observed range of eddy heat transport is 10 19 to 10 20 j largest observed eddy heat transport coincided with increased northward heat flow along the continental margin during the el nino winter of 1997 1998 fresh water volume was determined by evaluating the amount of fresh water required to reduce the salinity from a reference level to that observed in eddies this volume varied from 0 to 70 km 3 and was largest during the 1997 1998 el nino winter eddies formed in a typical winter transport 50 km 3 of fresh water seaward which is about 15 of the estimated fresh water input to the continental margin in winter between the columbia river and 54n attributed to local runoff plus direct rainfall and flow in major rivers

the north pacific climatology of winter mixed layer and mode waters abstract a climatology of the winter mixed layer in the north pacific ocean was constructed using hydrographic data from historical archives and recent observational programs including the world ocean circulation experiment the main aim was to provide better knowledge about source areas of upper water masses the authors have endeavored to preserve water properties near the frontal regions by keeping the smoothing scale as small as possible the resulting climatology shows considerable differences in the mixed layer depth and its water properties from those derived from the world ocean atlas woa maps of the potential vorticity field of the north pacific pycnocline are presented using the isopycnally averaged climatology hydrobase three distinct lateral minima of potential vorticity are identified as subtropical mode water stmw central mode water cmw and eastern subtropical mode water estmw in the western central and eastern parts of the subtropical gyre respectively the hydrobase isopy

rhizoplegma boreale radiolaria a tracer for mesoscale eddies from coastal areas 1 the impact of mesoscale eddies on the production of radiolarian species rhizoplegma boreale in the central subarctic pacific was investigated through analysis of sinking particle fluxes collected using sediment trap and altimetry data from satellite observations altimetry observations provided the locations of mesoscale eddies in time and space and indicated that mesoscale eddies propagating around sediment trap station sa were closely related to the high r boreale fluxes at the station the mesoscale eddies likely provided the deep sea region of the central subarctic pacific with coastal nutrient rich waters derived from the region around the aleutian islands and influenced the productivity of microzooplankton groups at station sa

geostatistical analysis of the borden aquifer hydraulic conductivity field abstract a total of 11 vertical cores spaced 1 m apart along a single transect were extracted from the borden aquifer at a location 60 m north northeast from the site studied by sudicky previously examination of these cores shows the upper 1 5 2 0 m of the aquifer to be comprised of relatively unstructured fine to medium sands underlain by a 0 1 0 8 m thick peaty layer and a 0 1 m thick organic rich horizon between depths of 3 05 and 6 10 m the aquifer is comprised of clean horizontally bedded fine to medium sands similar to those examined by sudicky previously statistical analysis of 642 subsamples of 5 cm length from this interval suggests that the permeability data may follow a log normal distribution with a mean lntransformed permeability m 2 of 25 67 and a variance of 0 585 no consistent trend with depth was detected for ln k or for the mean and variance of ln k on a core by core basis exponential spherical and gaussian models all provided excellent fits to the vertical experimental variogram calculated using the classical estimator without the removal of outliers these fits produced correlation scales ranging from 0 16 to 0 23 m of the three theoretical models only the gaussian model produced a reasonable fit to the horizontal experimental variogram with a correlation scale of 4 8 m a linear model was also found to fit the experimental variogram data well in comparison with earlier results of sudicky and woodbury and sudicky it can be concluded that similar deposits were examined in this study particularly with respect to correlation structure on the basis of statistical tests however it cannot be concluded that the mean and variance of ln k are stationary over the 60 m distance between the cores examined in this study and those of sudicky the results of this study indicate that the borden hydraulic conductivity field is relatively uniform over the scale examined but that it cannot be characterized by a single spatially invariant statistical distribution

semi empirical treatment of wave transformation outside and inside the breaker line a semi empirical method is developed which predicts the wave height shoaling up to the break point on laboratory and natural beaches linear shoaling is enhanced with empirical curves for the wave shape obtained from field measurements of wave height through the break point and the surf zone made on an ocean beach in southern australia from 1987 to 1989 wave height shoaling breaking and attenuation are unified in a mixed lagrangian eulerian numerical model of random wave height transformation which with the semi analytical enhancements provides improved predictions of the height transformation of individual waves through the surf zone this is demonstrated for a wide variety of cases from the field and laboratory

anomalous eddy heat and freshwater transport in the gulf of alaska characteristics of eddies in the gulf of alaska are assessed from january 2003 through april 2012 ensemble statistics for eddy subsurface water properties on isopycnals are computed using temperature and salinity profiles from argo profiling floats located within eddies which are identified in sea surface height using objective techniques ninety cyclonic and 154 anticyclonic eddies are identified during this period the anticyclonic eddies are strongly nonlinear and exhibit significant warm subsurface temperature anomalies and associated salty anomalies on isopycnals while no clear distinguishing subsurface anomalies on isopycnals are detected in association with the cyclonic eddies heat and freshwater fluxes for the eddies are estimated from integrations in depth coordinates the anticyclonic eddies transport heat both westward off the continental shelf into the subarctic gyre and westward within the alaskan stream however they transport salt into the subarctic gyre and freshwater within the alaskan stream in both pathways eddy heat and freshwater transport show possible year to year fluctuations varying from 0 to 50 4 1018 j a 1 and 16 8 to 7 4 km3 a 1 respectively the anticyclonic eddies are capped by relatively fresh water year round

model data comparisons of moments of nonbreaking shoaling surface gravity waves the predictions of linear and nonlinear boussinesq shoaling wave models for nonbreaking unidirectional surface gravity waves are compared to field observations with particular emphasis on quantities that may be important for cross shore sediment transport the extensive data sets were obtained on two natural beaches span water depths between 1 and 10 m and include incident wave power spectra with narrow broad and bimodal shapes significant wave heights varied between approximately 30 and 100 cm and peak periods between approximately 8 and 18 s the evolution of total variances of sea surface elevation cross shore velocity and horizontal acceleration is modeled at least qualitatively well by both linear and nonlinear theories only the nonlinear theory predicts the increasingly asymmetric sea surface elevations and horizontal velocities pitched forward wave shapes and the weaker variation of skewness difference between crest and trough profiles which are observed to occur during shoaling the nonlinear theory also models qualitatively well the large skewed accelerations which occur during the passage of asymmetric waves

bars formed by horizontal diffusion of suspended sediment abstract the mechanism responsible for the ubiquitous presence of convex beach profiles and shoreward migration of linear bars is examined using numerical circulation and sediment transport models the models are validated against laboratory measurements and observed natural beach cross sections while not discounting the importance of infragravity and advective horizontal circulation or bed return flow mechanisms a robust diffusive process explains the convex profile shape and bar formation in the presence of concentration gradients across the surf zone a diffusive sediment flux from high to low concentration results in the transfer of sediment outwards from the breakpoint both onshore and offshore and the subsequent formation of a diffusion bar and diffusion profile the profiles are characterised by single and double convex dome like shapes developing during shoreward migration of the bars by the diffusion mechanism the mechanism explains several phenomena observed on natural beaches including i convex beach profiles ii shoreward migration of the bar with concomitant beach accretion under narrow band swell iii reduced propensity for bar formation on low gradient fine sand beaches or under wide band wave spectra even though multiple bars are common on some low gradient beaches and iv offshore migration of the bar during periods of increasing wave height the diffusion mechanism can be dependent on orbital motion alone and as such requires no frequency selection or strong correlation between multiple processes for bar formation

coral mortality increases wave energy reaching shores protected by reef flats examples from the seychelles in the granitic seychelles many shores and beaches are fringed by coral reef flats which provide protection to shores from erosion by waves the surfaces of these reef flats support a complex ecology about 10 years ago their seaward zones were extensively covered by a rich coral growth which reached approximately to mean low water level but in 1998 this was largely killed by seawater warming the resulting large expanses of dead coral skeletons in these locations are now disintegrating and much of the subsequent modest recovery by new coral recruitment was set back by further mortalities a mathematical model of wave energy reaching shorelines protected by coral reef flats has been applied to 14 seychelles reefs it is derived from equations which predict 1 the raised water level or wave set up on reef flats resulting from wave breaking which depends upon offshore wave height and period depth of still water over the reef flat and the reef crest profile and 2 the decay of energy from reef edge to shoreline that is affected by width of reef flat surface roughness sea level rise and pseudo sea level rise created by increased depth resulting from disintegration of coral colonies the model treats each reef as one entity but because biota and zonation on reef flats are not homogenous all reefs are divided into four zones in each cover by both living and dead biota was estimated for calculation of parameters and then averaged to obtain input data for the model all possible biological factors were taken into account such as the ability of seagrass beds to grow upwards to match expected sea level rise reduction in height of the reef flat in relation to sea level as zones of dead corals decay and the observed rounding of reef crests as erosion removes corals from those areas estimates were also made of all these factors for a time approximately a decade ago representing a time before the mass coral mortality and for approximately a decade in the future when the observed rapid state of dead coral colony disintegration is assumed to have reached an end point results of increased energy over the past decade explain observations of erosion in some sites in the seychelles most importantly it is estimated that the rise in energy reaching shores protected by fringing reefs will now accelerate more rapidly such that the increase expected over the next decade will be approximately double than that seen over the past decade c 2005 elsevier ltd all rights reserved

comparison between natural and forced gradient tests to determine the vertical distribution of horizontal transport properties of aquifers a modified natural gradient point dilution test using a multilayer sampler was conducted in a 20 m thick confined aquifer in a research field near mobile alabama the horizontal component of the specific discharge along the profile varies by an order of magnitude from 2 0 to 21 1 m yr the modified point dilution test was capable of detecting very large q changes over small vertical intervals the results obtained by the point dilution test agree with the results obtained in the same aquifer by a forced gradient tracer test over a distance of 6 m molz et al 1988

observations from a yakutat eddy in the northern gulf of alaska 1 the impingement of deep basin eddies on the shelf in the gulf of alaska has been implicated as an important mechanism for cross shelf exchange the influence of eddies on biological processes has been confirmed with data from the sea viewing wide field of view sensor showing elevated chlorophyll associated with eddies altimetry data suggest that an eddy formed in the winter of 2003 near yakutat alaska and propagated along the shelf break reaching the head of the gulf by spring this eddy was sampled during may and september of 2003 the eddy core water was warm salty and high in nitrate relative to basin water of the same density but was similar to historical water properties from the shelf near yakutat this suggests a shelf origin for the eddy core water

temperature inversions in the subarctic north pacific abstract hydrographic data from the world ocean database 2001 and argo profiling floats were analyzed to study temperature inversions in the subarctic north pacific ocean the frequency distribution of temperature inversions f t inv at a resolution of 1 latitude 3 longitude was calculated temperature inversions seldom occurred around 50 n in the eastern subarctic north pacific but were more common in the northern gulf of alaska and the southeastern subarctic north pacific 42 48 n 140 170 w large temperature inversions occurred throughout the year in the western and central subarctic north pacific north of 42 n and west of 180 except near the aleutian and kuril islands near those islands f t inv was characterized by pronounced seasonal variations forced by surface heating cooling and strong tidal mixing

wave field modification by bathymetric anomalies and resulting shoreline changes a review with recent results this paper provides a review of available studies on wave transformation by bathymetric changes and the resulting shoreline impacts three case studies of beach nourishment projects with significant nearshore borrow areas are examined grand isle louisiana constructed in 1984 anna maria key florida in 1993 and martin county florida in 1996 a review is presented of field and laboratory scale studies that have examined the impact of offshore pits on the local wave field and sediment dynamics solutions for wave transformation by changes in bathymetry are outlined primarily in chronological order following the development from analytical solutions for long waves in one horizontal dimension 1 d through numerical models for arbitrary bathymetry that include many wave related nearshore processes modeling of shoreline responses due to wave field modification owing to changes in offshore bathymetry is examined with models that include both wave field and shoreline changes and by coupling models that evaluate these processes independently the wave transformation processes included in nearshore models are important factors in the capability to predict a salient leeward of a pit the shoreline responses observed in the limited laboratory experiments and at grand isle la

some characteristics of yakutat eddies propagating along the continental slope of the northern gulf of alaska abstract data from array for real time geostrophic oceanography argo profiling floats oil tanker thermosalinographs shipboard adcp and towed ctd surveys and satellite altimetry are used to examine properties of two 200 km diameter anticyclonic yakutat eddies that propagated westward at 1 5 km day 1 along the continental slope of the northern gulf of alaska goa in 2001 and 2003 the eddies had lifetimes of up to 5 years remained close to the shelfbreak and had relatively constant size and strength until they encountered the alaskan stream where they appeared to spawn smaller shorter lived anticyclones the azimuthal velocity field was vigorous 25 40 cm s 1 and in gradient wind balance with rossby numbers of 0 05 conservation of salt and azimuthal mass transports between 20 m and the depth of the 32 2 isohaline from shipboard surveys in may and august 2003 suggest little mass exchange occurred between the surface layers of the eddy and ambient waters chlorophyll concentrations were greater in the eddy than in ambient waters in both may and august in may the chlorophyll was patchily distributed while in august dense chlorophyll concentrations occurred in and beneath the seasonal thermocline within 50 km of the eddy center the high august chlorophyll concentrations might have been fostered by a broad and shallow it appears likely that as yakutat eddies approach the shelfbreak non linear processes will modify the slope flow field and the stability and structure of the shelfbreak front leading to cross slope flows and flow reversals this interaction may induce 30 km wide streamers of shelf water to flow around the trailing edge of the anticyclone the role of streamers in the freshwater and nutrient budgets of the goa shelf and basin is unknown but their contribution to these budgets will depend on the trajectory of a yakutat eddy especially its proximity to the shelfbreak as the eddy propagates along the goa continental slope

spectral wave dissipation over a barrier reef 1 a 2 week field experiment was conducted to measure surface wave dissipation on a barrier reef at kaneohe bay oahu hawaii wave heights and velocities were measured at several locations on the fore reef and the reef flat which were used to estimate rates of dissipation by wave breaking and bottom friction dissipation on the reef flat was found to be dominated by friction at rates that are significantly larger than those typically observed at sandy beach sites this is attributed to the rough surface generated by the reef organisms which makes the reef highly efficient at dissipating energy by bottom friction results were compared to a spectral wave friction model which showed that the variation in frictional dissipation among the different frequency components could be described using a single hydraulic roughness length scale surveys of the bottom roughness conducted on the reef flat showed that this hydraulic roughness length was comparable to the physical roughness measured at this site on the fore reef dissipation was due to the combined effect of frictional dissipation and wave breaking however in this region the magnitude of dissipation by bottom friction was comparable to wave breaking despite the existence of a well defined surf zone there under typical wave conditions the bulk of the total wave energy incident on kaneohe bay is dissipated by bottom friction not wave breaking as is often assumed for sandy beach sites and other coral reefs

circulation in shelikof strait alaska abstract extensive hydrographic surveys were conducted in shelikof strait in march and october 1985 the data are used to describe circulation and property distributions and the changes that occurred the upper layer flows to the southwest throughout the year but greatest speeds occur in the fall when surface waters are least saline because of a maximum in freshwater discharge the deep water has its source to the south and the properties seem to result from vertical mixing of this southern water thus shelikof strait has an estuarine like circulation with a northward deep inflow property distribution showed that isolines were usually deepest on the right side of the channel looking to the southwest greatest baroclinic speeds were often there also differential ekman pumping may contribute to the development of this structure and its changes volume transport estimates varied considerably in october the southwest flow bifurcated with part continuing along the alaska peninsula and the rest exiting t

potential shoreline changes induced by three dimensional bathymetric anomalies with gradual transitions in depth abstract the development of an analytic model for nearshore wave propagation and shoreline change shoreward of a bathymetric anomaly is presented the three dimensional 3 d step model bender c j dean r g 2003 wave transformation by axisymmetric 3 dimensional bathymetric anomalies with gradual transitions in depth in review coastal engineering propagates a linear wave field in a region of uniform depth over an axisymmetric bathymetric anomaly to a region representing the nearshore zone the bathymetric anomaly is represented by a series of steps which can approximate uniform or nonuniform slopes this paper presents the development and application of an approximate shallow water analytic shoaling and refraction method analytic s r model which establishes the breaking wave height and angle for arbitrary nearshore slopes thus extending the 3 d step model to the nearshore region where the depth is nonuniform the 3 d step model determines the wave transformation caused by the processes of wave refraction diffraction and reflection the wave heights and directions for transects located shoreward of the bathymetric anomaly are combined with the analytic s r model to determine the wave propagation in a nearshore zone of arbitrary slope employing the shoreline change model calculates the longshore transport and shoreline evolution for the nearshore shoaled and refracted wave field that occurs shoreward of the anomaly through the methods developed in this paper the wave transformation nearshore shoaling and refraction longshore transport and shoreline evolution induced by a 3 d bathymetric anomaly with gradual transitions in depth are investigated comparisons of the analytic nearshore shoaling model with a numerical model verify the results for several bathymetries including both pits and shoals the analytic shoreline change model predicts shoreline response for areas shoreward of bathymetric anomalies comparison to the laboratory experiment of horikawa et al horikawa k sasaki t and sakuramoto h 1977 mathematical and laboratory models of shoreline change due to dredged holes journal of the faculty of engineering the university of tokyo xxxiv no 1 pp 49 57 indicates the shoreline change model is able to predict the equilibrium planform shoreward of a pit when the transport caused by the gradient in breaking wave height is included the results demonstrate the importance of the longshore transport term driven by the gradient in breaking wave height

reply to comment on a natural gradient experiment on solute transport in a sand aquifer spatial variability of hydraulic conductivity and its role in the dispersion process by e a sudicky

iron transport by mesoscale haida eddies in the gulf of alaska abstract a two year study of the iron distributions in anticyclonic mesoscale haida eddies of the eastern north pacific ocean has shown that such eddies are a major source of iron to the high nitrate low chlorophyll hnlc waters of the central gulf of alaska basin these eddies which are typically about 100 km in diameter form off the west coast of canada in winter and then track roughly westward into the open ocean therefore they carry large quantities of iron rich coastal waters into iron limited waters of the oligotrophic gyre when the eddies had first formed their dissolved iron concentrations were nearly two orders of magnitude higher than is typically observed at station papa 50 n 145 w 3 n m versus less than 0 05 n m and the total iron in the eddies surface waters 10 40 m was more than 13 n m higher than open ocean waters of the alaska gyre 14 n m versus 0 5 n m while the overall iron content of the eddies decreased rapidly during the first year after they formed the eddy we were able to track the longest still contained 1 5 2 times more iron than the surrounding waters 16 months after its formation therefore although iron concentrations in the surface mixed layers of the eddies drop to levels observed outside very rapidly within 4 months upward transport along isopycnals and upwelling due to eddy decay as well as vertical advective and diffusive transports typical of north pacific waters probably provide steady fluxes of iron into the euphotic zone from the still iron rich eddy core waters throughout the lifetime of the eddy

depth limited design wave heights in very flat regions abstract engineers working on the flat tops of offshore coral reefs or offshore banks require design criteria for depth limited wave heights over horizontal beds particularly in regions leeward of the bank or reef edge surf zone this paper presents convincing evidence of the fact that in engineering practice both in the laboratory and in the field the value of 0 55 is the largest wave height to water depth ratio realizable for stable shallow water oscillatory waves propagating in water of constant depth horizontal bed this value is much lower than that often used in engineering practice namely a value of about 0 8 which is historically based on the theoretical considerations and laboratory experiments associated with solitary waves this result based on a review of laboratory data and the original results of a major field experiment undertaken on the great barrier reef of australia leads to a significant reduction in design wave forces design crest levels and wave induced scour velocities at the bed

migration of contaminants in groundwater at a landfill a case study 4 a natural gradient dispersion test abstract a natural gradient tracer test using a chloride solution with an initial injection volume of 0 7 m 3 was performed in the sandy aquifer at the borden site the solution was injected into five well points set 1 m below the water table in an uncontaminated zone situated above the contaminant plume at a location 450 m downflow from the landfill under conditions of natural groundwater flow the tracer slug was monitored for a period of 4 months by withdrawing small volume samples from points in a three dimensional array of bundle type multilevel samplers measurements of hydraulic head were obtained from a network of miniature piezometers soon after injection the tracer slug gradually split into two halves one half moving horizontally at an average velocity of 2 9 10 6 ms 1 and the other horizontally at 8 2 10 7 ms 1 although the split has been attributed to local lateral heterogeneity the nature of the heterogeneity and its influence on the hydraulic head distribution were not clearly distinguishable in the field data obtained before during or after the test the chloride patterns for each of the two halves of the tracer slug evolved into gaussian forms although the patterns demonstrated some irregularity at early time the relatively smooth gaussian forms were unexpected because the aquifer has numerous small scale heterogeneities observed in vertical cores obtained from the tracer zone and because the glaciofluvial origin of the aquifer suggests that heterogeneities are not laterally continuous simulated chloride distributions from a three dimensional analytical solution to the advection dispersion equation were fitted to the field data to obtain best fit estimates of the values of longitudinal transverse horizontal and transverse vertical dispersivity at various travel distances for each of the two halves of the tracer zone this is the first known field test that has permitted the estimation of three principal dispersion coefficients in layered media the longitudinal dispersivity was found to increase from 0 01 m at a distance of 0 75 m from the source to 0 08 m at 11 0 m the transverse horizontal dispersivity increased also to a value of 0 03 m at 11 0 m transverse vertical dispersion was very weak and was accounted for by molecular diffusion the relative lack of vertical dispersion is consistent with the shape of the plume of leachate contamination from the landfill it was concluded that the observed increase in dispersivity along the path of migration is likely caused by heterogeneities information on the dispersion controlling heterogeneities is not yet available as practical field methodologies for their identification and description have not yet been developed until such information is incorporated into mass transport models a realistic solution of the dispersion problem in heterogeneous media will remain elusive

wave setup a field study a new and efficient method is described for obtaining field measurements of surf zone mean water levels the method applies manometer tubes rather than the traditional pressure transducers and hence makes it unnecessary to survey the vertical positions of the sensors a substantial data base is obtained which apart from quantitative data for the field site and similar beaches gives clear general indications of where previous wave setup models need to be amended it is clear from the data that while traditional setup models work reasonably well seaward of the still water line the most landward part of the mean water surface on fairly steep beaches at least requires radically different models it is still possible however to obtain reasonable estimates of the shoreline setup by tying together the concepts of setup and runup and utilizing presently available empirical formulae for the maximum runup level

physical processes that enhance nutrient transport and primary productivity in the coastal and open ocean of the subarctic ne pacific abstract in comparison to the open ocean several additional processes including coastal upwelling river discharge tidal mixing estuarine circulation and benthic remineralization enhance nutrient supply to the surface waters of the continental shelf in general coastal waters become nitrate limited during the phytoplankton growing season whereas iron and dissolved silicate limit phytoplankton growth in the less productive oceanic waters of the gulf of alaska if coastal processes supply ample amounts of macro and micro nutrients during the growing season diatom communities dominated by species such as skeletomema costatum chaetoceros spp and thalassiosira spp will bloom growth rates of these bloom populations typically range from 0 5 to 1 5 doublings per day which place a high demand on nutrients any transport of coastal waters away from the shelf will enhance productivity in oceanic waters the general circulation of the eastern subarctic pacific does not allow for offshore transport except in special circumstances these include anticyclonic mesoscale eddy formation which can export as much as 5000 km 3 of nutrient rich waters from the shelf in a single eddy and recirculation of waters away from southwestern alaska due to the cyclonic circulation around the western edge of the alaskan gyre recirculation can carry nutrient rich water from the coast to the vicinity of ocean station papa 50 n 145 w within a few months for both eddies and gyre recirculation much of the water being carried into the open ocean lies below the euphotic zone iron enrichment occurs to a depth of at least 1000 m in the gulf of alaska as a result periods of enhanced eddy formation or recirculation may supply iron that enriches the open ocean for several years damming of the columbia river and human uses of its waters have resulted in more winter and less summer discharge of fresh water and dissolved si coastal currents in this area flow north in winter and south in summer as a consequence there has been a net temporal change in si inputs to the ocean since the mid 1970s with about 4 10 9 mol more si flowing north in winter and 9 10 9 mol less si flowing south in summer compared with the early 1900s since silicate limits diatom growth and diatoms are responsible for most carbon export in phytoplankton implications for ocean productivity are significant

a study of radiation stress and set up in the nearshore region abstract in this paper the variations of radiation stress and mean water level are studied for the two dimensional shoaling and breaking of progressive periodic waves on a plane gently sloping laboratory beach observations of radiation stress and mean water level were made for two initial conditions the observed variations are compared to the variations as calculated by a linear theory james nonlinear theory and a new nonlinear theory based on cokelet s work it is shown that the nonlinear theories are qualitatively and quantitatively superior to the linear theory thus indicating that the effects of finite amplitude are important for the present case

persistently declining oxygen levels in the interior waters of the eastern subarctic pacific abstract fifty years of measurements at ocean station papa osp 50 n 145 w show trends in the interior waters of the subarctic pacific that are both impacted by short term few years to bi decadal atmospheric or ocean circulation oscillations and by persistent climate trends between 1956 and 2006 waters below the ocean mixed layer to a depth of at least 1000 m have been warming and losing oxygen on density surfaces found in the depth range 100 400 m 26 3 27 0 the ocean is warming at 0 005 0 012 c y 1 whereas oxygen is declining at 0 39 0 70 mol kg 1 y 1 or at an integrated rate of 123 mmol m 2 y 1 decrease of 22 over 50 years during this time the hypoxic boundary defined as 60 mol o 2 kg 1 has shoaled from 400 to 300 m in the alaska gyre the 26 2 isopycnal occasionally ventilates whereas at osp 26 0 has not been seen at the ocean surface since 1971 as the upper ocean continues to stratify to interpret the 50 year record at osp the isopycnal transport of oxygenated waters within the interior of the subarctic pacific is assessed by using a slightly modified no parameter broecker w 1974 no a conservative water mass tracer earth and planetary science letters 23 100 107 the highest nitrate oxygen signature in interior waters of the north pacific is found in the bering sea gyre western subarctic gyre and east kamchatka current region as a consequence of winter mixing to the 26 6 isopycnal by mixing with low no waters found in the subtropics and okhotsk sea this signature is diluted as waters flow eastward across the pacific evidence of low no waters flowing north from california is seen along the coasts of british columbia and se alaska oxygen in the subsurface waters of the alaskan gyre was supplied 60 by subarctic and 40 by subtropical waters during woce surveys whereas such estimates are shown to periodically vary by 20 at osp other features discernable in the osp data include periods of increased ventilation of deeper isopycnals on an 18 year cycle and strong short term few month variability caused by passing mesoscale eddies the potential impacts of declining oxygen on coastal ecosystems are discussed

relationship between beach profiles and waves at duck north carolina determined by canonical correlation analysis abstract an 11 year long measurement time series of waves and profiles from duck north carolina was analyzed using canonical correlation analysis cca in order to determine the covariability between waves and profile response the main objectives of this analysis were 1 to detect simultaneously occurring patterns in the wave and profile data and if possible give such patterns a physical interpretation to increase the insight into the governing processes and 2 to investigate the possibility to use cca in a predictive mode with the aim to calculate the profile response from the waves the profile shape itself and the change between consecutively surveyed profiles were correlated with both the offshore deep water and nearshore wave conditions in the offshore the waves were described by composite probability density functions pdf derived based on the measured wave conditions prior to a profile survey nearshore wave conditions were calculated using a random breaker decay model and averaged local wave properties were used as input to the cca the profile response displayed significantly higher correlation with the nearshore wave properties as compared to the offshore waves and the highest correlation was found between the profile shape and the mean ratio of breaking waves for the time period preceding the profile survey the cca using nearshore wave properties indicates a potential for predicting the profile response with an acceptable degree of accuracy once a regression matrix relating the profiles to the waves has been established that represents the typical variability at the site

magnitude and cross shore distribution of bed return flow measured on natural beaches abstract field measurements of cross shore currents 0 25 m from the bed were made on two natural beaches under a range of incident wave conditions the results indicated the presence of a relatively strong offshore directed mean current both within and seaward of the surf zone typical velocities within the surf zone were of the order of 0 2 0 3 m s this bed return flow or undertow represents a mass conservation response returning water seaward that was initially transported onshore in the upper water column primarily above the trough of the incident waves the measurements demonstrated that the bed return flow velocity increases with the incident wave height in addition the crossshore distribution of the bed return flow is characterised by a mid surf zone maximum which exhibits a strong decrease in velocity towards the shoreline and a more gradual decay in the offshore direction several bed return flow models based on mass continuity were formulated to predict the cross shore distribution of the bed return flow under an irregular wave field and were compared with the field data best agreement was obtained using shallow water linear wave theory after including the mass transport associated with unbroken waves the contribution of the unbroken waves enables net offshore directed bottom currents to persist outside the region of breaking waves providing a mechanism other than rip currents to transport sediment offshore beyond the surf zone

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

wave generated flow on coral reefs an analysis for two dimensional horizontal reef tops with steep faces waves breaking on the seaward rim of a coral reef generate a flow of water from the exposed side of the reef to the sheltered side and or to either channels through the reef rim or lower sections of the latter this wave generated flow is driven by the water surface gradient resulting from the wave set up created by the breaking waves this paper reviews previous approaches to modelling wave generated flows across coral reefs and discusses the influence of reef morphology and roughness upon these flows laboratory measurements upon a two dimensional horizontal reef platform with a steep reef face provide the basis for extending a previous theoretical analysis for wave set up on a reef in the absence of a flow gourlay m r 1996b wave set up on coral reefs 2 set up on reefs with various profiles coastal engineering 28 1755 to include the interaction between a unidirectional flow and the wave set up the laboratory model results are then used to demonstrate that there are two basic reef top flow regimes reef top control and reef rim control using open channel flow theory analytical relationships are derived for the reef top current velocity in terms of the offreef wave conditions the reef top water depth and the physical characteristics of the reef top topography the wave set up and wave generated flow relationships are found to predict experimental values with reasonable accuracy in most cases the analytical relationships are used to investigate wave generated flows into a boat harbour channel on heron reef in the southern great barrier reef c 2005 elsevier b v all rights reserved

a numerical model of wave overtopping on seadikes this paper describes the development of a numerical model for wave overtopping on seadikes the model is based on the flux conservative form of the nonlinear shallow water equations nlsw solved with a high order total variation diminishing tvd roe type scheme the goal is to reliably predict the hydrodynamics of wave overtopping on the dike crest and along the inner slope necessary for the breach modelling of seadikes besides the mean overtopping rate the capability of simulating individual overtopping events is also required it is shown theoretically that the effect of wave breaking through the drastic motion of surface rollers in the surfzone is not sufficiently described by the conventional nonlinear shallow water equations neglecting wave setup from the mean water level and thus markedly reducing the model predictive capacity for wave overtopping this is significantly improved by including an additional source term associated with the roller energy dissipation in the depth averaged momentum equation the developed model has been validated against four existing laboratory datasets of wave overtopping on dikes the first two sets are to validate the roller term performance in improving the model prediction of wave overtopping of breaking waves the last two sets are to test the model performance under more complex but realistic hydraulic and slope geometric conditions the results confirm the merit of the supplemented roller term and also demonstrate that the model is robust and reliable for the prediction of wave overtopping on seadikes

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

validation of an advective deterministic approach to short wave breaking in a surf beat model abstract an advective deterministic approach ada to model wave energy dissipation through breaking is presented this is calibrated against experimental irregular wave data with a high spatial density of surface elevation records using a wave group forced surf beat model xbeach in the ada breaker model wave breaking is turned on and off by specifying upper and lower values of the breaker parameter the latter termed wave reforming as in dally et al 1985 and the state of breaking is advected shoreward at the individual wave celerity for the validation of the proposed ada model results are compared with the breaker formulation of roelvink 1993 using 10 prototype field experiment cases and 32 laboratory flume experiment cases the ada breaker model shows good results for short wave height transformation and significant improvement is obtained for the fraction of breaking waves over the roelvink 1993 formulation with the modelled data quantitatively and qualitatively representing measurements it is possible that the ada wave breaking model could influence other surf zone processes such as low frequency wave generation and nearshore circulation patterns

modification of a kenai eddy along the alaskan stream 1 a kenai eddy was studied through analyses of satellite altimeter data and hydrographic data from shipboard and argo float observations this eddy formed in december 2006 south of the kenai peninsula and propagated southwestward along the alaskan stream the eddy held horizontally uniform warm core water in january 2007 in late winter 2007 this core water was cooled from the top and a subsurface temperature maximum was formed around 26 5 two years later in summer 2009 warm and low dissolved oxygen low do water characterized by a temperature maximum around 26 5 was observed again in the eddy core and was likely the remnant of original core water at the same time cold and high do water intrusions occurred in the eddy core suggesting that strong modification of core water was ongoing after summer 2009 the core water was fully changed through interaction with another eddy

the morphodynamics of shore platforms in a micro tidal setting interactions between waves and morphology abstract the interactions between waves and morphology on shore platforms were investigated at four platforms located at kaikoura peninsula new zealand and the otway coast victoria australia waves were measured over six tidal peaks of a spring tidal sequence at each site during a six month period february 2007 july 2007 this paper reports the results of an investigation into the research question how are waves modified by platform morphology in a micro tidal setting through the investigation of wave interactions on shore platforms it was found that complex hydrodynamic patterns formed on the shore platforms studied through direct measurement of waves on the platforms it was found that wave attenuation was not dependent on platform width but rather influenced by platform gradient and depth of water on the platform spectral analysis was used to assess how wave energy was transformed across the platforms at three of the four platforms investigated energy gradients formed across the platform with wave energy recorded within the infragravity range

surf zone transformation of wave height to water depth ratios abstract a solid body of data exists on which to base engineering decisions regarding the maximum wave heights that can be achieved in shallow water at the point of incipient breaking effort is now being directed towards the study of how wave height varies as waves propagate through the surf zone and what parameters control this process early surf zone models assumed a constant value of c while later models incorporate a decay function for h h due to turbulence in the breaking wave a few more recent studies have recognised a second process by which h h can decay through the surf zone where there is a strong underlying infragravity wave motion the work presented here investigates the characteristics of this latter decay process on a natural exposed dissipative beach including its magnitude and dual dependence on local mean water depth and distance from the breaker line some comparisons are then made with the decay characteristics of the former process

a blind folded test of equilibrium beach profile concepts with new zealand data abstract methodology for calculating equilibrium beach profiles for uniform sand size characteristics is extended to the case of an arbitrary distribution of sediment characteristics across the profile the application of this method and comparison with actual profiles is posed as a means of interpreting whether the profile contains a deficit or excess of sediment and thus whether long term shoreline recession or advancement can be anticipated various types of profile disequilibrium are reviewed and the significance discussed the methodology is applied using measured profiles sediment sizes and beach face slopes for ten sites on the northern island of new zealand one profile was documented in this study whereas the data for the other nine were obtained from published sources the number of sediment samples available for each profile varied from three to twelve the agreement between the actual and calculated profiles differs considerably for the ten sites the degree of disequilibrium is quantified by calculating the shoreline adjustment y required for the actual profile to equilibrate for depths less than 7 m which represents the near maximum depth available on all profiles these shoreline adjustments ranged from 105 m recession to 159 m advancement with four of the ten sites having positive values three of the sites with negative shoreline adjustment have been or are presently sites of substantial sand extraction from the beach or in the nearshore waters however the differences between the actual and equilibrium profiles are not consistent with anticipated profile forms and or volumes and it is thus concluded that sand mining is not responsible for most of the observed deficits at this stage it is not possible to state with confidence whether differences between actual and calculated equilibrium profiles are due to true disequilibriums or to limitations in the equilibrium beach profile methodology studies of the type reported here when applied to many different areas will advance the methodology and contribute to the confidence in the resulting interpretations

experimental study of nearshore dynamics on a barred beach with rip channels 1 wave and current measurements are presented from a set of laboratory experiments performed on a fixed barred beach with periodically spaced rip channels using a range of incident wave conditions the data demonstrate that the presence of gaps in otherwise longshore uniform bars dominates the nearshore circulation system for the incident wave conditions considered for example nonzero cross shore flow and the presence of longshore pressure gradients both resulting from the presence of rip channels are not restricted to the immediate vicinity of the channels but instead are found to span almost the entire length of the longshore bars in addition the combination of breaker type and location is the dominant driving mechanism of the nearshore flow and both are found to be strongly influenced by the variable bathymetry and the presence of a strong rip current the depth averaged currents are calculated from the measured velocities assuming conservation of mass across the measurement grid the terms in both the cross shore and longshore momentum balances are calculated and their relative magnitudes are quantified the cross shore balance is shown to be dominated by the cross shore pressure and radiation stress gradients in general agreement with previous results however the rip current is shown to influence the wave breaking and the wave induced setup in the rip channel analysis of the longshore balance shows that the overall strength of the longshore feeder currents is governed by a balance between longshore pressure gradient forcing and an opposing radiation stress gradient in addition the longshore feeder currents show maxima in the bar trough region providing experimental evidence that longshore pressure gradients can shift longshore current maxima shoreward from the bar crest finally since the longshore radiation stress gradient in the surf zone is governed by the amount of wave dissipation on the rip current there exists a positive feedback mechanism whereby a strong rip current can weaken the radiation stress gradient opposing the feeder currents and lead to even stronger feeder currents and rips

the impeller meter for measuring aquifer permeability variations evaluation and comparison with other tests a knowledge of the variation of horizontal hydraulic conductivity with vertical position k z is important in understanding the transport and dispersive properties of aquifers using an impeller meter to measure the discharge distribution in a screened well while pumping at a constant rate is a promising technique for obtaining the k z function such an application is described herein and the resulting k z functions are compared with those obtained previously using tracer tests and multilevel slug tests impeller meter data were the most convenient to obtain and tracer data the most difficult the k z functions obtained by the three methods were not identical but quite similar overall this similarity between both borehole tests and the larger scale tracer test showed that nonstationary hydraulic conductivity trends in a stochastic hydrologic sense exist in the test aquifer the impeller meter method was better able to detect the higher k layers than was the multilevel slug approach overall the results suggest that a practical strategy for fitting impeller meter tracer or multilevel slug test data to a given aquifer is to use the selected testing procedure to obtain a dimensionless distribution and then a standard pumping test to measure combining both types of information enables dimensional values for k z to be calculated in low permeability aquifers or near the bottom of a test well the fluid velocity due to pumping may be below the stall velocity of an impeller thus there is a definite need for the commercial development of more sensitive flow measuring devices such as heat pulse flowmeters hess 1986 which will extend the resolution of this field method

equilibrium beach profile model for perched beaches abstract a beach profile equilibrium model for perched beaches is presented the model assumes that wave reflection at the seaward and leeward sides of the breakwater is the most important process that modifies dean s equilibrium profile model for non perched beaches the influence of wave breaking over the submerged structure is also discussed several laboratory data sets are used to analyze the merit of the proposed model for describing the equilibrium condition of a perched beach a good comparison is obtained results show that if the ratio between the water depth above the submerged structure d and the water depth at the toe of the structure h e is large d h e 0 5 only minor advance of the shoreline is achieved with the construction of a toe structure a considerable advance is obtained for d h e less that 0 1 in these situations however resonant effects may result in an inefficient structure the proposed model is used to provide an estimation for the required sand volume and the associated beach advance for the case of narrow breakwaters

hydrodynamic and morphodynamic response of isolated and multiple low crested structures experiments and simulations abstract low crested structures for beach defence purposes are frequently configured in the form of cells this paper investigates the hydrodynamic and morphological response of such defence schemes by means of laboratory experiments and numerical simulations experiments were carried out at the large mobile bed basin of the laboratorio di idraulica costiera of the politecnico di bari it tests peculiarity is the simultaneous simulation of three different types of lateral confinement a channel representative of an indefinitely long structure and two areas with narrow and wide gaps representative of a common scheme and of an almost isolated structure respectively submerged zero freeboard and emerged conditions were tested a typical storm of the northern adriatic sea was reproduced by 6 wave attacks water level and currents were measured in front and behind the structures at gaps and roundheads results focusing on rip current intensities and piling up are presented and discussed an extensive plan view of wave intensities and flow patterns inside the basin is provided through numerical simulations with mike 21 numerical suite the sand bed was surveyed along 30 profiles covering the narrow gap area and the isolated structure roundheads for the submerged conditions tests 15 of these profiles and the shoreline position were monitored after each step of the simulated storm average and maximum values of local erosion at the structure toe are presented time evolution of erosion at gaps is related to the main hydrodynamic variables through bijker sediment transport formula evaluation of volume changes in the protected area shows that sand is in average trapped behind the barriers being transported offshore from gaps and returning inshore over the crest the observed and reconstructed transport mechanism is a combination of bed load and suspended transport the latter being slightly more important bed level changes are well predicted by morphodynamic simulations performed with mike 21 cams

the shedding of mesoscale anticyclonic eddies from the alaskan stream and westward transport of warm water abstract the south flowing waters of the kamchatka and oyashio currents and west flowing waters of the alaskan stream are key components of the western sub arctic pacific circulation we use ctd data argo buoys woce surface drifters and satellite derived sea level observations to investigate the structure and interannual changes in this system that arise from interactions among anticyclonic eddies and the mean flow variability in the temperature of the upstream oyashio and kamchatka currents is evident by warming in mesothermal layer in 1994 2005 compared to 1990 1991 a major fraction of the water in these currents is derived directly from the alaskan stream the stream also sheds large anticyclonic aleutian eddies averaging approximately 300 km in diameter with a volume transport significant in comparison with that of the kamchatka current itself these eddies enclose pools of relatively warm and saline water whose temperature is typically 4 c warmer and salinity is 0 4 greater than that of cold core kamchatka eddies in the same density range aleutian eddies drift at approximately 1 2 km d 1 and retain their distinctive warm and salty characteristics for at least 2 years selected westward pathways during 1990 2004 are identified if the shorter northern route is followed aleutian eddies remain close to the stream and persist sufficiently long to carry warm and saline water directly to the kamchatka current this was observed during 1994 1997 with substantial warming of the waters in the kamchatka current and upstream oyashio if the eddies take a more southern route they detach from the stream but can still contribute significant quantities of warm and saline water to the upstream oyashio as in 2004 2005 however the eddies following this southern route may dissipate before reaching the western boundary current region

the unsteady nature of sea cliff retreat due to mechanical abrasion failure and comminution feedbacks sea cliff retreat is often linked to large waves heavy precipitation and seismic events but the specific operative mechanics have not been well constrained in particular what is the role of mechanical abrasion by beach sediments in cliff platform evolution and how does it relate to the episodic nature of cliff retreat observed at certain locations here we present a simple numerical model of sea cliff retreat that incorporates mechanical abrasion of a basal notch threshold controlled failure of the cantilevered block and a feedback mechanism wherein retreat is dependent on the rate of sediment comminution within the surf zone using shore platform and cliff characteristics found in two coastal settings the central california coast and the english north sea coast the model produces retreat rates comparable to those observed via field measurements the highest retreat rates coincide with the steepest shore platforms and increasing wave height steeper platforms promote wave access to the cliff toe and correspondingly the receding cliff face produces additional accommodation space for the platform beach preserving the erosive efficacy of the beach sediments when exposed to energetic wave forcing the slope of the inner platform segment controls retreat rates for concave platforms whereas the slope of the outer platform segment exerts greater control for convex platforms platform beaches approached a long term dynamic equilibrium on the concave profiles leading to more consistent and steady retreat platform beaches were ephemeral on convex profiles mirroring observed sand wave ord migration on the holderness coast uk these findings agree with previous field observations and support mechanical abrasion as a viable cause of temporal heterogeneity in cliff retreat rate for both coastlines

mesoscale eddies dominate surface phytoplankton in northern gulf of alaska abstract the hnlc waters of the gulf of alaska normally receive too little iron for primary productivity to draw down silicate and nitrate in surface waters even in spring and summer our observations of chlorophyll sensed by seawifs north of 54 n in pelagic waters 500 m depth of the gulf found that on average more than half of all surface chlorophyll was inside the 4 cm contours of anticyclonic mesoscale eddies the ratio approaches 80 in spring months yet these contours enclosed only 10 of the total surface area of pelagic waters in the gulf therefore eddies dominate the chlorophyll and phytoplankton distribution in surface pelagic waters we outline several eddy processes that enhance primary productivity eddies near the continental margin entrain nutrient and fe rich and chlorophyll rich coastal waters into their outer rings advecting these waters into the basin interior to directly increase phytoplankton populations there in addition eddies carry excess nutrients and iron in their core waters into pelagic regions as they propagate away from the continental margin as these anticyclonic eddies decay their depressed isopycnals relax upward injecting nutrients up toward the surface layer we propose that this transport brings iron and macro nutrients toward the surface mixed layer where they are available for wind forced mixing to bring them to surface these mesoscale eddies decay slowly but steadily perhaps providing a relatively regular upward supply of macro nutrients and iron toward euphotic layers they might behave as isolated oases of enhanced marine productivity in an otherwise iron poor basin we note that much of this productivity might be near or just below the base of the surface mixed layer and therefore poorly sampled by colour sensing satellites it is possible then that eddies enrich phytoplankton populations to a greater extent than noted from satellite surface observations only

global observations of large oceanic eddies 1 ten years of sea surface height ssh fields constructed from the merged topex poseidon t p and ers 1 2 altimeter datasets are analyzed to investigate mesoscale variability in the global ocean the higher resolution of the merged dataset reveals that more than 50 of the variability over much of the world ocean is accounted for by eddies with amplitudes of 5 25 cm and diameters of 100 200 km these eddies propagate nearly due west at approximately the phase speed of nondispersive baroclinic rossby waves with preferences for slight poleward and equatorward deflection of cyclonic and anticyclonic eddies respectively the vast majority of the eddies are found to be nonlinear

mathematical modeling of the fate of beach fill abstract this paper describes mathematical approaches for calculating the fate of beach fill under wave action general properties of the spatial and temporal behavior of fills under average longshore sand transport conditions are first reviewed through use of simple closed form solutions of the sediment continuity equation this well known solution procedure is then extended to describe the collective movement of sediment or longshore sand waves because of the increasing use of beach fills as storm protection barriers the paper focuses on prediction of storm induced beach erosion an empirically based model is described and tested with a high quality field data set of storm induced beach erosion one synthetic tropical storm and one synthetic extratropical storm representing typical mid atlantic storms with approximate 2 5 year return period are then used to simulate the erosion of two hypothetical beach fill configurations and the subsequent post storm recovery process eroded volume and contour movement are evaluated as a function of storm type fill cross section grain size and time quantitative and qualitative features of storm erosion are reasonably well reproduced and calculated changes in beach fills impacted by the synthetic storms indicate that little erosion protection benefit is gained for moderate storms 2 5 year return period by placing fills with grain sizes greater than 0 4 mm simulation of post storm beach recovery is presently limited to qualitative reproduction of observed trends

transmission of obliquely incident waves at low crested breakwaters theoretical interpretations of experimental observations the paper presents a series of analytical and numerical investigations of oblique wave transmission at low crested breakwaters for a smooth breakwater two important features of wave height and direction are analyzed to establish the generic nature of the wave transmission process at oblique incidence the proposed framework of research is validated against laboratory data from the eu sponsored project delos the numerical simulations exhibit a significant decrease of the transmission coefficient with increasingly oblique incidence at a smooth breakwater the roles of wave breaking nonlinearity wave induced currents and set up in determining the characteristics of oblique wave transmission are demonstrated in the paper it is found that both the amplitude dependent phase velocity and the decrease of mean wave period contribute to the change of mean wave direction on the transmission side an attempt has also been made to qualitatively explain the different behaviour of oblique wave transmission at a rubble mound breakwater

wave loads on rubble mound breakwater crown walls abstract crown walls are primarily built to reduce wave overtopping of mound breakwaters several methods have been proposed to calculate wave loads on the crown wall e g iribarren and nogales iribarren r nogales c 1964 obras maritimas dossat ed madrid 376 pp jensen jensen o j 1984 a monograph on rubble mound breakwaters danish hydraulic institute and gunbak and gokce gunbak a r gokce t 1984 wave screen stability of rubble mound breakwaters international symposium of maritime structures in the mediterranean sea athens greece pp 2 99 2 112 in this paper a new method based on those previous results and on further experimental work using monochromatic waves is presented the application of the new method requires waves breaking on the armour layer i e only broken waves will reach the crown wall the method is extended to irregular waves via the hypothesis of equivalence introduced by saville saville t 1962 an approximation of the wave run up frequency distribution proc 8th international conference on coastal engineering mexico city and is applied to the crown walls of gijon and bilbao breakwaters in spain the comparison of the probability force distributions obtained by the present method to that measured by burcharth et al burcharth h f frigaard p berenguer j m gonzalez b uzcanga j villanueva j 1995 design of the ciervana breakwater bilbao in t telford ed proc 4th coastal structures and breakwaters chap 3 institution of civil engineers and jensen 1984 is relatively good

longshore current on a barred beach field measurements and calculation measurements of the longshore current on a barred beach made during the 1990 duck experiment on low frequency and incident band longshore and across shore hydrodynamics delilah field data collection project conducted at duck north carolina revealed an unexpected and persistent broad peak in the current velocity in the trough between the nearshore bar and the shore this paper introduces longshore current and associated wave measurements from delilah together with a numerical model capable of describing the field observations an existing numerical model of the mean current is modified to include a general transport equation for the mean turbulent kinetic energy created by wave breaking and reynolds stress components needed to calculate the longshore current and mean water level are reexpressed to include the turbulent momentum transport in comparison to predictions from the original model the modified model produces much improved agreement with the measured current velocity on the barred profiles in the field measurements and with the velocity profile and mean water level generated on a uniformly sloping laboratory beach by monochromatic waves three forms of a bottom friction coefficient are examined and the open channel flow manning friction coefficient is selected because of best agreement and consistency values of the manning friction coefficient required to calibrate the model agree with values normally assigned to the related bottom roughness in open channel flow

wave transformation in the nearshore zone a review this paper reviews works related to nearshore wave propagation with an emphasis on several aspects related to coastal morphodynamic modelling including randomness and directionality of waves energy transfer and dissipation in the surf zone shallow water non linearities and long period motions the first part briefly reviews four main issues in laboratory experiments and field campaigns the second part is devoted to spectral and probabilistic approaches then recent developments of advanced numerical models based on boussinesq equations are reviewed the last part is devoted to low frequency waves and vortical motions

vertical and horizontal structure in cross shore flows an example of undertow and wave set up on a barred beach greenwood b and osborne p d 1990 vertical and horizontal structure in cross shore flows an example of undertow and wave set up on a barred beach coastal eng 14 543 580 eulerian measurements of the horizontal cross shore velocity field in the lowermost meter of the water column in association with measurements of waves and the mean elevation of the water surface across a nontidal low relief barred surf zone reveal a spatially coherent patterns of the timeaveraged first second and third moments of the velocity field which vary temporally in direct response to the incident waves b large asymmetries in the flow field with offshore directed mean flows upto 0 20 m s a and onshore directed velocity skewness the third moment normalized by the standard deviation upto 0 60 c mean flows decrease and oscillatory flows measured by the standard deviation of the velocity field increase towards the water surface d a fourth order polynomial provides the best fit to the cross shore set up reflecting the influence of variable energy dissipation due to topographic controls on wave breaking e significant linear correlations exist between the cross shore mean velocities and the maximum set up of the still water surface near to the shoreline upto 82 of the observed variability in the former can be accounted for by linear regressions f set up is highly correlated with the incident wave height 86 of the observed variability in the former can be accounted for by a linear regression g gradients in the mean water surface are significantly less than those predicted by a linear function of beach slope as originally proposed by bowen et al even using an appropriate breaking criterion 0 4 0 6 for the spilling breakers recorded cross shore circulation over the low relief barred nearshore slope is predominantly two dimensional over the outer bar in this case study the near bed mean flow is an undertow responding to the balance between the wave generated depth dependent momentum flux directed onshore the stress induced by the onshore mass transport under waves and wind and the hydraulic pressure gradient induced by set up of the mean water level

satellite and hydrographic observations of eddy induced shelf slope exchange in the northwestern gulf of alaska 1 satellite and hydrographic observations of oceanographic conditions in the northwestern gulf of alaska indicate that anticyclonic eddies propagating adjacent to the continental shelf alter the structure of the shelf break front and in doing so influence the shelf slope exchange of biota and water mass properties eddies typically form in the northern gulf of alaska during fall and winter and propagate southwestward within an 200 km wide corridor along and above the continental slope eddy activity within this corridor diminishes in the downstream direction the trajectories of faster propagating 4 km day eddies tend to lie closer to the shelf break than do the trajectories of slower propagating 1 5 km day eddies the interaction between azimuthal eddy currents and the shelf break frontal jet 1 establishes an upwelling zone associated with the leading flank of the eddy that strengthens cross slope gradients 2 weakens cross slope gradients and promotes shelf slope exchange where the eddy is adjacent to the shelf and 3 reestablishes a weak upwelling zone associated with the trailing flank of the eddy

evolution and modulation of a poleward propagating anticyclonic eddy along the japan and kuril kamchatka trenches to investigate the relationships between the movement of an eddy and its interior structure and water properties four profiling floats were deployed in an anticyclonic eddy in the western north pacific in 2013 april october daily float profiles showed rapid changes in temperature and salinity corresponding to strong interactions between eddies north of the subtropical kuroshio extension after the first interaction with a warm core eddy in april the isolation of the winter mixed layer from the surface was observed forming a subsurface remnant layer another interaction with a cold fresh eddy at middepths in may resulted in the formation of a multilayer structure the eddy then moved poleward along the japan and kuril kamchatka trenches indicating changes in its propagation pattern coupled to its interior structure the eddy then moved northward june july stalled july august and moved eastward august october in addition to a general declining trend the properties of the warm saline core changed over a short time period coinciding with changes in propagation a density anomaly at middepths of the eddy changed location during the stalled period however denser waters were continuously observed in the southeast part of the eddy during its northward and eastward movement this unidirectional density anomaly pattern was consistent with the structure of the poleward propagating eddy which interacted with the western topographic boundary meridional exchanges of heat and material were potentially elevated by the eddy s advection and movement as well as by water modifications in the eddy associated with exchanges along its perimeter

intertidal sand body migration along a megatidal coast kachemak bay alaska 1 using a digital video based argus beach monitoring system abms on the north shore of kachemak bay in south central alaska we document the timing and magnitude of alongshore migration of intertidal sand bed forms over a cobble substrate during a 22 month observation period two separate sediment packages sand bodies of 1 2 m amplitude and 200 m wavelength consisting of well sorted sand were observed to travel along shore at annually averaged rates of 278 m yr 0 76 m d and 250 m yr 0 68 m d respectively strong seasonality in migration rates was shown by the contrast of rapid winter and slow summer transport though set in a megatidal environment data indicate that sand body migration is driven by eastward propagating wind waves as opposed to net westward directed tidal currents greatest weekly averaged rates of movement exceeding 6 m d coincided with wave heights exceeding 2 m suggesting a correlation of wave height and sand body migration because kachemak bay is partially enclosed waves responsible for sediment entrainment and transport are locally generated by winds that blow across lower cook inlet from the southwest the direction of greatest fetch our estimates of sand body migration translate to a littoral transport rate between 4 400 6 300 m3 yr assuming an enclosed littoral cell minimal riverine sediment contributions and a sea cliff sedimentary fraction of 0 05 we estimate long term local sea cliff retreat rates of 9 14 cm yr applying a numerical model of wave energy dissipation to the temporally variable beach morphology suggests that sand bodies are responsible for enhancing wave energy dissipation by 13 offering protection from sea cliff retreat

anticyclonic eddies in the alaskan stream abstract anticyclonic eddies propagating southwestward in the alaskan stream as were investigated through analysis of altimetry data from satellite observations during 1992 2006 and hydrographic data from profiling float observations during 2001 06 fifteen long lived eddies were identified and categorized based on their area of first appearance three eddies were present at the beginning of the satellite observations another three formed in the eastern gulf of alaska off sitka alaska and four were first detected at the head of the gulf of alaska near yakutat alaska the other five eddies formed along the as between 157 and 169 w and were named as eddies while the eddies that formed in the gulf of alaska mainly decayed before exiting the gulf of alaska the as eddies mostly crossed the 180 meridian and reached the western subarctic gyre four of five as eddies formed under negative or weakly positive wind stress curls which possibly caused as separation from the coast comparison of eddy propag

numerical simulation of nearshore circulation on field topography under random wave environment abstract in order to investigate surf zone hydrodynamics through two dimensional numerical simulations of nearshore circulation under random wave environment a nearshore circulation model shorecirc and a random wave model swan were combined and utilized using this combined model a numerical simulation of the october 2 1997 sandyduck field experiment was performed for this simulation field topography and an input offshore spectrum were constructed using observed data sets synchronized with the experiment the wave breaking model in swan was modified by using breaker parameters varied according to bottom slope the simulation results were compared with the experimental data which revealed a well developed longshore current as well as with results using other combinations which were shorecirc and its original monochromatic wave driver and shorecirc and the default of swan the results from the novel combined model agreed well with the experimental data the results of the present simulation also indicate that alongshore field topography influences shear fluctuation of longshore currents

observations of a kenai eddy and a sitka eddy in the northern gulf of alaska 1 mesoscale eddies in the gulf of alaska are thought to contribute to the shelf slope exchange of nutrients and plankton enhancing biological production we report on a study of two anticyclonic mesoscale eddies in this region observed through in situ sampling during august and september 2007 both eddies exhibited in their cores s profiles with warmer fresher water relative to the properties of the ambient basin water between 150 and 300 m depths hydrographic properties and satellite altimetry data were analyzed to identify likely formation regions for each feature one eddy sampled near yakutat alaska originated in the sitka formation region 221 223 e the second eddy sampled south of kodiak island originated near the kenai peninsula southeast of the kennedy and stevenson entrances to cook inlet an area not previously studied as a formation region subsequent analysis of 16 years of satellite altimeter data from 1992 to 2008 with an algorithm designed to identify and track eddies revealed approximately six kenai eddies that have formed in this region although this number constitutes only 3 2 of the 188 eddies identified by the algorithm during this period it represents 15 4 of the 39 eddies that formed in or propagated westward into the alaskan stream

one dimensional modelling of individual waves and wave induced longshore currents in the surf zone a probabilistic model wavis model was developed to describe the propagation and transformation of individual waves wave by wave approach the individual waves shoal until an empirical criterion for breaking is satisfied wave height decay after breaking is modelled by using an energy dissipation method wave induced set up and set down and breaking associated longshore currents are also modelled laboratory and field data were used to calibrate and verify the model the model was calibrated by adjusting the wave breaking coefficient as a function of local wave steepness and bottom slope to obtain optimum agreement between measured and computed wave height four tests carried out in the large delta flume of delft hydraulics were considered generally the measured h13 wave heights are reasonably well represented by the model in all zones from deep water to the shallow surf zone the fraction of breaking waves was reasonably well represented by the model in the upsloping zones of the bottom profile verification of the model results with respect to wave induced longshore current velocities was not extensive because of a lack of data in case of a barred profile the measured longshore velocities showed a relatively uniform distribution in the trough zone between the bar crest and the shoreline which could to some extent be modelled by including space averaging of the radiation force gradient horizontal mixing and longshore water surface gradients related to variations in set up in case of a monotonically upsloping profile the cross shore distribution of the longshore current velocities is reasonably well represented

cross shore hydrodynamics within an unsaturated surf zone abstract this paper concerns the hydrodynamics induced by random waves incident on a steep beach new experimental results are presented on surface elevation and kinematic probability density functions cross shore variation in wave heights the fraction of broken waves and velocity moments the surf zone is found to be unsaturated at incident wave frequencies with a significant proportion of the incident wave energy remaining at the shoreline in the form of bores wave heights in both the outer and inner surf zones are best described by a full rayleigh distribution thornton e b guza r t 1983 transformation of wave height distribution j geophys res 88 5925 5938 rather than a truncated rayleigh distribution as used by battjes and janssen 1978 battjes j a janssen j p 1978 energy loss and setup due to breaking of random waves proc 16th int conf coastal eng asce new york pp 569 588 a new parametric wave transformation model is outlined which provides explicit expressions for the fraction of broken waves and the energy dissipation rate within the surf zone on steep beaches the model appears to offer improved predictive capabilities over the original battjes and janssen model cross shore variations in the velocity variance and velocity moments are best described using linear gaussian wave theory with less than 20 of the velocity variance in the inner surf zone due to low frequency energy

random breaking waves field verification of a wave by wave algorithm for engineering application abstract a simple numerical algorithm is utilized to test the wave by wave approach to modeling random wave transformation caused by shoaling breaking and reforming across nearshore profiles of arbitrary shape histograms of wave height and associated statistics predicted by the model show favorable comparison to measurements from the nine tests of the duck 85 field experiment with a root mean square error less than 10 for most wave statistics although suitable for use in many engineering applications the model does overpredict the number of waves that reform as they pass over a trough formation which is one facet that warrants improvement using the model predictions as a point of reference the qualitative effects of 1 an offshore wind 2 wave reflection and 3 surf beat are identified and discussed

a boussinesq model for waves breaking in shallow water abstract a simple description of wave breaking in shallow water is incorporated in the boussinesq equations by using the concept of surface rollers the roller is considered as a volume of water being carried by the wave with the wave celerity the effect of the roller is included in the vertical distribution of the horizontal velocity which leads to an additional convective momentum term the breaking criterion is related to the local slope of water surface and the thickness of the roller is determined from simple geometrical considerations although the model is simple it is capable of representing a variety of processes such as the initiation and cessation of wave breaking the evolution of wave profiles before during and after wave breaking the initial conversion of potential energy into forward momentum flux and the associated horizontal shift between the break point and the point where the setup in mean water level is initiated results are presented for regular and irregular wave trains and comparison with measurements shows good agreement

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

an eddy resolving model of circulation on the western gulf of alaska shelf 2 comparison of results to oceanographic observations currents generated by an eddy resolving semispectral primitive equation model are compared with those measured by moored current meters 1989 and 1991 and satellite tracked drifting buoys 1987 from shelikof strait alaska the model reproduced many of the dominant circulation features including the cross sectional spatial structure of the alaskan coastal current the estuarine inflow at the bottom of the sea valley and the mean transport the first mode empirical orthogonal functions of the model and of the observed data represent similar spatial structures and were significantly correlated in time while the model produced eddies 20 km diameter at a similar rate as observed the timing did not generally match the observations as a result correlations between the measured currents and model generated currents usually were not significant correlations between modeled and measured transport through the sea valley however were significant for both years

comment on a natural gradient experiment on solute transport in a sand aquifer spatial variability of hydraulic conductivity and its role in the dispersion process by e a sudicky

a numerical model of beach morphological evolution due to waves and currents in the vicinity of coastal structures a numerical model was developed of beach morphological evolution in the vicinity of coastal structures the model includes five sub models for random wave transformation surface roller development nearshore wave induced currents sediment transport and morphological evolution the model was validated using high quality data sets obtained during experiments with a t head groin and a detached breakwater in the basin of the large scale sediment transport facility at the coastal and hydraulics laboratory in vicksburg miss usa the simulations showed that the model reproduced well the wave conditions wave induced currents and beach morphological evolution in the vicinity of coastal structures both salient and tombolo formation behind a t head groin and a detached breakwater were simulated with good agreement compared to the measurements c 2011 elsevier b v all rights reserved

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