ordovician emplacement of the mount dingley diatreme western ranges of the rocky mountains southeastern british columbia external and internal morphologies are well shown by a newly discovered diatreme that is exceptionally well exposed in a cirque within the north face of mount dingley the diatreme contains abundan

arenigian early ordovician sea level history and the response of conodont communities western newfoundland four cluster analyses were performed which recognized 17 conodont communities in the arenigian lower ordovician of western newfoundland the analyses include 69 598 identifiable conodont specimens recovered from 153 conodont bearing samples from four stratigraphical sections representing the environmental settings of the platform upper proximal slope lower proximal slope and distal slope the distribution of conodont communities along the platform to slope environmental gradient shows that sea level changes simultaneously affected the development and replacement of the conodont communities in the different facies the pattern of change in conodont communities allows an interpretation of sea level change that is correlated precisely into the detailed graptolite biozonation a gradual transgression lasted most of tetragraptus approximatus zone time which was followed by a brief regression a transgression regression cycle occurred in the t akzharensis zone time a major transgression caused a highst

climatological features of the weakly and very stably stratified nocturnal boundary layers part iii the structure of meteorological state variables in persistent regime nights and across regime transitions abstractthe evolution of profiles of meteorological state variables during nights with and without transitions in the nocturnal stably stratified boundary layer sbl between weakly stable wsbl a

saltwater circulation patterns within the freshwater saltwater interface in coastal aquifers laboratory experiments and numerical modeling summary groundwater flow patterns within the freshwater saltwater interface in coastal aquifers include rotation in the flow direction of saltwater that originates from the sea and circulates in the aquifer using two types of tracer experiments we analyze the configuration of the rotating flow lines the experimental results are numerically reconstructed and quantitatively compared to the salinity distribution along the interface the results show that the rotation in the direction of the saltwater flow lines begins at the lowermost part of the interface i e contour c cmax 99 and completes within its lower tenth contour c cmax 94 at the upper part of the interface after the rotation is completed the flow is dictated by the freshwater flow seaward based on these results the well known chemical freshwater saltwater interface is divided into two different parts defined by their physical properties 1 the lower part is the flow rotation region defined by convective circulating flow lines and 2 the upper part is the dispersive region defined by dispersive dilution sensitivity analysis shows that the physical configuration of the interface depends on the transversal dispersivities at higher dispersivities the rotation width increases but completes within the lower third of the interface at most the sensitivity analysis also shows that the rotation begins at the lowermost part of the interface for dispersivities therefore since no flow occurs below a line of 99 the saline water that flows seaward is always diluted with respect to its original salinity these flow patterns might affect coastal processes such as submarine groundwater discharge sgd and chemicals transport through the aquifer

conodont color and textural alteration an index to regional metamorphism contact metamorphism and hydrothermal alteration experimental and field data are used to extend the utility of conodonts as semi quantitative thermal indices into the regimes of regional and contact metamorphism as well as hydrothermal alteration an arrhenius plot of data from induced conodont color alteration by pyrolysis in air at 1 atm was used to generate the geologic temperatures for conodont color alteration indices cai above 300 c that is for cai values of 5 through 8 such cai values occur in very low to medium grade regionally metamorphosed contact metamorphosed and hydrothermally altered rocks the uniformity or variability of cai values within a sample together with conodont texture can help to distinguish grades and environments of metamorphism particularly in metacarbonate sequences induced cai by pyrolysis in a water methane mixture at kbar results in retardation of cai and in a disparate mixture of both low and high cai values within each experimental sample in this system color alteration processes above a cai of 2 to 3 seem to change from predominantly carbonization to predominantly loss of organic matter presumably by oxidation and volatilization of oxides these experiments approximate the type of cai mixture characteristically found in conodonts recovered from hydrothermally altered rocks these data indicate that cai values of 6 to 8 cannot be used to assess precise temperatures of hydrothermally altered rocks but may serve as useful indicators of potential mineralization

analytical solutions of seawater intrusion in sloping confined and unconfined coastal aquifers sloping coastal aquifers in reality are ubiquitous and well documented steady state sharp interface analytical solutions for describing seawater intrusion in sloping confined and unconfined coastal aquifers are developed based on the dupuit forchheimer approximation specifically analytical solutions based on the constant flux inland boundary condition are derived by solving the discharge equation for the interface zone with the continuity conditions of the head and flux applied at the interface between the freshwater zone and the interface zone analytical solutions for the constant head inland boundary are then obtained by developing the relationship between the inland freshwater flux and hydraulic head and combining this relationship with the solutions of the constant flux inland boundary it is found that for the constant flux inland boundary the shape of the saltwater interface is independent of the geometry of the bottom confining layer for both aquifer types despite that the geometry of the bottom confining layer determines the location of the interface tip this is attributed to that the hydraulic head at the interface is identical to that of the coastal boundary so the shape of the bed below the interface is irrelevant to the interface position moreover developed analytical solutions with an empirical factor on the density factor are in good agreement with the results of variable density flow numerical modelling analytical solutions developed in this study provide a powerful tool for assessment of seawater intrusion in sloping coastal aquifers as well as in coastal aquifers with a known freshwater flux but an arbitrary geometry of the bottom confining layer this article is protected by copyright all rights reserved

groundwater flow and residence times below a meso tidal high energy beach a model based analyses of salinity patterns and 3h 3he groundwater ages abstract in this study 3h 3he ages in the intertidal zone based on both field measurements and numerical simulations are presented to provide insights into the flow and transport behavior within the subterranean estuary of a meso tidal high energy beach in a systematic modelling approach important hydrogeological parameters dispersivity hydraulic conductivity and fresh groundwater flux were varied in a cross shore transect at a beach on spiekeroog island in north western germany both measured and simulated salinity and age distribution within the intertidal zone suggest the existence of two at least temporally occurring saltwater recirculation cells accompanied by two fresh discharge location this is in contrast to the state of the art concept of a ste under tidal influence and is caused by a runnel and ridge system at the study site which is a rather wide spread type of beach morphology with topographical highs and interfering lows in the intertidal zone residence times within the two saline plumes were between weeks and several months freshwater from the island s freshwater lens resided up to 18 years in the brackish beach aquifer before exfiltrating at the discharge points field measurements confirmed the discharge of decade old water at the discharge points model results were highly dependent on the tested model parameters a change between a one and two plume system as well as overlapping conditions at the study site dependent on the change in beach topography are likely

regime transitions in near surface temperature inversions a conceptual model abstracta conceptual model is used in combination with observational analysis to understand regime transitions of near surface temperature inversions at night as well as in arctic conditions the model combines a surface energy budget with a bulk parameterization for turbulent heat transport energy fluxes or feedbacks due to soil and radiative heat transfer are accounted for by a lumped parameter closure which represents the coupling strength of the system observations from cabauw netherlands and dome c antarctica are analyzed as expected inversions are weak for strong winds whereas large inversions are found under weak wind conditions however a sharp transition is found between those regimes as it occurs within a narrow wind range this results in a typical s shaped dependency the conceptual model explains why this characteristic must be a robust feature differences between the cabauw and dome c cases are explained from differences in coupling strength being weaker in the antarctic f

a mechanistic study of nonlinear solute transport in a groundwater surface water system under steady state and transient hydraulic conditions two laboratory experiments were conducted to investigate the effects of tides and buoyancy on beach hydraulics in the presence of a seaward groundwater flow due to an elevated regional water table in the first experiment case 1 the difference in concentration between the salt water at sea and the water of the regional aquifer was small 2 4 g l 1 such that it did not engender density gradients the salt acts as a tracer in this case in the second experiment case 2 the difference was 32 0 g l 1 which creates a significant density gradient this case corresponds to the presence of fresh groundwater in the subsurface of the coasts of the continental united states the experiments were numerically simulated by the marine unsaturated marun model a numerical model for density and viscosity dependent flows in two dimensional variably saturated media the long term experimental and numerical results showed that the seawater plume entered the beach from the sea and occupied most of the intertidal zone the maximum depth of the seawater plume was near the midsection of the intertidal zone and it decreased near the low and high tide lines when viewed in the context of case 2 these results indicate an inverted salinity distribution in beaches subjected to tides with salt water from sea overtopping the freshwater lens for both cases water from the regional aquifer moved seaward beneath the seawater in the intertidal zone and pinched out near the low tide mark we also noted that beach hydraulics are highly two dimensional with water entering the beach at a near vertical angle and leaving it at a near horizontal angle which casts doubts on analyses of beach hydraulics based on the dupuit assumption findings from this work have direct implications within the practice of bioremediation of oil spills on beaches we found that applying dissolved nutrients on the beach surface at low tide is superior to applying them in a trench landward of the beach this is because the residence time of the nutrient plume in the bioremediation zone of the beach in the prior situation is longer than that in the latter

conodonts as biostratigraphic tools for redefinition and correlation of the cambrian ordovician boundary the cambrian ordovician boundary is recognized at different horizons on various continents by utilizing several fossil groups conodonts are abundant diverse and less provincial and facies controlled than other fossils in this interval many species are widespread and some are cosmopolitan strata representing the cambrian ordovician boundary interval from asia australia and north america can be correlated easily when those strata are from cratonal or shelf environments strata from slope facies have fewer conodonts fewer taxa and taxa may have different ranges compared with cratonal and shelf facies it may be easier to correlate intercontinentally within cratonal shelf facies than to correlate intracontinentally from cratonal shelf facies to slope facies a new hierarchical arrangement of conodont interval zones and subzones is proposed for western north america these include the proconodontus tenuiserratus zone the p posterocostatus zone new the p muelleri zone new the eoconodontus zone new with eoconodontus notchpeakensis and cambrooistodus minutus subzones the cordylodus proavus zone emended with hirsutodontus hirsutus fryxellodontus inornatus and clavohamulus elongatus subzones the cordylodus intermedius zone new with hirsutodontus simplex and clavohamulus hintzei subzones the cordylodus lindstromi zone new and cordylodus angulatus zone new the boundary point for the base of the ordovician system will be chosen so as to coincide with a correlatable conodont zonal boundary other fossil groups will support correlation of this boundary point three alternative horizons are being considered the base of the cordylodus proavus zone is the most distinctive but is regarded by some as older than is appropriate for the base of the ordovician the base of the cordylodus intermedius zone is recognizable by faunal changes in several evolutionary lineages at a level that is slightly younger than the presently recognized boundary in australia north america and parts of asia but slightly older than the base of the tremadoc series of europe the base of the c lindstromi zone can be recognized in most areas by the lowest occurrence of the nominate species which is of questioned taxonomic validity and uncertain biostratigraphic utility this horizon is closest to the base of the tremadoc series of europe choice of a stratotype section has been narrowed to the cow head group in newfoundland eastern canada and to the fengshan and yehli formations in jilin province northeastern china the cow head group was deposited on and near the base of the continental slope erosion by debrisslide breccias resulted in a significant hiatus near the boundary interval in the broom point sections a condition contrary to guidelines for choice of boundary sections this may be less of a problem in other sections such as green point the dayangcha section in china was deposited on the outer part of a continental shelf and has acritarchs conodonts graptolites and trilobites additional study of the china section is needed to document fully the ranges of critical conodont taxa

swash zone moisture dynamics and unsaturated infiltration in two sandy beach aquifers the intertidal zone of coastal aquifers is a dynamic region of mixing between saline surface water and fresh groundwater groundwater circulation in this zone is affected by complex forcing mechanisms that operate on a range of timescales and can regulate chemical fluxes to marine environments we evaluated wave swash induced infiltration and associated flow dynamics in the unsaturated region of two sandy beach aquifers with differing wave conditions and beach morphologies moisture and pressure sensors were used to measure fluctuations in water content water table elevation and hydraulic gradients at high frequencies 5 hz in the swash zone at mean lower low water mean sea level and mean higher high water water content in the unsaturated region of the swash zone responded to wave overtopping and swash infiltration with a rapid rise in water content followed by a slower decline swash induced unsaturated infiltration rates calculated from water content response were lowest near low tide and increased up the beachface with inflow highest near high tide at both sites consistent with an increase in water table depth up the beach unsaturated infiltration was 1 6 m 3 m per tidal cycle at the wavedominated beach and 0 4 m 3 m per tidal cycle at the tide dominated beach saturated pore pressure measurements show that a water table mound formed as a consequence of swash infiltration that migrated up the beach during rising tide leading to divergent seaward landward groundwater flow the results demonstrate the significant and spatially variable effects of wave swash on moisture dynamics in the unsaturated zone of beach aquifers and show that these effects depend on wave conditions and beach characteristics results have implications for understanding transport and reaction of solutes in this biogeochemically active zone

tide induced seawater groundwater circulation in shallow beach aquifers summary in this paper we investigated the tide induced seawater groundwater circulation in shallow beach aquifers using the finite element model marun the numerical solutions were generalized using a dimensionless formulation from a dimensionless tidal period and a dimensionless beach slope of 10 we obtained results that apply to a wide range of beach permeabilities from 10 4 m s to 10 3 m s beach slopes from 3 16 to 31 6 tidal amplitude 0 3 m 2 m and period diurnal or semidiurnal the numerical simulations demonstrated the following the maximum darcy velocity always occurs at the intersection of the watertable and the beach surface the offshore beach groundwater is almost stagnant compared with the onshore groundwater flow which may explain the previous observations that the major portion of the seaward groundwater seepage usually occurs in the shallow part of the submerged beach the outflow from the seepage face accounts for 41 97 average 55 of the outflow from the intertidal zone the amount of seawater infiltrating into the intertidal zone in a tidal cycle increases with the beach permeability and decreases when the inland recharge increases and ranges from 35 5 m 3 yr 1 m 1 to 505 8 m 3 yr 1 m 1 for all the cases considered smaller beach slopes smaller inland freshwater recharges and or greater beach permeability lead to larger saltwater plumes in the intertidal zone of the beach the results are in line with the existing results of field observations and numerical simulations by previous researchers a 2008 elsevier b v all rights reserved

impacts of evaporation on subsurface flow and salt accumulation in a tidally influenced beach we coupled a mass transfer formulation of evaporation to the density dependent variably saturated finite element model marun to predict the salinity under realistic conditions in a beach in the gulf of mexico the results showed that evaporation almost doubled the pore water salt concentration in the intertidal zone in comparison to the case with no evaporation the results also showed that for the relatively wet atmospheric conditions the maximum evaporation did not occur from the supratidal zone rather from the intertidal zone and it was due to the difference in moisture between pore water and atmosphere the highest salinity occurred during the spring tide period and extended into the neap tide period when the atmospheric condition was assumed to be constant and conducive to large evaporation high temperature and low air humidity the maximum salinity region shifted to the supratidal zone and persisted there due to low mixing the maximum salinity value in the intertidal zone for this case was not larger than that of the variable atmospheric condition case however the maximum was more landward than the more realistic variable atmospheric condition case which suggests that accurate characterization of pore water salinity in tidally influenced beaches requires accurate knowledge of atmospheric conditions in addition to beach and hydraulic properties the constant atmospheric condition simulations suggest that antecedent extreme conditions greatly affect the salinity in the supratidal zone but they are dampened in the intertidal zone

tidal influence on seawater intrusion in unconfined coastal aquifers studies of seawater intrusion in unconfined coastal aquifers typically neglect oceanic oscillations such as tides and assume a static seaward boundary condition defined by the mean sea level laboratory experiments and numerical simulations were conducted to investigate the influence of tidal oscillations on the behavior of the saltwater wedge for the conditions examined the experiments showed that an upper saline plume formed in the intertidal zone due to tide induced seawater circulation the presence of the upper saline plume shifted the fresh groundwater discharge zone seaward to the low tide mark and restricted the intrusion of the saltwater wedge the overall seawater intrusion extent as indicated by the wedge toe location was reduced significantly compared with the nontidal static case results from the numerical model matched these experimental observations and further demonstrated the similar type of tidal influence on the saltwater wedge in a field scale aquifer system the glover 1959 solution for predicting the saltwater wedge was modified to account for the tidal effect by including the tide induced circulation as a recharge to the aquifer the findings highlight the significant impact of the tide in modulating the groundwater behavior and salt freshwater dynamics not only within but also landward of the intertidal zone

effect of wind speed and leads on clear sky cooling over arctic sea ice during polar night abstracta simple analytical model of the atmospheric boundary layer abl coupled to sea ice is presented it describes clear sky cooling over sea ice during polar night in the presence of leads t

evolution of the early paleozoic cordilleran margin of laurentia tectonic and eustatic events interpreted from sequence stratigraphy and conodont community patterns several field seasons in the canadian cordillera have allowed the measurement description and sampling of over 20 000 m of lower paleozoic strata from 26 stratigraphic sections across four platform to basin transects with the recovery of over 100 000 conodonts from more than 1200 4 5 kg samples this work was part of the lithoprobe slave northern cordillera lithospheric evolution snorcle project but is also being extended through a pan lithoprobe project to understand the tectonic and eustatic response of much of the laurentian plate through the early paleozoic based on the abundant field data the complex stratigraphic framework is interpreted in terms of sequence stratigraphy and a derived relative sea level curve using detailed conodont taxonomic and biostratigraphic results cluster analysis of conodont distributional data identified an evolving series of conodont communities through space and time these communities were partitioned across the platform to basin gradient and provide an additional sensitive indicator of relative sea level change these two independent approaches generated comparable eustatic curves for this cordilleran laurentian margin during much of the early paleozoic and identified some global eustatic events noted by earlier workers this part of laurentia was not a simple passive margin during the early paleozoic but rather was affected by four main tectonic events complicated by six principal eustatic changes some success was achieved in filtering the global and regional tectonic eustatic effects and in proposing causes for some of the events

some measurements of turbulence over an antarctic ice shelf profiles of wind speed temperature and turbulent fluxes of heat and momentum in the lowest 32 m have been measured at a station on an antarctic ice shelf during the antarctic winter the surface layer often shows strong static stability with temperature gradients as large as 1 km 1 in the lowest few metres the surface inversion is destroyed during periods of high wind speed but the wind profile shows significant deviation from the expected logarithmic form under such conditions measurements of stress at 5 m indicate that the roughness length of the snow surface is about lo 4 m at 5 m height the variations of the dimensionless wind shear m and potential temperature gradient t agree with previously determined forms of the monin obukhov similarity functions above 5 m the behaviour of m and t is only qualitatively similar and surface layer similarity theory does not provide a good description of the profiles turbulence length scales have been deduced from vertical velocity power spectra under near neutral conditions the ratio of turbulence length scale to measurement height is observed to decrease with increasing height of measurement this observation is consistent with the variation of turbulence length scale with height implied by the measurements of m it is suggested that the stability of the overlying atmosphere restricts the depth of the turbulent boundary layer and hence the length scales of turbulence within this layer increasing stability causes a decrease of turbulence length scales at all levels the ratios of turbulence kinetic energy to stress and temperature variance to heat flux are examined measurements are somewhat scattered but the distribution of values varies little with height or stability the form of the distribution suggests that large scale motions possibly internal gravity waves may be playing an important role in boundary layer processes

driving mechanisms for groundwater flow and salt transport in a subterranean estuary this paper presents field measurements and numerical simulations of groundwater dynamics in the intertidal zone of a sandy meso tidal beach the study focusing on vertical hydraulic gradients and pore water salinities reveals that tides and waves provide important forcing mechanisms for flow and salt transport in the nearshore aquifer such forcing interacting with the beach morphology enhances the exchange between the aquifer and ocean the spatial and temporal variations of vertical hydraulic gradients demonstrate the complexity and dynamic nature of the processes and the extent of mixing between fresh groundwater and seawater in a subterranean estuary these results provide evidence of a potentially important reaction zone in the nearshore aquifer driven by oceanic oscillations land derived contaminants may undergo important biogeochemical transformations in this zone prior to discharge

spatial patterns of groundwater biogeochemical reactivity in an intertidal beach aquifer beach aquifers host a dynamic and reactive mixing zone between fresh and saline groundwater of contrasting origin and composition seawater driven up the beachface by waves and tides infiltrates into the aquifer and meets the seaward discharging fresh groundwater creating and maintaining a reactive intertidal circulation cell within the cell land derived nutrients delivered by fresh groundwater are transformed or attenuated we investigated this process by collecting pore water samples from multilevel wells along a shore perpendicular transect on a beach near cape henlopen delaware and analyzing solute and particulate concentrations pore water incubation experiments were conducted to determine rates of oxygen consumption and nitrogen gas production a numerical model was employed to support field and laboratory interpretations results showed that chemically sensitive parameters such as ph and orp diverged from salinity distribution patterns indicating biogeochemical reactivity within the circulation cell the highest respiration rates were found in the landward freshwater saltwater mixing zone supported by high dissolved inorganic carbon chlorophyll a a proxy for phytoplankton and particulate carbon did not co occur with the highest respiration rates but were heterogeneously distributed in deeper and hypoxic areas of the cell the highest rates of n2 production were also found in the mixing zone coinciding with elevated o2 consumption rates but closer to the lower discharge point model results were consistent with these observations showing heightened denitrification in the mixing zone the results of this work emphasize the relationship between the physical flow processes of the circulation cell and its biogeochemical reactivity and highlight the environmental significance of sandy beaches

groundwater flow and salt transport in a subterranean estuary driven by intensified wave conditions a numerical study based on a density dependent variably saturated groundwater flow model was conducted to investigate flow and salt transport in a nearshore aquifer under intensified wave conditions caused by offshore storms temporally varying onshore hydraulic gradients due to wave setup were determined as the seaward boundary condition for the simulated aquifer the results showed a rapid increase in influxes across the aquifer ocean interface in response to the wave event followed by a more gradual increase in effluxes the upper saline plume first widened horizontally as the wave setup point moved landward it then expanded vertically with recirculating seawater pushed downward by the wave induced hydraulic gradient the time for the salt distribution to return to the prestorm condition was up to a hundred days and correlated strongly with the time for seawater to recirculate through the aquifer the pathways of recirculating seawater and fresh groundwater were largely modified by the wave event these pathways crossed through the same spatial locations at similar times indicating significant salt freshwater mixing the flow and salt transport dynamics were more responsive to wave events of longer duration and higher intensity especially in more permeable aquifers with lower fresh groundwater discharge despite their larger response aquifers with higher permeability and beach slope recovered more rapidly postevent the rapid recovery of the flows compared with the salinity distribution should be considered in field data interpretation due to their long lasting impact wave events may significantly influence the geochemical conditions and the fate of chemicals in a subterranean estuary key points intensified waves perturb flow and transport in a subterranean estuary lengthy period months for salinity distribution to recover from a wave event exchange fluxes and flows respond and recover rapidly following a wave event

tidal influence on behaviour of a coastal aquifer adjacent to a low relief estuary the tidal influence on groundwater hydrodynamics salt water intrusion and submarine groundwater discharge from coastal estuarine aquifers is poorly quantified for systems with a mildly sloping beach in contrast to the case where a vertical beach face is assumed we investigated the effect of beach slope for a coastal aquifer adjacent to a low relief estuary where industrial waste was emplaced over the aquifer the waste was suspected to discharge leachate towards the estuary field observations at various locations showed that tidally induced groundwater head fluctuations were skewed temporally frequency analysis suggested that the fluctuation amplitudes decreased exponentially and the phase lags increased linearly for the primary tidal signals as they propagated inland salinisation zones were observed in the bottom part of the estuary and near the beach surface flow and transport processes in a cross section perpendicular to the estuary were simulated using seawat 2000 which is capable of depicting density dependent flow and multi species transport the simulations showed that the modelled water table fluctuations were in good agreement with the monitored data further simulations were conducted to gain insight into the effects of beach slope in particular the limiting case of a vertical beach face was considered the simulations showed that density difference and tidal forcing drive a more complex hydrodynamic pattern for the mildly sloping beach than the vertical beach as well as a profound asymmetry in tidally induced water table fluctuations and enhanced salt water intrusion the simulation results also indicated that contaminant transport from the aquifer to the estuary was affected by the tide where for the mildly sloping beach the tide tended to intensify the vertical mass exchange in the vicinity of the shoreline

steady state freshwater seawater mixing zone in stratified coastal aquifers summary the mixing zone between freshwater and intruding seawater which controls regional groundwater flow dynamics and reactive transport processes is the most important component in coastal aquifers laboratory experiments and numerical simulations were conducted to investigate the effects of aquifer stratification on the thickness of a steady state freshwater seawater mixing zone a series of experiments were implemented in a laboratory tank packed with three layers of coastal sands and manipulated by two flow cells for maintaining constant head boundary conditions packed aquifers included a homogenous aquifer a high hydraulic conductivity k low k high k stratified aquifer and a low k high k low k stratified aquifer both tank scale and field scale density dependent models were developed to simulate the laboratory experiments and to systematically investigate aquifer stratification effects on the thickness of a steady mixing zone with varying layer configurations results showed that when an aquifer layer with a low k overlies a layer with a relatively high k slanting upward flow of diluted saltwater and re circulated seawater flow are refracted at the interface between the two layers resulting in streamline separation and a broad mixing zone in the low k layer by contrast the mixing zone in a high k layer is slightly narrowed when it overlies a layer with a relatively low k because flow refraction squeezes the streamlines within the mixing zone the mixing zone profile in head controlled systems is a function of k contrast but independent of the magnitude of k our results demonstrated the significant impact of aquifer stratification on controlling groundwater flow and solute transport in coastal subsurface environments and would have significant implications for studying physical chemical and biological processes in coastal subsurface environments as aquifer stratification is naturally prevalent

tide induced recirculation across the aquifer ocean interface a parametric analysis is conducted to examine the influence of tides inland hydraulic conditions and aquifer properties on the rate of tide induced seawater recirculation through the nearshore aquifer understanding such influence is crucial for accurate prediction of subsurface chemical fluxes to coastal waters via groundwater discharge the analysis is based on numerical simulations of density dependent groundwater flow in a coastal aquifer subject to tidal oscillations across a sloping beach face the results reveal that the amplitude of tidal oscillations and the inland hydraulic gradient are the primary parameters controlling the tide induced recirculation rates significant tidal exchange is expected when the ratio of tidal to inland forcing is large the horizontal tidal shoreline excursion and aquifer depth both display asymptotic behavior influencing recirculation rates for only small values where the exchange process is limited by the potential for infiltration and shallowness of the aquifer respectively the analysis also indicates that tidal effects increase density driven recirculation rates due to enhanced convective flow within the saltwater wedge

an unusually large aulocopella winnipegensis and associated demosponges from the upper ordovician beaverfoot formation southeastern british columbia an unusually large specimen of the rare digitate to bladed aulocopella winnipegensis rauff and three relatively normal sized specimens of ashtray shaped hudsonospongia sp constitute the first record of demosponges from the upper ordovician beaverfoot formation in southeastern british columbia and the first record of these taxa from western canada gross form and canal structure are well preserved but dolomitization and or coarse microsphaeroidal silicification have obliterated spicules and other structural details we interpret these sponges as epifaunal recliners without means of attachment to the substrate a life mode rarely encountered in the modern sponge biota

shear flow instability in the stable nocturnal boundary layer as observed by doppler lidar during cases 99 abstract this study investigates a shear flow instability observed in the stably stratified nighttime boundary layer on 6 october 1999 during the cooperative atmosphere surface exchange study cases 99 in south central kansas a scanning doppler lidar captured the spatial structure and evolution of the instability and high rate in situ sensors mounted on a nearby 60 m tower provided stability and turbulence data with excellent vertical resolution data from these instruments are analyzed and linear stability analysis lsa is employed to carefully characterize the wave field its interaction with the mean flow and its role in turbulence generation the event persisted for about 30 min and was confined within the shear zone between the surface and a low level jet llj maximum eigenvalues corresponding to the fastest growing mode of the lsa showed good agreement with the basic wave parameters determined from the lidar data good qualitative agreement was also obtained between the eigenfunction of the f

tempo of earliest ordovician graptolite faunal succession conodont based correlations from the tremadocian of quebec successive tremadocian planktic dendroid graptolite assemblages from continental slope sequences in quebec can be correlated with north american platform biozonations on the basis of conodonts anisograptid bearing assemblage 2 middle tremadocian matane faunas are associated with early ordovician rossodus manitouensis zone new designation conodonts younger middle tremadocian faunas with adelograptids assemblage 3 are no younger than the rossodus manitouensis zone key dendroid evolutionary immigration events take place within the lower conodont fauna b interval rooted dendroids near cap des rosiers quebec and in eastern new york state occur with lower fauna b conodonts and the trilobites pareuloma and borthaspidella however the earliest tremadocian and earliest ordovician dendroid immigration event represented by the local lowest occurrence of faunas with dictyonema flabelliforme s l at localities in western newfoundland eastern new york state norway and eastern china also lies with

contrasts between the summertime surface energy balance and boundary layer structure at dome c and halley stations antarctica 1 the antarctic research stations of dome c and halley lie at similar latitudes 75 s and are thus subject to similar diurnal variation of solar radiation at the top of the atmosphere however the response of the atmospheric boundary layer to this diurnally varying forcing differs greatly at the two stations at dome c during summer there is a strong diurnal cycle in near surface temperature and wind speed and a shallow 350 m convective boundary layer is observed to grow in response to diurnal heating at halley diurnal variations in temperature and wind speed are smaller than those at dome c and there is no clear diurnal variability in boundary layer depth analysis of the summertime surface energy budget for both stations indicates that the main reason for the different diurnal variability at the two stations is the greater partitioning of available energy into latent heat flux at the warmer halley station we argue that the diurnally varying convective boundary layer observed at dome c will not be typical of the whole of the east antarctic plateau

antarctic boundary layer parametrization in a general circulation model 1 d simulations facing summer observations at dome c the parametrization of the atmospheric boundary layer abl is critical over the antarctic plateau for climate modelling since it affects the large scale temperature inversion and the katabatic winds this study challenges state of the art parametrizations used in general circulation models to represent the clear sky summertime diurnal cycle of the abl at dome c antarctic plateau the laboratoire de meteorologie dynamique zoom model is run in a 1d configuration on the fourth gewex atmospheric boundary layers study case simulations are analysed and compared to observations giving insights into the sensitivity of one model that participates to the intercomparison exercise snow albedo and thermal inertia are calibrated leading to better surface temperatures using the so called thermal plume model improves the momentum mixing in the diurnal abl in stable conditions four turbulence schemes are tested best simulations are those in which the turbulence cuts off above 35m in the middle of the night highlighting the contribution of the longwave radiation in the abl heat budget however the nocturnal surface layer is not stable enough to distinguish between surface fluxes computed with different stability functions the absence of subsidence in the forcings and an underestimation of downward longwave radiation are identified to be likely responsible for a cold bias in the nocturnal abl apart from model specific improvements the paper clarifies on which are the critical aspects to improve in general circulation models to correctly represent the summertime abl over the antarctic plateau

numerical study of solute transport in shallow beach aquifers subjected to waves and tides a numerical study was conducted to investigate the fate of solute in a laboratory beach in response to waves and tides a new temporal upscaling approach labeled net inflow was introduced to address impacts of waves on solute transport within beaches numerical simulations using a computational fluid dynamic model were used as boundary conditions for the two dimensional variably saturated flow and solute transport model marun the modeling approach was validated against experimental data of solute transport due to waves and tides exchange fluxes across the beach face and subsurface solute transport e g trajectory movement speed and residence time were quantified simulation results revealed that waves increased the exchange fluxes and engendered a wider exchange flux zone along the beach surface compared to tide only forcing waves superimposed on tide caused the plume to be deeper into the beach and to migrate more seaward the infiltration into the beach was found to be directly proportional to the general hydraulic gradient in the beach and inversely proportional to the matrix retention or capillary capacity the simulations showed that a higher inland water table would attenuate wave caused seawater infiltration which might impact beach geochemical processes e g nutrient recycle and redox condition especially at low tide zone the concept of biochemical residence time maps brtm was introduced to account for the net effect of limiting concentration of chemicals on biochemical reactions it was found that waves shifted the brtms downward and seaward in the beach and subsequently they engendered different biochemical conditions within the beach

submarine groundwater discharge and solute transport under a transgressive barrier island abstract many recent investigations of groundwater dynamics in beaches employed groundwater models that assumed isotropic numerically convenient hydrogeological conditions real beaches exhibit local variability with respect to stratigraphy sediment grain size and associated topographic profile so that groundwater flow may diverge significantly from idealized models we used a combination of hydrogeologic field methods and a variable density saturated unsaturated transient groundwater flow model to investigate sgd and solute transport under cabretta beach a small transgressive barrier island seaward of sapelo island georgia we found that the inclusion of real beach heterogeneity drove important deviations from predictions based on theoretical beaches cabretta beach sustained a stronger upper saline plume than predicted due to the presence of a buried silty mud layer beneath the surface infiltration of seawater was greater for neap tides than for spring tides due to variations in beach slope the strength of the upper saline plume was greatest during spring tides contrary to recent model predictions the position and width of the upper saline plume was highly dynamic through the lunar cycle our results suggest that field measurements of salinity gradients may be useful for estimating rates of tidally and density driven recirculation through the beach finally our results indicate that several important biogeochemical cycles recently studied at cabretta beach were heavily influenced by groundwater flow and associated solute transport

near surface temperature inversion growth rate during the onset of the stable boundary layer abstractthis study aims to find the typical growth rate of the temperature inversion during the onset of the stable boundary layer around sunset the sunset transition is a very challenging period for numerical weather prediction since neither accepted theories for the convective boundary layer nor those for the stable boundary layer appear to be applicable to gain more insight in this period a systematic investigation of the temperature inversion growth rate is conducted a statistical procedure is used to analyze almost 16 years of observations from the cabauw observational tower supported by observations from two additional sites dome c and karlsruhe the results show that on average the growth rate of the temperature inversion normalized by the maximum inversion during the night weakly declines with increasing wind speed the observed growth rate is quantitatively consistent among the sites and it appears insensitive to various other parameters the results were also insensitive to the afte

wave induced water table fluctuations sediment transport and beach profile change modeling and comparison with large scale laboratory experiments coastal groundwater systems can have a considerable impact on sediment transport and foreshore evolution in the surf and swash zones process based modeling of wave motion on a permeable beach taking into account wave aquifer interactions was conducted to investigate the effects of the unconfined coastal aquifer on beach profile evolution and wave shoaling on the water table the simulation first dealt with wave breaking and wave runup rundown in the surf and swash zones nearshore hydrodynamics and wave propagation in the cross shore direction were simulated by solving numerically the two dimensional navier stokes equations with a k e turbulence closure model and the volume of fluid technique the hydrodynamic model was coupled to a groundwater flow model based on seawat 2000 the latter describing groundwater flow in the unconfined coastal aquifer the combined model enables the simulation of wave induced water table fluctuations and the effects of infiltration exfiltration on nearshore sediment transport numerical results of the coupled ocean aquifer simulations were found to compare well with experimental measurements wave breaking and infiltration exfiltration increase the hydraulic gradient across the beachface and enhance groundwater circulation inside the porous medium the large hydraulic head gradient in the surf zone leads to infiltration across the beachface before the breaking point with exfiltration taking place below the breaking point in the swash zone infiltration occurs at the upper part of the beach and exfiltration at the lower part the simulations confirm that beaches with a low water table tend to be accreted while those with a high water table tend to be eroded

stable boundary layer regimes at dome c antarctica observation and analysis investigation of meteorological measurements along a 45 m tower at dome c on the high east antarctic plateau revealed two distinct stable boundary layer sbl regimes at this location the first regime is characterized by strong winds and continuous turbulence it results in full vertical coupling of temperature wind magnitude and wind direction in the sbl the second regime is characterized by weak winds associated with weak turbulent activity and very strong temperature inversions reaching up to 25 k in the lowest 10 m vertical temperature profiles are generally exponentially shaped convex in the first regime and convex concave convex in the second the transition between the two regimes is particularly abrupt when looking at the near surface temperature inversion and it can be identified by a 10 m wind speed threshold with winds under this threshold the turbulent heat supply toward the surface becomes significantly lower than the net surface radiative cooling the threshold value including its range of uncertainty appears to agree with recent theoretical predictions from the so called minimum wind speed for sustainable turbulence mwst theory for the quasi steady clear sky winter cases the relation between the near surface inversion amplitude and the wind speed takes a characteristic s shape closer analysis suggests that this relation corresponds to a critical transition between a steady turbulent and a steady radiative regime with a dynamically unstable branch in the transition zone these fascinating characteristics of the antarctic boundary layer challenge present and future numerical models to represent this region in a physically correct manner

exceptional astronomical seeing conditions above dome c in antarctica one of the most important considerations when planning the next generation of ground based optical astronomical telescopes is to choose a site that has excellent seeing the jitter in the apparent position of a star that is caused by light bending as it passes through regions of differing refractive index in the earth s atmosphere the best mid latitude sites have a median seeing ranging from 0 5 to 1 0 arcsec refs 1 5 sites on the antarctic plateau have unique atmospheric properties that make them worth investigating as potential observatory locations previous testing at the us amundsen scott south pole station has however demonstrated poor seeing averaging 1 8 arcsec refs 6 7 here we report observations of the wintertime seeing from dome c ref 8 a high point on the antarctic plateau at a latitude of 75 s the results are remarkable the median seeing is 0 27 arcsec and below 0 15 arcsec 25 per cent of the time a telescope placed at dome c would compete with one that is 2 to 3 times larger at the best mid latitude observatories and an interferometer based at this site could work on projects that would otherwise require a space mission

numerical experiments on interactions between wave motion and variable density coastal aquifers a comprehensive two dimensional cross shore process based numerical model of nearshore hydrodynamics based on the navier stokes equations k e turbulence closure and the volume of fluid method beach morphology and variable density groundwater flow seawat 2000 was developed this model which was applied at the field scale relaxes simplifications in existing models that do not include such detailed mechanistic descriptions numerical experiments were conducted to investigate the effects of varying aquifer beach and wave characteristics e g inland groundwater head sand grain size different wave heights and periods on the coupled system spilling and plunging breakers on dissipative and intermediate beaches were simulated for a given set of boundary conditions the model was run for 1 y without the hydrodynamic sub model to achieve a realistic salt freshwater interface then the hydrodynamic component was run for 15 min and the model results analyzed the main features considered were groundwater circulation saltwater wedge position in exfiltration across the beach face and beach morphology the predictions of the numerical model agree well with existing understanding and experimental measurements for an inland watertable that is lower than the still water level swl such that the groundwater flow is mainly landward on both coarse and fine sand beaches the addition of wave motion moves the saltwater wedge further landward for an inland watertable that is higher than the swl the opposite behavior occurred the numerical experiments showed that more sediment transport takes place on intermediate beaches than on dissipative beaches in addition beach profile variations are greater under plunging breakers while coarse sand beaches are steeper than fine sand beaches for the same wave conditions there is a strong correlation between in exfiltration and beach face deposition erosion for the coarse beaches while in exfiltration has a slight effect on sediment transport for fine beaches the model is capable of simulating the short term evolution of foreshore profile changes and beach watertable and saltwater wedge movement due to interactions between wave motion and coastal groundwater

radon 222 budget in catalina harbor california 2 flow dynamics and residence time in a tidal beach we measured the flux of water through a beach at the head of catalina harbor california by monitoring the water table in a transect of wells perpendicular to the shoreline during a 24 h period the volume of sediments filled and drained the tidal wedge was 7 4 m 3 m shoreline 1 and the flux of water pumped across the beach face was 1 0 0 3 m 3 d 1 m shoreline 1 222 rn concentrations measured in four wells were used to calculate the minimum age of water in the beach radon samples collected below the tidal wedge were not in equilibrium with the production rate suggesting vertical mixing across the base of the tidal wedge the age of water ranged from up to 8 0 d landward of the high water mark to less than 2 0 d in the littoral zone this latter age agreed with an independent estimate of 1 7 0 5 d on the basis of a mass balance for radon at the head of the harbor however a mass balance for water in the tidal wedge was significantly greater 3 0 0 5 d the difference was most likely due to evasion of radon from wet unsaturated sediments water draining out of the beach was a mixture of water that infiltrated the beach on the previous high tide and older water from either below or the back of the tidal wedge

comparison of four numerical models for simulating seepage from salt marsh sediments a boundary integral equation method biem model and three differently formulated finite element method fem models were implemented to explore the spatial and temporal patterns in marsh pore water seepage that each generated the biem model is based on the laplace equation coupled to a dynamic free surface condition that assumes that as the water table changes the aquifer instantaneously loses or gains an amount of water equal to the change in head times the specific yield the fem models all implement a simplified richards equation that allows gradual desaturation or resaturation and thus flow in both the saturated and unsaturated zones of the aquifer two of the fem models are based on the governing equation for the usgs model sutra and thus take into account fluid and aquifer compressibility one of these was modified to take into account the effect of tidal loading on the total stress which is assumed to be constant in the derivation of the original version of sutra the third fem model assumes that neither the fluid or aquifer matrix is compressible so that changes in storage are due solely to changes in saturation the unmodified sutra model generated instantaneous boundary fluxes that were up to two orders of magnitude greater and spatially more uniform than those of the other models the fem model without compressibility generated spatial and temporal patterns of the boundary fluxes very similar to those produced by the biem model the sutra model with the tidal stress modification gave fluxes similar in magnitude to the biem and no compressibility models but with distinctly different distributions in space and time these results indicate that accurate simulation of seepage from marsh soils is highly sensitive to aquifer compressibility and to proper formulation of the effect of tidal loading on the total stress in the aquifer they also suggest that accurate simulation may require total stress correction not only for tidal loading but for changes in the water table as well finally to aid the development of methods for the measurement of compressibility we present a schematic pore scale model to illustrate the factors that may govern the compressibility of marsh soils

density driven transport in the umbrella region of volcanic clouds implications for tephra dispersion models this work has benefited from funding provided by the italian presidenza del consiglio dei ministri dipartimento della protezione civile dpc agreement ingv dpc 2012 2013 this paper does not necessarily represent dpc official opinion and policies a f acknowledges funding by the spanish project atmost cgl2009 10244

transitions in the wintertime near surface temperature inversion at dome c antarctica in this work we study the dynamics of the surface based temperature inversion over the antarctic plateau during the polar winter using 6 years of observations from the french italian antarctic station concordia at dome c we investigate sudden regime transitions in the strength of the near surface temperature inversion here we define near surface as being within the domain of the 45 m measuring tower in particular we consider the strongly nonlinear relation between the 10 m inversion strength t 10m t s and the 10 m wind speed to this end all individual events for which the 10 m inversion strength increases or decreases continuously by more than 15 k in time are considered composite time series and vertical profiles of wind and temperature reveal specific characteristics of the transition from weak to very strong inversions and vice versa in contrast to midlatitudes the largest variations in temperature are not found at the surface but at a height of 10 m a similar analysis was performed on results from an atmospheric single column model scm overall the scm results reproduce the observed characteristics of the transitions in the near surface inversion remarkably well using model output the underlying mechanisms of the regime transitions are identified the nonlinear relation between inversion strength and wind speed at a given level is explained by variations in the geostrophic wind speed changes in the depth of the turbulent layer and the vertical divergence of turbulent fluxes moreover the transitions between different boundary layer regimes cannot be explained without considering the contribution of subsidence heating

groundwater transport and the freshwater saltwater interface below sandy beaches summary current conceptual models for groundwater flow in beaches highlight an upper saline plume which is separated from the lower salt wedge by a zone of brackish to fresh groundwater discharge there is currently limited knowledge of what conditions allow an upper saline plume to exist and what factors control its formation we used variable density saturated unsaturated transient groundwater flow models to investigate the configuration of the freshwater saltwater interface in beaches with slopes varying from 0 1 to 0 01 in the absence of waves we also varied hydraulic conductivity dispersivity tidal amplitude and inflow of fresh groundwater the simulated salinity configuration of the freshwater saltwater interfaces varied significantly no upper saline plumes formed in any beach with hydraulic conductivities less than 10 m d the slope of the beach was also a significant control steeper beach faces allowed stronger upper saline plumes to develop median sediment grain size of the beach is strongly correlated to both beach slope and permeability and therefore the development of an upper saline plume prior studies of groundwater flow and salinity in beaches have used a range of theoretical dispersivities and the appropriate values of dispersivity to be used to represent real beaches remains unclear we found the upper saline plume to weaken with the use of larger values of dispersivity our results suggest that upper saline plumes do not form in all beaches and may be less common than previously considered

night time measurements of astronomical seeing at dome a in antarctica seeing the angular size of stellar images blurred by atmospheric turbulence is a critical parameter used to assess the quality of astronomical sites at optical infrared wavelengths median values at the best mid latitude sites are generally in the range of 0 6 0 8 arcseconds1 3 sites on the antarctic plateau are characterized by comparatively weak turbulence in the free atmosphere above a strong but thin boundary layer4 6 the median seeing at dome c is estimated to be 0 23 0 36 arcseconds7 10 above a boundary layer that has a typical height of 30 metres10 12 at domes a and f the only previous seeing measurements have been made during daytime13 14 here we report measurements of night time seeing at dome a using a differential image motion monitor15 located at a height of just 8 metres it recorded seeing as low as 0 13 arcseconds and provided seeing statistics that are comparable to those at a height of 20 metres at dome c this indicates that the boundary layer was below 8 metres for 31 per cent of the time with median seeing of 0 31 arcseconds consistent with free atmosphere seeing the seeing and boundary layer thickness are found to be strongly correlated with the near surface temperature gradient the correlation confirms a median thickness of approximately 14 metres for the boundary layer at dome a as found from a sonic radar16 the thinner boundary layer makes it less challenging to locate a telescope above it thereby giving greater access to the free atmosphere

quantifying hydrological and tidal influences on groundwater discharges into coastal waters 1 in coastal aquifers the dynamic mixing zone between intruding seawater and fresh groundwater constitutes a zone of salinity transition that may supply brackish groundwater along with chemical

transient groundwater dynamics in a coastal aquifer the effects of tides the lunar cycle and the beach profile 1 detailed field measurements are combined with a numerical modeling to characterize the groundwater dynamics beneath the discharge zone at waquoit bay massachusetts groundwater salinity values revealed a saline circulation cell that overlaid the discharging freshwater and grew and disappeared with the lunar cycle the cell was initiated by a greater bay water infiltration during the new moon when high tides overtopped the mean high tide mark flooding the flatter beach berm and inundating a larger area of the beach the dynamics of this cell were further characterized by a tracer test and by constructing a density dependent flow model constrained to salinity and head data the numerical model captured the growing and diminishing behavior of the circulation cell and provided the estimates of freshwater and saline water fluxes and travel times furthermore the model enabled quantification of the relationship between the characteristics of the observed tidal cycle maximum minimum and mean tidal elevations and the different components of the groundwater circulation freshwater discharge intertidal saline cycling and deep saline cycling we found that 1 recharge to the intertidal saline cell is largely controlled by the high tide elevation 2 freshwater discharge is positively correlated to the low tide elevation whereas deep saline discharge from below the discharging freshwater is negatively correlated to the low tide elevation so when the low tide elevation is relatively high more freshwater discharges and less deep saltwater discharges in contrast when low tides are very low less freshwater discharges and more deep salt water discharges 3 offshore inflow of saline water is largely insensitive to tides and the lunar cycle

comparative lower middle ordovician conodont oxygen isotope palaeothermometry of the argentine precordillera and laurentian margins abstract stratigraphic palaeontologic and palaeomagnetic data support a hypothesis that argues for the argentine precordillera rifting from the southwestern margin of laurentia in low latitudes during the cambrian migrating across the iapetus ocean colliding with the gondwanan margin in the late middle ordovician and receiving glaciogenic sediments in the late ordovician an alternative model proposes that the precordillera originated as a low latitude segment of gondwana migrated southward through major transform faulting toward high latitudes in the late middle ordovician to reach its present position in the devonian new conodont oxygen isotope compositions 18ophos have been determined by ion microprobe shrimp ii using samples from both the precordillera and laurentia marathon area of texas wilcox pass in alberta and western newfoundland significantly the 18o values of conodonts from all four widely separated areas show a consistent pattern of a cyclic but overall increasing trend in 18o ca 16 to 18 hence ocean cooling through the early and middle ordovician an apparent change occurs at the basal late ordovician where 18o values obtained from conodonts in the uppermost sample from the precordillera are significantly higher 1 5 than those from laurentia albeit from a single sample this higher value implies significantly cooler conditions as would be anticipated with a southerly poleward migration of the precordillera irrespective of either hypothesis the virtual absence of conodont bearing carbonates in most of the precordilleran upper ordovician precluded analysis of younger samples when combined with existing macrofaunal and palaeomagnetic data the oxygen isotope data would tend to favour the model of a drift of the precordillera from tropical to higher latitudes during the ordovician however further studies are needed to determine unequivocally whether the precordillera originated from southern laurentia ouachita embayment these new oxygen isotope values provide the best and regionally most consistent data through the early middle ordovician

a look at the surface based temperature inversion on the antarctic plateau data from radiosondes towers and a thermistor string are used to characterize the temperature inversion at two stations the amundsen scott station at the south pole and the somewhat higher and colder dome c station at a lower latitude ten years of temperature data from a 22 m tower at the south pole are analyzed the data include 2 and 22 m temperatures for the entire period and 13 m temperatures for the last 2 yr statistics of the individual temperatures and the differences among the three levels are presented for summer december and january and winter april september the relationships of temperature and inversion strength in the lowest 22 m with wind speed and downward longwave flux are examined for the winter months two preferred regimes one warming and one cooling are found in the temperature versus longwave flux data but the physical causes of these regimes have not been determined the minimum temperatures and the maximum inversions tend to occur not with calm winds but with winds of 3 5 m s 1 likely due to the inversion wind this inversion wind also explains why the near surface winds at south pole blow almost exclusively from the northeast quadrant temperature data from the surface to 2 m above the surface from south pole in the winter of 2001 are presented showing that the steepest temperature gradient in the entire atmosphere is in the lowest 20 cm the median difference between the temperatures at 2 m and the surface is over 1 0 k in winter under clear skies this difference increases to about 1 3 k monthly mean temperature profiles of the lowest 30 km of the atmosphere over south pole are presented based on 10 yr of radiosonde data these profiles show large variations in lower stratospheric temperatures and in the strength and depth of the surface based inversion the near destruction of a strong inversion at south pole durin g7ho n 8september 1992 is examined using a thermal conductivity model of the snowpack driven by the measured downward longwave flux the downward flux increased when a cloud moved over the station and it seems that this increase in radiation alone can explain the magnitude and timing of the warming near the surface temperature data from the 2003 04 and 2004 05 summers at dome c station are presented to show the effects of the diurnal cycle of solar elevation over the antarctic plateau these data include surface temperature and 2 and 30 m air temperatures as well as radiosonde air temperatures they show that strong inversions averaging 10 k between the surface and 30 m develop quickly at night when the sun is low in the sky but are destroyed during the middle of the day the diurnal temperature range at the surface was 13 k but only 3 k at 30 m

review of wave turbulence interactions in the stable atmospheric boundary layer flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods understanding turbulence intermittency and wave turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans the stable atmospheric boundary layer sabl commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land surfaces or even daytime over snow and ice surfaces and when warm air is advected over cold surfaces intermittent turbulence intensification in the sabl impacts human activities and weather variability yet it cannot be generated in state of the art numerical forecast models this failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow in which wave turbulence interaction is a potential mechanism for turbulence intermittency a workshop on wave turbulence interactions in the sabl addressed the current understanding and challenges of wave turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory observations and numerical parameterization there have been a number of reviews on waves and a few on turbulence in stably stratified flows but not much on wave turbulence interactions this review focuses on the nocturnal sabl however the discussions here on intermittent turbulence and wave turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general

salt freshwater dynamics in a subterranean estuary over a spring neap tidal cycle this paper presents field measurements and numerical simulations of pore water salinities and groundwater flow in the intertidal zone of an unconfined coastal aquifer over a spring neap tidal cycle the study provides insight into the extent and time scales of mixing between fresh groundwater and recirculating seawater in a tidally influenced subterranean estuary salt freshwater dynamics in subterranean estuaries are currently not well understood despite their potentially important implications for fluxes of chemicals to coastal waters via submarine groundwater discharge the data and simulation results show that changes in the tidal shoreline excursion over the spring neap cycle induce significant variations in the intertidal salinity structure observed higher frequency salinity fluctuations demonstrate further the intensity and complexity of the salt freshwater mixing process in contrast with the salinity variations fresh groundwater was found to discharge around a distinct intertidal beach slope break throughout the spring neap period this suggests that the slope break may affect significantly groundwater flow and salt transport near the shore measurements of ph and dissolved oxygen distributions revealed important biogeochemical zonations in the system these zonations are expected to strongly influence the fate of many reactive chemicals in the nearshore aquifer and their subsequent discharge to coastal waters

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

dynamic hydrologic and biogeochemical processes drive microbially enhanced iron and sulfur cycling within the intertidal mixing zone of a beach aquifer intertidal aquifers host a reactive zone comprised of fe mineral coated sands where fresh and saline groundwaters mix this zone may significantly influence the export of c n p fe and other metals in submarine groundwater discharge sgd toward determining the roles of microbes in fe and s mineralization and the interplay of microbiology with geochemistry and physical hydrology we conducted a biogeochemical study of pore waters at cape shores delaware here fresh groundwater provides fe ii which precipitates as feiiiooh predominantly through microbial fe ii oxidation candidate division op3 was the dominant microbial group associated with fe ii and fe iii rich regions of the aquifer suggesting that this uncharacterized phylum may be involved in fe ii oxidation saline water brings o2 sulfate and organic c into the intertidal mixing zone microbial reduction of sulfate produces sulfide that is transported to the fe mineralized zone leading to the transformation of feooh to fe ii sulfides microbial populations are structured by the availability of chemical species supplied along groundwater flow paths seasonal changes in the relative supply of fresh and saline groundwater affect solute fluxes and therefore microbial controls on the location and composition of the fe mineralized zone ultimately the composition extent and dynamics of the fe mineralized zone will affect the sequestration affinity and residence time of solutes bound for export to coastal oceans through sgd

simulations of nocturnal drainage flows by a q2l turbulence closure model abstract nocturnal drainage flows observed over a nearly two dimensional ridge called rattlesnake hills near richland washington are simulated by using a simplified turbulence closure model in which only turbulence kinetic energy and turbulence length scale equations are solved prognostically the present model is slightly simpler than a level 2 5 model which has been extensively used in previous simulations of various atmospheric boundary layer phenomena wind and temperature profiles computed by the present model are generally in excellent agreement with observations made by towers erected on the slope of rattlesnake hills strong coupling between the mean and turbulence variables is also demonstrated

intermittent turbulence in the stable boundary layer over land part iii a classification for observations during cases 99 abstract in this paper a classification of stable boundary layer regimes is presented based on observations of near surface turbulence during the cooperative atmosphere surface exchange study 1999 cases 99 it is found that the different nights can be divided into three subclasses a turbulent regime an intermittent regime and a radiative regime which confirms the findings of two companion papers that use a simplified theoretical model it is noted that its simpliflied structure limits the model generality to near surface flows the papers predict the occurrence of stable boundary layer regimes in terms of external forcing parameters such as the effective pressure gradient and radiative forcing the classification in the present work supports these predictions and shows that the predictions are robust in a qualitative sense as such it is for example shown that intermittent turbulence is most likely to occur in clear sky conditions with a moderately weak effective pressure gradient the quantit

carbon nutrient and trace metal cycling in sandy sediments a comparison of high energy beaches and backbarrier tidal flats abstract in order to evaluate the importance of coastal sandy sediments and their contribution to carbon nutrient and metal cycling we investigated two beach sites on spiekeroog island southern north sea germany and a tidal flat margin located in spiekeroog s backbarrier area we also analyzed seawater and fresh groundwater on spiekeroog island to better define endmember concentrations which influence our study sites intertidal sandy flats and beaches are characterized by pore water advection seawater enters the sediment during flood and pore water drains out during ebb and at low tide this pore water circulation leads to continuous supply of fresh organic substrate to the sediments remineralization products of microbial degradation processes i e nutrients and dissolved trace metals from the reduction of particulate metal oxides are enriched in the pore water compared to open seawater concentrations the spatial distribution of dissolved organic carbon doc nutrients po43 no3 no2 nh4 si oh 4 and total alkalinity trace metals dissolved fe and mn as well as sulfate suggests that the exposed beach sites are subject to relatively fast pore water advection which leads to organic matter and oxygen replenishment frequent pore water exchange further leads to comparatively low nutrient concentrations sulfate reduction does not appear to play a major role during organic matter degradation high nitrate concentrations indicate that redox conditions are oxic within the duneward freshwater influenced section while ammonification denitrification manganese and iron reduction seem to prevail in the ammonium dominated seawater circulation zone in contrast the sheltered tidal flat margin site exhibits a different sedimentology coarser beach sands versus finer tidal flat sands and nutrients dissolved manganese and doc accumulate in the pore water ammonium is the dominant pore water nitrogen species and intense sulfate reduction leads to the formation of sulfide which precipitates dissolved iron as iron sulfide these findings are due to slower advective pore water exchange in the tidal flat sediments this study illustrates how different energy regimes affect biogeochemical cycling in intertidal permeable sediments

introduction to the special issue commemorating the 30th anniversary of the royal tyrrell museum of palaeontology with a summary of the museum s early history and its research contributions located just west of drumheller in southern alberta canada the royal tyrrell museum of palaeontology rtmp is nestled among outcrops of the upper cretaceous horseshoe canyon formation exposed along the red deer river valley fig 1 since it officially opened on 25 september 19851 the museum has become one of alberta s must see tourist attractions a significant contributor to the local economy and earned an international reputation for the quality of its palaeontological collections and the research conducted by its scientists the rtmp is unique within canada in being the only government supported museum dedicated to palaeontology and it is one of the few such institutions in the world fig 1 the royal tyrrell museum of palaeontology a front of museum and main entrance circa 2010 looking westwards and with horizontal beds of the upper cretaceous horseshoe canyon formation exposed in the walls of the red deer river valley in the distance b aerial photograph oblique angle and looking to the north northeast the museum sits on top of the number 7 coal seam sensu gibson 1977 and at the base of the horsethief member of the horseshoe canyon formation d a eberth pers comm 2015 that stratigraphic position correlates with an age of about 71 5 ma i e late campanian and lies within the upper part of the edmontosaurus regalis pachyrhinosaurus canadensis dinosaur assemblage zone see eberth et al 2013 fig 6 c the iconic running theropod logo that until recently graced the exterior of the museum below a life sized tyrannosaurid sculpture by brian cooley one of many such sculptures by cooley that have been featured at the museum since its opening in 1985 and with the education wing opened in 2003 as the atco tyrrell learning centre in the background d the cretaceous alberta life sized diorama opened in 2007 an example of a rtmp exhibit that relies heavily on discoveries and interpretations by museum researchers in this case work done in the albertosaurus bonebed and at other localities throughout the horseshoe canyon formation all photographs courtesy of the royal tyrrell museum of palaeontology this special issue of the canadian journal of earth sciences presents a collection of papers commemorating the rtmp s 30th or pearl anniversary our rationale for doing a 30th anniversary volume was two fold first it is an opportunity to showcase the breadth of research conducted by current and former museum scientists as well as by some colleagues having a history of collaboration with the rtmp the 13 invited papers included in this volume are a mix of review and original research papers all thematically focused on the geology and palaeontology of alberta to varying degrees each contribution is the result of work supported by the rtmp and relies on specimens housed in the museum s collections second the 30th anniversary is an opportunity to reflect on the rtmp s history and its research program as is typical for most institutions the rtmp has done little to formally document its own history this year likely will be the last major milestone for which the original generation of museum staff are still working and available to share their recollections about the museum fieldwork and research already deaths and departures have winnowed away part of the original

quantitative analysis of seabed mixing and intertidal zone discharge in coastal aquifers 1 contaminant loading from an inland source zone to the nearshore marine environment is examined using a saturated unsaturated simulation model which incorporates both the influence of the growth and the extinction of the seepage face in the intertidal zone and the inclusion of hydromechanical stress coupling due to tidal loading the system analyzed represents a site where an unconfined aquifer extends offshore with a broad intertidal zone the volumetric discharge of groundwater in the intertidal zone dominates the discharge occurring beyond the low tide line for most of the cases examined within the intertidal zone the recirculated saline component of the discharge is greater than the freshwater component the majority of the contaminant mass exits through the seepage face located above the instantaneous tide line the peak contaminant loading rate occurs around the time of the falling midtide at low tide the contaminant loading rate is more than 2 orders of magnitude lower than the peak rates even though groundwater discharge rates are highest as low tide is approached sensitivity studies indicate that the relative proportion of recirculated intertidal zone discharge to fresh intertidal zone discharge is most sensitive to the magnitude of the freshwater flux the spatial variation of the outflow across the intertidal zone as influenced by anisotropy in hydraulic conductivity and tidal pumping as influenced by specific storage dilution of contaminant concentrations due to mixing with seawater beneath the sediment water interface is represented in terms of a dilution factor defined relative to the onshore source concentration for our base case the dilution factor for the contaminant concentration averaged over one tidal cycle at the high tide midtide and low tide lines was 1 3 3 9 and 560 respectively the key factors determining contaminant dilution at the sediment interface are location within the intertidal zone and the vertical extent of the contaminant plume as it enters the intertidal zone

development of a three dimensional meso γ primitive equation model katabatic winds simulation in the area of terra nova bay antarctica the spatial evolution of antarctic katabatic winds in the area of terra nova bay is examined using the three dimensional version of the universite catholique de louvain modele atmospherique regional ucl mar mesoscale primitive equation models the ability of the model to replicate classical linear mountain wave simulations is verified then three dimensional experiments are performed for the terrain configuration of terra nova ross sea coastal zone using different horizontal resolutions 5 10 and 20 km the model converges for resolutions lower than 10 km results are in qualitative agreement with available observations and previous modeling work strong katabatic winds are simulated with a jet over terra nova bay the model seems able to initiate the mesocyclonic activity in the ross sea due to the katabatic circulation

tidally driven multiscale pore water flow in a creek marsh system intertidal wetlands are complex hydrological systems characterized by strong dynamic interactions between coastal surface water and groundwater driven particularly by tides we simulated such interactions with a focus on three dimensional variably saturated pore water flow in a creek marsh system that bordered a tidally dominated main channel simulated intra tidal groundwater dynamics exhibited significant flow asymmetry with non zero mean flow velocities over the tidal period the tidally averaged flow led to pore water circulation with three dimensionality linked strongly to the marsh topography over a range of spatial scales near the creek bank around the creek meander and over long marsh sections inclined towards the main channel particle tracking revealed that time scales associated with these circulations differed by orders of magnitude under the simulated conditions the creek served as the main outlet of the pore water circulation paths especially those linked with infiltration into the upper marsh surface areas away from the main channel local net efflux influenced by the creek channel curvature varied along the creek but produced a total discharge largely proportional to the creek length water infiltrating the soil in the lower marsh surface areas away from the creek tended to discharge directly to the main channel however the total discharge to the main channel was much less than that into the creek this study highlights the hydrological complexity of intertidal marshes and the need for further research on interactions among marsh morphology hydrology and ecology which underpin the functionalities of these wetland systems

saltwater freshwater mixing dynamics in a sandy beach aquifer over tidal spring neap and seasonal cycles the biogeochemical reactivity of sandy beach aquifers is closely linked to physical flow and solute transport processes thus a clearer understanding of the hydrodynamics in the intertidal zone is needed to accurately estimate chemical fluxes to the marine environment a field and numerical modeling study was conducted over a 1 year timeframe to investigate the combined effects of tidal stage spring neap variability in tidal amplitude and seasonal inland water table oscillations on intertidal salinity and flow dynamics within a tide dominated microtidal sandy beach aquifer measured and simulated salinities revealed an intertidal saline circulation cell with a structure and cross sectional mixing zone area that varied over tidal spring neap and seasonal time scales the size of the circulation cell and area of the mixing zone were shown for the first time to be most affected by seasonal water table oscillations followed by tidal amplitude and tidal stage the intertidal circulation cell expanded horizontally and vertically as the inland water table declined displacing the fresh discharge zone and lower interface seaward over monthly spring neap cycles the center of the circulation cell shifted from beneath the backshore and upper beachface to the base of the beach salinity variations in the intertidal zone over semidiurnal tidal cycles were minimal the dynamics of the circulation cell were similar in simulations with and without a berm the highly transient nature of intertidal salinity over multiple time scales may have important implications for the types and rates of chemical transformations that occur in groundwater prior to discharge to the ocean

evidence for late rifting of the cordilleran margin outlined by stratigraphic division of the lower cambrian gog group rocky mountain main ranges british columbia and alberta the lower cambrian mcnaughton formation of the gog group occupies a stratigraphic position transitional between the rift related rocks of the underlying upper proterozoic miette group and the overlying paleozoic passive margin succession a major regional unconformity overlain by a distinctive orthoquartzite marker has been traced within the mcnaughton formation this unconformity has been shown to truncate normal faults active during the deposition of the lower mcnaughton formation the lower mcnaughton formation consists of mature coarse grained fluvial sediments accumulated in hanging wall half grabens of active normal faults these faults represent the final stage of rifting on the continental margin the unconformity on the footwall blocks of these faults can be traced into the hanging wall and is overlain by the shoreface sediments of the transgressive upper mcnaughton formation formal subdivision of the mcnaughton formation into four lithostratigraphic members is proposed in order to describ

coastal aquifer response to extreme storm events in emilia romagna italy with global warming and sea level rise many coastal systems will experience increased levels of inundation and storm flooding especially along sandy lowland coastal areas such as the northern adriatic coast italy understanding how extreme events may directly affect groundwater hydrology in shallow unconfined coastal aquifers is important to assess coastal vulnerability and quantifying freshwater resources this study investigates shallow coastal aquifer response to storm events the transitory and permanent effects of storm waves is evaluated through the real time monitoring of groundwater and soil parameters in order to characterize both the saturated and unsaturated portions of the coastal aquifer of ravenna and ferrara southern po delta italy results highlight a general increase in hydraulic head and soil moisture along with a decrease in groundwater salinity and pore water salinity due to rainfall infiltration during the 2 days storm event the only exceptions are represented by the observation wells in proximity to the coastline within 100 m which recorded a temporary increase in soil and water salinity caused by the exceptional high waves which persist on top of the dune crest during the storm event this generates a saline plume that infiltrates through the vadose zone down to the saturated portion of the aquifer causing a temporary disappearance of the freshwater lens generally present although limited in size below the coastal dunes despite the high hydraulic conductivity the aquifer system does not quickly recover the pre storm equilibrium and the storm effects are evident in groundwater and soil parameters after 10 days past the storm overwash recess

two dimensional vertical moisture pressure dynamics above groundwater waves sand flume experiments and modelling this paper presents a new laboratory dataset on the moisture pressure relationship above a dispersive groundwater wave in a two dimensional vertical unconfined sand flume aquifer driven by simple harmonic forcing a total of five experiments were conducted in which all experimental parameters were kept constant except for the oscillation period which ranged from 268 s to 2449 s between tests moisture content and suction head sensor pairings were co located at two locations in the unsaturated zone both approximately 0 2 m above the mean watertable elevation and respectively 0 3 m and 0 75 m from the driving head boundary for all oscillation periods except for the shortest t 268s the formation of a hysteretic moisture pressure scanning loop was observed consistent with the decay of the saturated zone groundwater wave the size of the observed moisture pressure scanning loops decayed with increasing distance landward and the decay rate is larger for the shorter oscillation periods at the shortest period t 268s the observed moisture pressure relationship was observed to be non hysteretic but with a capillary capacity that differs from that of the static equilibrium wetting and drying curves this finding is consistent with observations from existing one dimensional vertical sand column experiments the relative damping of the moisture content with distance landward is higher than that for the suction head consistent with the fact that transmission of pressure through a porous medium occurs more readily than mass transfer this is further supported by the fact that observed phase lags for the unsaturated zone variables i e suction head and moisture content relative to the driving head are greater than the saturated zone variables i e piezometric head harmonic analysis of the data reveals no observable generation of higher harmonics in either moisture or pressure despite the strongly non linear relationship between the two in addition a phase lag of moisture content relative to the suction head was observed indicating that the response time of the moisture content to watertable motion is greater than that of the pore water pressure the observed moisture pressure dynamics are qualitatively reproduced using a hysteretic richards equation model however quantitative differences exist which are likely to be due to previous findings that demonstrated that the richards equation model is unable to accurately reproduce the observed watertable wave dispersion particularly at shorter period oscillations

conodont biostratigraphy of the latest cambrian early ordovician upper mckay group southeastern british columbia the age of the upper mckay group based on conodont biostratigraphy is latest cambrian cordylodus proavus zone to late early ordovician middle floian oepikodus communis zone a collection of 12 940 conodont elements was recovered from 306 samples of upper mckay group strata exposed in the western main ranges of the southern canadian rocky mountains southeastern british columbia the conodont fauna is assigned to 53 species representing 30 genera twelve zones are recognized two of which are cosmopolitan cordylodus proavus zone and iapetognathus zone seven midcontinent realm zones in ascending order include polycostatus falsioneotensis rossodus tenuis rossodus manitouensis low diversity interval scolopodus subrex and acodus kechikaensis zones and tropodus sweeti subzone of the oepikodus communis zone three atlantic realm zones in ascending order include cordylodus angulatus acodus deltatus and paroistodus proteus zones the zonation for the upper mckay group establishes correlation w

direct determination of total and fresh groundwater discharge and nutrient loads from a sandy beachface at low tide cape henlopen delaware total groundwater discharge from a sandy seepage site to the delaware bay at cape henlopen delaware was determined together with the associated nutrient loads by trapping the discharge from a length of the shoreline in a tidal pond at low tide and measuring the discharge of the trapped water through a weir at steady state salinity was used to parse the total groundwater discharge from the beachface at low tide into a recycled estuarine component and a new fresh groundwater component based on 16 measurements over 18 months average total discharge and average freshwater discharge at low tide were found to be 2 76 6 1 08 and 0 87 6 0 43 l min21 m21 of shoreline respectively the estuarine component of discharge varied with the maximum height of the immediately preceding high tide owing to the control of freshwater discharge by the average upland hydraulic gradient away from the beach individual measurements of freshwater discharge at low tide represent a good estimate of this discharge component over time scales of hours to days based on the nutrient concentrations in the discharge waters nutrient loads from the beach to the adjacent estuary at low tide were 148 6 79 7 5 6 5 1 and 197 6 101 mmol min21 m21 of shoreline for total dissolved n p and si respectively groundwater discharge and these nutrient fluxes contribute significantly to the unusually productive benthic communities that inhabit the seepage and nearby intertidal zones estuaries receive their primary inputs from fluvial discharges and exchange with the ocean but it is increasingly evident that atmospheric deposition and direct groundwater discharges from uplands also play a significant role in estuarine biogeochemical processes paerl 1997 burnett et al 2003 although groundwater discharge is thought to represent only a small fraction of the total freshwater discharge to estuaries and the ocean there is increasing evidence that nutrients and contaminants associated with this discharge may play a more significant ecological role than implied by the relatively small discharge valiela et al 1992 burnett et al 2003 shaw 2003 this is particularly true in coastal plain settings where nutrient and contaminant inputs to the groundwater from domestic industrial municipal and agricultural practices may be high the hydraulic conductivity of soils and aquifer sediments is large and the topographically driven groundwater flow to shallow upland streams is low submarine groundwater discharge in many settings appears to be associated with productive benthic communities johannes and hearn 1985 bussmann et al 1999 zipperle and reise 2005 and may influence sediment water exchange through the imposition of hydraulic gradients the modification of subbottom flow paths and the alteration of diagenetic reactions and rates moore

the geochemistry of dissolved inorganic carbon in a surficial groundwater aquifer in north inlet south carolina and the carbon fluxes to the coastal ocean abstract we report measurements of ph total dissolved inorganic carbon dic total or titration alkalinity talk ca2 mg2 sulfate and sulfide data at the seawater freshwater interface in a shallow groundwater aquifer in north inlet south carolina these measurements and a diagenetic modeling analysis indicate that the groundwaters at north inlet are mixtures of seawater and freshwater end members and are seriously modified by carbon dioxide inputs from organic carbon degradation via so42 reduction across the entire salinity range and fermentation and caco3 dissolution in the low salinity region dic and talk are several times higher than the theoretical dilution line whereas ca2 is slightly higher and so42 is somewhat lower than the dilution line partial pressure of co2 in the groundwater is extremely high 0 05 to 0 12 atm these deviations are consistent with theoretical predictions from known diagenetic reactions estimated groundwater dic fluxes to the south atlantic bight from either the surficial aquifer via salt marshes or the upper floridan aquifer direct input are significant when compared to riverine flux in this area

effects of inland water level oscillation on groundwater dynamics and land sourced solute transport in a coastal aquifer abstract inland groundwater level variation widely exists but is usually neglected when conducting research on flow and solute transport in coastal aquifers a variable saturation and variable density flow and transport model feflow is applied to investigate groundwater dynamics and land sourced solute transport in a coastal aquifer under the influence of groundwater level oscillation at inland boundary and tidal fluctuation at seaward boundary over a period of two years the wave number shows that the damping rate of the seasonal oscillation at the inland boundary when propagating in the aquifer is much smaller than that of the tidal fluctuation thus the seasonal oscillation can propagate a longer distance the damping forms of the amplitude of both signals are exponential when propagating in the aquifer even though the amplitudes and the periods are different for the base conditions simulated the size of the upper saline plume usp i e recirculated seawater driven by tidal fluctuation fluctuates periodically in response to the groundwater level oscillation at inland boundary the fluctuation of the usp controls the movement of freshwater discharge tube fdt and the upper part of seawater wedge sw therefore the sw freshwater interface shows a rotating instead of parallel movement as groundwater system in a coastal aquifer is a mixed convection system a modified rayleigh number is adopted to investigate the density induced instabilities associated with the transport of dense solute under the effect of groundwater level oscillation at inland boundary and tidal fluctuation the more obvious gravity induced instabilities i e stronger solute downwelling and freshwater upwelling are observed at lower groundwater level the finger plume and the upwelled freshwater mix well when approaching the discharge zone where strongly affected by tidal fluctuation consequently the high concentration of the plumes is diluted when migrating toward the sea sensitive analysis indicates that the hydraulic conductivity and the density of the solute are the dominant impact factors for the morphology horizontal and vertical movements of the land sourced solute plume the amplitude and period of the fluctuating signal at the inland boundary have minor influence on the morphology and instabilities of the finger plume

measuring pore water oxygen of a high energy beach using buried probes abstract we conducted six field campaigns to investigate the spatial and temporal evolution of pore water oxygen content on a high energy sandy beach aquifer during several tidal cycles at different seasons we buried autonomous probes in intertidal sands to record dissolved oxygen saturation salinity temperature and water head at a 2 10 min frequency oxygen concentrations display significant changes both with time tide and seasons and space cross shore and vertical variations seawater circulation in tidal sands forms a saline pore water circulation cell with oxygen saturated pore water in the zone of seawater recharge oxygen depleted pore water in the lower beach is the result of in situ respiration processes that occur during seawater circulation oxygen depletion varies throughout the year and anoxic conditions are reached at the end of spring as planktonic organic matter becomes abundant in seawater and more organic matter is therefore supplied to pore water on a shorter time scale weeks to minutes oxygen variations are driven directly by physical forcing tidal amplitude affects the extent of the saltwater circulation cell and the associated location of the recharging and discharging zones of the beach the evolution of the water table level during the tidal cycle influences the circulation of pore water in the sand and ultimately the timing of oxygen variations during flood and ebb this first in situ study in a high energy sandy beach shows that the dynamics of pore water oxygen are governed by biogeochemical processes at the seasonal scale and by physical forcing at the time scale of minutes to a few days

tsunami wave run up on a vertical wall in tidal environment we solve analytically a nonlinear problem of shallow water theory for the tsunami wave run up on a vertical wall in tidal environment shown that the tide can be considered static in the process of tsunami wave run up in this approximation it is possible to obtain the exact solution for the run up height as a function of the incident wave height this allows us to investigate the tide influence on the run up characteristics

snow atmosphere coupled simulation at dome c antarctica using a snow atmosphere coupled model the evolution of the surface and near surface snow temperature is modeled at dome c antarctica during the period 20 30 january 2010 firstly the detailed multilayer snow model crocus is run in stand alone mode with meteorological input forcing data provided by local meteorological observations the snow model is able to simulate the evolution of surface temperature with good accuracy it reproduces the observed downward propagation of the diurnal heatwave into the upper 50 cm of the snowpack reasonably well secondly a fully coupled 3 d snow atmosphere simulation is performed with the arome regional meteorological model for which the standard single layer snow parameterization is replaced by crocus in spite of a poor simulation of clouds the surface and near surface snow temperatures are correctly simulated showing neither significant bias nor drifts during the simulation period the model reproduces particularly well the average decrease of the diurnal amplitude of air temperature from the surface to the top of the 45 m instrumented tower this study highlights the potential of snow atmosphere coupled models over the antarctic plateau and the need to improve cloud microphysics and data assimilation over polar regions

importance of the advection scheme for the simulation of water isotopes over antarctica by atmospheric general circulation models a case study for present day and last glacial maximum with lmdz iso abstract atmospheric general circulation models agcms are known to have a warm and isotopically enriched bias over antarctica we test here the hypothesis that these biases are partly consequences of a too diffusive advection exploiting the lmdz iso model we show that a less diffusive representation of the advection especially on the horizontal is very important to reduce the bias in the isotopic contents of precipitation above this area the choice of an appropriate representation of the advection is thus essential when using gcms for paleoclimate applications based on polar water isotopes too much diffusive mixing along the poleward transport leads to overestimated isotopic contents in water vapor because dehydration by mixing follows a more enriched path than dehydration by rayleigh distillation the near air surface temperature is also influenced to a lesser extent by the diffusive properties of the advection scheme directly via the advection of the air and indirectly via the radiative effects of changes in high cloud fraction and water vapor a too diffusive horizontal advection increases the temperature and so also contributes to enrich the isotopic contents of water vapor over antarctica through a reduction of the distillation the temporal relationship from last glacial maximum lgm to present day conditions between the mean annual near air surface temperature and the water isotopic contents of precipitation for a specific location can also be impacted with significant consequences on the paleo temperature reconstruction from observed changes in water isotopes

an early cambrian rift to post rift transition in the cordillera of western north america the upper proterozoic and lower palaeozoic wedge of miogeoclinal strata in the north american cordillera is widely regarded as evidence for a proto pacific passive margin1 3 the rifting history of this margin appears to have been protracted possibly spanning 200 myr in a tectonic setting that is not well understood3 quantitative subsidence analyses of lower palaeozoic strata between british columbia and utah however provide indirect evidence that the transition from rifting to post rift cooling occurred within a relatively short interval of time although probably not synchronously between 600 and 555 myr refs 4 6 this age is significantly younger than that implied in previous studies1 2 we describe here new field data which together with published geological data provide direct evidence of a latest proterozoic or early cambrian age for the rift to post rift transition the data support recent arguments for widespread initiation of passive margins around the edge of the north american craton close to the cambrian precambrian boundary7

regional scale impact of tidal forcing on groundwater flow in unconfined coastal aquifers summary this paper considers the impact of tidal forcing on regional groundwater flow in an unconfined coastal aquifer numerical models are used to quantify this impact for a wide range of hydrogeological conditions both a shallow and a deep aquifer are investigated with regard to three dimensionless parameter groups that determine the groundwater flow to a large extent analytical expressions are presented that allow for a quick estimate of the regional scale effect of tidal forcing under the same conditions as used in the numerical models quantitatively the results in this paper are complementary to previous studies by taking into account variable density groundwater flow dispersive salt transport and a seepage face in the intertidal area qualitatively the results are in line with previous investigations the time averaged hydraulic head at the high tide mark increases upon a decrease of each of the three considered dimensionless parameter groups r including the ratio of the hydraulic conductivity and the precipitation excess a the slope of the intertidal area and al the ratio of the width of the fresh water lens and the tidal amplitude the relative change of the location and the hydraulic head of the groundwater divide which together characterize regional groundwater flow increase as a and al decrease but decrease as r decreases the difference between the analytical solutions and numerical results is small therefore the presented analytical solutions can be used to estimate the bias that is introduced in a numerical model if tidal forcing is neglected the results should be used with caution in case of significant wave forcing as this was not considered

the surface windfield over the antarctic ice sheets the intense radiative cooling of air over the ice slopes of antarctica generates a surface wind regime that is strongly controlled by topography and plays a key role in determining the behaviour of the atmosphere and ocean in high southern latitudes1 7 resultant surface winds are intimately linked to the orientation of the ice terrain fig 1 and display the highest degree of persistence found on earth the close coupling between wind and topography allows estimation of the former if the latter is known with some precision here we report on time averaged near surface airflow over the antarctic continent during winter diagnosed from a recent accurate synthesis of terrain slopes and from estimates of the lower atmospheric temperature structure the simulated drainage pat tern exhibits strong spatial variability with the airflow concentrated into several zones near the coastal margin these confluence regions are responsible for strong persistent katabatic winds over downstream coastal stretches and are indicative of zones of greatest katabatic potential

effects of wave forcing on a subterranean estuary wave and tide are important forcing factors that typically co exist in coastal environments a numerical study was conducted to investigate individual and combined effects of these forces on flow and mixing processes in a near shore subterranean estuary a hydrodynamic model based on the shallow water equations was used to simulate dynamic sea level oscillations driven by wave and tide the oscillating sea levels determined the seaward boundary condition of the coastal aquifer where variably saturated variable density flow was modeled the simulation results showed that waves induced an onshore upward tilt in the phase averaged sea level wave set up the resulting hydraulic gradient generated pore water circulations in the near shore zone of the coastal aquifer which led to formation of an upper saline plume usp similar to that due to tides however mixing of recirculating seawater in the usp with underlying fresh groundwater was less intensive under the high frequency wave oscillations in the case of combined forcing wave induced circulations coupled with the intra tidal flows strengthened the averaged circulating pore water flows in the near shore zone over the tidal period the circulating flows increased exchange between the subterranean estuary and ocean contributing 61 of the total submarine groundwater discharge for the simulated condition in comparison with the 40 and 49 proportions caused by the same but separate tidal and wave forcing respectively the combined forces also created a more extensive usp with the freshwater discharge zone shifted further seaward the freshwater flow paths in the intertidal subterranean estuary were altered with a significant increase of associated transit times the interplay of wave and tide led to increased mixing between discharging fresh groundwater and recirculating seawater these results demonstrated the complexity of near shore groundwater systems and have implications for future investigations on the fate of land sourced chemicals in the subterranean estuary prior to discharge to the ocean

multiple regimes of wind stratification and turbulence in the stable boundary layer abstracta long time series of temporally high resolution wind and potential temperature data from the 213 m tower at cabauw in the netherlands demonstrates the existence of two distinct regimes of the stably stratified nocturnal boundary layer at this location hidden markov model hmm analysis is used to objectively characterize these regimes and classify individual observed states the first regime is characterized by strongly stable stratification large wind speed differences between 10 and 200 m and relatively weak turbulence the second is associated with near neutral stratification weaker wind speed differences between 10 and 200 m and relatively strong turbulence in this second regime the state of the boundary layer is similar to that during the day the occupation statistics of these regimes are shown to covary with the large scale pressure gradient force and cloud cover such that the first regime predominates under clear skies with weak geostrophic wind speed and the second regime predomin

the initiation of the early paleozoic cordilleran miogeocline evidence from the uppermost proterozoic lower cambrian hamill group of southeastern british columbia the uppermost proterozoic lower cambrian hamill group of southeastern british columbia contains geologic evidence for a phase of extensional tectonism that led directly to the onset of thermally controlled subsidence in the cordilleran miogeocline moreover the hamill group contains the sedimentological record of the passage of the ancient passive margin from unstable tectonic conditions associated with rifting and or the earliest phases of thermal subsidence to post rift conditions characterized by stabilization of the margin and dissipation of the thermal anomaly generated during the rift phase the rift to post rift transition widespread uplift that occurred prior to and during the deposition of the lower hamill group is indicated by an unconformable relation with the underlying windermere supergroup and by stratigraphic relations between middle and upper proterozoic strata and unconformably overlying upper lower cambrian quartz arenites upper hamill group in the southern borderlands of the hami