climate fluctuations of the weddell sea and its surroundings in a transient climate change scenario the response of the weddell sea and antarctic peninsula to anthropogenic forcing simulated by a global climate model is analyzed the model despite its low resolution is able to capture several aspects of the observed regional pattern of climate change a strong warming and depletion of the sea ice cover in the western weddell sea contrasts with a slight cooling and a sea ice extension in the eastern weddell sea this simulated long term climate change is modulated by interdecadal variability but also affected by some abrupt regional changes in the oceanic mixed layer depth between 1960 and 2030 a reorganization of the deep convection activity in the weddell sea sustains the opposition between the eastern and western weddell sea the deep convection collapses in the western weddell sea in the 2030s the sea ice retreat trend is then followed by an increase of the sea ice cover in the western weddell sea in the eastern weddell sea another abrupt collapse of the deep convection activity occurs around 2080 this event is followed by a rapid cooling and sea ice extension during the next 20 years most of the surface changes are associated with large scale atmospheric circulation changes that project on the dominant mode of natural variability but also with oceanic convection and circulation changes

intersite comparison of interannual nearshore bar behavior 1 long term years bathymetric data sets collected in six multiple near shore sandbar systems were analyzed with complex empirical orthogonal function analysis to quantify intersite differences and similarities in cyclic offshore progressive bar behavior the observations came from a 37 year annually sampled data set of four regions along the dutch coast spanning 70 km of coastline an 18 year fortnightly to monthly sampled data set at duck north carolina alongshore extent 1 km and a 7 year daily sampled data set of a single cross shore profile at the hasaki coast of japan the first complex mode typically representing 50 70 of the total depth variance described the long term offshore progressive behavior and allowed for an objective separation of the barred part of the profile from the shoreward and seaward located nonbarred parts by considering a threshold bar amplitude below which the spatial results from the first mode were not considered reliable the sandbars at the six examined sites share common lengths and nondimensional amplitude characteristics which can be described by a negatively skewed gaussian function the absolute amplitude dimensions and the cycle return intervals differ however considerably between the sites the key geometric parameters that steer this intersite variation are the time averaged mean depths at the shoreward and seaward side of the bar zone shore and sea respectively as well as their difference bz the degree to which intersite differences in shore sea and bz are related linearly to intersite differences in bulk statistics of external forcings wave tide sediment and bed profile characteristics is inconclusive

physical modeling of intermediate cross shore beach morphology transients and equilibrium states laboratory experiments on cross shore beach morphodynamics are presented a lightweight sediment density rho s 1 19 g cm 3 model is used in order to fulfill a shields number and rouse number scaling this choice aims at correctly reproducing bed load transport as well as suspension dynamics terraces and barred beach profiles obtained in the experiments also present close similarities with profiles observed in the field in order to question the concept of equilibrium beach profile wave forcings conforming to a jonswap spectrum were imposed over long periods up to more than a hundred hours an average bottom evolution velocity is defined and used to determine when the profile reaches equilibrium usually beach profiles are characterized according to the wright and short 1984 classification based on the dean number w this well known classification is investigated and refined in the intermediate range that is for 1 omega 5 for w close to 1 a typical reflective profile is obtained terraces are obtained for the omega 2 5 cases for omega approximate to 3 7 the profiles exhibit two parts a mild dissipative offshore slope producing low reflection and a steeper beach face with slightly higher reflection the wave dissipation velocity skewness and acceleration skewness are computed from the free surface elevation time series the dissipation and wave nonlinearities patterns are similar for similar equilibrium beach profiles that is with the same dean number dissipation peaks coincide with bottom slope transitions as higher energy dissipation occurs with milder bottom slope sections besides the uniformity of volumetric wave energy dissipation seems to concern only a limited zone of beaches with a widely developed surf zone

study of the impact of ice formation in leads upon the sea ice pack mass balance using a new frazil and grease ice parameterization abstractleads are cracks in sea ice that often form because of deformation during winter months leads expose the ocean to the cold atmosphere resulting in supercooling and the formation of frazil ice crystals within the mixed layer here the authors investigate the role of frazil ice formation in leads on the mass balance of the sea ice pack through the incorporation of a new module into the los alamos sea ice model cice the frazil ice module considers an initial cooling of leads followed by a steady state formation of uniformly distributed single size frazil ice crystals that precipitate to the ocean surface as grease ice the grease ice is pushed against one of the lead edges by wind and water drag that the authors represent through a variable collection thickness for new sea ice simulations of the sea ice cover in the arctic and antarctic are performed and compared to a model that treats leads the same as the open ocean the processes of ice formation in the new module slow down the refreezing o

physical structural and isotopic characteristics and growth processes of fast sea ice in lutzow holm bay antarctica a sea ice ocean study was conducted off queen maud land and enderby land antarctica from 1990 to 1991 by the japanese antarctic research expedition observations of multiyear land fast sea ice were made in lutzow holm bay over a period of 2 years to determine the snow and ice characteristics and ice growth processes the snow depth in the bay reached large values of 1 0 to 1 5 m during the winter season at offshore locations from the analysis of ice thickness measurements it is confirmed that the fast ice with deep snow cover grew little in winter but substantially thickened during the summer months on the basis of ice core structure salinity and stable isotopic composition we conclude that the summer growth was caused by upward growth at the top of the ice to which snow ice and superimposed ice formation contribute these processes were the primary contributors to sea ice growth and characteristics only where the snow accumulation was large in areas of low snow accumulation there was no surface growth superimposed ice formation on sea ice in antarctica has not been reported previously evidence for snow cover melting which is a prerequisite for superimposed ice formation was also found

modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates abstract a parallel ocean and ice model poim in generalized orthogonal curvilinear coordinates has been developed for global climate studies the poim couples the parallel ocean program pop with a 12 category thickness and enthalpy distribution ted sea ice model although the poim aims at modeling the global ocean and sea ice system the focus of this study is on the presentation implementation and evaluation of the ted sea ice model in a generalized coordinate system the ted sea ice model is a dynamic thermodynamic model that also explicitly simulates sea ice ridging using a viscous plastic rheology the ted model is formulated such that all the metric terms in generalized curvilinear coordinates are retained following the pop s structure for parallel computation the ted model is designed to be run on a variety of computer architectures parallel serial or vector when run on a computer cluster with 10 parallel processors the parallel performance of the poim is close to that of a correspon

experimental shock decomposition of siderite and the origin of magnetite in martian meteorite alh 84001 shock recovery experiments to determine whether magnetite could be produced by the decomposition of iron carbonate were initiated naturally occurring siderite was first characterized by a variety of techniques to be sure that the starting material did not contain detectable magnetite samples were shocked in tungsten alloy holders w 90 ni 6 cu 4 to further ensure that any iron phases in the shock products were contributed by the siderite rather than the sample holder each sample was shocked to a specific pressure between 30 to 49 gpa transformation of siderite to magnetite as characterized by tem was found in the 49 gpa shock experiment compositions of most magnetites are 50 fe 2 in the octahedral site of the inverse spinel structure magnetites produced in shock experiments display the same range of sizes 50 100 nm compositions 100 magnetite to 80 magnetite 20 magnesioferrite and morphologies equant elongated euhedral to subhedral as magnetites synthesized by golden et al 2001 and as the magnetites in martian meteorite allan hills alh 84001 fritz et al 2005 previously concluded that alh 84001 experienced 32 gpa pressure and a resultant thermal pulse of 100 110 c however alh 84001 contains evidence of local temperature excursions high enough to melt feldspar pyroxene and a silica rich phase this 49 gpa experiment demonstrates that magnetite can be produced by the shock decomposition of siderite as a result of local heating to 470 c therefore magnetite in the rims of carbonates in martian meteorite alh 84001 could be a product of shock devolatilization of siderite as well

shock temperatures of sio2 and their geophysical implications the temperature of sio 2 in high pressure shock states has been measured for samples of single crystal quartz and fused quartz pressures between 60 and 140 gpa have been studied using projectile impact and optical pyrometry techniques at lawrence livermore national laboratory both data sets indicate the occurrence of a shock induced phase transformation at 70 and 50 gpa along the and fused quartz hugoniots respectively the suggested identification of this transformation is the melting of shock synthesized stishovite with the onset of melting delayed by metastable superheating of the crystalline phase some evidence for this transition in conventional shock wave equation of state data is given and when these data are combined with the shock temperature data it is possible to construct the stishovite liquid phase boundaries the melting temperature of stishovite near 70 gpa pressure is found to be 4500 k and melting in this vicinity is accompanied by a relative volume change and latent heat of fusion of 2 7 and 2 4 mj kg respectively the solid stishovite hugoniot centered on quartz is well described by the linear shock velocity particle velocity relation u s 1 822 up 1 370 km s while at pressures above the melting transition the hugoniot centered on quartz has been fit with u s 1 619 u p 2 049 km s up to a pressure of 200 gpa the melting temperature of stishovite near 100 gpa suggests an approximate limit of 3500 k for the melting temperature of sio 2 bearing solid mantle mineral assemblages all of which are believed to contain si 4 in octahedral coordination with o 2 thus 3500 k is proposed as an approximate upper limit to the melting point and the actual temperature in the earth s mantle moreover the increase of the melting point of stishovite with pressure at 70 gpa is inferred to be 11 k gpa using various adiabatic temperature gradients in the earth s mantle and assuming creep is diffusion controlled in the lower mantle the current results could preclude an increase of viscosity by more than a factor of 10 3 with depth across the mantle

effect of hydrodynamics and bathymetry on video estimates of nearshore sandbar position remote sensing of wave breaker patterns clearly visible as high intensity bands in time exposure video images has become a powerful tool to obtain large scale kilometers and long term years time series of nearshore sandbar position however intensity based bar crest positions xi differ from directly measured positions xb by a time varying distance x which is of o 10 m and depends on the offshore wave height h0 the water level 0 and the bathymetry itself the effect of these parameters on x was investigated from simultaneous video observations and bathymetric surveys obtained in the double barred system at egmond aan zee netherlands and from wave model predictions assuming that the roller energy represents image intensity when the wave field over a bar was predicted to be nonsaturated xi was observed and predicted to move offshore as either 0 decreased or h0 increased under saturated conditions x only responded to changes in 0 additional model investigations showed that an increase in outer bar crest depth similar to that observed during interannual bar behavior significantly reduced the x variability at the outer bar and increased the x variability at the inner bar implications of our observational and model findings for studying sandbar position from video imagery are outlined

beach cusp morphodynamics detailed measurements of three dimensional beach cusp morphology were made on a steep gradient low energy microtidal beach in perth western australia during the field campaign a variety of wave conditions and tidal ranges were experienced and these differing hydrodynamic conditions were reflected in a consistent pattern of morphological changes to the beach cusp system a useful parameter to delineate between trends of cusp destruction and re formation appeared to be the surf similarity parameter tan i0 l0 where h0 is offshore wave height l0 is deep water wave length and tan is beach gradient for 1 2 a small storm was experienced at the start of the field campaign period and resulted in considerable erosion of the beach face the cusp morphology across the lower beachface was destroyed but a subtle remnant of the pre storm cusp morphology was preserved on the upper beachface when cusps reformed after the storm under the influence of declining wave conditions they appeared at the same location and with the same dimensions as the pre storm cusp morphology hence it is considered that the cusp re formation was controlled more by the antecedent morphology than the hydrodynamic conditions this indicates that positive feedback between swash hydrodynamics and beachface morphology necessary to form beach cusps does not require a large variation in relief 1997 john wiley sons ltd

shock compression and isentropic release of granite summary new equation of state data for a weathered granite shocked to about 125 gpa are reported and combined with the westerly granite data of mcqueen marsh fritz 1967 the shock velocity us particle velocity up relations can be fitted with two linear regressions us 4 40 0 6up for a range of up up to about 2 km s 1 and us 2 66 1 49up for a range of about 2 to 5 km s 1 the third order birch murnaghan equation of state parameters are kos 51 57 gpa and k os 1 4 1 8 for the low pressure regime and kos 251 30 gpa and an assumed k os 4 for the high pressure regime compressive waveforms in dry and water saturated granite were measured at 10 15 gpa using the visar technique the measured wave profiles were successfully modelled using a maxwellian stress relaxation material model water saturated granite is characterized by a 25 per cent lower yield strength and a 75 per cent longer material relaxation time than dry granite

contributions of the siberian shelf polynyas to the arctic ocean intermediate and deep water the role of the open water regions or polynyas in the winter ice pack over the siberian continental shelves in the production of arctic ocean intermediate and deep water is examined through use of a combination of passive microwave satellite data coastal weather station data and oceanographic data the satellite data allow us to derive a time series of the open water areas of selected polynyas for the 1978 1982 winters the polynyas which occur north of svalbard around franz josef land along the west coast and north end of novaya zemlya and to the east of severnaya zemlya and the taymyr peninsula are the primary oceanographic contributors the open water time series for these polynyas are used in combination with coastal weather station data to estimate the heat loss from each polynya for the region north of svalbard which is historically known as whalers bay the study shows that the heat loss is sufficient to provide the observed cooling of the west spitsbergen current for the other polynyas the heat loss is used to compute the ice production rates and the oceanic salt flux we then use the historic oceanographic salinities with the salt fluxes to estimate the contribution of each polynya to the arctic ocean water masses if we assume that the salt contributes only to the arctic intermediate water our results show that the shelves are capable of producing about 20 60 of this water alternatively if the salt contributes only to the deep water of the eurasian basin then without consideration of the mixing of the bottom water with the greenland and norwegian sea water the contribution from the shelves yields a renewal time of about 100 years our results imply that there is insufficient water produced in the shelf polynyas to perform all of the roles that have been historically assigned to it

polynya dynamics a review of observations and modeling 1 polynyas are nonlinear shaped openings within the ice cover ranging in size from 10 to 105 km2 polynyas play an important climatic role first winter polynyas tend to warm the atmosphere thus affecting atmospheric mesoscale motions second ocean surface cooling and brine rejection during sea ice growth in polynyas lead to vertical mixing and convection contributing to the transformation of intermediate and deep waters in the global ocean and the maintenance of the oceanic overturning circulation since 1990 there has been an upsurge in polynya observations and theoretical models for polynya formation and their impact on the biogeochemistry of the polar seas this article reviews polynya research carried out in the last 2 decades focusing on presenting a state of the art picture of the physical interactions between polynyas and the atmosphere sea ice ocean system observational and modeling studies the surface heat budget and water mass transformation within these features are addressed

the origin of swash cusps on beaches abstract genetically there are two types of beach cusps those formed in the surfzone by the nearshore circulation system and those formed on the beachface by the swash and backwash the latter are here called swash cusps and a simple model relating the physical dimensions of swash cusps to the properties of the incident wave field and the mean beach slope is developed as in some previous models the cusp wavelength is controlled by the longshore wavelength of edge waves but the edge waves are now required only to provide small periodic perturbations on an originally uniform beach further cusp growth occurs because of the interactions between the incident waves and the perturbed topography the maximum cusp height apex to valley is hypothesized to be proportional to the significant vertical excursion of swash motions it follows from the above assumptions that the maximum possible cusp steepness cusp height cusp longshore wavelength is proportional to the mean on offshore beach slope this result agrees with field data and the value of the ratio of maximum cusp height to beach slope differs from that obtained theoretically by guza and bowen 1981 using a complicated non linear model with rather different physics the present model implies that edge waves although necessary for initiating the initial bedform perturbation need not persist for the development of mature cusp topography

a simple model for interannual sandbar behavior time and length scales of beach variability have been quantified using 16 years of beach surveys sampled at the army corps of engineers field research facility located on the u s atlantic coast between 50 and 90 of the bathymetric variability at this site was explained by alongshore uniform response over the approximately 1 km alongshore span of the surveys although the incident wave height variance was dominated by frequencies at or higher than 1 cycle yr more than 80 of the bathymetric variance at all cross shore locations was explained by frequencies 1 cycle yr interannual cycles consisting of sandbar formation migration and decay contributed to the low frequency variability the observed behavior can be explained by a simple heuristic model the model assumes that bars migrate toward a wave height dependent equilibrium position this position was shown to coincide with the wave breakpoint additionally the rate of bar response is taken to be variable and was empirically determined to be proportional to the wave height cubed the net effect of a variable response rate is to shift the expected long term mean sandbar position offshore toward the equilibrium position associated with the largest waves the model explained up to 80 of the observed bar position time series variance and up to 70 of the variance of bar crest velocity time series which were extracted from three different sandbars characteristic bar response times related to the inverse of the response rate were found to be long relative to the characteristic timescale of the forcing 1 year in our case as a result transient response i e bar position far from equilibrium tended to persist for many cycles of the forcing transient bar behavior appears in the observations when bars formed near the shoreline or when outer bars decayed and inner bars faced a changed wave climate while the present model is able to explain the evolution of these transients it does not contain a mechanism for their introduction

morphological evolution of beach cusps and associated swash circulation patterns abstract a numerical model capable of simulating the motion of water particles on beach cusp morphology under the influence of an initial velocity and gravity is presented the model indicates that the typical swash pattern on beach cusps is three dimensional with wave uprush diverging at the cusp horns resulting in concentrated backwash streams in the embayment the degree of horn divergence is an increasing function of the parameter e s 2 where e quantifies the prominence of the beach cusps s is the horizontal swash excursion length and is the cusp spacing the numerical experiments are supplemented with detailed field measurements of beach cusp morphological change the field data include three types of morphological response each characterised by a particular pattern of swash circulation that can be delineated using e s 2 when e s 2 beach cusp morphology is large and or subdued in relation to the swash length swash circulation is essentially two dimensional oscillatory flow and results in steepening of the beachface and infilling of the cusp embayments for e s 2 0 015 to 0 15 wave uprush is deflected from the cusp horns and flows into the embayments where it exits in a concentrated backwash stream horn divergent flow the ensuing swash backwash inequality reinforces cusp development and maintains existing cusp morphology when e s 2 0 15 beach cusps are small and or pronounced in relation to the length of the swash overtopping and ponding of the cusp horn takes place and swash circulation is from the embayment to the horn horn convergent flow as a result cusp horns are eroded and accretion occurs in the embayments

field observations of beach cusps and swash motions abstract we tested the hypothesis of cusp formation by the longshore structure of synchronous or subharmonic mode zero edge waves using detailed field measurements of foreshore topography incident waves and swash motions two distinct intervals of cusp formation were observed alongshore separated swash measurements were analyzed to detect structures at wavelengths and frequencies consistent with the measured cusp spacings for both events no statistical support for cusp generation by the traditional subharmonic or synchronous edge wave mechanisms was found however once cusps became well developed there was evidence of interaction between fluids and topography at a wavelength equal to the cusp spacing but at the period of the incident swash we propose that this interaction could have been responsible for the generation of the second set of cusps with a spacing of half the pre existing cusp wavelength

experimental constraints on shock induced microstructures in naturally deformed silicates abstract planar deformation features pdfs in various minerals have long been accepted as evidence of impact induced deformation the uniqueness of this association was challenged in the context of the k t boundary extinction debate after mosaicism and microstructures similar to pdfs were reported from the products of explosive volcanism as a result of this debate a significant volume of new experimental and observational data on the development of shock induced microstructures has become available over the last ten years the results reveal that factors such as pre shock temperature pulse duration and crystallographic orientation of target minerals to the shock wave have a primary influence on how these microstructures develop data from diamond anvil cell and high pressure friction experiments reveal that the same solid state amorphization process that produces shock induced pdfs at low temperatures also occurs at much lower strain rates in static experiments the experimental data indicate that the amorphization process is thermally activated and that the character of the resulting pdfs is a function of the applied strain rate shock induced amorphization occurs along those crystallographic planes that are most readily transformed to the high pressure phase during very short pulse durations and produces pdfs that are visible at the optical scale lower strain rate deformation produces tem scale amorphization with orientations that are more homogeneously distributed throughout the target mineral and produces no optically visible pdfs the data confirm the uniqueness of multiple intersecting sets of optically visible pdfs as a diagnostic indicator of hypervelocity impact the data also support the hypothesis that the amorphization process can occur at a wide range of strain rates and that the limiting pressure for the process is controlled by the phase stability of the target mineral under the applied loading conditions not by the hel the data also suggest that the onset pressure the maximum pressure and the pressure range for producing optically visible pdfs decrease with increasing temperature and decreasing strain rate as the pressure range for optically visible pdf formation decreases it is replaced by homogeneous amorphization as observed in the anvil cell experiments thus the uniqueness of multiple intersecting sets of optically visible pdfs to hypervelocity impact is not due to a unique process but rather to a specific set of loading conditions that produce an optically visible microstructure likewise single sets of microdeformations observed in volcanic rocks are produced by the same process but at different loading conditions that preclude the development of multiple intersecting sets of pdfs the data also indicate that shock mosaicism which occurs above the hel represents a plastic response of the target mineral to loading rates that are too large to be accommodated by crystal plastic mechanisms observational data for some naturally deformed samples from the k t boundary the vredefort dome and volcanic rocks along with the experimental observations are used to constrain the range of conditions under which the natural microstructures form and to understand the differences between microstructures produced by impact volcanic and other natural processes finally some possible mechanisms for producing the microstructures observed in volcanic rocks are proposed

a video based technique for mapping intertidal beach bathymetry abstract measuring the location of the shoreline and monitoring foreshore changes through time are core tasks carried out by coastal engineers for a wide range of research monitoring and design applications with the advent of digital imaging technology shore based video systems provide continuous and automated data collection encompassing a much greater range of time and spatial scales than were previously possible using field survey methods a new video based technique is presented that utilises full colour image information which overcomes problems associated with previous grey scale methods which work well at steep reflective sites but are less successful at flatter dissipative sites identification of the shoreline feature is achieved by the automated clustering of sub aqueous and sub aerial pixels in hue saturation value hsv colour space and applying an objective discriminator function to define their boundary i e shoreline within a time series of consecutive geo referenced images the elevation corresponding to the detected shoreline features is calculated on the basis of concurrent tide and wave information which is incorporated in a model that combines the effects of wave set up and swash at both incident and infragravity frequencies validation of the technique is achieved by comparison with dgps survey results to assess the accuracy of the detection and elevation methods both separately and together the uncertainties associated with the two sub components of the model tend to compensate for each other the mean difference between image based and surveyed shoreline elevations was less than 15 cm along 85 of the 2 km study region which corresponded to an horizontal offset of 6 m the application of the intertidal bathymetry mapping technique in support of czm objectives is briefly illustrated at two sites in the netherlands and australia

seasonal variations in the properties and structural composition of sea ice and snow cover in the bellingshausen and amundsen seas antarctica sixty three ice cores were collected in the bellingshausen and amundsen seas in august and september 1993 during a cruise of the r v nathaniel b palmer the structure and stable isotopic composition 18 o 16 o of the cores were investigated in order to understand the growth conditions and to identify the key growth processes particularly the contribution of snow to sea ice formation the structure and isotopic composition of a set of 12 cores that was collected for the same purpose in the bellingshausen sea in march 1992 are reassessed frazil ice and congelation ice contribute 44 and 26 respectively to the composition of both the winter and summer ice core sets evidence that the relatively calm conditions that favour congelation ice formation are neither as common nor as prolonged as the more turbulent conditions that favour frazil ice growth and pancake ice formation both frazil and congelation ice layers have an av erage thickness of 0 12 m in winter evidence that congelation ice and pancake ice thicken primarily by dynamic processes the thermodynamic development of the ice cover relies heavily on the formation of snow ice at the surface of floes after sea water has flooded the snow cover snow ice layers have a mean thickness of 0 20 and 0 28 m in the winter and summer cores respectively and the contribution of snow ice to the winter 24 and summer 16 core sets exceeds most quantities that have been reported previously in other antarctic pack ice zones the thickness and quantity of snow ice may be due to a combination of high snow accumulation rates and snow loads environmental conditions that favour a warm ice cover in which brine convection between the bottom and top of the ice introduces sea water to the snow ice interface and bottom melting losses being compensated by snow ice formation layers of superimposed ice at the top of each of the summer cores make up 4 6 of the ice that was examined and they increase by a factor of 3 the quantity of snow entrained in the ice the accumulation of superimposed ice is evidence that melting in the snow cover on antarctic sea ice floes ran reach an advanced stage and contribute a significant amount of snow to the total ice mass

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

analysis of the effects of different storm events on shoreline dynamics of an artificially embayed beach a five year dataset of argus derived mean intertidal positions has been analysed to characterize the shoreface variability in a beach protected by a system of groynes and a parallel low crested structure lido di dante ravenna italy for the period 2004 2009 84 intertidal beach bathymetries and shorelines at the zero sea level were used as indicators to assess beach changes in between a number of selected surveys and to determine characteristic patterns of the beach response to storm events from different directions variations in the shoreline at the zero sea levels have been quantified and analysed in conjunction with nearshore wave conditions and provenance linked to storm events these fall into two categories 1 storm events occurring during bora north eastern wind conditions and 2 storm events occurring during scirocco south eastern wind conditions the results show that apart from main beach advances of the whole protected beach due to nourishments periodically carried out a marked variability is observed among the four sub cells into which the shoreface behaviour has been separately analysed in particular a dependence of beach rotation in the artificially embayed area on the substantially bi directional wave climate has been shown bora and scirocco storm events produce shoreline rotation in counterclockwise and clockwise directions respectively due to the occurrence of longshore currents in the opposite direction in the nearshore an attempt was made to correlate the shoreface dynamics for the main rotation events 14 selected ones to the wave attack intensity as the total energy flux due to storm events a relationship seems to occur for each storm category between the shoreline displacements estimated for each sub cell and the total energy flux computed for inter survey periods supporting the occurrence of a link between the observed morphological changes and the hydrodynamic forcing associated with storm events in the five year monitoring period copyright 2011 john wiley sons ltd

dynamic compression of sio2 a new interpretation 1 in light of recent discoveries of post stishovite phases of sio2 with the cacl2 and pbo2 structures we have reassigned the regimes along the hugoniots for initial quartz coesite cristobalite porous coesite and fused silica calculated hugoniots for fused silica cristobalite and porous coesite indicate transition to stishovite and then melt hugoniots for crystal quartz and coesite indicate that transition occurs to stishovite then the cacl2 structure and finally to melt

shock induced melting of mgsio3 perovskite and implications for melts in earth s lowermost mantle 1 new shock wave equation of state eos data for enstatite and mgsio3 glass constrain the density change upon melting of mg silicate perovskite up to 200 gpa the melt becomes denser than perovskite near the base of earth s lower mantle this inference is confirmed by shock temperature data suggesting a negative pressure temperature slope along the melting curve at high pressure although melting of earth s mantle involves multiple phases and chemical components this implies that the partial melts invoked to explain anomalous seismic velocities in the lowermost mantle may be dynamically stable index terms 3919 mineral physics equations of state 3944 mineral physics shock wave experiments 8124 tectonophysics earth s interior composition and state 1212 citation akins j a s n luo p d asimow and t j ahrens 2004 shock induced melting of mgsio3 perovskite and implications for melts in earth s lowermost mantle geophys res lett 31 l14612 doi 10 1029 2004gl020237

research on snow and ice this review unlike its predecessor martinelli et al 1979 is an intentionally selective survey of recent advances in selected areas of snow and ice research i have chosen to concentrate on studies relating to large scale aspects of the cryosphere and to consider their wider significance for other disciplines results obtained by new measurement techniques and the application of remote sensing methods are also stressed at the same time the broad lines of advance in glaciological research as represented in books conference themes and major field or laboratory programs are noted and a detailed bibliography is appended

shock experiments with the h6 chondrite kernouve pressure calibration of microscopic shock effects shock recovery experiments were carried out on samples of the h6 chondrite kernouve at shock pressures of 10 15 20 25 30 35 45 and 60 gpa and preheating temperatures of 293 k low temperature experiments and 920 k high temperature experiments using a calculated equation of state of kernouve pressure pulse durations of 0 3 to 1 2 s were estimated the shocked samples were investigated by optical microscopy to calibrate the various shock effects in olivine orthopyroxene oligoclase and troilite the following pressure calibration is proposed for silicates 1 undulatory extinction of olivine gpa 2 weak mosaicism of olivine from 10 15 gpa to 20 25 gpa 3 onset of strong mosaicism of olivine at 20 25 gpa 4 transformation of oligoclase to diaplectic glass completed at 25 30 gpa low temperature experiments and at 20 25 gpa high temperature experiments 5 onset of weak mosaicism in orthopyroxene at 30 35 gpa low temperature experiments and at 25 30 gpa high temperature experiments and 6 recrystallization or melting of olivine starting at 45 60 gpa low temperature experiments and at 35 45 gpa high temperature experiments and completed above 45 60 gpa in the high temperature experiments troilite displays distinct differences between the samples shocked at low and high temperatures in the low temperature experiments the following effects can be observed in troilite 1 undulatory extinction up to 25 gpa 2 twinning up to 45 gpa 3 partial recrystallization from 30 to 60 gpa and 4 complete recrystallization 35 gpa whereas in the high temperature experiments troilite shows 1 complete recrystallization from 10 up to 45 gpa and 2 melting and crystallization above 45 gpa localized shock induced melting is observed in samples shocked to pressures 15 gpa in the high temperature experiments and 30 gpa for the low temperature experiments in the form of feni metal and troilite melt injections and intergrowths and as pockets and veins of whole rock melt obviously the onset and abundance of shock induced localized melting strongly depends on the initial temperature of the sample

ice production and deep water entrainment in shelf break polynya off enderby land antarctica aircraft observations off enderby land antarctica verified that a coastal polynya forms even in severe winters and that new ice production continuously occurs there in the polynya water temperature profiles were measured for the first time using the aircraft launched expendable bathythermograph axbt the axbt data show that the thickness of the winter mixed layer is 350 m or more and that the layer temperatures are near the freezing point according to the water mass analysis of the winter mixed layer the active haline convection by the high ice production in the winter polynya contributes to the formation of more homogeneous and saline mixed layer than that under the fast ice cover where the ice grows slowly and convective mixing is calm furthermore the active convection leads to entrainment of the oxygen poor deep water under winter water consequently in the polynya located over the continental shelf break the oxygen content of the mixed layer is somewhat lower than that in a coastal polynya that forms on the continental shelf where the haline convection reaches to the sea bottom the oxygen undersaturation of the thick mixed layer in the shelf break polynya suggests that the deep water entrainment rate is more intense than that under the pack ice region in the weddell sea with a relatively thin mixed layer it is therefore important to consider such polynya processes which may contribute to water mass modification in the antarctic coastal region

dynamics of a nearshore bar system in the northern adriatic a video based morphological classification abstract the aim of this paper is to define a simplified morphodynamic classification suitable for low energy beaches exposed to microtidal conditions the study site is located in the northern adriatic in italy it is an almost 2 km long rectilinear beach bordered at the northern edge by coastal structures and at the southern end by a small river inlet the mechanisms related to the evolution of the submerged part of the beach were derived from video monitoring using argus technology the morphodynamic evolution of the system was studied using an automatic procedure on images for the characterisation of nearshore bars that showed good correspondence with hand based visual interpretation to apply this automatic procedure the bar s plan crest shape was mapped using cross shore pixel luminosity transects traced on time averaged video images a careful sensitivity analysis was undertaken to determine the best spacing between transects for the correct tracing of the shape of the bar crest the error associated to a transect spacing every 25 m resulted in being comparable with the pixel resolution in the area and with the error found comparing the video interpretation with bathymetric surveys from the study of a four and a half year dataset february 2003 may 2007 the submerged beach was found to be characterised by the presence of a single bar in the area next to coastal protection structures however moving southwards of these inner and outer bars were present the morphodynamics of the outer bar and its plan shape modifications were dominated by rhythmic forms occasionally after high energy events the bar became rectilinear but during the following lower energy periods rhythmicity was re established supporting the hypothesis of self organization mechanisms the cross shore position of the bar s crests only showed limited cross shore mobility through time

test of self organization in beach cusp formation 1 field observations of swash flow patterns and morphology change are consistent with the hypothesis that beach cusps form by self organization wherein positive feedback between swash flow and developing morphology causes initial development of the pattern and negative feedback owing to circulation of flow within beach cusp bays causes pattern stabilization the self organization hypothesis is tested using measurements from three experiments on a barrier island beach in north carolina beach cusps developed after the beach was smoothed by a storm and after existing beach cusps were smoothed by a bulldozer swash front motions were recorded on video during daylight hours and morphology was measured by surveying at 3 4 hour intervals three signatures of self organization were observed in all experiments first time lags between swash front motions in beach cusp bays and horns increase with increasing relief representing the effect of morphology on flow second differential erosion between bays and horns initially increases with increasing time lag representing the effect of flow on morphology change because positive feedback causes growth of beach cusps third after initial growth differential erosion decreases with increasing time lag representing the onset of negative feedback that stabilizes beach cusps a numerical model based on self organization initialized with measured morphology and alongshore uniform distributions of initial velocities and positions of the swash front at the beginning of a swash cycle reproduces the measurements except for parts of one experiment where limited surveys and a significant low frequency component to swash motions might have caused errors in model initialization

seasonal variations of the antarctic coastal ocean in the vicinity of lutzow holm bay during the period of 1990 1992 year round oceanographic observations were conducted in the vicinity of lutzow holm bay east antarctica it was found that the thickness of the winter water ww layer characterized by a cold fresh oxygen rich water exhibits its maximum in the austral fall typically 500 m and its minimum in the austral summer typically 350 400 m the associated density variation of the water column explains only about one third of the seasonal variations in sea level at the coast which suggests a large seasonal variation in barotropic coastal flow prominent freshening occurs in the ww layer during fall this appears to be caused by the accumulation of ww whose upper portion is freshened in the preceding summer these seasonal variations appear to occur every year we propose that the seasonal variation in the ww layer is mainly caused by the seasonal variation in the wind over the coastal ocean in fall the prevailing easterly wind intensifies which increases the ekman convergence of ww in the coastal ocean while in summer the opposite occurs

morphodynamics of intertidal bars in wave dominated coastal settings a review abstract intertidal bar systems are ubiquitous features on wave dominated beaches in coastal settings with a significant 1 m tidal range depending primarily on the wave conditions and the tidal range and to a lesser extent on the nearshore gradient they can assume a variety of forms slip face bars represent the most pronounced and dynamic intertidal bar morphology and are generally found on their own around the mean high tide level they usually form low on the intertidal beach after storm induced beach erosion and develop into a berm under prolonged calm wave conditions low amplitude ridges and sand waves represent multiple bar morphologies the bars occur across the entire intertidal profile and they remain present throughout the year multiple intertidal bars tend to be rather subdued and relatively static especially sand waves and their origin remains unclear the morphological response of intertidal bars to changing wave conditions is largely forced bars build up and migrate onshore under calm waves and are flattened and may migrate offshore during storms the morphological response is however significantly affected by relaxation time effects and morphological feedback particularly on beaches with multiple intertidal bars despite their morphological differences the intertidal bar types exhibit pronounced similarities in their morphodynamics sediment transport processes and morphological response are principally controlled by the tidal water levels on the beach because these together with the offshore wave energy level and the beach morphology determine the type intensity and duration of the wave processes operating on the cross shore profile it is the dominant importance of tidal water level variations and wave processes in shallow water depths swash and surf zone bores rather than wave height variability and deeper water wave processes breaking and shoaling waves that constitutes the main difference between intertidal and subtidal bar morphodynamics

empirical model of morphodynamic beachface behaviour for low energy mesotidal environments abstract four years of monthly monitoring were carried out on a south atlantic beach in spain in a low energy mesotidal environment where beaches change slowly from reflective to dissipative states following a typical seasonal behaviour in this work a two dimensional study of beach morphological variations has been made related to the incident wave variations after applying several morphodynamic parameters to the field data poor or null representative results were obtained it was then necessary to design other type of characterisation of the incident wave energy in this sense the intertidal normalised beach slope was compared with the erosive potential of the incident waves expressed as a combination of the dimensionless grain fall velocity parameter and the energy density of waves median grain size did not vary significantly during the surveys for this reason a new parameter named wave erosivity factor was introduced by considering the fall velocity of grains as a constant in the parameter the resulting ratio between normalised beach slope and wave erosivity expresses the equilibrium state of the beach for any given energy level the departure from the equilibrium curve is largest in the intermediate situations while at the extremes the points are better adjusted to asymptotic tendencies towards equilibrium on reflective states small increases in the wave erosivity will produce important beach changes on dissipative beaches important increases in the wave erosivity will not produce significant morphological modifications the resulting equilibrium curve is presented as a function of the natural range of morphological variation of this beach

winter mixed layer entrainment of weddell deep water observations from the somov during the us ussr weddell polynya expedition show that the mixed layer below the sea ice just prior to the austral spring retreat in the 60 s greenwich meridian region has an oxygen content of 7 4 ml 1 this is 86 of full oxygen saturation representing an oxygen deficit relative to full saturation of 1 1 ml 1 the source of this deficit is believed to be a consequence of oxygen poor 4 5 ml 1 weddell deep water wdw entrainment by the winter mixed layer assuming effective cutoff of ocean atmosphere oxygen exchange by the nearly complete snow and sea ice cover with no net impact of oxygen content as a result of biological factors a mixing ratio of 1 3 for wdw to beginning of winter surface water is required to explain the end of winter mixed layer oxygen content accompanying the wdw transfer into the mixed layer is heat transfer of approximately 7 103 cal cm2 2 9 108 j m2 during the five winter months of sea ice coverage as well as salt transfer which requires 34 cm of fresh water to produce typical mixed layer salinity during the seven ice free months when entrainment is expected to be minor diffusive heat and salt flux continues a mean annual heat flux of 12 w m2 is suggested with an annual demand for freshwater of 46 cm yr consideration of the winter period salinity budget indicates net sea ice melting of 20 cm which can be attributed to regional convergence of sea ice the remaining freshwater is derived from excess precipitation and possibly iceberg melt oxygen undersaturation of the winter surface water suggests slightly less potential for abyssal water ventilation than might be expected from a fully saturated condition

measurements of ice shelf water beneath the front of the ross ice shelf using gliders measurements made by an underwater glider deployed near the ross ice shelf were used to identify the presence of ice shelf water isw which is defined as seawater with its potential temperature lower than its surface freezing point temperature properties logged by the glider included in situ temperature electrical conductivity pressure gps location at surfacings and time for most of the first 30 recorded dives of its deployment evidence suggests the glider was prevented from surfacing due to being under the ice shelf for dives under the ice shelf farthest from the ice shelf front isw layers of varying thicknesses and depth locations were observed between 2 m thick centred at 231 m depth to 93 m thick centred at 360 m for dives under the ice shelf close to the ice shelf front either no isw was observed or isw layers were centred at shallower depths 116 127 m thicker isw layers e g up to 250 m thickness centred at 421 m were observed for some glider dives in open water in front of the ross ice shelf no in situ supercooling water colder than the pressure dependent freezing point temperature was observed

postshock temperatures in silica experimental postshock temperatures for crystalline quartz released from shock states between 86 and 127 gpa and for fuset silica released from 59 to 73 gpa have been determined using previously measured spectral radiance data the temperatures range from 3660 to 4150 k and are consistent with the interpretation based on shock temperature measurements that the hugoniot of sio sub 2 crosses the phase boundary between stishovite and liquid the new postshock temperatures were used to determine the grueneisen parameter of liquid silica at high pressures and temperatures and the specific volume of the release state gamma v 3 5 mg m sup 3 and f sub r 0 266 m sup 3 mg respectively although there is some ambiguity as to whether this volume corresponds to a partial or total release state to show the validity of these postshock temperatures a radiative transport model was extended to times after free surface arrival of the shock wave copyright american geophysical union 1988

crystal structure stable isotopes δ18o and development of sea ice in the ross amundsen and bellingshausen seas antarctica the crystal structure and oxygen isotopic composition of ice cores obtained from floes at the end of summer in the eastern ross sea the amundsen sea and the western bellingshausen sea were investigated to determine the ice growth processes and conditions that contribute to sea ice development in the eastern pacific sector of the southern ocean the isotope data indicate that a moderate amount of snow contributes to the development of the sea ice however even the combined use of isotopes and crystal structure analysis does not unambiguously explain the means by which all of the snow is entrained in the ice nevertheless it seems clear that much of the snow is contained in granular snow ice that results from seawater flooding of floes and the base of the snow cover the snow cover in the ross amundsen region was as much as 2 m deep and supported by 7 to 8 m thick floes primarily composed of frazil ice in the bellingshausen region the snow cover and the floes were thinner than in the ross amundsen region the bellingshausen cores were composed primarily of multiple layers of frazil and congelation ice in addition in both regions there were numerous tipped or inclined blocks of congelation ice and layers of rafted nilas in the cores the data indicate that the sea ice develops by multiple mechanisms in a turbulent environment

erosion accretion patterns and multiple beach cusp systems on a meso tidal steeply sloping beach abstract this study examines daily variations in intertidal topography and beach cusps on a meso tidal steeply sloping beach during a five month period the observations are based on coastal imagery and frequent topographic surveys and are extracted from patterns of contours positioned 1 and 3 m above msl lower higher beach face respectively the intertidal topography was very sensitive to variations in the wave regime triggering rapid transitions from erosive to accretive states and vice versa as well as transformations of the cusp systems often involving severe horn erosion and beach face scarping distinct beach cusp systems were observed at different levels of the beach with their evolution being controlled by i wave forcing ii tidal modulation of the wave power at different levels of the beach and iii interactions between the existing beach cusp systems the lower beach face rhythmical patterns changed constantly and merged with the upper beach face cuspate features typically when the significant wave height exceeded h o 1 5 m the upper beach face pattern was persistent during the monitoring period re emerging with similar spacing and alignment despite being eroded during energetic events this persistence is also maintained by the interactions between swash and irregularities e g embayments in the dune backshore morphology the spacing of the observed beach cusps ranged from c min 8 m to c max 67 m these values were underestimated by the edge wave and self organization theories and were better predicted by the sunamura 2004 formula beach cusp growth was linked to breaker angles of near normal incidence and narrow banded frequency wave conditions bay infilling was found to be the most dominant cusp reduction mechanism for larger features c 30 m while smaller features vanished during erosive conditions the most intense cusp growth episodes were linked to accretive conditions while larger features were shown to emerge during more energetic erosion events these findings highlight the need for more longer term observations of diverse beach morphologies to formulate a global theory regarding beach cusp formation and evolution

test of edge wave forcing during formation of rhythmic beach morphology 1 this paper reports on concurrent measurements of evolving rhythmic beach morphology and the associated water motion on a macrotidal coarse sandy beach beach cusps with a spacing of 19 m developed over a 3 day period of low energy swell after which they were destroyed by energetic wind waves the beach cusps were clearly accretionary features and developed mainly during the rising tide detailed hydrodynamic measurements were conducted at three locations in the swash and inner surf zone in the vicinity of a developing cusp horn and revealed that energetic standing mode zero subharmonic edge waves were not present during the initiation of the beach cusps specifically analysis of the hydrodynamic data indicated that 1 the amount of subharmonic energy was limited 10 of the total energy 2 none of the computed energy spectra exhibited a significant peak at the subharmonic frequency 3 the cross shore velocity amplitude at the subharmonic frequency was 2 3 times larger than the longshore velocity amplitude 4 the longshore current motion at the subharmonic frequency was barely coherent between adjacent locations in the surf zone and 5 the time series of pressure and cross shore current were in phase at either side of the developing cusp horn it is concluded that at least during this event of beach cusp formation energetic standing edge waves are not a prerequisite to initiate the development of rhythmic beach morphology

satellite passive microwave studies of the sea of okhotsk ice cover and its relation to oceanic processes 1978 1982 this paper describes the use of the nimbus 7 scanning multichannel microwave radiometer smmr satellite data to study the ice cover in the sea of okhotsk during the four winters of 1978 1982 the ice concentration estimates obtained from smmr are used to study two different polynyas one over the kashevarova bank and the other over the northwest continental shelf for the kashevarova polynya this study shows that the polynya which may be related to the upwelling observed in historic summer cruises occurs directly over the bank for the continental shelf which because of strong offshore winds and cold temperatures is a region of high ice production the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice salt and dense shelf water as a previous study by kitani 1973 shows the mixing of this dense shelf water with pacific water yields a water mass unique to the okhotsk which is the layer of cold low salinity intermediate water between depths of 150 and 800 m from our calculations we estimate that the dense shelf water is produced at an annual rate of about 0 5 sv and that the intermediate water is produced at a rate of 1 2 sv which yields a renewal time for this layer of 10 40 years

relation between beachface morphology and wave climate at trafalgar beach cadiz spain abstract two years of offshore wave data and daily time exposure images from trafalgar beach a 2 km long sandy beach located on the southwest coast of spain that frequently exhibits rhythmic features were used to 1 explore the variability of the beachface morphology and 2 determine environmental conditions associated with the different morphological states the beachface morphology at three distinct alongshore sectors was analyzed and classified and five different morphological states were found that are related with the presence or absence of beach cusps and a berm 1 large beach cusps 2 small beach cusps 3 low tide terrace 4 plane beach berm and 5 plane beach the predominant beachface morphology is characterized by the presence of large beach cusps and the main wave climate consisted of offshore significant wave heights ranging from 0 5 1 m and wave periods between 4 and 12 s an alongshore variation of the morphology is found which might be related to the nearshore wave variability swan wave model results the morphologies are in some cases well correlated with the daily offshore incident wave climate described by the daily maximum significant wave height and the corresponding period particularly for the moderate to high energy wave conditions small beach cusps appear under short period waves whereas when the wave periods are longer the morphology tends to change to large beach cusps this transition only occurs if the forcing is maintained as constant for a certain duration which depends itself on the wave energy it is concluded that correlations over 90 are only found for the highest wave energy conditions or under long wave periods for the remainder it is not possible to generally correlate the beachface morphology based only on the wave forcing because the previous morphological state cannot be ignored

morphodynamic characteristics and classification of beaches in england and wales abstract the use of beach classification models has become widespread in literature in recent years beach classification models that recognise distinct modal beach states in response to environmental conditions are most widely used these models were developed largely in high energy micro to meso tidal sandy environments and subsequent attention has focussed on extending their use into other beach environments here the applicability of these traditional beach classification models to the highly diverse coastline of england and wales was assessed through collection of detailed morphodynamic characteristics of 92 beaches yielding a comprehensive multi variate data set containing morphological sedimentological and hydrodynamic information the complex and diverse study region incorporates beach morphology covering the full spectrum from reflective to dissipative and non barred to multi barred cluster analysis supplemented by mds ordination resulted in the identification of 9 distinct beach types traditional morphodynamic indices and rtr were found to be effective in discriminating between beach groups providing some support for the beach state models derived using information from australian beaches it was found that absolute wave energy wave power is important as well in controlling beach type for intermediate beaches a wave energy flux p h 2 t value of 3 kw m 1 was found to differentiate between beaches with p 3 kw m 1 and without p 1 three dimensional bar rip morphology a key component controlling recreational beach hazard levels observations presented here inform a beach classification model to be used as the basis for a national beach risk assessment programme beach classification models based on environmental parameters are by necessity simplifications and should be used as tools for understanding morphodynamic systems rather than beach type prediction

a predictive relationship for the spacing of beach cusps in nature abstract modeling is carried out to obtain a relationship that enables the prediction of the spacing of beach cusps using wave and sediment parameters the modeling is based on the concepts that 1 the path of wave uprush flow diverging at a cusp horn has a close connection with the cusp spacing and 2 the flow path is affected by the grain size of beach sediment the following equation is derived a t g h in which is the cusp spacing h is the nearshore wave height t is the wave period is a dimensionless quantity representing the effect of sediment grain size exp 0 23d0 55 where d is the grain size in mm units g is the gravitational acceleration and a 1 35 the value of a is determined using a large amount of existing field data applicability of the predictive equation is examined by using the data from an embayed beach in new south wales australia the result indicates that this equation is capable of reasonably explaining a general trend of the alongshore variation in cusp spacings

regularity and randomness in the formation of beach cusps abstract controversy still exists on whether rhythmic features such as beach cusps are the result of the presence of standing edge wave motions in the hydrodynamics or if they are the result of self organising processes the compatibility between the two mechanisms is here investigated through the use of a numerical model simulating the formation and development of beach cusps simulations characterised by different forcing conditions have been performed a series of random simulations each individual run simply differing from the others in the seed used in the random number generator showed the typical self organisation behaviour with the features appearing at different locations and even with slightly different spacing regular series of simulations have been run by changing the wavelength of the template superimposed by the hydrodynamic forcing and the number of cycles when the template was present results surprisingly indicate that even a minimum number of cycles with a regular forcing can deterministically induce the final shoreline configuration furthermore if the forcing template has the same wavelength as the one resulting from purely random simulations growth rates are much faster than those obtained with random conditions implications for the kind of field measurements necessary to discern which of the two mechanisms is responsible for beach cusp formation have also been considered

the anatomy of a freezing lead winter leads are regions of intense ice growth with resultant large fluxes of heat to the atmosphere and salt to the ocean they constitute a major source of new ice in the arctic basin during the 1988 drift phase of the coordinated eastern arctic experiment we were afforded a unique opportunity to conduct a detailed long term study of a freezing lead measurements were made from september 17 to november 18 during which time the ice grew from open water to a thickness of 0 56 m cores were removed from the lead ice on a routine basis and analyzed for ice temperature salinity density and structure from these measurements the derived quantities of brine volume porosity heat flux to the atmosphere and salt flux to the ocean were computed in addition to this 2 month time series study of ice cores the spatial variation in lead ice properties was investigated on september 30 thin section studies of ice structure indicated that the upper 0 05 0 15 m of the ice sheet was granular and that the lower portion was columnar typically a portion of the granular layer was snow ice once the transition from granular to columnar ice had occurred granular ice did not reappear as the ice grew thicker the c axes of the ice crystals became aligned within the horizontal plane this alignment direction corresponded closely with the inferred direction of the current at the ice water interface vertical temperature profiles in the ice were approximately linear salinity profiles were usually c shaped with bulk salinities ranging from 9 to 6 before stabilizing at 6 for ice thicker than 0 35 m core data were used to compute the flux of heat to the atmosphere and the flux of salt to the ocean for seven time intervals during the experiment heat fluxes ranged from 89 to 29 w m2 with an average of 50 w m 2 roughly 3 times the corresponding value from multiyear ice the flux of salt from the lead ice to the ocean varied from 0 51 to 0 06 kg m 2 d 1 averaging 0 21 kg m 2 d 1

the microstructural response of quartz and feldspar under shock loading at variable temperatures shock recovery experiments were carried out on westerly granite and hospital hill quartzite targets in the peak pressure range 8 to 25 gpa preshock temperatures of 25 450 and 750 c and pulse durations of 2 to 7 s using internally heated momentum traps and explosive plane wave generators optical and transmission electron microscopy analyses of quartz and feldspar shocked at 25 c revealed the previously documented progression with increasing pressure 1 fracturing 2 planar fractures and shock mosaicism 3 shock mosaicism and planar deformation features pdfs and 4 isotropization this same sequence is observed for experiments at elevated preshock temperature but with specific microstructures occurring at lower pressures than those in previous experiments at room temperature at 750 c strong shock mosaicism partially thermally recovered is characteristic of feldspar shocked to 8 gpa whereas 15 gpa is required for its development in quartz and for the generation of pdfs in both minerals the results suggest that threshold pressures for formation of the various microstructures and phases are expected to vary systematically as a function of the preshock temperature of the target material we suggest that pdfs are generated in the shock transition by progressive heterogeneous phase transformation of the crystal structure to form dense glass or high pressure polymorphs the onset pressures for pdfs in specific crystallographic orientations is not influenced strongly by temperature but the character of the pdfs does change as preshock temperature is increased at the same peak shock stress the change from multiple sets of thin pdfs at low temperature to thicker single sets of pdfs at moderate temperature and finally to complete isotropization at high temperatures reflects a change in the phase transformation mechanism as a function of temperature in contrast development of shock mosaicism in quartz and feldspar occurs throughout the duration of shock loading and is better developed at elevated temperatures where the kinetics are enhanced by the additional thermal energy in the target

observations of platelet ice growth and oceanographic conditions during the winter of 2003 in mcmurdo sound antarctica 1 platelet ice is the name given to ice crystals that nucleate in the ocean and grow either at depth or loosely attached to the ice water interface related to the proximity of ice shelves it is known to form in supercooled seawater this study details the conditions for its growth during the austral winter of 2003 in mcmurdo sound antarctica a key finding is that the presence of platelet ice in the sea ice cover is conclusively linked to the time history of the appearance of ice crystals in the water column monitored using the strength of the backscattered signal from an acoustic doppler current profiler as a proxy generally these crystals appeared from mid may as water near the interface became supercooled this near surface supercooling appears to be related to a simultaneous abrupt change in the structure of the upper 250 m of the water column from one that behaved dynamically and contained both the warmest and coolest measured temperatures to one in which the water was essentially isothermal near its surface freezing temperature near surface ocean temperature was also affected by tidal mixing and by an increase in the thickness and density over the course of winter of the surface mixed layer created by salt rejection during ice growth these processes allowed cold water trapped by buoyancy in a band at the base of the mixed layer in early winter to gain access to the ice water interface by midwinter this band of cold water probably had its origin beneath the mcmurdo ice shelf

physical properties of sea ice discharged from fram strait it is estimated that 84 percent of the ice exiting the arctic basin through fram strait during june and july 1984 was multiyear ice and that a large percentage of this ice is ridged or otherwise deformed while freeboard and thickness data together with salinity measurements on cores usually sufficed to distinguish between first and multiyear floes preliminary identification could usually be made on the basis of snow cover measurements with snow cover being much thicker on multiyear ice cores from the top half meter of multiyear floes were generally very much harder and more transparent than cores from first year floes age estimates of multiyear floes based on petrographic and salinity characteristics of cores did not exceed 4 to 5 years for any of the floes that were observed exiting fram strait

large scale sediment bodies and superimposed bedforms on the continental shelf close to the strait of gibraltar interplay of complex oceanographic conditions and physiographic constraints a previously unknown field of large scale sedimentary bodies has been mapped and studied on the continental shelf off the cape trafalgar near the strait of gibraltar with particular emphasis on the relationship between large scale sediment bodies and the superimposed bedforms this study is based on a grid of 975 km of high resolution seismic profiles collected at water depths ranging between 15 and 60 m high variability of large scale sedimentary bodies is attributed to the complex interaction of hydrodynamic agents the most prominent sedimentary features are sand banks and ridges that indicate long term southwest and southward directed sediment transport patterns possibly due to the interplay of two dominant current systems flowing southward and westward these sediment bodies evolve laterally to distinct external geometries such as sand shoals in shallow water and sand sheets in the vicinity of larger sand banks that indicate moderate current velocities in addition pre existing physiography is considered to play a role in the generation of certain sediment bodies developed over inclined surfaces or confined laterally by elevations relationships between superimposed bedforms mostly very large dunes and underlying sediment bodies vary across the study area most superimposed bedforms occur over the complex mosaic of sediment banks and sheets suggesting the interaction of several high energy currents with different directions such as tidal and or wind driven currents copyright 2010 john wiley sons ltd

beach cusps as self organized patterns computer simulations of flow and sediment transport in the swash zone on a beach demonstrate that a model that couples local flow acceleration and alongshore surface gradient is sufficient to produce uniformly spaced beach cusps the characteristics of the simulated cusps and the conditions under which they form are in reasonable agreement with observations of natural cusps the self organization mechanism in the model is incompatible with an accepted model in which standing alongshore waves drive the regular pattern of erosion and deposition that gives rise to beach cusps because the models make similar predictions it is concluded that currently available observational data are insufficient for discrimination between them

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

morphodynamics of intermediate beaches a video imaging and numerical modelling study four years of time exposure images of palm beach sydney australia are used to a develop a phenomenological scheme based on surf zone properties for the classification of the four intermediate beach states low tide terrace ltt transverse bar rip tbr rhythmic bar beach rbb and longshore bar trough lbt identified by wright l d short a d 1984 morphodynamic variability of surf zones and beaches marine geology 56 93 118 and b determine environmental conditions associated with the different beach states the overall agreement between beach state classifications obtained by visual classifications of images and those predicted by the phenomenological scheme exceeds 90 analysis of time series of intermediate beach states and wave data indicates that the nearshore morphology continuously cycles through the four beach states in response to variations in the incident wave energy the results also indicate that lbt morphology is produced by high energy wave conditions erosive while the progression towards ltt occurs under lower waves accretive a depth averaged morphodynamic model is employed to determine the morphodynamic processes governing the rbb to tbr and tbr to ltt transitions model results indicate that the rbb to tbr transition is governed by the erosion of the original longshore bars in the initial rbb morphology and the formation and subsequent welding of shoals in the lee of the original longshore bars model results also indicate that rbb to tbr transitions can occur under shore normal and oblique wave conditions the tbr to ltt model simulations indicate that under obliquely incident waves progressive erosion of the transverse shoals and deposition of the eroded sediment in rip channels gradually diminishes the longshore variability in morphology resulting in an ltt morphology

estimation of seasonal morpho sedimentary changes at headland bound and exposed beaches along south maharashtra west coast of india knowledge on seasonal variation of morpho sedimentary processes of tropical beaches is essential to evaluate inter annual variations to devising best protection strategy for the coastal zone a study was taken up to understand the seasonal changes of physical processes at the headland bound and compared with exposed beaches the spatio temporal morpho sedimentary dynamics were carried out through beach profiles sediment samples and simulated wave climates across two complete annual cycle the beach profile survey was carried out using rtk gps wherein the gradistat was used for analysing sediment samples the seasonal wave climates were studied with the swan model coupled with wavewatch iii observation shows the sediment environment at headland bound beach is strongly dominated by fine sand throughout the year whereas the exposed beach is illustrated from fine to medium sand across seasonal scale the seasonal change in beach morphology occurs considerably in the exposed beach than that compared to headland bound successively the occurrence of shoreline retreat is shown maximum up to 20 m in at the exposed beach during the monsoon both the locations showed strong seasonal variation in the wave energy as well as direction whereas the nearshore wave energy at exposed beach is comparatively high with an average of 8342 j m2 than the headland bound due to less deviation in the wave propagation the analysis of seasonal wave pattern together with beach morpho sedimentary processes exhibit the influence of wave conditions at the exposed beach when compared with headland bound beach and so the study implies for offset morphological changes and tailored management to protect the beaches from natural coastal hazards

alongshore variation in beach cusp morphology in a coastal embayment the variation in beach cusp characteristics was examined along a 1km long embayed beach pearl beach new south wales australia the beach cusp morphology had formed during the previous day and or night and displayed a marked alongshore variation in cusp spacing the edge wave mechanism of beach cusp formation could not account for the observed trend in cusp spacing because no relationship could be established between the spacing of the cusps and the gradient of the beachface on the other hand the cusp spacing was strongly related to the horizontal swash excursion providing some support for the self organization model of beach cusp formation copyright 1999 john wiley sons ltd

thermohaline stratification below the southern ocean sea ice the end of winter stratification within the cold cyclonic trough of the weddell gyre near 60 s between 5 e and the greenwich meridian is resolved with the mikhail somov data set the temperature maximum of the weddell deep water wdw is for the most part less than 0 5 c but warmer cells of wdw are found these warm wdw cells have temperature salinity and oxygen properties similar to the wdw characteristic of the weddell gyre inflow which is situated to the southeast of the mikhail somov study region the warm wdw cells are accompanied by domes in the pycnocline of 40 m amplitude over the surrounding pycnocline while deeper isopycnals are depressed anticyclonic shear below the 27 83 isopycnal within the warm wdw cells is compensated by the cyclonic shear associated with the pycnocline dome the pycnocline domes are exposed to about 50 greater entrainment by the turbulently active winter mixed layer relative to the regional entrainment rate this entrainment can significantly erode the warm cells in a single winter season introducing excess heat and salt into the mixed layer while the heat is lost to the atmosphere the excess salt is not necessarily compensated by increased fresh water introduction it is hypothesized that the warm wdw cells within the weddell gyre trough are derived from instability within the frontal zone which extends from maud rise to the northeast separating the weddell warm regime from the cold regime greater than normal injection of warm wdw cells into the weddell gyre trough would increase the surface salinity which would tend to destabilize the pycnocline increasing the probability of deep convection and polynya events

southern ocean winter mixed layer austral winter 1986 observations from the polarstern along the greenwich meridian from the ice edge to the antarctic margin show the mixed layer beneath the winter sea ice cover to be significantly depressed in oxygen saturation incorporation of weddell deep water wdw into the winter mixed layer responsible for this undersaturation also introduces heat and salinity into the surface layer which strongly influences the mixed layer sea air exchanges and sea ice formation processes the total wdw transfer into the mixed layer averages 45 myr 1 implying a residence time for the surface water of 2 5 years the associated winter heat flux is 41 w m 2 which limits ice thickness to about 0 55 m agreeing quite well with observations the air temperatures during the cruise are just sufficient to remove the wdw heat input in the presence of observed ice thickness and concentration this suggests that the sea ice cover and wdw heat input into the mixed layer are in approximate balance by midwinter the annual heat flux from wdw to the surface layer and hence into the atmosphere is estimated as 16 w m 2 extrapolation of the greenwich meridian wdw entrainment value to the full circumpolar 60 70 s belt yields total up welling of 24 106 m3 s 1 similar extrapolation of the heat flux value gives a circumpolar total of 2 8 1014 w as a consequence of circulation topography interaction the maud rise water column stands out as an anomaly relative to the surrounding region with a significantly more saline and dense mixed layer below the mixed layer the water column over the crest of the rise is identical to that over the flanks if the latter water column is upwelled by 400 m this uplifting is believed to be a response of the upstream flow encountering the rise increased upstream flow would be expected to increase maud rise upwelling and the dependent salinity density of the mixed layer slight increases in the mixed layer density could trigger a convective mode and generation of a polynya it is hypothesized that spin up of the weddell gyre s barotropic circulation induced by an increase of the regional wind stress curl would enhance the probability of polynya development over maud rise

beach cusp morphology on sand and mixed sand and gravel beaches south island new zealand abstract the morphology of beach cusps on a number of beaches around the south island new zealand is described cusp dimensions such as spacing elevation amplitude depth and spacing variance are interrelated cusp dimensions co vary in regular fashion under different process conditions such that the cusp form displays a high degree of regularity beach cusp amplitude is an exception to this regularity that appears to be controlled by factors such as grain size and beach slope analysis of cusp spacing and elevation dimensions on mixed sand and gravel beaches reveal that cusps having particular spacings form at distinct elevations on the beachface with the largest spacings occurring at the highest levels on the beachface the relationship between cusp elevation and spacing provides a technique through which beach cusp spacing can be used to infer mean sea level

structure and kinematics of the south iberian paleomargin and its relationship with the flysch trough units extensional tectonics within the gibraltar arc fold and thrust belt western betics abstract the superposition of structures observed in a selected area of the external zones of the betic orogen situated in the westernmost segment of the peri mediterranean mountain belt reveals an alternation of compressional and extensional events during the overall convergence of the african and eurasian plates that bound the system an early miocene compressional event produced the formation of the so called gibraltar arc fold and thrust belt formed by the units derived from the south iberian paleomargin and the flysch trough this wedge constitutes the footwall of the gibraltar thrust whose hanging wall corresponds to the alboran domain the outward migration of the compressional front w to nwward in the south iberian segment was followed by the outward migration of the extensional locus related to the middle miocene rifting that led to the alboran basin subsidence the tectonic inversion of the gibraltar thrust was accompanied by normal faulting of the innermost part of the paleomargin and the flysch trough units finally the alboran region underwent n s to nw se compression from late miocene onwards which caused the uplift of the gibraltar arc area

platelet ice the southern ocean s hidden ice a review basal melt of ice shelves is not only an important part of antarctica s ice sheet mass budget but it is also the origin of one of the most peculiar types of sea ice found in the polar oceans platelet ice in many regions around coastal antarctica tiny ice crystals form and grow in supercooled plumes of ice shelf water releasing heat into the surrounding ocean they usually rise towards the surface eventually becoming trapped under an ice shelf as marine ice frequently masses of those crystals are advected out of the ice shelf cavity and accumulate below a solid sea ice cover to form a semiconsolidated layer when the overlying sea ice grows into this so called sub ice platelet layer the loose crystals are consolidated adding additional thickness to the sea ice these phenomena are generally referred to as platelet ice although confusion about the terminology is widespread in the literature the presence of platelet ice has a profound impact on sea ice properties and processes in several regions of antarctica with numerous implications for the local polar marine biosphere most notably sub ice platelet layers provide a stable sheltered nutrient and food rich habitat which usually results in a highly productive and uniquely adapted ecosystem it has also been hypothesised that platelet ice may be an indicator of the state of an ice shelf although comprehensive time series are limited to the ross sea this paper clears up the terminology by providing exact definitions of the relevant terms we review platelet ice formation observational methods as well as geographical and seasonal occurrence the physical properties and ecological implications are merged in a way understandable for physicists and biologists alike to lay the foundation for the interdisciplinary research that is necessary to tackle the current knowledge gaps

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

investigation of medium term barred beach behavior using 28 year beach profile data and rotated empirical orthogonal function analysis abstract a 28 year beach profile dataset for a stretch of the hasaki coast in japan was examined using rotated empirical orthogonal function reof analysis to investigate the cross shore variation in the characteristics of beach profile change the data were obtained weekly on a micro tidal wave dominated intermediate beach along a survey line extending from the backshore to a water depth of approximately 5 m reof analysis using the first eight empirical orthogonal functions led to the study area being divided into five unique zones based on beach profile change patterns namely the backshore the foreshore the inner and outer transition zones and the bar trough zone although these zones were notably distinct from one another the profiles in foreshore and the shoreward part of the inner transition zone changed in the same way over periods of 6 and 12 months