run up of internal waves on a gentle slope in a two layered system this paper describes the dissipative phase of internal wave run up on uniform slopes of 0 030 and 0 054 rad as observed in a series of laboratory experiments the waves were generated continuously at the interface of two miscible layers of differing density as each wave in the perodic train propagated onto the slope it steepened and developed into a solitary like wave before finally overturning surrounding fluid was engulfed into the wave as it overturned and the resulting gravitational instability produced considerable turbulence and mixing the broken wave took the form of a discrete bolus of dense fluid which propagated for some distance up the slope bulk parameters which characterize the nature of the bolus were defined and the dependence of these on the incident wave parameters and their behaviour during the run up phase were examined

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 initial response of a stratified lake to a surface shear stress laboratory experiments are used to study the initial response of a stratified fluid to the action of a wind stress the experiments are described in the context of a parameterization scheme that quantifies the strength of the applied stress relative to the bulk stability of the fluid and also the duration of the wind stress relative to the periods of the waves generated by the stress this study concentrates on the first fundamental internal wave period in experiments where the fluid is considered to have upwelled i e the stratified region of the fluid reaches the surface at the upwind endwall the majority of the experiments use three layer initial density profiles as an approximation to a continuously stratified water column a linear model using normal modes proved successful prior to the commencement of upwelling and this enabled an estimate to be made of the time at which upwelling occurred at this point the wave development ceased and the flows developed via entrainment mechanisms consideration of the energy budget showed that little of the input energy was stored in the system the initial mixing efficiency defined as the ratio of the mean potential energy gained to the energy imparted by the belt never exceeded 30 peak efficiency occurred when the surface stress was just sufficient to bring the interfacial region to the surface

numerical simulation of shoaling broad crested internal solitary waves abstractthe interaction between fully nonlinear miyata choi camassa mcc internal solitary waves and topographic slopes are modeled by direct numerical simulation the immersed boundary method is

internal waves in a small reservoir horizontally distributed temperature time series recorded in the thermocline of a small reservoir during autumn are used to identify both basin scale and higher frequency internal waves stationary and nonstationary spectral analyses are used to identify dominant frequencies the horizontal distribution of data allows a map of the basin scale wave energy to be determined three layer normal mode modeling incorporating damping emulates the basin scale behavior well this provides estimates of velocity shear and hence the internal stability the nonstationary frequency analysis identifies times of high frequency internal wave activity wave periods of 2 10 min this is definitely linked to the basin scale wave driven shear and hence to deceases in stability estimates of dissipation for the thermocline and hypolimnion are 3 10 8 and 6 10 9 m 2 s 3 respectively the inferred variability in the hypolimnetic value is demonstrated

modal response of reservoirs to wind stress an analysis of the response of a density stratified reservoir to surface shear stress is presented the reservoir is assumed to be two dimensional and to have a constant depth in the limit that the bulk wedderburn number wb and the bulk richardson number rib are both infinite the resulting equations are linear and solutions can be found in terms of the individual responses of a set of orthogonal normal modes for the case of a steady wind stress the solution consists of periodic motions and steady isopycnal displacements however the steady state isopycnal slope at the base of the mixed layer is infinite implying that upwelling can occur when the wedderburn number is quite large this is attributed to blocking of the stratified fluid below the mixed layer by the endwall the modal theory presented in this paper is compared with experimental observations made using a belt to impart shear stress to a stratified fluid contained in a box the comparison shows that the present theory is qualitatively corr

on the breaking of internal solitary waves at a ridge an experimental laboratory study has been carried out to investigate the propagation of an internal solitary wave of depression and its distortion by a bottom ridge in a two layer stratified fluid system wave profiles density fields and velocity fields have been measured at three reference locations namely upstream downstream and over the ridge experiments have been performed with wave amplitudes in the range 0 2 1 9 times the depth of the upper layer and a ratio between the lower and the upper layer in the range 3 0 8 5 the ridge slope was varied from 0 1 to 0 33 and the maximum ridge height was two thirds of the thicker fluid layer over the ridge the flow has been classified into i cases when the bottom ridge has little influence on the propagation and spatial structure of the internal solitary wave ii cases where the internal solitary wave is significantly distorted by the blocking effect of the ridge though no wave breaking occurs and iii cases for which the internal solitary wave is broken as it encounters and passes over the bottom ridge a detailed description of the processes leading to wave breaking is given breaking has been found to take place when the fluid velocity in the lower layer exceeds 0 7 of a local nonlinear wave speed defined at the top of the ridge the breaking condition is also expressed in terms of the amplitude of the incident wave the layer thickness ratio and the relative height of the ridge the wave breaking can be determined from the input parameters of the experiment the transmitted waves have been found to always consist of a leading pulse solitary wave followed by a dispersive wavetrain the solitary wave amplitude is significantly reduced only when breaking takes place at the ridge internal waves of mode two are generated in cases with strong breaking

upwelling rebound ephemeral secondary pycnoclines and the creation of a near bottom wave guide over the monterey bay continental shelf several sequential upwelling events were observed in fall 2012 using measurements from the outer half of the continental shelf in monterey bay during which the infiltration of dense water onto the shelf created a secondary near bottom pycnocline this deep pycnocline existed in concert with the near surface pycnocline and enabled the propagation of near bottom cold semidiurnal internal tidal bores as well as energetic high frequency nonlinear internal waves of elevation iwoe the iwoe occurred within 20 m of the bottom had amplitudes of 8 24 m periods of 6 45 min and depth integrated energy fluxes up to 200 w m 1 iribarren numbers 0 03 indicate that these iwoe were nonbreaking in this region of the shelf these observations further demonstrate how regional upwelling dynamics and the resulting bulk cross margin hydrography is a first order control on the ability of internal waves at tidal and higher frequencies to propagate through continental shelf waters

shallow velocity structure of stromboli volcano italy derived from small aperture array measurements of strombolian tremor abstract the properties of the tremor wave field at stromboli are analyzed using data from small aperture arrays of short period seismometers deployed on the north flank of the volcano the seismometers are configured in two semi circular arrays with radii of 60 and 150 m and a linear array with length of 600 m the data are analyzed using a spatiotemporal correlation technique specifically designed for the study of the stationary stochastic wave field of rayleigh and love waves generated by volcanic activity and by scattering sources distributed within the island the correlation coefficients derived as a function of frequency for the three components of motion clearly define the dispersion characteristics for both rayleigh and love waves love and rayleigh waves contribute 70 and 30 respectively of the surface wave power the phase velocities of rayleigh waves range from 1000 m sec at 2 hz to 350 m sec at 9 hz and those for love waves range from 800 to 400 m sec over the same frequency band these velocities are similar to those measured near puu oo on the east rift of kilauea volcano hawaii although the dispersion characteristics of rayleigh waves at stromboli show a stronger dependence on frequency such low velocities are consistent with values expected for densely cracked solidified basalt the dispersion curves are inverted for a velocity model beneath the arrays assuming those dispersions represent the fundamental modes of rayleigh and love waves

beyond the spac method exploiting the wealth of circular array methods for microtremor exploration we explore the wealth of alternative methods for inferring phase velocities of rayleigh waves using vertical component seismograms of microtremors from a circular array of seismic sensors which are formulable along the extension of the popularly used spatial autocorrelation spac method four such methods are illustrated here the centerless circular array cca method the henstridge methods of the zeroth and first orders the h0 and h1 methods respectively and what we tentatively call the fifth v method different methods of phase velocity estimation have different wavelength ranges of good resolution implementation to field data from two sites reveals that the traditional spac method and the h0 method are both capable of producing reasonable estimates of rayleigh wave phase velocities within a relatively narrow range on the short wavelength side whereas the h1 method is valid in a relatively narrow range on the long wavelength side the cca and v methods both remain valid over a very broad range of wavelengths the upper limit extending as far up as several 10s of times the array radius use of a noise compensation technique can further prolong the maximum resolvable wavelength of the cca method we also illustrate the field performance of circle phase methods which give without recourse to the conventional frequency wavenumber analysis estimates for the principal arrival directions of rayleigh waves on the basis of circular array seismograms of microtremors

nonlinear internal waves in the south china sea observation of the conversion of depression internal waves to elevation internal waves 1 the conversion of depression nonlinear internal solitons to elevation internal waves has been observed twice at the south china sea continental shelf break shipboard x band radar tow yo ctd adcp and high frequency acoustic flow visualization of the process are presented the data focuses on up slope propagation of depression internal solitons from a water depth of 264 m to a water depth of 110 m dissipation by large amplitude shear instabilities was observed the kinetic energy density was found to be a decreasing monotonic function of range with an energy dissipation rate coefficient of 0 063 km 1 the rate of energy dissipation over the 16 5 km soliton propagation path was 0 17 w m m simple numerical models of the waveform evolution are qualitatively compared to the observations the observations extracted scale parameters and dissipation rates should be useful for testing a variety of evolution equation representations of internal soliton propagation

dynamics of large polymictic lake i field observations the internal dynamics of clear lake california a large multibasin and polymictic lake under stratified conditions is described in this work particular attention is paid to one of the subbasins of clear lake oaks arm several field experiments were conducted in the lake to obtain data of wind currents and water temperature using a wide range of devices based on field observations and previously published results on basin responses to wind stress a conceptual model of the internal circulation of the oaks arm is proposed its internal dynamics are characterized by diurnal cycles of setup and relaxation of horizontal temperature gradients driven by the wind forcing the setup and relaxation processes are modulated by the influence of the earth s rotation and create a residual cyclonic circulation this circulation mechanism is here referred to as baroclinic pumping it is in all likelihood not exclusive to clear lake but probably exists in other large and relatively shallow lakes forced by strong and almost periodic wind events where basin scale internal waves do not play a major role in the dynamics of the system

the structure and dynamics of internal waves in baldeggersee1 analysis of long records of temperature depth distribution determined at lo or 20 min intervals at several stations and extending over three stratification seasons provides a detailed picture of the characteristics dynamics and seasonal variation in activity of internal waves in a small lake baldeggersee switzerland wind stress in general was low with occasional bursts of higher energy the ensuing slightly damped internal seiches govern the dynamics of the stratified lake the vertical structure displays a dominant response of the first vertical mode responses in the second vertical mode hitherto rarely recorded are also demonstrated with the help of spectral analysis and models the horizontal structure of the seiches motion displays dominance and persistence of the fundamental basin mode spectral analysis also discloses responses of the second and third basin modes multiplying of the spectra with the local buoyancy frequency leads to a collapse of all spectra into a narrow band pointing toward the possibility of a universal spectrum new light is shed on apparently common examples of waveform asymmetry and on their interpretation it is concluded that in this small basin low energy example internal waves provide motions at all levels but little vertical mixing

internal solitary wave reflection near dongsha atoll the south china sea internal solitary wave isw reflection is rarely observed in satellite images even in the south china sea scs where the strongest and most energetic isws in the world have been observed compared to the large number of satellite images showing shoaling isw in the scs fewer than ten satellite images have been reported showing isw reflection in this study we collect recent satellite images and implement a numerical model to analyze isw reflection near dongsha atoll in the scs satellite observations show that the reflection appears to be associated with the large amplitude isws generated by strong tidal currents in luzon strait numerical simulations show that isws break when reaching the sloping bottom part of isw energy is reflected by mode 1 waves and their trailing mode 2 waves the mode 1 waves have two types long inertial gravity waves and breaking isw induced short waves they propagate quickly but induce weak vertical velocity and surface imprints mode 2 waves induce strong vertical velocity showing visible signature in satellites horizontal distribution of the energy indicates that a maximum energy of about 2 of the incident energy is contained in a single reflected wave this could explain why the reflected waves are rarely observed because reflected waves must be sufficiently large to be detected in satellite images although individual wave s energy is small in total up to 20 of the incident wave is reflected by the groups of mode 1 and mode 2 waves this suggests that isw reflection has a significant impact on energy distribution over the continental slopes

tests of an extension to internal seiches of defant s procedure for determination of surface seiche characteristics in real lakes the success of a defant s method of calculating surface seiche periods and structures in real lakes is well known to test whether it can be adapted and applied with similar success in studies of internal seiches in stratified lakes in which density structure is simulated by two homogeneous layers we compare the predictions of a computerized version of mortimer s modified defant procedure against observations of internal seiche motion in eight lake basins and in three examples against the results of more elaborate models the acceptably close agreement inspires confidence that the modified method is useful for practical predictions which although approximate described the principal characteristics of the often large water mass displacements and oscillations through their influence on mixing and dispersal those motions profoundly affect the chemical and biological economies of many lakes to aid in microcomputer and even pocket calculator applications we set out steps in the calculation in tabular flow chart form a comparable table for surface seiche calculation is added the procedure is not applicable to large lakes in which effects of the earth s rotation are dominant but for the two largest basins tested here leman and ness a modification is introduced to take approximate account of rotation

on the reflectance of uniform slopes for normally incident interfacial solitary waves abstract the collision of interfacial solitary waves with sloping boundaries may provide an important energy source for mixing in coastal waters collision energetics have been studied in the laboratory for the idealized case of normal incidence upon uniform slopes before these results can be recast into an ocean parameterization contradictory laboratory findings must be addressed as must the possibility of a bias owing to laboratory sidewall effects as a first step the authors have revisited the laboratory results in the context of numerical simulations performed with a nonhydrostatic laterally averaged model it is shown that the simulations and the laboratory measurements match closely but only for simulations that incorporate sidewall friction more laboratory measurements are called for but in the meantime the numerical simulations done without sidewall friction suggest a tentative parameterization of the reflectance of interfacial solitary waves upon impact with uniform slopes

a two radius circular array method inferring phase velocities of love waves using microtremor records 1 we present a new method to estimate phase velocities of love waves from horizontal motion seismograms of microtremors obtained with seismic sensors placed around two circumferences of different radii under the assumption that the fundamental mode dominates we applied our new method to field data acquired at a test site where the shallow underground seismic velocity profile is known and have confirmed that the phase velocities of the fundamental mode love waves could be inferred with sufficient precision within certain wavelength ranges outside the wavelength ranges suitable for analysis the spectral ratio an intermediary quantity calculated from measurement records prior to phase velocity evaluation deviated from theoretical expectations the pattern of deviations could satisfactorily be accounted for by considering three factors theoretically the presence of higher mode surface waves directional aliasing related to the finite number of sensors and the presence of incoherent noise

dynamics of bottom currents in a small lake1 the dynamics of bottom currents in baldeggersee switzerland were investigated with a specially designed recording current meter sensitive to current velocities of 0 3 2 5 cm s l supporting information was obtained from thermistor chain temperature recordings and from records of atmospheric boundary layer parameters measured in the center of the lake during 1980 1981 bottom currents recorded for l week periods on the central bottom plateau of the lake 65 m water depth were highly variable the mean speed was slightly 1 cm sk with no seasonal trend speeds 2 5 cm s l occurred after periods of high wind quiescent periods were rare and seldom lasted more than 1 h spectral analysis shows that the primary mechanism generating bottom currents during stratification is internal gravity waves in the thermocline during winter mixing when chemical stratification is observed below 30 m the wind stress distribution is directly reflected in the bottom current pattern in both periods wind induced disturbances were felt in the bottom layer with little time delay indicating the event dominated structure of bottom current dynamics bursts of particle transport in the bottom layer are observed during periods of high wind suggesting episodic particle resuspension such events may be important for the control of mass exchange at the sediment water interface

turbulent mixing induced by nonlinear internal waves in mono lake california describing the spatial and temporal occurrence of turbulent mixing and the mechanisms of turbulence production are fundamental problems in physical limnology and oceanography here we present results from mono lake california that illustrate pronounced steepening of the pycnocline upon cessation of strong wind forcing and the enhanced turbulence resulting from this nonlinearity three events occurred with wind speed of 10 m s21 upwind the upper pycnocline upwelled but on relaxation of the wind it downwelled 6 10 m and compressed the similarity of wave amplitude during compression to mixed layer depth and lake numbers 4 were indicative of significant nonlinearity energy in the internal wave field increased by two orders of magnitude but 50 of the energy was lost within 24 h the largest energy losses occurred at low frequencies rather than via an energy flux from low to moderate and high frequencies eddy diffusivities computed over 6 d intervals using the heat budget method averaged 1026 m2 s21 in the energized pycnocline but were five to 10 times higher during the initial upwelling and downwelling periods microstructure casts taken 1 2 d after the first event revealed that the percentage of the pycnocline that was turbulent varied with bottom slope being 80 turbulent where bottom slopes were up to 10 6 0 where bottom slopes were 3 and less than 7 where bottom slopes were 0 1 the threshold for turbulent transport was exceeded only 10 of the time and only where bottom slopes were highest

does specialization imply rare fossil records of some benthic foraminifera late palaeocene examples from the eastern neo tethys meghalaya ne india abstract the palaeoecological characteristics of late palaeocene benthic foraminifera from the eastern neo tethyan sediments of meghalaya ne india are poorly understood the assignment of taxa as generalists or specialists is a fundamental aspect of ecology that is not given sufficient attention in palaeoecological analyses the first records of haymanella elongata and keramosphaera iranica from the upper palaeocene carbonate sedimentary rocks outcropping in the east khasi hills meghalaya ne india are documented herein these species occurred in warm hydrodynamically energetic shallow marine environments as indicated by their associations only with grain supported microfacies and co occurrence with taxa assumed to have hosted algal endosymbionts including operculina nummulites assilina orbitoclypeus and discocyclina h elongata and k iranica were found in very narrow horizons of the evaluated sections which was interpreted as indicating specialization to very specific habitats rare records of both these benthic foraminifera can be attributed to their specialist behavior that did not allow the populations to persist in fluctuating environments in comparison to these specialists more abundant and potential generalist foraminiferal taxa thrived in the region for longer periods it is deduced that h elongata and k iranica migrated to the study area from the mediterranean regions but did not thrive

lake morphometry sediment mixing and the selection of sites for fine resolution palaeoecological studies abstract palaeoecologists are increasingly using close interval or continuous sampling of lake sediments to construct fine resolution records of environmental change the degree of temporal resolution sought in these studies is typically decades or years the use of lake sediments for such fine resolution reconstructions assumes that temporal mixing of the sediments is negligible in this paper we examine the physical and biological processes that cause sediment mixing in small lakes we use physical models and empirical data to develop a set of heuristics relating lake depth and area to sediment mixing by slumping waves currents and bioturbation we also develop a heuristic that allows information on lake depth and area to be used to determine if the sediments of a lake will likely be massive or annually laminated in general the degree of sediment mixing likely to occur in a small lake is directly related to the depth and surface area of the lake however each of the agents of mixing has a different critical relationship with lake depth and surface area we present a series of equations and a summarizing figure that based on lake surface area and maximum depth allows the type of thermal stratification polymictic dimictic or meromictic and the degree of sediment mixing present in the lake to be inferred

a generic formulation for microtremor exploration methods using three component records from a circular array summary we present a generic formulation for analysis methods that estimate phase velocities of rayleigh and love waves by way of intermediary quantities called spectral ratios using three component records of microtremors from a circular array of sensors at each time instant the set of records are expanded in a fourier series with respect to azimuth so that we obtain a set of fourier coefficients that are represented in the form of complex time histories we then estimate power and cross spectral densities of those fourier coefficients the spectral densities thus obtained generally contain information on the phase velocities powers and arrival directions of individual modes of rayleigh and love waves by taking the quotient of two different sorts of such spectral densities we can cancel out information on their powers and arrival directions and extract information on their phase velocities alone the spectral ratios have to be estimated in practice on the basis of records from a finite number of seismic sensors that are either evenly or unevenly spaced around a circumference we describe a general procedure for their estimation and discuss the effects of directional aliasing that the finite number of sensors and their configuration have on the estimates of spectral ratios we also discuss biases in the estimates of spectral ratios caused by the presence of incoherent noise by using our method it is also possible to estimate the central arrival direction of the microtremors the ellipticity of the rayleigh waves and whether the rayleigh waves are prograde or retrograde

a multitracer study of radionuclides in lake zurich switzerland 2 residence times removal processes and sediment focusing residence and settling times of particles and particle reactive nuclides evaluated from in situ tracer studies can be used as diagnostic indicators of trace element pathways in lakes natural e g 210pb 7be and 10be and artificial i e chernobyl 137cs radionuclide fluxes through lake zurich at 50 and 130 m depth from 1983 to 1987 atmospheric fluxes of the same nuclides and fluxes of 10be during 1987 allowed the calculation of nuclide residence times as well as particle settling and transit velocities in lake zurich the residence time of 210pb in the lake is approximately 1 month and hence of the same order as the residence times of particles and stable pb steady state residence times for 7be were calculated as 150 170 days while non steady state instantaneous removal residence times ranged from 50 to 800 days polonium 210 was removed from lake zurich with removal times of 10 26 months indicating slow removal processes or efficient recycling in the lake water transit velocities of particles calculated from the attenuation of chernobyl 137cs fluxes at 50 m and 130 m depth during early may 1986 were 17 m d 1 while 2 4 5 m d 1 was calculated as an effective settling velocity from the attenuation of 7be fluxes at 130 m depth as compared to 50 m depth model calculations reveal that the overall removal process of atmospherically deposited 7be from the water column to the sediments is mainly controlled by the adsorption coagulation step and not by the rate of particle settling extra inputs of 10be 210pb or 137cs into the lower trap i e rebound flux originating from episodic lateral inputs of fine particles with a high content of 210pb 10be and 137s were observed during the lake stratification period i e summer this novel observation of summertime radionuclide and sediment focusing is different from previously described wind generated resuspension and focusing effects caused by river plumes and lake sediments during the stagnation period boundary and focusing effects for radionuclide bearing particles are proposed to explain observed summertime enhancements of longer lived nuclide fluxes at 130 m depth as well as the decrease in calculated effective settling velocities

evidence for enhanced boundary mixing in the santa monica basin transients in the heat content in santa monica and san pedro basins imply a basin wide diapycnal eddy diffusivity greater than 1 cm sup 2 s this is significantly larger than the value for sf sub 6 of 0 25 0 08 cm sup 2 s determined for the interior of santa monica basin for september 1985 to february 1986 by ledwell and watson however the exodus of sf sub 6 from santa monica basin after february 1986 by which time the tracer had mixed to the boundaries of the basin was fast enough to be consistent with a greatly enhanced vertical flux since the kinetic energy in the basin had not changed significantly it is unlikely that a temporal increase in forcing resulted in enhanced fluxes in the interior of the basin the most likely interpretation is that diapycnal fluxes in the basin are dominated by processes in the boundary regions temperature and sf sub 6 profiles from near the edges of the basin do not give conclusive evidence either for or against such enhanced mixing 20 refs 19 figs 5 tabs

the climatology of internal waves in a deep temperate lake kootenay lake is a long 100 km deep 140 m dimictic lake in southeastern british columbia internal waves were observed over an 18 month period using three thermistor chains moored along the major axis of the lake to characterize their seasonal aspects four types of oscillations are recognized 1 classical seiches with amplitudes of 10 30 m and periods of 1 2 weeks 2 intrabasin waves with periods of 2 4 days 3 large amplitude waves resembling nonlinear surges and 4 high frequency waves associated with both the internal surge and large amplitude internal seiche motions the periods of the major components of the internal wave field are determined mainly by morphometry but vary seasonally with stratification thus the wind which not only forces internal waves but can also modify stratification is important in large lakes like kootenay the thermal structure may vary not only spatially but also temporally at periods comparable to those of the internal waves themselves hence the shape and frequency of these waves may be altered as they pass through the lake

dissolved silica budget in the north basin of lake lugano we studied the dissolved silica cycle in the water column of the north basin of lake lugano switzerland italy lake lugano is a meromictic eutrophic lake permanently stratified below 100 m depth a one box model was used to calculate a silica mass balance over 1993 based on various lake measurements such as sediment traps sediment cores water analysis and biota countings we found that the north basin of lake lugano is at steady state as far as dissolved silica is concerned the primary source of dissolved silica in the lake is river input about 80 with diffusion from bottom sediments and groundwater input also playing a role atmospheric input is negligible the main export of dissolved silica occurs via biogenic uptake by diatoms and final burial of their frustules in the bottom sediment loss of dissolved silica through the lake outflow only represents 15 of the total output of the total amount of si exported to the lake bottom through diatom sinking less than 20 is re supplied to the surface water by diffusion thus the lake acts as an important permanent sink for silica the long residence time of dissolved silica in the lake 7 years is related to the strong physical stratification of the lake only about 10 of the standing stock are available to phytoplankton uptake

forced resonant oscillations as a response to periodic winds in a stratified reservoir the response of the sau reservoir to a wind field characterized by having marked periodicities of 12 h and 24 h has been studied measurements of temperature with a thermistor string and currents with an acoustic doppler current meter show that the reservoir also responds with the same water periodicities during certain times of the stratified period some of the natural oscillation modes of the reservoir are close to these forcing wind periods in particular in mid july the vertical mode v2 is close to 12 h and in mid to end of september the vertical mode v3 is close to 24 h in these situations these modes are selected out of the spectrum of possible internal waves and the reservoir behaves as a forced oscillator in resonance with the wind the structure and the period of these vertical modes have been elucidated by using the 3d model elcom both modes are affected by the earth s rotation at the widest part of the reservoir

universal similarity and the thickness of the viscous sublayer at the ocean floor experiments conducted on the oregon continental shelf in june 1979 indicate that the boundary layer flow at the seafloor was hydrodynamically smooth fine resolution velocity profiles are used to test the assumption that the flow behaved like a universally similar neutrally buoyant flow over a smooth wall the non dimensional thickness of the viscous sublayer is far more variable than has been observed in laboratory studies over perfectly smooth walls this variability may conceivably be related to upstream changes of surface roughness or to the presence of distributed roughness elements laboratory results indicate that the near bed flow adjusts extremely slowly to upstream roughness changes and suggests that flow near the sublayer in the ocean may be influenced by roughness changes as far as tens of meters upstream

internal solitons on the pycnocline generation propagation and shoaling and breaking over a slope in part 1 a study is made of the internal solitary wave on the pycnocline of a continuously stratified fluid a korteweg de vries kdv equation for the interfacial displacement is developed following benney s method for long nonlinear waves experiments were conducted in a long wave tank with the pycnocline at several different depths below the free surface while keeping the total depth approximately constant a step like pool of light water trapped behind a sliding gate served as the initial disturbance condition the number of solitons generated was verified to satisfy the prediction of inverse scattering theory the fully developed soliton was found to satisfy the kdv theory for all ratios of upper layer thickness to total depth in part 2 of this study we investigate experimentally the evolution and breaking of an internal solitary wave as it shoals on a sloping bottom connecting the deeper region where the waves were generated to a shallower shelf region it is found through quantitative measurements that the onset of wave breaking was governed by shear instability which was initiated when the local gradient richardson number became less than the internal solitary wave of depression was found to steepen at the back of the wave before breaking in contrast with waves of elevation two slopes were used with ratios 1 16 and 1 9 and the fluid was a boussinesq fluid with weak stratification using brine solutions

characteristics of seismic waves composing hawaiian volcanic tremor and gas piston events observed by a near source array a correlation method specifically designed for describing the characteristics of a complex wave field is applied to volcanic tremor and gas piston events recorded by a semicircular array of geos instruments set at the foot of the puu oo crater on the east rift of kilauea volcano hawaii the spatial patterns of correlation coefficients obtained as functions of frequency for the three components of motion over the entire array are similar for gas piston events and tremor and clearly depict dispersive waves propagating across the array from the direction of puu oo the wave fields are composed of comparable amounts of rayleigh and love waves propagating with similar and extremely slow phase velocities ranging from 700 m s at 2 hz to 300 m s at 8 hz the highly cracked solidified lava flow on which the array was deployed and subjacent structure of alternating lava and ash layers formed during repeated eruptions of puu oo since 1983 appear to be responsible for the low velocities observed the results from puu oo stand in sharp contrast to those obtained in an experiment conducted in 1976 on the partially solidified lava lake of kilauea iki rayleigh waves were not observed in kilauea iki but well developed trains of love waves were seen to propagate there with velocities twice as high as those observed near puu oo these differences in the propagation characteristics of surface waves at the two sites may be attributed to the presence of a soft horizontal layer of molten rock in kilauea iki which may have lowered the phase velocity of rayleigh waves more drastically than that of love waves resulting in severe scattering of the rayleigh wave mode on the other hand the thin superficial pahoehoe flow under our array at puu oo may have favored the development of vertical columnar joints more extensively at this location than at kilauea iki which may have reduced the shear moduli controlling the love wave mode the average phase velocities in the frequency band from 2 to 5 hz found at puu oo are roughly similar to those determined for tremor at klyuchevskoy volcano kamchatka but the frequency dependence appears much stronger at puu oo

dynamics of mixed bottom boundary layers and its implications for diapycnal transport in a stratified natural water basin here we report on two field experiments from lake alpnach surface area 4 8 km 2 maximum depth 34 m that were designed to study the process of boundary mixing and to estimate its efficiency the ratio between the turbulent kinetic energy converted into potential energy and dissipated into heat for diapycnal tracer transport lake alpnach is particularly suited for this purpose because it is known from earlier experiments that 1 its currents follow a regular oscillatory pattern associated with basin wide standing internal waves seiches period similar to 0 5 days and 1 day respectively and 2 diapycnal tracer transport is mainly caused by boundary mixing during one of the experiments reported here strong seiches were excited regularly and damped on a timescale of the order of 3 days during the other experiment seiching motion was comparably weak if seiching is excited regularly we find a persistent well mixed bottom layer of 4 5 m height at the deepest part of the lake in the absence of regular seiching the layer disappears within 10 20 days on the sloping bottom boundaries the well mixed layers 1 are of much more transient nature 2 exhibit different thermal structure and 3 decrease in thickness toward shallower depth inversely proportionally to the stability at the same depth in the lake interior their reduced thickness is possibly the result of repeatedly occurring intrusions of boundary mixed water masses that are observed to extend horizontally similar to 100 200 m into the lake interior as a consequence of repeated generation of intrusions mixing on the sloping boundaries is expected to be considerably more efficient compared to mixing over flat bottom boundaries the observed mixing efficiency the ratio of the rate of change of potential energy below depth z caused by turbulence to the energy loss by bottom friction below depth z increases indeed from 0 01 0 01 in the deepest well mixed layers to 0 15 0 04 in the upper pycnocline

topographic response of nearshore currents to wind an empirical model abstract observations of winds and currents along the northshore of lake ontario are analyzed to evaluate effects of topographic wave propagation on wind driven currents lagged cross correlations and spectral transfer functions between winds and currents are found to be consistent with the mechanism of resonant topographic wave response in the presence of bottom friction transfer function models in the time domain are shown to explain 70 to 80 percent of the variance of observed currants

internal wave breaking at concave and convex continental slopes abstract internal wave reflection from a sloping topographic boundary may lead to enhanced shear if the topographic angle to the horizontal is close to that of the internal wave group velocity vector previous analytic studies have suggested that shear enhancement is reduced at concave slopes as compared with convex and planar slopes near the critical angle here the internal wave reflection from concave and convex slopes that pass through the critical angle is investigated numerically using the nonhydrostatic massachusetts institute of technology general circulation model mitgcm overturning shear instability and resultant mixing are examined results are compared with simulations of wave reflection from planar slopes with angles greater than less than and equal to the critical angle in contrast to the analytic predictions no reduction in mixing is found for the concave slope as compared with the other slopes in all cases stratification is eroded in a band above the slope bounded at its outer

a new method to determine phase velocities of rayleigh waves from microseisms we have developed a new method to determine phase velocities from the vertical component of microseisms recorded with an array of seismic sensors spaced around the circumference of a circle we calculate two different time histories by taking the average of the seismograms with differing sets of weights for the sensor stations the spectral ratio of these two time histories contains no information on the arrival directions or on the amplitudes of the incoming waves but depends solely on the phase velocities of the arriving modes theoretical considerations indicate that the effects of directional aliasing caused by the use of a finite number of sensors in the field implementation of our method are small in most situations except for short wavelengths the presence of incoherent noise limits the efficacy of our method for long wavelengths in field tests using arrays of three seismic sensors we obtained appropriate estimates of phase velocities in the wavelength range from 5r to 30r where r the array radi

transport by breaking internal gravity waves on slopes we use the results of a direct numerical simulation dns with a particle tracking model to investigate three dimensional transport by breaking internal gravity waves on slopes onshore transport occurs within an upslope surge of dense fluid after breaking offshore transport occurs due to an intrusion of mixed fluid that propagates offshore and resembles an intermediate nepheloid layer inl entrainment of particles into the inl is related to irreversible mixing of the density field during wave breaking maximum onshore and offshore transport are calculated as a function of initial particle position and can be of the order of the initial wave length scale for particles initialized within the breaking region an effective cross shore dispersion coefficient is also calculated and is roughly three orders of magnitude larger than the molecular diffusivity within the breaking region particles are transported laterally due to turbulence that develops during wave breaking and this lateral spreading is quantified with a lateral turbulent diffusivity lateral turbulent diffusivity values calculated using particles are elevated by more than one order of magnitude above the molecular diffusivity and are shown to agree well with turbulent diffusivities estimated using a generic length scale turbulence closure model based on a favourable comparison of dns results with those of a similar two dimensional case we use two dimensional simulations to extend our cross shore transport results to additional wave amplitude and bathymetric slope conditions

the degeneration of large scale interfacial gravity waves in lakes mechanisms for the degeneration of large scale interfacial gravity waves are identified for lakes in which the effects of the earth s rotation can be neglected by assuming a simple two layer model and comparing the timescales over which each of these degeneration mechanisms act regimes are defined in which particular processes are expected to dominate the boundaries of these regimes are expressed in terms of two lengthscale ratios the ratio of the amplitude of the initial wave to the depth of the thermocline and the ratio of the depth of the thermocline to the overall depth of the lake comparison of the predictions of this timescale analysis with the results from both laboratory experiments and field observations confirms its applicability the results suggest that for small to medium sized lakes subject to a relatively uniform windstress an important mechanism for the degeneration of large scale internal waves is the generation of solitons by nonlinear steepening since solitons are likely to break at the sloping boundaries leading to localized turbulent mixing and enhanced dissipation the transfer of energy from an initial basin scale seiche to shorter solitons has important implications for the lake ecology

miniature array analysis of microtremors we suggest observing microtremors by using a miniature array consisting of vertical component seismometers that are placed at the center andon the circumferenceofa circlewith a radius of several tens of centimeters for identifying the phase velocities of rayleigh waves with wavelengths exceeding several tens or a hundred meters we present as tools for the analysis a set comprised of the analysis methods for the phase velocity and the evaluation method for the analysis limit which were recently developed by the authors on the basis of a rigorous theory derived by generalizing a spatial autocorrelation method we conducted miniature array observations using four or six servo type seismometers ju 215 manufactured by hakusan corporation at about 50 observation points throughout a test site and urban areas in tsukuba city and its surroundings which have various topographical and geologic environments the time required from arrival at an observation point to retrieval averaged about 30 min we could determine the phase velocities of rayleigh waves with wavelengths of 40 and 100 m at 91 and 51 of all the observation points respectively miniature array analyses can significantlyimprovethemobilityofobservationtoinfershallow subsurface velocity structures to the depth of several tens of meters

internal wave weather in a stratified lake thermistor chain data collected in lake biwa japan during a period of strong stratification were used to determine the nature of the water column response to wind forcing the evolution of the basin scale waves in the lake were reproduced in three dimensional numerical simulations and the time variability of the internal wave spectrum is discussed based on spectral analysis of the thermistor chain records severe winds associated with the passage of three typhoons during the sampling period excited basin scale kelvin and poincare waves which by interaction with the topography of the lake and non linear effects generate trains of high frequency internal waves time frequency analysis of the temperature signals suggests that the 2 slope of the internal wave spectrum is probably the result of the composition of groups of waves with high intermittence travelling through the wave guide the observed rapid decay of internal wave energy after severe wind events seemed to be due mostly to high dissipation at the sloping boundaries of the lake

the temporal evolution of baroclinic basin scale waves in a rotating circular basin the temporal evolution of baroclinic basin scale waves in a rotating circular basin following an initial forcing event is investigated using a laboratory study experiments conducted in the circular domain containing a two layer fluid with a flat bottom and vertical sidewalls demonstrate that the response is essentially linear with frictional effects at the boundaries steadily dissipating wave energy experiments conducted in the same configuration but with the addition of simple topographic features either a radially protruding cape or a bathymetric ridge exhibit wave topography interactions that result in the formation of an eddy field and an offshore flow respectively the rate of wave decay as well as the amount of horizontal mixing occurring within the basin is significantly enhanced by such interactions the results of this study are then considered in terms of their implications for the baroclinic basin scale wave energy pathways in large stratified lakes influenced by the earth s rotation

shallow velocity models at the kilauea volcano hawaii determined from array analyses of tremor wavefields the properties of the surface wavefield at kilauea volcano are analysed using data from small aperture arrays of short period seismometers deployed in and around the kilauea caldera tremor recordings were obtained during two japan us cooperative experiments conducted in 1996 and 1997 the seismometers were deployed in three semi circular arrays with apertures of 300 300 and 400 m and a linear array with length of 1680 m data are analysed using a spatio temporal correlation technique well suited for the study of the stationary stochastic wavefields of rayleigh and love waves associated with volcanic activity and scattering sources distributed in and around the summit caldera spatial autocorrelation coefficients are obtained as a function of frequency and are inverted for the dispersion characteristics of rayleigh and love waves using a grid search that seeks phase velocities for which the l 2 norm between data and forward modelling operators is minimized within the caldera the phase velocities of rayleigh waves range from 1400 to 1800 m s 1 at 1 hz down to 300 400 m s 1 at 10 hz and the phase velocities of love waves range from 2600 to 400 m s 1 within the same frequency band outside the caldera rayleigh wave velocities range from 1800 to 1600 m s 1 at 1 hz down to 260 360 m s 1 at 10 hz and love wave velocities range from 600 to 150 m s 1 within the same frequency band the dispersion curves are inverted for velocity structure beneath each array assuming these dispersions represent the fundamental modes of rayleigh and love waves the velocity structures observed at different array sites are consistent with results from a recent 3 d traveltime tomography of the caldera region and point to a marked velocity discontinuity associated with the southern caldera boundary

boundary versus internal diapycnal mixing in stratified natural waters using the fluorescent dye uranin tracer release experiments to study the contribution of bottom boundary mixing to diapycnal transport in stratified natural waters were performed in lake alpnach central switzerland during 1992 1995 a first experiment involved injecting the tracer from a point source into the center of the hypolimnion that part of the lake below the surface mixed layer an in situ fluorometer was then employed to detect the horizontal and vertical spreading of the tracer cloud allowing rates of diapycnal diffusivity to be determined as long as the tracer was confined to the interior water region the diapycnal diffusivity was relatively small however after the tracer cloud had reached the lake boundary the diapycnal diffusivity increased by approximately one order of magnitude in a second experiment the tracer was released near the sediment water interface in this case the dynamics of vertical tracer spreading were opposite during the first few hours after tracer release diapycnal diffusivities were large subsequently decreasing as the tracer cloud drifted away from the lake boundary basin wide diapycnal diffusivities calculated from heat flux measurements based on temperature profiles obtained from thermistor chains or conductivity temperature depth casts agreed well with the values obtained from the vertical tracer diffusion after horizontal homogenization the results of the tracer experiments corroborate the hypothesis that diapycnal fluxes are determined predominantly by mixing in the bottom boundary region

high frequency internal waves in large stratified lakes observations are presented from lake biwa and lake kinneret showing the ubiquitous and often periodic nature of high frequency internal waves in large stratified lakes in both lakes high frequency wave events were observed within two distinct categories 1 vertical mode 1 solitary waves near a steepened kelvin wave front and vertical mode 2 solitary waves at the head of an intrusive thermocline jet were found to have wavelengths 64 670 m and 13 65 m respectively and were observed to excite a spectral energy peak near 10 23 hz 2 sinusoidal vertical mode 1 waves on the crests of kelvin waves vertically coherent in both phase and frequency and bordering the thermocline jets in the high shear region trailing the vertical mode 2 solitary waves vertically incoherent in both phase and frequency were found to have wavelengths between 28 37 and 9 35 m respectively and excited a spectral energy peak just below the local maximum buoyancy frequency near 10 22 hz the waves in wave event categories 1 and 2 were reasonably described by nonlinear wave and linear stability models respectively analysis of the energetics of these waves suggests that the waves associated with shear instability will dissipate their energy rapidly within the lake interior and are thus responsible for patchy turbulent events that have been observed within the metalimnion conversely the finite amplitude solitary waves which each contain as much as 1 of the basinscale kelvin wave energy will propagate to the lake perimeter where they can shoal thus contributing to the maintenance of the benthic boundary layer

observations of highly nonlinear internal solitons over the continental shelf surface disturbances caused by strong near surface internal waves are widely seen in coastal regions as bands of slick and rough water propagating shoreward these surface slicks are typically manifestations of optical and radar backscatter properties above internal solitons and have strong surface current pulses associated with them during a recent experiment studying coastal internal waves extremely strong solitary internal wave packets were observed over a three week period on a very shallow and strongly stratified pycnocline off northern oregon during periods of strongest tidal forcing solitons were consistently observed on the leading edge of a semidiurnal internal tide bore with pycnocline displacements up to 25m downward from a 7m initial depth in the first few solitons the extreme nonlinearity of these internal waves is believed to be unique in ocean observations this note characterizes these highly nonlinear solitary internal waves siw and presents a second order kdv model which reproduces the form of the displacements and the small change in soliton width with amplitude predicted by this model

breaking of internal kelvin waves shoaling on a slope in stratified flow breaking of internal waves over slopes induces resuspension of bottom sediments and transport of mass when internal waves shoal and break flow dynamics and mass transport diff

a parametric study of the generation and degeneration of wind forced long internal waves in narrow lakes the generation and energy downscaling of wind forced long internal waves in strongly stratified small to medium sized narrow lakes are studied a two layer nonlinear model with forcing and damping is employed even though the wave field is fundamentally bidirectional in nature a domain folding technique is employed to simulate the leading order internal wave field in terms of a weakly nonlinear weakly dispersive model equation of korteweg devries type parametric effects of wind forcing and environmental conditions including variable topography and variable basin width are examined energy downscaling from basin scale waves to shorter scales are quantified by means of a time evolution of the wave energy spectra it is demonstrated that an internal wave resonance is possible when repetitive wind forcing events arise with a frequency near the linear seiche frequency an attempt is made to apply the model to describe the shoaling of long waves on sloping endwall boundaries modelling of the energy loss and energy reflection during a shoaling event is calibrated against laboratory experiments

bottom stress estimates and their prediction on the northern california continental shelf during code 1 the importance of wave current interaction abstract high quality near bottom boundary layer measurements obtained at a midshelf location 90 m water depth in the code region off northern california are described bottom tripod velocity measurements and supporting data obtained during typical spring and early summer conditions june 1981 during code 1 are analyzed to obtain bath velocity profiles and mean bottom stress and bottom roughness estimates during the time period described the mean near bottom 0 997 approximately 30 percent of the time effects induced by unsteadiness from internal waves result in some degradation of the profiles 0 96 r 0 997 the rest of the time mean stress profiles indicate the logarithmic layer is approximately a constant stress layer the near bottom flow field is composed of mean currents and oscillatory currents due to well typing mean u values estimated from measurements greater than 30 cm above the bottom have magnitudes of 0 5 1 0 cm s 1 mean stress valu

cyclonic brine flow pattern recorded by oriented gypsum crystals in the badenian evaporite basin of the northern carpathian foredeep abstract in the middle miocene badenian within sulfate evaporites formed in the northern carpathian foredeep basin of poland ukraine and the czech republic the apices of the primary bottom grown gypsum crystals selenites are similarly aligned over broad areas and have a common azimuth this crystal orientation is interpreted as the product of a consistent direction of a brine inflow during gypsum crystallization and such a unique commonality is used as a tool for paleocurrent analysis in order to recognize both the local and the regional brine paleocurrents in the basin earlier sedimentologic and stratigraphic studies proved that these beds of oriented selenites were deposited at the same or nearly the same time in a brine not more than a few meters deep it is interpreted that the oriented selenites recorded only the mean flow within the basin mainly from the periods of mixing in the dry season lowstands when the whole brine column down to the bottom was ca sulfate oversaturated the measured paleocurrent vectors showed that the brines flowed along the marginal zone of the carpathian foredeep basin predominantly in a counterclockwise direction this longshore flow is interpreted as a typical cyclonic circulation analogous to those present in recent lakes and semi closed basins in the northern hemisphere where counterclockwise mean water drift is directly or indirectly forced by earth rotation the coriolis effect the detected brine flow directions do not reflect downslope gravity flow of dense brines into the central basinal depths or subbasins that were filling with the halite facies

horizontal and vertical variations in sedimentation and resuspension rates in a stratifying lake effects of internal seiches the temporal and spatial variations in the rate of sedimentation and sediment resuspension in lake rehtijarvi southern finland were studied by sediment traps deployed in the stratifying and non stratifying regions of the lake both the gross sedimentation rate and the resuspension rate recorded by near bottom traps were significantly higher in the stratifying region 20 m depth than in the shallow part of the lake 2 m depth these rate changes were caused by temporarily elevated hypolimnetic resuspension rates exceeding 40 g dry weight m 2 day 1 in july 2005 whereas in the shallow station no such peak was observed and the resuspension rate remained below 30 g dry weight m 2 day 1 throughout the study the elevated resuspension rate in the hypolimnion could not be attributed to surface wave action or sediment disturbance by fish but was due to the occurrence of internal seiches the seiche amplitude was on average the highest in july although the wind velocities were low this was because winds temporarily were blowing along the longitudinal axis of the lake due to the steep slopes the sediments of lake rehtijarvi are prone to redistribution and sediment focusing towards the accumulation areas also affected trap catches in the deep stations

burst resuspension of seabed material at the foot of the continental slope in the rockall channel to better understand the relationship between near bottom hydrodynamics and sediment resuspension in the transition zone between the continental slope and the abyssal plain an array of three moorings equipped with near bottom sediment traps and current meters was deployed in a triangular configuration of at the foot of the south east slope of the rockall channel north atlantic in addition a fast sampling adcp was moored in the centre of the triangle microscopic observations combined with grain size analysis revealed that the material intercepted by the traps was mainly composed of loose phytodetritus and aggregates organic carbon and 13corg analyses further indicate that this material is relatively fresh and hence probably only transported over short distances the total mass flux measured by the traps suggests input from either laterally advected or resuspended material during the deployment period the measured flux was variable in time and space with a strong increase at the deepest site at the very foot of the slope the measured flux did not correlate significantly with daily averaged current speed suggesting that processes other than those related to elevated bed shear stress are involved in the resuspension mechanism rapid changes in the hydrodynamics probably related to internal motions are evidenced by abrupt bursts in the current velocity and in the near bottom turbidity their occurrence at slack tidal waters appears to be at the origin of the resuspension observed at the foot of the slope of the rockall channel high resolution current velocity measurements suggest that resuspension is dominated by energetic highly localised and short term resuspension events despite the abyssal depths part of these events resemble in many ways the solibores which have been previously observed to enhance sediment transport at much shallower depths over the continental slope while others rather appear to be associated to gravity waves

reply to the comment on does specialization imply rare fossil records of some benthic foraminifera late palaeocene examples from the eastern neo tethys meghalaya ne india

permanent tremor of masaya volcano nicaragua wave field analysis and source location the masaya volcano nicaragua is a basaltic caldera in a subduction zone the permanent source of the volcanic tremor was located inside santiago crater at the lava lake s position and 400 m below the ne rim and therefore corresponds to superficial magma activity we used two tripartite arrays 90 m side one semicircular array r 120 m in 1992 and two semicircular arrays r 60 m and a 2500 m long linear array radiating out from the source and on the flank of the crater in 1993 we used both a cross spectrum method and a correlation method to determine the wave delay time between the reference station and the other stations of an array and to quantify the wave field using the delays therefore by intersecting the back azimuth wave directions from the arrays we could pinpoint the source additionally the correlation coefficients obtained as functions of frequency for the three components of motion confirm the inferred position of the source of tremor the tremor s wave field is composed of comparable quantities of dispersed rayleigh and love surface waves whose phase velocities lie in the ranges 730 1240 m s at 2 hz and 330 550 m s at 6 hz the dispersive phase velocities were inverted to obtain crustal structures with a minimal number of layers the resulting velocity models are similar for the northern and southern parts of the volcano after geometrical spreading corrections q2hz 14 and q3hz 31 were determined along the northern linear array the typical low velocities and low q corresponding to the cone structure and are similar to those of other basaltic volcanoes like puu oo hawaii and klyuchevskoy kamchatka

cold intrusions in lake baikal direct observational evidence for deep water renewal we studied cold deep water intrusions in the south basin of lake baikal on the basis of 2 yr of data december 1995 november 1997 from near bottom and near surface thermistor strings monthly conductivity temperature depth ctd profiles and a near bottom current meter all collected near the south basin maximum depth of 1 461 in the data show intrusions into the greatest depths with temperatures of 0 08 0 20degreesc below ambient similar to3 33 to similar to3 38degreesc at maximum depth the intrusions were observed three times per year between january and june when surface water is always cooler than deep water with durations of a few at least 1 3 days the estimated water input ranged from 1 to 10 km 3 per event and the annually accumulated volume was estimated to be 10 30 km 3 which is significantly less than the steady state indirect estimates of 30 70 km 3 yr 1 to the permanently stratified deep water depth 300 in this indicates that not all of the cold intrusions reach the deepest area because the cooling of the near bottom waters was not accompanied by a significant increase in ion or particle content and because deep sediment traps did not contain significant enrichments of minerogenic particles we concluded that selenga river inflow is not a possible source of the cold intrusions two ctd profiles in june 1996 and 1997 showed lower temperature throughout the deep water as expected from thermobaric instabilities the required downwelling is definitely not occurring in the pelagic interior but most probably by near coast counterclockwise currents the source of the regularly occurring deep intrusions is clearly cold surface water but the actual mechanism is uncertain

seasonal evolution of the basin scale internal wave field in a large stratified lake the response of the water column to varying conditions of stratification and wind forcing was investigated in lake kinneret israel using data collected from thermistor chains and acoustic doppler current profilers during 1997 and 1998 the strong daily sea breeze was found to generate a vertical mode 1 internal kelvin wave and basin scale internal poincarewaves of vertical modes 1 2 and 3 the kelvin wave the dominant component of the internal wave field was responsible for alongshore velocities in the nearshore regions in the upwind nearshore regions velocities were dominated by the forced response to the wind and were cross shore in nature in the lake interior the kelvin wave effect on the horizontal velocity field was minor compared to the higher vertical mode poincarewaves the kelvin wave is shown to exist in resonant and nonforced states with the wind whereas the vertical mode 1 poincarewave energy remained relatively constant despite large variability in the forcing condi tions the energy in the higher mode poincarewaves varied greatly both on daily and seasonal timescales the results demonstrate that the wind energy forces multiple basin scale internal wave modes and that prior motion in the water column must be considered when determining the subsequent internal wave response in periodically forced systems lake kinneret israel has long been an important regional resource providing a substantial supply of drinking water as well as supporting a commercial fishery the monomictic lake is forced daily during the summer by a powerful sea breeze with stratification and wind patterns showing little variation from year to year these factors along with a fa vorable bathymetric pattern combine to make lake kinneret an ideal place for the field investigation of large scale inter nal waves and related phenomena such as the benthic bound ary layer horizontal transport and vertical mixing processes in addition to providing substantial insight into the local pro cesses and hence influencing local management study of the lake also provides fundamental knowledge of the dynam ics of enclosed basins on a geophysical scale during summer the internal rossby radius in lake kin neret is typically one half the basin width hence large scale motion in the lake will be affected by the earth s rotation and basin scale internal waves may be of topographic ross by kelvin or poincareform topographic rossby waves are sub inertial frequency oscillations that exist only in rotating fluids with variable bathymetry mysak et al 1985 stocker and hutter 1987 and these waves result from changes in depth affecting the relative vorticity of fluid elements in the absence of vertical boundaries wavelike solutions to the lin ear inviscid equations of motion for a flat bottomed region of homogeneous fluid with a constant rate of rotation are 1

s wave velocity profiling by joint inversion of microtremor dispersion curve and horizontal to vertical h v spectrum a joint inverse analysis using both microtremor dispersion curve and horizontal to vertical h v spectrum is proposed for estimating the s wave velocity vs profiles of subsurface soils in the inversion both microtremor dispersion and h v data are assumed to be the rayleigh wave dispersion curve and the surface both rayleigh and love wave h v spectrum that have been theoretically derived by taking into account the effects of their fundamental and higher modes the proposed joint inversion as well as the conventional one using dispersion data alone is per formed at four sites where shallow vs profiles down to engineering bedrock are available the vs profiles estimated by the proposed joint inversion are more con sistent with available down hole velocity logs than those by the conventional method in particular the proposed inversion shows significant improvement in estimating bedrock vs structures compared to the conventional inversion sensitivity analyses indicate that the surface wave h v ratio is sensitive to the bedrock vs structure more than the rayleigh wave phase velocity confirming that the proposed joint inversion including h v spectrum is promising

residual circulation due to internal waves shoaling on a slope we describe the residual circulation induced in a two layer system when internal waves with a wave length equal to or longer than the slope length propagate over a sloping bottom and either reflect or break for the case of no wave breaking scaling is used to derive boussinesq type equations the solution of which leads to an expression for the residual circulation adjacent to the sloping bottom this residual circulation is maintained by a weak slope on the density interface for breaking waves laboratory experiments and numerical modeling were used to ascertain the details of the residual circulation arising from the formation of gravitational intrusions results from these three investigative tools were used to determine as a function of bottom slope and incident wave amplitude the internal wave reflection coefficient and the strength of the residual circulation pattern with and without wave breaking the ocean and most lakes are thermally stratified for at least part of the year in stratified fluids the density anomaly associated with the thermal stratification supports internal waves with a range of vertical modal structures antenucci et al 2000 antenucci and imberger 2001 antenucci and imberger 2003 the gravest or first vertical mode induces a large current over the lake or ocean bottom and when the bottom slopes the waves shoal causing them to break and lose energy to dissipation the associated currents and turbulence can often lead to sediment resuspension and mixing of the water column gloor et al 1994 pierson and weyhenmeyer 1994 steinman et al 1997 the gravitational motions in turn induced by the mixing may combine with secondary internal wave motions to drive a residual circulation that may transport resuspended and dissolved material to the central area of a lake hakanson 1982 ostrovsky et al 1996 inall 2009 also demonstrated mass transport due to intrusion caused by internal wave breaking in the fjord loch etive by using a fluorescent dye tracer such intrusions have been observed but their dynamics do not seem to have received any attention in this paper the processes leading to residual circulation are described when a continuous train of internal waves with an individual wavelength equal to or longer than the slope length supported by a two layer stratification impinges perpendicularly onto a sloping bottom two cases were investigated when the waves break and when they are reflected perfectly without breaking internal waves and their associated mass transport in lakes fjords and coastal oceans are reviewed in ostrovsky and stepanyants 1989 and huthnance 1989 whereas solitary internal waves are reviewed by brown and christie 1998 lamb 2002 and grue et al 2000 regarding mass transport lamb 2002 investigated shoaling of largeamplitude internal waves and demonstrated that trapped

structure and generation of turbulence at interfaces strained by internal solitary waves propagating shoreward over the continental shelf abstract detailed observations of the structure within internal solitary waves propagating shoreward over oregon s continental shelf reveal the evolving nature of interfaces as they become unstable and break creating turbulent flow a persistent feature is high acoustic backscatter beginning in the vicinity of the wave trough and continuing through its trailing edge and wake this is demonstrated to be due to enhanced density microstructure increased small scale strain ahead of the wave trough compresses select density interfaces thereby locally increasing stratification this is followed by a sequence of overturning high density microstructure and turbulence at the interface which is coincident with the high acoustic backscatter the richardson number estimated from observations is larger than 1 4 indicating that the interface is stable however density profiles reveal these preturbulent interfaces to be o 10 cm thick much thinner than can be resolved with shipboard velocity measurements by as

a wintertime temperature inversion in kootenay lake british columbia we describe the wintertime development and persistence of an anomalous temperature inversion layer in a deep temperate lake with emphasis on the roles of convective mixing and river induced circulation the layer is about 20 m thick 100 km long and lies at a depth of 60 80 m the destabilizing temperature distribution is compensated by a very weak 0 015 ppt salinity increase across the inversion layer we observe that neither the energy available from the wind nor the buoyancy extracted at the surface via a negative heat flux are sufficient to penetrate the depth of the inversion calculations of a thermal diffusion coefficient for this layer indicate a weak turbulent exchange below the halocline lake overturn does not follow the classical pattern of surface processes driving complete winter mixing rather full circulation is made possible only by the input of relatively saline river water

spatial structure of the dominant basin scale internal waves in lake kinneret field data and numerical simulations were used to investigate the effects of basin shape continuous stratification and rotation on the three dimensional structure of the dominant natural basin scale internal wave modes in lake kinneret a stratified lake large enough so that the earth s rotation influences the wave motion the structure of the modes was inferred from power spectral density of measured and simulated isotherm vertical displacements and from rotary power spectral density of isopycnal velocities obtained from numerical simulations the shape of the lake at the level of the thermocline in conjunction with the dispersion relationship determines the horizontal configuration of the natural modes the dominant response to wind forcing was an azimuthal and vertical mode 1 kelvin wave with a natural period of 22 6 h that propagated around the entire basin the second most dominant response was a vertical mode 1 wave with a natural period close to 10 5 h and composed of two counter rotating

the degeneration of internal waves in lakes with sloping topography in a laboratory study we quantified the temporal energy flux associated with the degeneration of basin scale internal waves in closed basins the system is two layer stratified and subjected to a single forcing event creating available potential energy at time zero a downscale energy transfer was observed from the wind forced basin scale motions to the turbulent motions where energy was lost due to high frequency internal wave breaking along sloping topography under moderate forcing conditions steepening of nonlinear basin scale wave components was found to produce a high frequency solitary wave packet that contained as much as 20 of the available potential energy introduced by the initial condition the characteristic lengthscale of a particular solitary wave was less than the characteristic slope length leading to wave breaking along the sloping boundary the ratio of the steepening timescale required for the evolution of the solitary waves to the travel time until the waves shoaled controlled their development and degeneration within the domain the energy loss along the slope the mixing efficiency and the breaker type were modeled using appropriate forms of an internal iribarren number defined as the ratio of the boundary slope to the wave slope amplitude wavelength this parameter allows generalization to the oceanographic context analysis of field data shows the portion of the internal wave spectrum for lakes between motions at the basin and buoyancy scales to be composed of progressive waves both weakly nonlinear waves sinusoidal profile with frequencies near 10 24 hz and strongly nonlinear waves hyperbolic secant squared profile with frequencies near 10 23 hz the results suggest that a periodically forced system may sustain a quasi steady flux of 20 of the potential energy introduced by the surface wind stress to the benthic boundary layer at the depth of the pycnocline

relative sea level change in western new guinea recorded by regional biostratigraphic data we present new biostratigraphic analyses of approximately 200 outcrop samples and review biostratigraphic data from 136 public domain exploration wells across western new guinea biostratigraphic ages and palaeodepositional environments were interpreted from occurrences of planktonic and larger benthic foraminifera together with other fossils and environmental indicators where possible these data were compared with existing geological maps and exploration well data to reconstruct the palaeogeography of western new guinea from the carboniferous to present day in addition we used the known bathyal preferences of fossils to generate a regional sea level curve and compared this with global records of sea level change over the same period our analyses of the biostratigraphic data identified two major transgressive regressive cycles in regional relative sea level with the highest sea levels recorded during the late cretaceous and late miocene and terrestrial deposition prevalent across much of western new guinea during the late paleozoic and early mesozoic an increase in the abundance of carinate planktonic foraminifera indicates a subsequent phase of relative sea level rise during a regional transgressive event between the late jurassic and late cretaceous however sea levels dropped once more during a regressive event between the late cretaceous and the paleogene this resulted in widespread shallow water carbonate platform development in the middle to late eocene a minor transgressive event occurred during the oligocene but this ceased in the early miocene likely due to the collision of the australian continent with intra pacific island arcs this miocene collision event resulted in widespread uplift that is marked by a regional unconformity carbonate deposition continued in platforms that developed in shallow marine settings until these were drowned during another transgressive event in the middle miocene this transgression reached its peak in the late miocene and was followed by a further regression culminating in the present day topographic expression of western new guinea

the sulu sea internal soliton experiment abstract we present the results of a comprehensive study of large amplitude internal solitons generated in the sulu sea in the philippines by intense tidal flow over a sharp bathymetric feature surface signatures of these waves have been observed in images from the dmsp landsat and nimbus 7 satellites and the space shuttle sir a synthetic aperture radar a two week experiment was conducted in the sulu sea in may 1980 from r v oceanograher during which a three mooring phased array of current meters and thermistors was implanted near the wave source and at 82 km and 200 km from the source seventeen soliton packets were observed whose properties underwent significant change as they propagated across the sea vertical profiles of density temperature and acoustic backscatter as well as radar and photographic surface signatures were obtained from the ship data from satellites moorings and the ship give unprecedented information on the spatial and temporal characteristics of solitary waves which ha

internal seiche dynamics in lake geneva we analyzed season long water level records at 12 stations around the lake of geneva local name leman for evidence of internal seiches modified by coriolis force and compared the results with predictions from a two layer numerical model with real bottom topography for typical wind situations results are also compared with those obtained from current and temperature measurements in the lake agreement was satisfactory in all cases model predictions and measurements both indicated that only three internal seiche modes are excited the 1st mode and the 3rd mode which are kelvin seiche oscillations and the 12th mode which is a poincare seiche the model driven by winds from different directions demonstrates that the wind field constrained by the local topography determines which of the modes is generated

basin scale motion in stratified upper lake constance this paper describes experimental and modeled wind induced oscillations in upper lake constance with an emphasis on a coherent understanding of the basin scale internal dynamics in this example of a large and stratified lake data were collected with eight lake diagnostic systems ldss consisting of thermistor chains and wind anemometers the isotherm displacements as measured by the ldss were interpreted using the three dimensional hydrodynamic estuary and lake computer model elcom three types of basin scale waves were found to dominate the wave motion the vertical mode one kelvin wave that had an observed period around 90 h two vertical mode one poincare waves that had periods near 8 h and 12 h and a vertical mode two poincare wave that had a period near 14 h after strong westerly winds upwelling of cold bottom water was observed east of the sill of mainau where the lake s two subbasins connect the width and length ratios of the subbasins spatial variations of the wind field and rotational effects over the lake are shown to play critical roles in the details of the upwelling structure a sudden fall of the isotherms in lake uberlingen formed a surge the reflection of the surge from the northwestern boundary induced a vertical mode two response leading to an intrusion in the metalimnion that caused a three layer velocity structure in the smaller subbasin