sediment activation depth values for gentle and steep beaches abstract this paper analyzes methods and terminologies used in literature for the determination and characterization of vertical distribution of sediment activation depth which is bottom sediment layer affected by hydrodynamic processes studies on this topic include assessments carried out during short time spans from minutes to few hours or longer periods from a tidal cycle to several days in the first case activation is generally named mixing depth and is calculated by evaluating vertical distribution of fluorescent tracers in the second case it is referred to as disturbance depth and is generally evaluated using plugs of marked sand and rods or rods with a loose fitting washer vertical cross and longshore distribution of mixing and disturbance depth values recorded in different works with different techniques were also analyzed highlighting the conceptual differences between used methods and obtained results in a further step a data set from literature on this topic was gathered to obtain new formulations between disturbance depth and beach and wave characteristics as well as morphodynamic beach state expressed throughout the surf scaling parameter and the surf similarity index good linear regressions were observed between these variables obtaining expressions that can be easily used in a wide range of beach states from dissipative and intermediate to reflective ones

beach nourishment effects on sand porosity variability abstract a standard assumption in coastal engineering is that the porosity of natural beach sand non cohesive is 40 however is this assumption correct for all beach sand this paper proposes an accurate and simplified method to assess changes in sand porosity after beach nourishment by means of in situ density surveys through a nuclear densimeter this novel application has been applied to different beaches in the southwest of spain according to the tidal range grain size and beach morphology in several terms general results show that sand porosities range from 25 6 to 43 4 after beach nourishment works this research can be considered a support tool in coastal engineering to find shifting sand volumes as a result of sand porosity variability after beach nourishment and later marine influence

seasonal variations in sr mg and p in modern speleothems grotta di ernesto italy sub annual variations in trace element chemistry and luminescence have recently been demonstrated from speleothems and offer the potential of high resolution palaeoclimatic proxies however no studies have yet examined microscopic trace element variations in relation to modern cave conditions in this study the spatial variations in trace element sr mg and p concentrations in speleothems a stalagmite and a soda straw stalactite from the alpine ernesto cave temperature 6 6 0 1 c in a forested catchment in ne italy have been studied using secondary ion mass spectrometry sims and compared with environmental parameters and waters in the modern cave an annual lamination exists in the stalagmite and soda straw stalactite in the form of clear calcite with narrow visible layers which are uv fluorescent and interpreted to contain soil derived humic fulvic acids washed into the cave during autumn rains microanalyses were undertaken of seven annual laminae probably deposited during the 1960s in the stalagmite and seven laminae in the 1990s for the stalactite the analysis results show that sr consistently has a trough and p a peak centred on the inclusion rich layer mg shows mainly a negative covariation with sr in laminae formed in the 1990s but a positive covariation in the stalagmite formed in 1960s the spatial scale of the main geochemical variations is the same as that of annual laminae of inclusion poor and inclusion rich couplets mass balance arguments are used to show that the p is inorganic in form and presumably occurs as individual phosphate ions within the calcite most drip waters show limited chemical variations but a summer peak in trace elements in 1995 and a decrease in mg ca in the following winter are notable more pronounced covariations in mg ca and sr ca are shown by a site with highly variable drip rates where ratios increase at slow drip rates the strongest seasonal variations are found in pool waters where ratios increase reflecting significant ca removal from the water into the calcite during the winter in response to seasonal pco2 variations in cave air thus the cave waters compositions tend to reflect climate conditions such that mg ca and sr ca are tentatively interpreted to be higher when climate conditions are dry combining results from the speleothems and cave water along with the behaviour of each trace species mg ca variations in the speleothems are considered to reflect their variation in the cave waters whereas sr incorporation is also dependent on precipitation rate in this case mainly controlled by temporal variations in pco2 in the cave and conceivably also by inhibitors such as phosphate p adsorption a fraction of which is subsequently incorporated within calcite depends on aqueous phosphate concentration and water flux both of which should increase during the autumn therefore multiple trace element profiles in speleothems reflect multiple aspects of environment seasonality and conditions and hence a calibration against weather records is desirable to establish their palaeoclimatological meaning the strong annual variation of trace elements and particularly p can provide chronological markers for high resolution studies of other climate proxies such as stable isotopes

late holocene annual growth in three alpine stalagmites records the influence of solar activity and the north atlantic oscillation on winter climate annual growth rates and the ratio of dark to light colored calcite within single annual laminae in three contemporaneously deposited holocene speleothems from grotta di ernesto an alpine cave in northern italy respond to changes in surface temperature rather than precipitation based on monitoring of present day calcite growth and correlation with instrumental data for surface climatic conditions we interpret a higher ratio of dark to light colored calcite and the simultaneous thinning of annual laminae as indicative of colder than present winters such dark and thin laminae occur in those parts of the three stalagmites deposited from ad 1650 to 1713 and from ad 1798 to 1840 as reconstructed through lamina counting these periods correspond to the well known maunder and dalton minima of solar activity an 11 yr cyclicity in growth rate coupled with reduced calcite deposition during the historic minima of solar activity is indicative of a solar influence on lamina thickness spectral analysis of the lamina thickness data also suggests that the north atlantic oscillation variability influenced winter temperatures based on the present day controls on cave calcite formation we infer that high frequency changes in solar activity modulated the seasonal duration of soil co2 production

field experiments on vertical mixing of sand in the surf zone abstract the depth to which sand in the surf zone is vertically mixed by waves was determined from large numbers of cores taken in situ in eight tracer experiments performed on high energy beaches the most common tracer concentration profile showed a maximum at the bed surface and a monotonic decrease with depth significant numbers of irregular profiles were also found and classified several methods of estimating the mixing depth were compared in the method finally selected the mixing depth was defined as that depth which includes 80 of the tracer in a core reliability of the results was reinforced by a consistency check made possible by the use of different colored tracers local mixing depths exhibited considerable variation however the average value for the surf zone was found to increase only slightly over time intervals of 2 to 5 hr the most common on offshore distribution of the mixing depth was bimodal with maxima near the breaker line and near the shoreline the average mixing depth alongshore was almost constant for distances of up to 200 m the experiment average mixing depth z was well correlated with the significant breaking wave height hb and the relation z 0 027 hb was obtained

variations in atmospheric sulphate recorded in stalagmites by synchrotron micro xrf and xanes analyses abstract we report here the first speleothem time series of the variability of sulphate a species whose abundance in catchments is strongly influenced by atmospheric anthropogenic and volcanic sources annually resolved archives of s mg si and p were generated by applying synchrotron radiation micro x ray fluorescence xrf to two speleothems from different sites in northern italy x ray absorption edge spectrometry proves that the s is in the form of sulphate and xrf mapping demonstrates that s is within calcite and enriched zones are predominantly as layers a post 1850 a d record from the ernesto cave shows a substantial rise in sulphate interpreted as reflecting the largely anthropogenically forced variation of sulphate of the atmospheric boundary layer moderated by some ecosystem storage analysis of the circa 5 2 to circa 5 0 ka interval of a speleothem from savi cave where ecosystem retention of s is likely to have been minimal shows a spiky sulphate record resembling that of ice cores a series of sulphate peaks suggest that multiple volcanic sulphate aerosol emissions at that time this probably enhanced summer temperature cooling thus favouring the preservation of the human mummy of neolithic copper age the iceman on the watershed between italy and austria both examples illustrate the power of speleothems to record atmospheric sulphate variability

controls on trace element sr mg compositions of carbonate cave waters implications for speleothem climatic records abstract at two caves clamouse s france and ernesto ne italy cave drip and pool waters were collected and sampled at intervals over a 2 3 year period mg ca and sr ca concentration ratios corrected for marine aerosols are compared with those of bedrocks and in some cases aqueous leachates of soils and weathered bedrocks cave waters do not lie along mixing lines between calcite and dolomite of bedrock carbonate but typically show enhanced and covarying mg ca and sr ca four factors are considered as controlling processes 1 the much faster dissolution rate of calcite than dolomite allows for the possibility of increase of mg ca if water rock contact times are increased during drier conditions a theoretical model is shown to be comparable to experimental leachates 2 prior calcite precipitation along a flow path is a powerful mechanism for generating enhanced and covarying mg ca and sr ca ratios this mechanism requires the solution to lose co 2 into pores or caverns 3 incongruent dolomite dissolution has only limited potential and is best regarded as two separate processes of dolomite dissolution and calcite precipitation 4 selective leaching of mg and sr with respect to ca is shown to be important in leachates from ernesto where it appears to be a phenomenon of calcite dissolution in general selective leaching can occur whenever ca is sequestered into precipitates due to freezing or drying of soils or if there is derivation of excess sr and mg from non carbonate species the ernesto cave has abundant water supply which in the main chamber is derived from a reservoir with year round constant p co 2 of around 10 2 4 and no evidence of calcite precipitation in the karst above the cave two distinct but overlying trends of enhanced and covarying mg ca and sr ca away from the locus of bedrock compositions are due to calcite precipitation within the cave and at a variable drip site due to enhanced selective leaching at slow drip rates mg enhancement in the first chamber is due to a more dolomitic bedrock and longer residence times the clamouse site has a less abundant water supply and presents geochemical evidence of prior calcite precipitation both in the cave and in overlying porous dolomite dedolomitized limestone bedrock initial p co 2 values as high as 10 1 are inferred experimental incubations of clamouse soils which generated enhanced p co 2 and precipitated caco 3 had compositions similar to the karst waters calcite precipitation is inferred to be enhanced in drier conditions hydrological controls on cave water chemistry imply that the trace element chemistry of speleothems may be interpretable in palaeohydrological terms drier conditions tends to promote not only longer mean residence times enhancing dolomite dissolution and hence mg ca but also enhances degassing and calcite precipitation leading to increased mg ca and sr ca

field observations of sand mixing depths on steep beaches abstract a series of field studies were carried out on three portuguese beaches garra o faro and culatra to assess sand mixing depths under a range of wave heights 0 34 0 80 m wave periods 5 1 7 0 s and mean grain sizes 0 26 and 0 38 mm all the studied beaches had a reflective profile with a steep upper foreshore tan of 0 10 0 14 and a more gentle low tide terrace in all experiments plunging waves were breaking on the beach face the study has identified a linear correlation between significant wave height at breaking h b and average sand mixing depth z m whereby z m 0 27h b the empirical relationship is ten times larger than a previous one proposed by other authors working on gentle slope dissipative beaches and confirms previous findings on similar reflective beaches carried out in the usa it was also confirmed that z m is related to wave period but does not seem to be a function of mean sand size

longshore drift estimation using fluorescent tracers new insights from an experiment at comporta beach portugal abstract a fluorescent sand tracer experiment was performed at comporta beach portugal with the aim of acquiring longshore sediment transport data on a reflective beach the optimization of field and laboratory tracer procedures and the improvement of the conceptual model used to support tracer data interpretation the field experiment was performed on a mesotidal reflective beach face in low energetic conditions significant wave height between 0 4 and 0 5 m two different colour tracers orange and blue were injected at low tide and sampled in the two subsequent low tides using a high resolution 3d grid extending 450 m alongshore and 30 m cross shore marked sand was detected using an automatic digital image processing system developed in the scope of the present experiment results for the two colour tracers show a remarkable coherence with high recovery rates attesting data validity sand tracer displayed a high advection velocity but with distinct vertical distribution patterns in the two tides in the first tide there was a clear decrease in tracer advection velocity with depth while in the second tide the tracer exhibited an almost uniform vertical velocity distribution this differing behaviour suggests that in the first tide the tracer had not reached equilibrium within the transport system pointing to a considerable time lag between injection and complete mixing this issue has important implications for the interpretation of tracer data indicating that short term tracer experiments tend to overestimate transport rates in this work therefore longshore estimates were based on tracer results obtained during the second tide the estimated total longshore transport rate at comporta beach was 2 10 3 m3 s more than four times larger than predicted using standard empirical longshore formulas this discrepancy which results from the unusually large active moving layer observed during the experiment confirms the idea that most common longshore transport equations under estimate total sediment transport in plunging surging waves

swash zone sediment transport step dynamics and morphological response on a gravel beach abstract state of the art morphodynamic field data were collected from slapton sands uk a fine gravel beach d50 2 10 mm over a 10 day period under a range of wave tide conditions comprising a mixture of southerly swell and easterly wind waves hs 0 5 1 m ts 4 8 s tide range 3 4 m over the field period the upper beach experienced accretion and berm formation during tides with low steepness swell dominated wave conditions h l 0 01 surprisingly the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves and suggests that upper beach morphological change can be decoupled from the overall sediment budget a submerged accretionary feature the beach step grew and migrated onshore on the rising tide typically reaching a maximum relief of around 0 5 m then gradually decreased in prominence while migrating offshore as the tide fell resulting in little net morphological change the step was better developed during the falling tide than the rising tide and through its control on the swash hydro and sediment dynamics the step had a significant effect on the development of the berm swash flow velocities under the conditions measured were often in excess of 2 m s 1 for both the uprush and the backwash onshore mean flows occurred in the upper swash region 40 inundation was characterised by offshore mean flows swash infiltration losses in the swash zone increased from 40 in the lower swash region to 100 in the upper swash region the most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone 90 100 inundation

morphological drainage and eolian controls on the microtidal patara beach sediments eastern mediterranean textural geochemical and mineralogical investigations abstract the effects of dominant hydrodynamic morphological fluvial and hinterland geological source conditions on the texture and composition of the microtidal and dissipative patara beach mediterranean coast of sw turkey sediments were investigated at 47 locations patara beach sediments are composed entirely of sand fine sand 5 94 was more abundant in the northwestern section while medium sand contents 2 94 increased in the central and southeastern sections moderately to well sorted mostly 0 3 0 7 o sediments tend to show overall better sorting towards the southeast in the net longshore current direction terrigenous carbonate grains derived from the hinterland constituted 6 50 as caco3 with varying tendencies to increase or decrease within sections alongshore total heavy mineral concentrations in bulk sediments 1 17 mostly

record of volcanism since 7000 b c from the gisp2 greenland ice core and implications for the volcano climate system sulfate concentrations from continuous biyearly sampling of the gisp2 greenland ice core provide a record of potential climate forcing volcanism since 7000 b c although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions only about 30 percent of the events from 1 to 7000 b c were matched to such events several historic eruptions may have been greater sulfur producers than previously thought there are three times as many events from 5000 to 7000 b c as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions this increased volcanism in the early holocene may have contributed to climatic cooling

origin and migration of the alpine iceman the alpine iceman provides a unique window into the neolithic copper age of europe we compared the radiogenic strontium and lead and stable oxygen and carbon isotope composition of the iceman s teeth and bones as well as 40ar 39ar mica ages from his intestine to local geology and hydrology and we inferred his habitat and range from childhood to adult life the iceman s origin can be restricted to a few valleys within 60 kilometers south east of the discovery site his migration during adulthood is indicated by contrasting isotopic compositions of enamel bones and intestinal content this demonstrates that the alpine valleys of central europe were permanently inhabited during the terminal neolithic

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

migration of swash zone step and microtopographic features during tidal cycles on an estuarine beach delaware bay new jersey u s a abstract a time series analysis of changes in surface elevation on the foreshore of an estuarine beach was conducted to compare movement of topographic features in the swash and breaker zones with results derived from study of ocean beaches wave heights on the upper foreshore during the field study averaged 0 15 m with an average period of 2 4 s the average height of the beach step was 21 mm smaller elevation changes up to 12 mm in height occurred at 10 15 min periods there were more small elevation changes greater longshore variations in these changes and greater variation in the form of the beach step during the rising tide than during the falling tide the variation in the small elevation changes and the beach step are attributed to greater short term fluctuations in beach saturation during rising tides causing greater variability in the velocity of swash and backwash

the chemical composition of rivers and snow affected by the 2014 2015 barðarbunga eruption iceland abstract the 2014 15 bar arbunga volcanic eruption was the largest in iceland for more than 200 years this eruption released into the atmosphere on average 60 000 tonnes day of so2 30 000 tonnes day of co2 and 500 tonnes day of hcl affecting the chemical composition of rain snow and surface water the interaction of these volcanic gases with natural waters decreases fluid ph and accelerates rock dissolution this leads to the enhanced release of elements including toxic metals such as aluminium to these waters river monitoring including spot and continuous osmotic sampling shows that although the water conductivity was relatively stable during the volcanic unrest the dissolution of volcanic gases increased the so4 f and cl concentrations of local surface waters by up to two orders of magnitude decreasing the carbon alkalinity in addition the concentration of sio2 ca mg na and trace metals rose considerably due to the water molten lava and hot solid lava interaction the presence of pristine lava and acidic gases increased the average chemical denudation rate calculated based on na flux within jokulsa a fjollum catchment by a factor of two compared to the background flux melted snow samples collected at the eruption site were characterised by a strong dependence of the ph on so4 f and cl and metal concentrations indicating that volcanic gases and aerosols acidified the snow protons balanced about half of the negatively charged anions the rest was balanced by water soluble salts and aerosols containing a variety of metals including al fe na ca and mg the concentrations of f al fe mn cd cu and pb in the snowmelt water surpassed drinking and surface water standards snowmelt river water mixing calculations indicate that low alkalinity surface waters such as numerous salmon rivers in east iceland will be more affected by polluted snowmelt waters than high alkalinity spring and glacier fed rivers

measuring sediment transport and bed disturbance with tracers on a mixed beach abstract a new tracer deployment method is applied to the problem of resolving rates and patterns of littoral sediment transport on mixed beaches we applied the method at the morphologically complex meso tidal beach fringing the elwha river delta washington clasts were transformed into tracers using radio frequency identifier rfid tags these tracers were deployed in and on the bed along a cross shore oriented beach transect along and cross shore variations in tracer velocity were used to estimate sediment transport patterns including the depth and cross sectional area of the disturbed bed and bulk alongshore transport rates we found that the peak bed disturbance averaged 22 of the tidal maximum significant wave height and that tracer velocity declined approximately logarithmically with depth in the bed across all deployments the maximum alongshore tracer velocity occurred between 1 0 and 2 0 m above mean lower low water mllw corresponding to elevations 0 3 m below and 0 7 m above mean sea level msl at this location alongshore bulk sediment transport rates estimated from the advection of tracers ranged from 1 1 to 173 1 m3 d under significant wave heights of 0 1 to 2 1 m and these transport rates related linearly to measured wave energy transport both the volumetric sediment transport rates and a cerc type k coefficient derived from the results agreed well with results from other published studies

one year along beach variation in the maximum depth of erosion resulting from irregular shoreline morphology abstract beach erosion and accretion occur across multiple time scales over long time scales decades to millennia the shoreface ravinement surface which is recognized as a coarse lag deposit forms at the shoreface toe as a result of wave and current induced erosion during shoreline transgression over short time scales hours to days the depth of sediment disturbance which is recognized as coarse lamina and measured at the foreshore by devices and monitoring tracer beds forms as a result of wave and current induced reworking during a tidal cycle the maximum depth of erosion mdoe quantified here over 1 year is modulated by processes that operate over a time scale that is between the drivers of short term e g tides and waves and long term e g sea level rise beach erosion the mdoe integrates the erosion that occurs over a discrete time interval and records the maximum depth of erosion that is likely principally induced by storms which is difficult to quantify by other methods that rely on discrete observations e g changes in elevation or movement of the mean high water line a novel technique for quantifying the mdoe based on comparing the bedding and stratigraphy between cores collected at the same locations over a discrete time interval is presented here and applied at onslow beach nc usa this 12 km long barrier island has irregular shoreline morphology characterized by two embayments separated by a central headland this shape is largely the result of variations in the depth of underlying rock strata and produces a steeper beachface at the headland than at the embayments at each of the six sites examined along the barrier the mdoe is found to increase from the backshore to the middle intertidal zone and is higher at the sites closer to the headland these variations in the mdoe are likely due to the increase in average wave energy impacting the beachface from an offshore direction and steeper beaches intermediate beach state at the headland where the mdoe is within the beach facies it is not associated with a coarsening which is due to the heterolithic nature of the onslow beach strata where the mdoe is the contact between back barrier and beach facies it is always associated with a coarsening and a gravel rich lag deposit because in this case the mdoe is an amalgamation of multiple erosional events which is similar to the shoreface ravinement surface along beach variation in the mdoe does not correspond with discrete observations of beach change over the same period and is likely a better indicator of erosion potential than long term discrete observations such as changes in surface elevation or the position of the mean high water line

carbon transfer dynamics from bomb 14c and δ13c time series of a laminated stalagmite from sw france modelling and comparison with other stalagmite records twenty two ams 14c measurements have been made on a modern stalagmite from sw france in order to reconstruct the 14c activity history of the calcite deposit annual growth laminae provides a chronology up to 1919 a d results show that the stalagmite 14c activity time series is sensitive to modern atmosphere 14c activity changes such as those produced by the nuclear weapon tests the comparison between the two 14c time series shows that the stalagmite time series is damped its amplitude variation between pre bomb and post bomb values is 75 less and the time delay between the two time series peaks is 16 years 3 a model is developed using atmosphere 14c and 13c data fractionation processes and three soil organic matter components whose mean turnover rates are different the linear correlation coefficient between modeled and measured activities is 0 99 these results combined with two other stalagmite 14c time series already published and compared with local vegetation and climate demonstrate that most of the carbon transfer dynamics are controlled in the soil by soil organic matter degradation rates where vegetation produces debris whose degradation is slow the fraction of old carbon injected in the system increases the observed 14c time series is much more damped and lag time longer than that observed under grassland sites the same mixing model applied on the 13c shows a good agreement r2 0 78 between modeled and measured stalagmite 13c and demonstrates that the suess effect due to fossil fuel combustion in the atmosphere is recorded in the stalagmite but with a damped effect due to som degradation rate the different sources of dead carbon in the seepage water are calculated and discussed

first sulfur isotope measurements in central greenland ice cores along the preindustrial and industrial periods 1 sulfur isotopes of sulfate have been measured in a discontinuous set of polar ice core samples from summit central greenland covering the preindustrial from the fourteenth to the eighteenth century and industrial from 1872 to 1969 a d periods results have been used to estimate the different source contributions to the deposited sulfate and their evolution along the last centuries they indicate that the preindustrial background sulfate budget is slightly dominated on a year round average by marine biogenic emissions amounting to close to half of the non sea salt sulfate 49 the second contribution is provided by continental sources of secondary sulfate including background volcanism and to a lesser extent continental biota 44 of the non sea salt sulfate sulfur emitted by relatively weak eruptions is found to be largely depleted in 34s compared to bulk volcanic s suggesting an efficient washout of the heavier isotope during the tropospheric transport the impact of human driven emissions on the sulfate deposited in central greenland ice is visible in isotope data as early as 1870 a d the isotopic signature of anthropogenic sulfur deposited during the twentieth century is found to be constant 34s 3 0 1 5 regardless of the changes of dominant source regions and emission processes this signature is slightly but measurably lighter than the one reported for arctic haze pollution events

depth of activation of sediment by plunging breakers on a steep sand beach abstract field data were collected over a lunar tidal cycle on a meso tidal medium sand estuarine beach in delaware bay usa to document the relationship between wave height and depth of sediment activation in a low wave energy environment dominant energy was at the frequencies of locally generated waves and ocean swell significant wave heights ranged from 0 06 m to 0 52 m periods of locally generated waves averaged 4 0 s during strong onshore winds and 2 6 s during low speed winds waves on the foreshore were always plunging the foreshore maintained a slope of approximately 6 0 throughout the study period mean grain size at mid foreshore was 0 46 mm the greatest net surface elevation change in response to storm erosion and post storm recovery was 0 26 m results confirm previous observations that depths of sediment activation are greater for steeper beaches the spatial variability in depths of activation across the foreshore is comparable to results of tidal cycle studies where the ratio of depth of activation to wave height is great because a large percentage of the foreshore comes under the influence of the breakers the ratio of depth of activation to wave height on the portion of the foreshore that is not transgressed by the breakers is lower and comparable to results of short term investigations provided that the influence of beach slope is considered in the calculation of breaking wave height

landward migration of inner bars abstract a field investigation was carried out to collect data of inner bar migration profiles were measured once or twice a week for a two year period at naka beach ibaraki prefecture japan it was found that the onshore migration of inner bars could be described by two dimensionless quantities as 5d h b max h b max gt 2 max 20d h b max where h b max is the maximum value of daily average breaker height during one interval between surveys t max is the average wave period of the day giving h b max d is the mean size of the beach sediment and g is the acceleration due to gravity analyses based on surfzone sediment dynamics yields v wd b 2 10 11 h b d 3 where v is the average speed of onshore bar migration b is the bar height h b is the average breaker height and w is the fall velocity of the beach sediment nomographs for the speed of landward migrating bars are also presented

prediction of average mixing depth of sediment in the surf zone abstract a predictive model for the average depth of mixing of sediment in the surf zone is formulated on the basis of the wave induced shear stress on the bottom the model is calibrated using field data obtained through tracer experiments performed on pacific beaches of japan the result gives z d 81 4 b c where z is the average depth of sediment mixing in the surf zone d is the grain size of the sediment b is the shields parameter at the wave breaking point and c is the critical shields number for oscillatory flow the predicted mixing depth is found to increase in an approximately linear fashion with the breaking wave height for significant breaking wave heights up to about 1 5 m for greater breaking wave heights the rate of increase in the mixing depth decreases with increasing wave height the mixing depth is also a strong function of the wave period in the larger wave height region finally the predicted mixing depth is found to be a weakly increasing function of the sediment grain size

annual to sub annual resolution of multiple trace element trends in speleothems this study aims to establish evidence for the widespread existence of preserved high resolution trace element variations in speleothems that may have climatic significance ion microprobe analysis of speleothems reveals that annual to sub annual variations in element chemistry exist at five shallow western european cave sites crag cave county kerry and ballynamintra county waterford ireland uamh an tartair sutherland scotland grotte pere noel belgium grotta di ernesto ne italy with widely varying climatic geomorphic and geological settings the variations are not restricted to species mg sr and ba known to substitute directly for ca in the calcite lattice but include h f na and p phosphorus as phosphate displays the greatest variability and may have the most significance as a proxy for the seasonal temperature cycle because of its role as a nutrient element the technique allows estimation of growth rate of speleothems at any interval of interest which is one of several possible uses in palaeoclimatology

short term morphological change and sediment dynamics in the intertidal zone of a macrotidal beach abstract this paper describes the morphological and sedimentological evolution of amacrotidal beach over a 20 day period under varying hydrodynamicconditions signi cant breaker heights of 0ae3 2 m and tidal ranges of 2 5 m during the eld campaign an intertidal bar developed around the mid tidelevel migrated onshore welded to the upper beach and was then attenedunder energetic wave conditions the bar had a wave breakpoint origin and itsformation was triggered by a reduction in tidal range causing more stationarywater level conditions rather than an increase in wave height most of theonshore bar migration took place while the bar was positioned in the inner tomid surf zone position such that the bar moved away from the breakpoint andexhibited divergent behaviour the depth of disturbance over individual tidalcycles was 10 20 of the breaker height such values are more typical of steepre ective beaches than gently sloping dissipative beaches and are consideredto re ect the maximum height of wave generated ripples the grain sizedistribution of sur cial sediments did not vary consistently across the beachpro le and temporal changes in the sedimentology were mostly unrelated tothe morphological response the lack of clear links between beach morphologyand sedimentology may be in part due to shortcomings in the samplingmethodology which ignored the vertical variability in the sediment sizecharacteristics across the active layer keywords beach sediment depth of disturbance intertidal bar macrotidalbeach morphology introductionbeaches respond rapidly to changing wave andtide conditions through the redistribution of theirsediments by oscillatory and quasi steady cur rents resulting in spatial patterns of erosion sediment divergence and accretion sedimentconvergence given suf cient time these bed level changes modify the beach shape by theformation modi cation destruction and ormigration of secondary morphological features such as berms beach cusps swash bars ripchannels and nearshore bars the dynamics ofthese secondary morphological features and theirrole in affecting beach stability has been a majorfocus of beach research over the last few decades e g komar 1998 short 1999 most short term days to weeks eld investi gations addressing the morphological response ofsandy beaches to wave and tide forcing have beenconducted in microtidal or mesotidal settings beaches in macrotidal settings have on the otherhand only received limited attention despitetheir common occurrence short 1991 a mainreason for this imbalance is that macrotidalbeaches are often planar and lack pronouncedsecondary morphological features indeed theonly type of macrotidal beach that does featureprominently in the coastal literature is the ridgeand runnel beach which is characterized bysedimentology 2007 54 39 53

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years

causal loop analysis of coastal geomorphological systems as geomorphologists embrace ever more sophisticated theoretical frameworks that shift from simple notions of evolution towards single steady equilibria to recognise the possibility of multiple response pathways and outcomes morphodynamic modellers are facing the problem of how to keep track of an ever greater number of system feedbacks within coastal geomorphology capturing these feedbacks is critically important especially as the focus of activity shifts from reductionist models founded on sediment transport fundamentals to more synthesist ones intended to resolve emergent behaviours at decadal to centennial scales this paper addresses the challenge of mapping the feedback structure of processes controlling geomorphic system behaviour with reference to illustrative applications of causal loop analysis at two study cases 1 the erosion accretion behaviour of graded mixed sediment beds and 2 the local alongshore sediment fluxes of sand rich shorelines these case study examples are chosen on account of their central role in the quantitative modelling of geomorphological futures and as they illustrate different types of causation causal loop diagrams a form of directed graph are used to distil the feedback structure to reveal in advance of more quantitative modelling multi response pathways and multiple outcomes in the case of graded sediment bed up to three different outcomes no response and two disequilibrium states can be derived from a simple qualitative stability analysis for the sand rich local shoreline behaviour case two fundamentally different responses of the shoreline diffusive and anti diffusive triggered by small changes of the shoreline cross shore position can be inferred purely through analysis of the causal pathways explicit depiction of feedback structure diagrams is beneficial when developing numerical models to explore coastal morphological futures by explicitly mapping the feedbacks included and neglected within a model the modeller can readily assess if critical feedback loops are included