the mesozoic and tertiary basins of the bohemian massif and their evolution abstract the bohemian massif is a major positive element within the structural framework of the alpine carpathian foreland its basement became consolidated during the variscan orogeny crustal thicknesses range between 32 5 km and 40 km during the late carboniferous and early permian the bohemian massif became dissected by a conjugate system of wrench faults which controlled the accumulation of a continental coal bearing series late permian red beds were deposited on intramontane topographic depressions in triassic to mid jurassic times the bohemian massif formed a high from which clastics were shed into adjacent basins during the late jurassic and late cretaceous it became transected by nw se trending sedimentary basins the sub hercynian and laramide phases of foreland compression resulted in deformation and uplift of the bohemian massif the eger graben a 350 km long volcanotectonic zone cutting across the bohemian massif in an ene wsw direction came into evidence during the oligocene and is at present inactive the crust of the bohemian massif forms the autochthonous substratum of the outer carpathians which are paralleled by the neogene carpathian foredeep the neogene intramontane neo autochthonous vienna basin is superimposed on the alpine carpathian nappe systems and developed under a tensional setting

modeling study of turbulent mixing over the continental shelf comparison of turbulent closure schemes limitation is imposed during upwelling favorable winds the majority of turbulent mixing occurs in the top and the bottom boundary layers and in the vicinity of the vertically and horizontally sheared coastal jet turbulent mixing in the coastal jet is primarily driven by shear production the near surface flow on the inner shelf becomes convectively unstable as wind stress forces the upwelled water to flow offshore in the surface layer during downwelling favorable winds the strongest mixing occurs in the vicinity of the downwelling front the largest turbulent kinetic energy and dissipation are found near the bottom of the front turbulence in the bottom boundary layer offshore of the front is concentrated between recirculation cells which are generated as a result of symmetric instabilities in the boundary layer flow index terms 4219 oceanography general continental shelf processes 4568 oceanography physical turbulence diffusion and mixing processes 4255 oceanography general numerical modeling 4279 oceanography general upwelling and convergences

modeling semidiurnal internal tide variability in the southern california bight abstractthe regional oceanic modeling system roms is applied in a nested configuration with realistic forcing to the southern california bight scb to analyze the variability in semidiurnal internal wave generation and propagation the scb has a complex topography with supercritical slopes that generate linear internal waves at the forcing frequency the model predicts the observed barotropic and baroclinic tides reasonably well although the observed baroclinic tides feature slightly larger amplitudes the strongest semidiurnal barotropic to baroclinic energy conversion occurs on a steep sill slope of the 1900 m deep santa cruz basin this causes a forced near resonant semidiurnal poincare wave that rotates clockwise in the basin and is of the first mode along the radial azimuthal and vertical directions the associated tidal mean depth integrated energy fluxes and isotherm oscillation amplitudes in the basin reach maximum values of about 5 kw m 1 and 100 m and are strongly modulated by the sprin

nearshore internal bores and turbulent mixing in southern monterey bay 1 we observed transient stratification and mixing events associated with nearshore internal bores in southern monterey bay using an array of instruments with high spatial and temporal resolution the arrival of the bores is characterized by surging masses of dense cold water that tend to stratify the water column the bore is followed by a gradual drop in the temperature throughout the water column over several hours defined here as the bore period until a sharp warm front relaxation followed by high frequency temperature fluctuations returns the column back to nearly its original state defined here as the mixing period mixing periods revealed increased temperature variance at high frequencies n as well as a greater percentage of events where dynamic instabilities may be present ri 0 25 suggesting active mixing of the stratified water column turbulent dissipation rates in the stratified interior during the mixing period estimated using the technique of isopycnal slope spectra revealed mean values the same order of magnitude as near bed bottom generated turbulence observations indicate that local shear produced turbulent kinetic energy by the warm front relaxations dominates mixing in the stratified interior the non canonical nature of these bore and relaxation events is also investigated with a numerical model and the dynamics are shown to depend on the internal iribarren number our results suggest that nearshore internal bores interacting with local bathymetry dramatically alter local dynamics and mixing in the nearshore with important ecological implications

the geography of semidiurnal mode 1 internal tide energy loss 1 the semidiurnal mode 1 internal tide receives 0 1 0 3 tw from the surface tide and is capable of propagating across ocean basins the ultimate fate of mode 1 energy after long distance propagation is poorly constrained by existing observations and numerical simulations here global results from a two dimensional semi analytical model indicate that topographic scattering is inefficient at most locations deeper than 2500 m next results from a one dimensional linear model with realistic topography and stratification create a map of mode 1 scattering coefficients along the continental margins on average mode 1 internal tides lose about 60 of their energy upon impacting the continental margins 20 transmits onto the continental shelf 40 scatters to higher modes and 40 reflects back to the ocean interior these analyses indicate that the majority of mode 1 energy is likely lost at large topographic features e g continental slopes seamounts and mid ocean ridges where it may drive elevated turbulent mixing

lagrangian assessment of simulated surface current dispersion in the coastal ocean 1 a purely lagrangian assessment of dispersion from modeled surface current trajectories in the coastal ocean is presented modeled trajectories come from roms simulations for the southern california bight during the 1996 through 1999 period data are from surface current trajectories collected primarily in the santa barbara channel with code style drifters distributions of particle positions from trajectories emanating from launch locations within 10 kilometers of the coast throughout the santa barbara channel that advect for one through four days lagrangian pdfs are evaluated descriptively and quantitatively the two dimensional kolmogorov smirnov k s statistical test for comparing discrete sampled data with a known probability distribution is the quantitative basis in general dispersion distributions from observations are similar to lagrangian pdfs computed from modeled trajectories and the k s statistic quantifies this accordingly a few specific regions of poor model data agreement are indicated and discussed the purely lagrangian assessment elucidates an improved understanding of model performance and ocean circulation beyond that offered in a eulerian sense and is necessary when modeled trajectories are utilized for applied oceanographic and marine ecology problems

simulations of nearshore particle pair dispersion in southern california knowledge of horizontal relative dispersion in nearshore oceans is important for many applications including the transport and fate of pollutants and the dynamics of nearshore ecosystems two particle dispersion statistics are calculated from millions of synthetic particle trajectories from high resolution numerical simulations of the southern california bight the model horizontal resolution of 250m allows the investigation of the two particle dispersion with an initial pair separation of 500m the relative dispersion is characterized with respect to the coastal geometry bathymetry eddy kinetic energy and the relative magnitudes of strain and vorticity dispersion is dominated by the submesoscale not by tides in general headlands are more energetic and dispersive than bays relative diffusivity estimates are smaller and more anisotropic close to shore farther from shore the relative diffusivity increases and becomes less anisotropic approaching isotropy 10km from the coast the degree of anisotropy of the relative diffusivity is qualitativelyconsistentwiththat foreddy kinetic energy thetotal relative diffusivity asa functionof pairseparation distance r is on average proportional to r 5 4 additional lagrangian experiments at higher horizontal numerical resolution confirmed the robustness of these results structures of large vorticity are preferably elongated and aligned with the coastline nearshore which may limit cross shelf dispersion the results provide useful information for the design of subgrid scale mixing parameterizations as well as quantifying the transport and dispersal of dissolved pollutants and biological propagules

horizontal dispersion of ocean tracers in internal wave shear 1 the horizontal dispersion of ocean tracers due to the interaction of vertical diffusion and the vertical shear from internal waves is examined using a lagrangian particle tracking model for idealized sinusoidal horizontal velocity profiles of unbounded vertical extent the irreversible horizontal dispersion of particle clouds is maximal when the timescale of particle diffusion across the velocity variations and the period of shear oscillation are comparable for measured velocity profiles from the thermocline in the gulf of aqaba red sea the total dispersion and irreversible dispersion of particle clouds both tend to increase with vertical diffusion cloud height and cloud age the total and irreversible horizontal cloud variances typically grow with time t like t0 to t3 and t1 to t3 respectively estimates of the irreversible horizontal dispersivity from an existing analytical model based on vertically constant oscillating shear agree remarkably well with estimates from the particle tracking model with differences dependent on the vertical variability in vertical diffusion and shear that are not incorporated in the analytical model

scale dependent dispersion within the stratified interior on the shelf of northern monterey bay abstractautonomous underwater vehicle measurements are used to quantify lateral dispersion of a continuously released rhodamine wt dye plume within the stratified interior of shelf waters in northern monterey bay california the along shelf evolution of the plume s cross shelf lateral width provides evidence for scale dependent dispersion following the 4 3 law as previously observed in both surface and bottom layers the lateral dispersion coefficient is observed to grow to 0 5 m2 s 1 at a distance of 700 m downstream of the dye source the role of shear and associated intermittent turbulent mixing within the stratified interior is investigated as a driving mechanism for lateral dispersion using measurements of time varying temperature and horizontal velocities both an analytical shear flow dispersion model and a particle tracking model generate estimates of the lateral dispersion that agree with the field measured 4 3 law of dispersion without explicit appeal to any assumed turbulence structure

evolution of the lower saxony basin abstract the lower saxony basin is a 300 km long and 65 km wide late jurassic and early cretaceous trough which parallels the northern margin of the rhenish massif this basin became inverted during the senonian and paleocene the lower saxony basin is the most important oil province of germany past production amounts to 200 10 6 t of oil 1 5 10 9 bbl the lower saxony basin is superimposed on the late carboniferous variscan foredeep basin and the frontal structures of the variscan fold belt during the permian to middle jurassic the area formed part of the northwest european basin differential subsidence of the lower saxony basin was initiated during the late jurassic and persisted till albian time this involved reactivation of permo carboniferous fracture systems by divergent wrenching a major aptian deep seated laccolith is evident in the western part of the lower saxony basin during the senonian and paleocene sinistral convergent wrenching induced uplift of the basin floor and folding of its sedimentary fill the margins of the inverted lower saxony basin are thrust over the adjacent stable platform areas the differential subsidence of the lower saxony basin can be related to a period of major crustal extension in the north sea rift basin inversion coincides with important orogenic events in the alpine system and is thought to have been induced by intra plate compressional stresses

crustal fracturing and intraplate tectonics in the area between the north sea and the alps a comparison of landsat derived fractures with existing map data abstract after a short review of late permian to recent structural development in the area between the north sea and the alps known major faults and fault systems and their role in intraplate tectonics are discussed it is shown that landsat derived trends and patterns of upper crustal fracturing correlate with known regional and local fault patterns and that pre existing trends and patterns of crustal fracturing have played a major role in late permian to recent intraplate deformation

statistical aspects of surface drifter observations of circulation in the santa barbara channel argos tracked drifters are used to study the near surface circulation in the santa barbara channel the mean consists of a cyclonic cell in the western santa barbara channel with weaker flow in the eastern channel drifter mean velocities agree well with record means from near surface current meters at the eastern entrance to the channel drifter velocities are biased toward outflow eastward velocity conditions drifter variability at synoptic and seasonal scales shows a tendency for upwelling and eastward flow in spring a strong cyclonic circulation in summer poleward relaxation in fall and weak variable circulation in winter drifter estimates of eddy stress divergence indicate advective terms play a secondary role in the mean surface momentum balance lagrangian time and space scales are about 1 day and under 10 km respectively the mismatch between lagrangian and eulerian timescales indicates advective terms are important to the fluctuating circulation

lateral dispersion over the continental shelf analysis of dye release experiments lateral dispersion over the continental shelf was examined using dye studies performed as a part of the coastal mixing and optics experiment four experiments performed at intermediate depths each lasting 2 5 5 days were examined in some cases the dye patches remained fairly homogeneous both vertically and horizontally throughout an experiment in other cases significant patchiness was observed on scales ranging from 2 to 10 m vertically and a few hundred meters to a few kilometers horizontally the observations showed that the dye distributions were significantly influenced by shearing and straining on scales of 5 10 m in the vertical and 1 10 km in the horizontal superimposed on these larger scale distortions were simultaneous increases in the horizontal second moments of the dye patches with corresponding horizontal diffusivities based on a fickian diffusion model of 0 3 4 9 m 2 s 1 analysis of the dye data in concert with shear estimates from shipboard acoustic doppler current profiler observations showed that the existing paradigms of shear dispersion and dispersion by interleaving water masses cannot account for the observed diffusive spreading of the dye patches this result suggests that some other mechanisms provided an additional diffusivity of order 0 2 4 6 m 2 s 1 an alternative mechanism dispersion by vortical motions caused by the relaxation of diapycnal mixing events may explain the observed dispersion in some cases

breaking of a single asperity rupture process and seismic radiation the problem of spontaneous shear rupture of a single circular asperity on an infinite fault plane is studied initially the fault plane is broken everywhere except at a circular asperity an applied displacement at infinity results in a stress concentration along the bounding edge of the asperity the frictional stress on the broken part of the fault plane is taken to be a constant once a point on the asperity breaks the stress there drops to the same value as on the main fault surface the rupture is started by relaxing the shear stress at a point on the asperity edge and is then allowed to propagate spontaneously using a critical stress level fracture criterion the rupture process is calculated numerically it is found that for asperities of constant strength the rupture first propagates around the edge of the asperity and then inward a phenomenon best described by the well known term of classic military maneuver the double encircling pincer movement in the appendix the expressions for the far field seismic radiation due to the rupture of such an asperity are derived it is shown that the nth cartesian component of the far field displacement at x t for p sv and sh waves using the notation of aki and richards 1980 is given by un x t dni 4 c2r s0 i3 t r c ds thus the far field pulses can be directly found from the stress drops on the fault plane this formula is also true for crack or dislocation problems the directivity function dni for displacement for the asperity problem is found to be that for the double couple modified by some factor in particular the fault plane is a nodal plane for sv waves for the rupturing of asperities on a finite fault these directivity functions are applicable only to the initial part of observed pulses at a receiver provided the receiver is not located on the fault plane outside the broken part of the main crack edge in which case it is inapplicable for all time

evidence for active tilting of the nw german basin from correlations between fluvial landscape and geological subground the catchment basin of the river hunte lower saxony nw german basin was studied on a mesoscale length of 90 km to investigate the influence of the geological subground on modern morphology a geo information system gis was used to calculate linear correlation coefficients between the depth of geological strata base zechstein to base quaternary and the height of the modern landscape holocene alluvial plain lower weichselian terrace catchment basin and watershed high linear correlation coefficients between the base of tertiary and the height of the modern topography catchment basin r2 0 87 lower weichselian terrace r2 0 95 and holocene alluvial plain r2 0 95 indicate control of the modern topography by the depth of the geological subsurface via tilting of the entire basin most likely northward tilting of the nw german basin forces the river hunte to flow in a northerly direction by relative uplift of the hinterland wiehengebirge rhenish massif and subsidence of the north sea area

complex mean circulation over the inner shelf south of martha s vineyard revealed by observations and a high resolution model 1 inner shelf circulation is governed by the interaction between tides baroclinic forcing winds waves and frictional losses the mean circulation ultimately governs exchange between the coast and ocean in some cases oscillatory tidal currents interact with bathymetric features to generate a tidally rectified flow recent observational and modeling efforts in an overlapping domain centered on the martha s vineyard coastal observatory mvco provided an opportunity to investigate the spatial and temporal complexity of circulation on the inner shelf adcp and surface radar observations revealed a mean circulation pattern that was highly variable in the alongshore and cross shore directions nested modeling incrementally improved representation of the mean circulation as grid resolution increased and indicated tidal rectification as the generation mechanism of a counter clockwise gyre near the mvco the loss of model skill with decreasing resolution is attributed to insufficient representation of the bathymetric gradients h h which is important for representing nonlinear interactions between currents and bathymetry the modeled momentum balance was characterized by large spatial variability of the pressure gradient and horizontal advection terms over short distances suggesting that observed inner shelf momentum balances may be confounded given the available observational and modeling data this work defines the spatially variable mean circulation and its formation mechanism tidal rectification and illustrates the importance of model resolution for resolving circulation and constituent exchange near the coast the results of this study have implications for future observational and modeling studies near the mvco and other inner shelf locations with alongshore bathymetric variability

late cretaceous and cenozoic intra plate compressional deformations in the alpine foreland a geodynamic model abstract the mesozoic grabens and wrench induced troughs of western and central europe developed in response to triassic early cretaceous intra plate tensional stresses which affected the arctic north atlantic and the tethys borderlands during the rifting phase preceding the opening of the respective oceans this resulted in the fragmentation of the continental crust of the alpine foreland during the late cretaceous and tertiary alpine orogeny collision related compressive stresses exerted on the foreland induced the reactivation of these fracture systems causing the inversion of mesozoic grabens and the uplifting of major basement blocks at distances up to 1300 km to the north of the present alpine deformation front the structural style of these inverted basins and basement uplifts is indicative of compressional and transpressional deformations the total amount of crustal shortening associated with these deformations is unlikely to exceed a few tens of kilometres these displacements require a coupling between the foreland and the orogen at the alpine a subduction zones and within the foreland a decoupling at intra crustal levels between the crust and mantle and or at deeper lithospheric levels the example of the alpine foreland indicates that compressive stresses inducing major deformations can be transmitted from a collisional plate boundary through continental lithosphere over distances of up to 1300 km circumstantial evidence suggests that collision related compressive stresses not large enough to give rise to significant deformations can be transmitted through continental lithosphere over even greater distances

unraveling multiple thermotectonic events accommodated by crustal scale faults in northern iberia spain insights from k ar dating of clay gouges

evolution of the molasse basin germany switzerland abstract in the molasse basin 500 1000 m thick mesozoic sediments overlie the variscan basement and locally permo carboniferous grabens containing a largely unknown thickness of clastic sediments the vindelician basement high extended southwestward from the bohemian massif and separated the southern part of the german basin from the tethys shelf triassic early and middle jurassic sediments progressively transgressed over this high which became fully inundated during the late jurassic following a temporary regression sedimentation resumed in the early cretaceous and after another hiatus in the late aptian to campanian during the latest cretaceous to earliest tertiary the area of southern germany became uplifted resulting in a progressive northwestward truncation of cretaceous strata and the late jurassic carbonates at the same time the bohemian massif became upthrusted along northwest striking wrench faults similar faults controlled the upthrusting of the landshut neuoetting high over which some 1 000 m of mesozoic sediments were eroded these wrench and thrust tectonics are part of an extensive compressional deformation in central europe that is supposed to be caused by the latest cretaceous earliest tertiary collision of the adriatic african and european plates during the alpine orogeny the area subsided again during the late eocene and developed into the molasse basin proper in which oligocene to miocene elastics reach a thickness of some 5 000 m near the alpine thrust front subduction and flexuring of the foreland caused numerous essentially basin parallel synthetic and antithetic normal faults the latter form the primary traps for oil and gas accumulations in the molasse basin

the evolution of the south hunsruck and taunus borderzone abstract the main fabric development of the south hunsruck and taunus borderzone htb occurred during late variscan homoaxial backfolding of an early variscan stack of thrust sheets in a narrow wsw ene trending zone several hundred kilometres long rotation and uplift of the southern rhenohercynian zone was accompanied by the subsidence of the southward adjacent northernmost parts of the saxothuringian zone and the development of the saar nahe basin during the latest carboniferous changing stress conditions gave rise to the development of normal faults along the htb and an extensive tholeiitic and rhyolitic volcanism contemporaneous uplift of the hunsruck is reflected by coarse elastics in the saar nahe basin subsequently the htb became covered by latest carboniferous early permian and mesozoic sediments cretaceous uplift of the rhenish shield caused their erosion the faultzone separating the rhenohercynian hunsruck and taunus from the permo carboniferous saar nahe basin is characterised by reverse and normal faults conjugate shear indicated by slickensides on steep oblique fracture planes as well as slight folding and small scale thrusting in post variscan sediments may be attributed to compressional foreland deformation reactivating variscan joint fabrics and fault systems timing of these deformations is ambiguous and could partly be related to dextral shear during the cenozoic subsidence of the rhine graben cenozoic sediments of the upper rhine graben overstep the northeastern parts of the htb seismic investigations indicate that the htb is associated with a system of southeast hading listric planes extending beneath the moho occasional dip slip earthquakes occur along these fractures

compressional intra plate deformations in the alpine foreland an introduction abstract the recognition of the basin inversion phenomenon dates back to the 1920 s and 1930 s the true scope of the latest cretaceous and cenozoic basin inversions became apparent only in the 1970 s it is proposed that these intra plate deformations are related to compressional stresses exerted on the foreland during the alpine orogeny

shear flow dispersion internal waves and horizontal mixing in the ocean abstract two models of advection diffusion in the oscillatory sheared velocity field of an internal wave are discussed our goal is to develop intuition about the role of such currents in horizontal ocean mixing through the mechanism of shear dispersion the analysis suggests simple parameterizations of this process i e those in eqs 7 36 and 42 the enhanced horizontal diffusion due to the interaction of the vertical diffusion and vertical shear of the wave field can be described by an effective horizontal diffusivity which is equal to the actual horizontal diffusivity plus a term equal to the mean square vertical shear of horizontal displacement times the vertical diffusivity provided the vertical length scale of the horizontal velocity field is not too small in the limit of small vertical length scale the expression reduces to taylor s 1953 result in which the effective horizontal diffusivity is inversely proportional to the actual vertical diffusivity the solutions also incidentally

the inner shelf response to wind driven upwelling and downwelling abstract a two dimensional numerical model is used to study the response to upwelling and downwelling favorable winds on a shelf with a strong pycnocline during upwelling or downwelling the pycnocline intersects the surface or bottom forming a front that moves offshore the characteristics of the front and of the inner shelf inshore of the front are quite different for upwelling and downwelling for a constant wind stress the upwelling front moves offshore at roughly a constant rate while the offshore displacement of the downwelling front scales as t because the thickness of the bottom layer increases as the front moves offshore the geostrophic alongshelf transport in the front is larger during downwelling than upwelling for the same wind stress magnitude because the geostrophic shear is near the bottom in downwelling as opposed to near the surface in upwelling during upwelling weak stratification is maintained over the inner shelf by the onshore flux of denser near bottom water this weak stratif

compression and right lateral strike slip movement at the southern hunsruck borderfault southwest germany abstract compressional tectonic structures have been known from the southern hunsruck borderzone since the end of the last century in the western part of the borderzone the saar nahe syncline is upthrown whereas in the eastern part the hunsruck is upthrown against the saar nahe syncline folds with axes parallel and oblique to the 60 trending fault zone have been described in the past in the area between idar oberstein and kirn permian lava sheets are displaced in such a way that their recent distribution can be explained by a right lateral strike slip movement of 5 8 km the block of the saar nahe basin between the southern hunsruck borderfault and the saarbrucken anticline has been tilted to the ene since the late palaeozoic the transcurrent movement can only be related to the opening of the upper rhine graben ne sw and nne ssw trending folds in the rotliegend sediments are considered to be transpression structures related to strike slip movement in early tertiary times recent seismicity along the southern hunsruck borderzone indicates that this zone is still active

connectivity and larval dispersal along the oregon coast estimated by numerical simulations 1 connectivity and larval dispersal is explored off the oregon coast during the summer upwelling season of 2001 using numerical ocean circulation simulations the study region with strong wind driven currents and variable topography is modeled using the regional ocean modeling system roms forced by the coupled ocean atmosphere mesoscale prediction system a large number of passive particles as models of planktonic larvae are released daily for 120 days from 1 may to 28 august at depths of 1 7 15 20 50 and 75 m at every grid point shoreward of the 200 m isobath on average 32 km offshore the particles are transported by the three dimensional currents of the model simulation the competency time window for larval settlement is assumed to be in between days 15 and 35 after larvae are released larval settlement occurs at the shallowest location during the competency time window connectivity matrices reveal that some of the places of highest retention are similar to the proposed oregon marine reserve sites especially cape perpetua the heceta bank region has high probabilities as both a source and a destination for settled larvae larvae released in the heceta bank region often settle at higher latitudes than their release location there are strong correlations between the number of settled larvae shallower than the 50 m isobath and a 6 to 8 day running mean of the alongshore wind stress larvae are retained near the shore when the winds averaged over the previous 6 to 8 days are relaxed or downwelling favorable

structure of velocity and temperature in the northeast pacific as measured with lagrangian drifters in fall 1987 abstract in october 1987 49 lagrangian surface drifters tristar ii were released in a 200 km 200 km square area southeast of ocean station papa as part of the ocean storms experiment the drifters measured temperature at the drogue level and reported their position through argos approximately 11 times per day thirty one of the drifters retained drogues for longer than three months and data from those instruments are used to describe the evolving fall 1987 pattern of current and temperature structures at 15 m in the area between 46 and 49 n 142 w and 132 w time variable currents were dominated by mesoscale eddies of anticyclonic rotation with horizontal radii of 53 86 km and rotational speeds of 10 20 cm s 1 these eddies persisted for at least 90 days as evidenced by successive drifter trajectories through the eddies currents with periods longer than 1 day had a mean to the east of 4 4 cm s 1 and a mean to the north of 0 7 cm s 1 background eddy kinetic energy levels were 40 cm s 2 thus eddy

semidiurnal baroclinic tides on the central oregon inner shelf abstractsemidiurnal velocity and density oscillations are examined over the mid and inner continental shelf near heceta bank on the oregon coast measurements from two long term observation networks with sites on and off the submarine bank reveal that both baroclinic velocities and displacements are dominated by the first mode with larger velocities on the midshelf and northern parts of the bank midshelf sites have current ellipses that are near the theoretical value for single progressive internal tidal waves compared to more linearly polarized currents over the inner shelf baroclinic current variability is not correlated to the spring neap cycle and is uncorrelated between mooring locations an idealized model of two internal waves propagating from different directions reproduces some of the observed variability in semidiurnal ellipse parameters at times the phasing between moorings along a cross shelf transect are consistent with onshelf wave propagation a characteristic also present in the out

cross shore surfzone tracer dispersion in an alongshore current 1 cross shore surfzone tracer dispersion in a wave driven alongshore current is examined over a range of wave and current conditions with 6 continuous dye releases each roughly 1 2 hours in duration at huntington beach california fluorescent dye tracer released near the shoreline formed shore parallel plumes that were sampled on repeated cross shore transects with a jet ski mounted fluorometer ensemble averaged cross shore tracer concentration profiles are generally shoreline attached maximum at or near the shoreline with increasing cross shore widths and decreasing peak values with downstream distance more than a few 100 m from the source tracer is often well mixed across the surfzone i e saturated with decreasing tracer concentrations farther seaward for each release cross shore surfzone absolute diffusivities are estimated using a simple fickian diffusion solution with a no flux boundary at the shoreline and range from 0 5 2 5 m2 s 1 surfzone diffusivity scalings based on cross shore bore dispersion surfzone eddy mixing length and undertow driven shear dispersion are examined the mixing length scaling has correlation r2 0 59 and the expected best fit slope 1 indicating that horizontal rotational motions are important for cross shore tracer dispersion in the surfzone

a lagrangian stochastic model of surf zone drifter dispersion 1 drifter derived cross shore and alongshore surf zone diffusivities were previously estimated on an alongshore uniform beach over 1000 s for five huntington beach california 2006 hb06 experiment release days the cross shore diffusivity kx had a nonmonotonic time dependence potentially due to the shoreline or to weaker diffusivity seaward of the surf zone the alongshore diffusivities ky were qualitatively consistent with shear dispersion but differed from the classic taylor laminar theory here modeled and analytic diffusivities for the five release days are derived from a lagrangian stochastic model lsm that uses the drifter derived bulk cross shore averaged velocity variance and cross shore dependent mean alongshore current the lsm modeled and analytic cross shore diffusivities are nonmonotonic due to the shoreline and strongly suggest that the observed cross shore diffusivity is shoreline affected the lsm typically reproduce well the observed kx with lagrangian time scale between 75 and 200 s consistent with surf zone eddy time scales hb06 drifter trajectories were too short to observe the analytic long time kx limit and weaker diffusivity seaward of the surf zone may be important at longer times 1000 s on all release days the lsm model and analytic alongshore diffusivity reproduce well the observed ky with alongshore lagrangian time scales between 95 and 155 s the isolated shear induced diffusivity is very well represented by an analytic theory which incorporates a nonzero lagrangian time scale many of the stochastic model parameters can be specified a priori with reasonable assumptions to predict surf zone dispersion of an initial value problem pollution spill