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

a numerical study of stratified tidal rectification over finite amplitude banks part ii georges bank abstract tidal rectification over a two dimensional finite amplitude symmetrical bank is studied using the blumberg and mellor primitive equation coastal ocean circulation model ecom si in the homogeneous case the nonlinear interaction of tidal currents with the variable bottom topography generates an along isobath residual circulation over the bank which tends to increase as either the slope or height of the bank is increased in the stratified case internal waves at tidal and higher frequencies are generated over the sloping sides of the bank tidal mixing occurs in the bottom boundary layer leading to horizontal tidal mixing fronts the resulting stratified tidal rectification associated with the tidal mixing front the generation of internal tides and the modification of internal friction due to stratification leads to a subsurface intensification of the along isobath residual current at the front and at the top of the bottom mixed layer over the slope and a cross bank double cell circulation

frontogenesis in the agulhas return current region simulated by a high resolution cgcm abstractdetailed mechanisms for frontogenesis frontolysis of the sea surface temperature sst front in the agulhas return current arc region are investigated using outputs from a high resolution coupled general circulation model the sst front is maintained throughout the year through an approximate balance between frontolysis by surface heat flux and frontogenesis by horizontal advection although a southward northward cross isotherm flow on the northern southern side of the front is weaker than a strong eastward along isotherm current in the frontal region this cross isotherm confluent flow advects warmer cooler temperature toward the sst front north south of the front and acts as the dominant frontogenesis mechanism in addition stronger weaker frontogenesis in austral summer winter is attributed to the stronger weaker cross isotherm confluence which may be linked to seasonal variations of the agulhas current arc and antarctic circumpolar current on the other hand the contributi

pyrite textures and trace element compositions from the granodiorite hosted gold deposit at jonnagiri eastern dharwar craton india implications for gold mineralization processes

three dimensional nonhydrostatic numerical simulation of nonlinear internal wave generation and propagation in the south china sea 1 we present the results of three dimensional nonhydrostatic simulations of internal tides and waves in the south china sea scs using the suntans model model results accurately predict the observed wave arrival times at two mooring locations in the scs internal wave amplitudes are underpredicted which causes underprediction of internal wave speeds due to a lack of amplitude dispersion we show that the well known a and b waves arise from the steepening of semidiurnal internal tides that are generated due to strong barotropic flow over ridges in the luzon strait a wave generation is stronger in the southern portion of the luzon strait because diurnal internal tidal beams augment the amplitude of the semidiurnal a waves b wave generation is stronger in the northern portion where the distance between the eastern and western ridges is approximately equal to one internal tidal wavelength and leads to semidiurnal internal tidal resonance the orientation of the ridges produces large a waves that propagate into the northern portion of the western scs basin and stronger b waves that propagate into the southern portion when traced back in time along linear characteristics a waves consistently line up close to peak ebb eastward barotropic currents while b waves consistently line up with peak flood westward barotropic currents this reinforces the notion that the lee wave mechanism and associated hydraulic or nonlinear effects are weak as demonstrated by a simple linear model relating the amplitude of the simulated waves to the excursion parameter at the ridges

initial expansion of the columbia river tidal plume theory and remote sensing observations 1 analysis of the columbia river tidal plume using lagrangian frontal equations provides a concise description of the evolution of frontal depth h velocity u reduced gravity g and frontal internal froude number fr because the estuary mouth is narrow the initial radial plume motion is supercritical fr 1 for up to 12 hours understanding this supercritical phase is vital because plume properties change rapidly with strong ecosystem impacts to analyze this expansion analytical and numerical models the latter with three mixing formulations were tested model results are compared to synthetic aperture radar images to verify that the predicted frontal properties are realistic lagrangian theory provides especially simple constraints independent of the mixing model on spatial variations in fr and ug h for parameters representative of the columbia river plume the plume spreads 10 35 km and thins to 25 60 of its initial depth before becoming subcritical after liftoff fr increases as the front accelerates and thins it then decreases to unity g decreases but more slowly than h and u h controlled by a balance between spreading and mixing first decreases then increases the strength of vertical mixing and the mixing efficiency ef ratio of buoyancy flux to dissipation both play a significant role in determining plume properties and it is important to include both the horizontal gradient in g and surface slope component of the pressure gradient a model with an ellison turner type entrainment scheme predicts the plume trajectory better than one that assumes a constant interfacial gradient richardson number

ekman layers and two dimensional frontogenesis in the upper ocean a two dimensional modified semi geostrophic model is used to study the evolution of oceanic fronts in the presence of vertical mixing the parameterization used for mixing is an elevated constant value of vertical viscosity and friction hence the ekman layer acts as a surrogate mixed layer with however vertical shear allowed everywhere an initial condition representative of the observed fields in frontal air sea interaction experiment fasinex is used and its modification in the presence of vertical mixing alone is investigated without external forcing an ekman layer results because of the presence of vertical geostrophic shear at the surface the maximum density gradient moves toward the dense side of the front driven by this flow convergence of ekman flow results in downward bowing of the isopycnals beneath the surface expression of the front a feature reminiscent of density sections taken during fasinex this feature is not evident when a barotropic convergence field is applied in the absence of mixing or in fully nonlinear simulations of the evolution of fronts with baroclinic instability an analytic theory suggests that the maximum density gradient will increase over time when vertical mixing alone is present in the presence of negative uniform wind stress in the direction opposite to the surface geostrophic flow the front moves toward the denser water and the jet uniformly decreases in strength in the presence of a positive uniform wind in the direction of the surface geostrophic flow the surface jet initially weakens but then strengthens again as the wind driven ekman flow opposes the frictionally driven ekman flow and the cross front density gradient increases

alteration pattern and fluid inclusions of gold bearing quartz veins in archean trondhjemite near wawa ontario canada systems of auriferous quartz veins occur in archean granitic rocks within 1 6 km of the wawa greenstone belt 80 km northeast of wawa ontario the vein system at the renabie mine strikes west for approximately 850 m dips steeply to a depth of at least 950 m and hosts orebodies up to 30 m wide and 210 m long the six vein systems at the braminco prospect strike north to northwest dip steeply and are up to 20 m wide alteration of feldspar to quartz calcite white mica albite and of biotite amphibole to chlorite intensifies within 2 to 4 m of quartz vein systems bearing native gold mass balance calculations suggest that the alteration of granitic rocks added k co2 h20 rb and ba and removed na three types of primary fluid inclusions coexist in quartz from the auriferous vein systems type i the most abundant type is an aqueous solution with 10 to 25 vol percent co2 with density of 0 75 g cm3 homogenization temperatures range from 220 o to 360oc type ii is nearly 100 vol percent liquid co2 with a density of 0 95 g cm 3 type iii the least abundant type is an aqueous liquid with 10 to 50 vol percent h20 gas homogenization temperatures range from 120 o to 220oc apparent salinities of types i ii and iii based on clathrate and ice melting points are estimated to be 4 to 8 0 and 11 to 14 equiv wt percent naci respectively the preferred interpretation is that the gold bearing quartz veins formed from co2 1aden fluids of less than 10 equiv wt percent naci during regional greenschist metamorphism of granitic rocks the three types of fluid inclusions may represent two or three different generations of fluids trapped over a range of temperature and pressure another possibility is that the fluid inclusions represent samples of a fluid comprised of immiscible co2 and nacih20 phases entrapped during quartz crystallization the source of the gold is not known

repetitive hydraulic fracturing and shear zone inflation in an archean granitoid hosted ribbon banded au quartz vein system renabie area ontario canada abstract economically significant tonalite 2722 ma and trondhjemite 2728 ma hosted archean au quartz vein mineralization in the renabie area ontario located in a marginal part of the 10 15 km thick wawa domal gneiss terrane shows strong structural control major ore zones occur in e w and nw nnw striking ductile brittle high strain zones that are superimposed on an earlier regional foliation mineralized zones are up to 20 30 m wide mineable to a depth of 1300 vertical metres and dip typically at 60 80 angles production and reserves for the renabie mine totalled 6 million tonnes at 6 6 g t au and 2 g t ag net shear from kinematic indicators is oblique reverse south side up sinistral on e w structures e g nudulama renabie main zone depth 2475 level and west side up sinistral on nw nnw structures e g braminco 21 zone the strain features of the shear zone hosted mineralization together with evidence of reaction enhanced ductility associated with hydrothermal fluid wallrock interaction indicate that mineralization and hydrothermal alteration occurred synchronously with shear deformation the characteristic banded appearance book ribbon structure of the renabie veins which is typical of many archean and cordilleran au quartz vein systems is interpreted to be the result of inflationary vein formation by repeated increments of hydraulic fracturing and mineral deposition 250 750 associated with hydrothermal fluid overpressuring within and below the actively deforming ductile brittle shear zones crack seal type process fracture orientation was largely controlled by the anisotropy in rock tensile strength associated with the approximately planar shear fabric the element mineral association of renabie is typical of oxidized archean au quartz vein systems containing anhydrite hematite carbonate and tourmaline with a chalcophile association consisting of mos 2 cu pb sulphides native au ag and pb bi au ag tellurides key factors in the development of significant mineralization at renabie as compared with other usually small low grade archean granitoid hosted au quartz vein systems include the repetitive nature of the mineralizing process and the focusing of au bearing fluids within the actively deforming shear zones a specific and sufficiently large reservoir of overpressured hydrothermal archean au bearing fluid was generated at some location not yet identified in the archean crustal structure represented by the kapuskasing section

the structural evolution of the missanabie renabie gold district pre orogenic veins in an orogenic gold setting and their influence on the formation of hybrid deposits

impacts of a mesoscale eddy pair on internal solitary waves in the northern south china sea revealed by mooring array observations abstractboth internal solitary waves isws and mesoscale eddies are ubiquitous in the northern south china sea scs in this study the authors examine the impacts of mesoscale eddies on the isws transiting the northern scs deep basin that evolve from the steepening internal tide generated in the luzon strait using in situ data collected from a specifically designed mooring array from november 2013 to january 2014 an energetic mesoscale eddy pair consisting of one anticyclonic eddy ae and one cyclonic eddy ce propagated across the mooring array observations revealed that the amplitude propagation direction and speed of the transbasin isws were significantly modulated by the eddy pair when the moorings were covered by the southern portion of the ae the isw amplitudes decreased by as much as 67 because of the thermocline deepening along the wave direction and the energy divergence along the wave front when the moorings were covered by the northern portions of both eddies the amplitude of is

remote sensing evidence for baroclinic tide origin of internal solitary waves in the northeastern south china sea 1 evidence for baroclinic tide origin of internal solitary waves isws in the northeastern south china sea is presented based on 116 internal wave packets observed in satellite images from 1995 to 2001 these wave packets can be divided into two types a single wave isw packet containing only one isw with without an oscillating tail and a multiple wave isw packet composed of a group of rank ordered isws all of the 22 single wave isw packets occur in the deep water zone it is suggested that the isws instead of being generated by the lee wave mechanism are developed by nonlinear steepening of the baroclinic tides which are produced by the strong tidal currents flowing over a ridge in luzon strait this suggestion is verified by an ers 2 sar image which records such an evolution process from a baroclinic tide to a single isw in its spatial domain

energetics of barotropic and baroclinic tides in the monterey bay area abstracta detailed energy analysis of the barotropic and baroclinic m2 tides in the monterey bay area is performed the authors first derive a theoretical framework for analyzing internal tide energetics based on the complete form of the barotropic and baroclinic energy equations which include the full nonlinear and nonhydrostatic energy flux contributions as well as an improved evaluation of the available potential energy this approach is implemented in the stanford unstructured nonhydrostatic terrain following adaptive navier stokes simulator suntans results from three dimensional high resolution suntans simulations are analyzed to estimate the tidal energy partitioning among generation radiation and dissipation a 200 km 230 km domain including all typical topographic features in this region is used to represent the monterey bay area of the 152 mw energy lost from the barotropic tide approximately 133 mw 88 is converted into baroclinic energy through internal tide generation and 42 56

preliminary simulations of internal waves and mixing generated by finite amplitude tidal flow over isolated topography much recent observational evidence suggests that energy from the barotropic tides can be used for mixing in the deep ocean here the process of internal tide generation and dissipation by tidal flow over an isolated gaussian topography is examined using two dimensional numerical simulations employing the mitgcm four different topographies are considered for five different amplitudes of barotropic forcing thereby allowing a variety of combinations of key nondimensional parameters while much recent attention has focused on the role of relative topographic steepness and height in modifying the rate of conversion of energy from barotropic to baroclinic modes here attention is focused on parameters dependent on the flow amplitude for narrow topography large amplitude forcing gives rise to baroclinic responses at higher harmonics of the forcing frequency tall narrow topographies are found to be the most conducive to mixing dissipation rates in these calculations are most efficient for the narrowest topography

temporal variability of internal tides in the northeast south china sea 1 the northeast south china sea is perhaps the largest internal tide energy source in the world the temporal variability of internal tides was investigated on the basis of 8 month moored acoustic doppler current profiler observations on the continental slope at the dongsha plateau the daily amplitude and phase of diurnal and semidiurnal internal tides were determined from complex demodulation and the dominant spatial and temporal patterns were extracted with empirical orthogonal function eof analysis the eof modal structures showed good agreement with the normal mode solution although vertical phase propagations were apparent the first semidiurnal eof mode corresponded to the first normal mode and the first two diurnal eof modes corresponded to the second and third normal modes respectively the modal structure and energy flux also were consistent with previous observations near the shelf break from the asian seas international acoustic experiment on the other hand the amplitudes of diurnal and semidiurnal eof modes both indicated large irregular fortnightly variations that were not phase locked incoherent with astronomical forcing the study highlighted the importance of incoherent internal tidal motion which accounted for about three fourths of the observed tidal energy

the role of internal tides in mixing the deep ocean abstract internal wave theory is used to examine the generation radiation and energy dissipation of internal tides in the deep ocean estimates of vertical energy flux based on a previously developed model are adjusted to account for the influence of finite depth varying stratification and two dimensional topography specific estimates of energy flux are made for midocean ridge topography weakly nonlinear theory is applied to the wave generation at idealized topography to examine finite amplitude corrections to the linear theory most internal tide energy is generated at low modes associated with spatial scales from roughly 20 to 100 km the richardson number of the radiated internal tide typically exceeds unity for these motions and so direct shear instability of the generated waves is not the dominant energy transfer mechanism it also seems that wave wave interactions are ineffective at transferring energy from the large wavelengths that dominate the energy flux instead it appears that most of

three dimensional numerical simulation of m2 internal tides in the east china sea the east china sea and adjacent seas are one of the most significant generation regions of the m 2 internal tide in the world s oceans in the present study we investigate the distribution and energetics of the m 2 internal tide around the continental shelf edge in the east china sea using a three dimensional numerical model the numerical experiment shows that m 2 internal tides are effectively generated over prominent topographic features such as the subsurface ridges in the bashi luzon and tokara straits the ridges along the ryukyu island chain and the continental shelf slope in the east china sea the former particularly so all of these topographic features are characterized by steep slopes at the depth of the thermocline onto which the m 2 barotropic tide is almost normally incident the m 2 internal tides propagating away from these multiple source regions interfere with each other to create a complicated wave pattern it is found that the calculated pattern of the m 2 internal tide agrees well with topex poseidon altimeter observations the conversion rate from m 2 barotropic to baroclinic energy over the whole analyzed model domain is estimated to be 35 gw roughly 10 of the energy in the m 2 surface tide incident on the prominent topographic features is converted to the m 2 internal tide although about half of the m 2 internal tidal energy is subject to local dissipation in close proximity to the generation sites

large scale realistic laboratory modeling of m2 internal tide generation at the luzon strait 1 the complex double ridge system in the luzon strait in the south china sea scs is one of the strongest sources of internal tides in the oceans associated with which are some of the largest amplitude internal solitary waves on record an issue of debate however has been the specific nature of their generation mechanism to provide insight we present the results of a large scale laboratory experiment performed at the coriolis platform the experiment was carefully designed so that the relevant dimensionless parameters which include the excursion parameter criticality rossby and froude numbers closely matched the ocean scenario the results advocate that a broad and coherent weakly nonlinear three dimensional m2 internal tide that is shaped by the overall geometry of the double ridge system is radiated into the south china sea and subsequently steepens as opposed to being generated by a particular feature or localized region within the ridge system

tidal conversion by supercritical topography calculations are presented of the rate of energy conversion of the barotropic tide into internal gravity waves above topography on the ocean floor the ocean is treated as infinitely deep and the topography consists of periodic obstructions a green function method is used to construct the scattered wavefield the calculations extend the previous results of balmforth et al for subcritical topography wherein waves propagate along rays whose slopes exceed that of the topography everywhere by allowing the obstacles to be arbitrarily steep or supercritical so waves propagate at shallower angles than the topographic slopes and are scattered both up and down a complicated pattern is found for the dependence of energy conversion on e the ratio of maximum topographic slope to wave slope and the ratio of obstacle amplitude and separation this results from a sequence of constructive and destructive interferences between scattered waves that has implications for computing tidal conversion rates for the global ocean

the generation of large amplitude unsteady lee waves by subinertial k1 tidal flow a possible vertical mixing mechanism in the kuril straits numerical experiments with a two dimensional nonhydrostatic model are performed to investigate tidally generated internal waves in the kuril straits and their effect on vertical mixing the results show that sill scale internal waves at the k1 tidal frequency are confined to the sill slopes because the k1 tide is subinertial in the kuril straits in contrast to previous theories the authors show that intense short internal waves generated at the sill breaks by the subinertial k1 tidal current can propagate upstream as the tidal current slackens theoretical considerations identify these short waves as unsteady lee waves which tend to be trapped at the generation region and grow into large amplitude waves eventually inducing vigorous mixing along their ray paths in particular superposition of a propagating unsteady lee wave and a newly generated lee wave over a sill causes significant wave breaking leading to a maximum vertical diffusivity of 103 cm2 s21 this quite intense mixing reaches down to the density layer of the north pacific intermediate water npiw in contrast the m2 tidal current does not cause such strong vertical mixing because most of generated internal waves propagate away as first mode internal tides and because the barotropic flow amplitude is small the authors therefore suggest the possibility that generation of lee waves through interactions between the k1 current and the bottom topography of the kuril straits contributes to the observed modification of the okhotsk sea water required in the formation of the npiw

the formation and fate of internal waves in the south china sea internal oceanic waves are subsurface gravity waves that can be enormous and travel thousands of kilometres before breaking but they are difficult to study here observations of such waves in the south china sea reveal their formation mechanism extreme turbulence relationship to the kuroshio current and energy budget internal waves are the underwater version of more familiar surface waves they can be enormous and travel thousands of kilometres before breaking the south china sea is known to be home to the largest internal waves in the world s oceans but their size generation mechanisms and role in the regional energy budget are unknown matthew alford and colleagues now present the results from the iwise observational campaign and reveal that internal waves more than 200 metres high break in the south china sea and create turbulence that is orders of magnitude larger than in the open ocean and that wave formation is influenced by the kuroshio current these results now allow for a complete energy budget of the south china sea and for a more accurate incorporation of internal waves into climate models internal gravity waves the subsurface analogue of the familiar surface gravity waves that break on beaches are ubiquitous in the ocean because of their strong vertical and horizontal currents and the turbulent mixing caused by their breaking they affect a panoply of ocean processes such as the supply of nutrients for photosynthesis1 sediment and pollutant transport2 and acoustic transmission3 they also pose hazards for man made structures in the ocean4 generated primarily by the wind and the tides internal waves can travel thousands of kilometres from their sources before breaking5 making it challenging to observe them and to include them in numerical climate models which are sensitive to their effects6 7 for over a decade studies8 9 10 11 have targeted the south china sea where the oceans most powerful known internal waves are generated in the luzon strait and steepen dramatically as they propagate west confusion has persisted regarding their mechanism of generation variability and energy budget however owing to the lack of in situ data from the luzon strait where extreme flow conditions make measurements difficult here we use new observations and numerical models to 1 show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena 2 reveal the existence of 200 metre high breaking internal waves in the region of generation that give rise to turbulence levels 10 000 times that in the open ocean 3 determine that the kuroshio western boundary current noticeably refracts the internal wave field emanating from the luzon strait and 4 demonstrate a factor of two agreement between modelled and observed energy fluxes which allows us to produce an observationally supported energy budget of the region together these findings give a cradle to grave picture of internal waves on a basin scale which will support further improvements of their representation in numerical climate predictions

a new analytical model for internal solitons in the ocean abstract a new model for tidally generated internal solitons in the ocean is advanced based on a little known asymptotic analytical solution to the weakly nonlinear korteweg de vries equation the solution has many of the properties observed in oceanic internal solitary waves solitons it has been adapted to simulate the dynamics of stratified fluid flow driven by tidal forcing at continental shelves and sills and the adaptation describes the canonical behavior of such solitary wave trains it is shown that the solitons are positioned at the leading edge of an internal tidal bore on the shelf and that the distance between successive packets of solitons constitutes the internal tidal wavelength a future paper will apply the model to field observations from four geographical regions

internal tidal currents and solitons in the southern bay of bengal abstract tidal currents and higher frequency internal solitons are observed from current and hydrographic fields that were recently measured at six deep water moorings in the southern bay of bengal by the naval research laboratory current temperature and salinity were measured in the upper 500 m of the water column between december 2013 and august 2015 harmonically fitted coherent tidal currents in the upper 500 m showed maximum amplitudes for the m2 constituent with velocities of the order of 3 cm s 1 m2 tidal ellipses were generally oriented towards the north northeast incoherent internal tides accounted for at least 60 of the total semidiurnal tide energy solitons were generated at multiple source regions along the andaman islands and contribute significantly to the high frequency energy greater than 1 cph solitons were present throughout the measurement period but their activity was reduced during the 2014 2015 winter monsoon soliton and internal tide amplitudes show a fortnightly modulation consistent with the spring neap cycle of the semidiurnal tide the interaction of tides and the associated high frequency waves 20 40 min periods with mesoscale eddies produced regions of enhanced shear and strain in the thermocline high strain regions were found within cyclonic eddies and high shear regions were found within anticyclonic eddies shear strain based dissipation models indicate that mixing rates can be enhanced by a factor of 3 5 by tidal and higher frequencies during interactions with eddies this study further suggests that tidal harmonics and internal tides have an important impact on the near surface currents away from coastal boundaries in the interior of the bay of bengal while the effects of the depth averaged tides are more important deeper in the water column

contrasting fluid chemistries alteration characteristics and metamorphic timing relationships recorded in hybridized orebodies of the missanabie renabie gold district archean wawa subprovince ontario canada

frontogenesis in mixed layers abstract a unified theory of frontogenesis in mixed layers is proposed analytical solutions of the nonlinear mass and density balances in a mixed layer are found in the lagrangian frame for a wide class of entrainment parameterizations these solutions show mixed layer depth and density to be functions of particle position and separation where mixing is represented by an integral over time following a particle thus given a knowledge of only the crossfront velocity field the likelihood of frontal formation can be predicted both surface convergence and divergence in conjunction with vertical mixing can be frontogenetic three different types of fronts distinguished by their associated crossfront velocity fields are discussed large scale fronts such as the subtropical front are described by a convergent surface flow acting upon an initial horizontal density gradient the powerful divergence caused by an offshore ekman flow forced to zero at a coast causes upwelling fronts the divergence associat

generation mechanism of internal waves by tidal flow over a sill the generation mechanism of internal waves by relatively strong tidal flow over a sill is clarified analytically special attention is directed to the role of the tidal advection effect which is examined by use of characteristics an internal wave which propagates upstream is gradually formed over the sill through the interference among infinitesimal amplitude internal waves elementary waves emanated from the sill at each instant of time in the accelerating decelerating stage of tidal flow the effective amplification of an internal wave takes place as the froude number exceeds falls below unity because during this period the internal wave slowly travels downstream upstream crossing over the sill where elementary waves are efficiently superimposed when the strength of the tidal advection effect is appropriate the internal wave formed in the accelerating stage ac wave and that formed in the decelerating stage dc wave overlap so that the resultant wave height becomes very large since the relative position of ac and dc waves varies depending on the strength of the tidal advection effect the resultant internal wave form is strongly affected by it when the tidal advection effect is strong the ac wave is carried too far downstream to interfere with the dc wave and hence the resultant wave form consists of two crests and two troughs when the tidal advection effect is moderate the optimum interference between ac and dc waves occurs and the resultant wave form consists of one crest and one trough with its horizontal scale approaching that of the sill when the tidal advection effect is weak the internal wave height becomes very small since elementary waves propagate almost freely in the tidal flow without coming close together and the resultant wave form approaches a sinusoidal wave of tidal frequency

energy of nonlinear internal waves in the south china sea 1 four sets of adcp measurements were taken in the south china sea scs these results were combined with previous satellite observations and internal tide numerical model results analysis suggests that strong internal tides are generated in luzon strait propagate as a narrow tidal beam into the scs are amplified by the shoaling continental slope near tungsha island become nonlinear and evolve into high frequency nonlinear internal waves niw internal waves in the scs have geographically distinct characteristics 1 west of luzon strait the total internal wave energy eiw is 10 that predicted by garrett munk spectra egm levine 2002 there is no sign of niw 2 near tungsha island eiw 13 egm strong nonlinear and high harmonic tides are present repetitive trains of large amplitude niw appear primarily at a semidiurnal periodicity with their amplitudes modulated at a fortnightly tidal cycle the rms vertical velocity of niw shows a clear spring neap tidal cycle and is linearly proportional to the barotropic tidal height in luzon strait with a 1 85 day time lag consistent with the travel time of internal tides from luzon strait to tungsha island 3 at the northern scs shelfbreak eiw 4 egm single depression waves are found but no multiple waves packets are evident 4 on the continental shelf eiw 2 egm both depression and elevation niw exist

on the generation and evolution of nonlinear internal waves in the south china sea the nonhydrostatic regional ocean modeling system is applied to the nonlinear internal waves or solitons that are generated at the luzon ridge in the south china sea the luzon ridge near the batan islands is represented by an idealized ridge with a height of 2 6 km on a flat bottom model runs are performed for various ridge shapes and a symmetric tidal forcings the model is in the mixed tidal lee wave regime the barotropic tide over the ridge generates first mode waves through the internal tide release mechanism westward traveling solitons emerge from these first mode waves through nonlinear steepening in the internal tide release mechanism asymmetric tides with strong eastward currents can generate strong westward solitons the eastward current creates an elevation wave with a higher energy density west of the ridge and as soon as the current slackens the wave is released westward on its backslope strong solitons develop the energy density is further enhanced by nonlinearities such as differences in phase speeds and energy fluxes related to lee waves a modal and harmonic decomposition shows the generation of vertical modes and higher temporal harmonics and indicates significant wave wave interaction e g triads in the mixed tidal lee wave regime more energy is contained in the first mode compared to the higher modes hence linear internal tide beams are less well defined and strong solitons develop

energy flux and dissipation in luzon strait two tales of two ridges abstractinternal tide generation propagation and dissipation are investigated in luzon strait a system of two quasi parallel ridges situated between taiwan and the philippines two profiling moorings deployed for about 20 days and a set of nineteen 36 h lowered adcp ctd time series stations allowed separate measurement of diurnal and semidiurnal internal tide signals measurements were concentrated on a northern line where the ridge spacing was approximately equal to the mode 1 wavelength for semidiurnal motions and a southern line where the spacing was approximately two thirds that the authors contrast the two sites to emphasize the potential importance of resonance between generation sites throughout luzon strait baroclinic energy energy fluxes and turbulent dissipation were some of the strongest ever measured peak to peak baroclinic velocity and vertical displacements often exceeded 2 m s 1 and 300 m respectively energy fluxes exceeding 60 kw m 1 were measured at spring tide at the wester

application of a transient reduced gravity plume model to the denmark strait overflow a hydrostatic reduced gravity two dimensional primitive equation numerical model for the simulation of transient bottom arrested gravity plumes was developed by adopting an algorithm from a wadden sea model a model that simulates the wetting and drying of mud flats sand banks etc with a movable lateral boundary the vertically integrated nonlinear rotational model accounts for the dissipation of momentum due to bottom friction and for the entrainment of water mass properties from a spatially structured but stagnant ambient water body it predicts the temporal and spatial evolution of the flow field and the water mass modification within a gravity plume that descends on an arbitrary topography previous model investigations considered a laterally integrated streamtube whereas our model resolves the plume horizontally in the streamtube approach it was assumed that the plume descends in a stationary almost geostrophic balance modified only by bottom drag and entrainment the results of this model demonstrate that this balance may be disturbed whenever the plume encounters topographic disturbances which for the initial intruding phase in particular accounts for its highly transient character the model results are in good agreement with theoretical and laboratory investigations and with observations as is demonstrated by some basic test experiments an application to the overflow of dense water through the denmark strait is presented

internal hydraulic jumps and overturning generated by tidal flow over a tall steep ridge abstract recent observations from the hawaiian ridge indicate episodes of overturning and strong dissipation coupled with the tidal cycle near the top of the ridge simulations with realistic topography and stratification suggest that this overturning has its origins in transient internal hydraulic jumps that occur below the shelf break at maximum ebb tide and then propagate up the slope as internal bores when the flow reverses a series of numerical simulations explores the parameter space of topographic slope barotropic velocity stratification and forcing frequency to identify the parameter regime in which these internal jumps are possible theoretical analysis predicts that the tidally driven jumps may occur when the vertical tidal excursion is large which is shown to imply steep topographic slopes such that dh dxn 1 the vertical length scale of the jumps is predicted to depend on the flow speed such that the jump froude number is of order unity the numerical results agree with the theoreti

enhancement of fronts by vertical mixing microstructure observations near upwelled fronts indicate considerable variation in the structure of vertical mixing across the frontal region observations of cool filaments off northern california indicate that within the cool dense core of filaments the raised pycnocline inhibits the penetration to middepths of surface generated mixing the microstructure profiles are used to estimate the available wind energy for mixing as a function of pycnocline or mixed layer depth a greater portion of energy input at the surface is available for entrainment of dense fluid through the pycnocline and into the surface mixed layer where the pycnocline is shallow hence surface forced mixing may cause a more rapid increase in mixed layer density within the cool filament than outside the filament resulting in an enhanced horizontal density gradient in the mixed layer assuming the flow adjusts towards geostrophy the enhanced horizontal density gradient at the front could result in an accelerated mixed layer in the direction of the preexisting geostrophic flow proportions relating the gain in potential energy to the wind energy vary with pycnocline depth and differ by as much as an order of magnitude from the findings of denman and miyake 1973 and davis et al 1981 horizontal variability of pycnocline erosion may not be properly taken into account in some models and should more realistically be parameterized by including dependence on pycnocline depth during spring and early summer april july the northerly winds along the california coast induce coastal upwelling bringing anomalously cool st 2oc saline 5s 2 0 water to the surface raising the pycnocline over the continental shelf satellite images have revealed large cool features extending offshore beyond the shelf break often hundreds of kilometers seaward of the upwelling region e g bernstein et al 1977 ikeda and emery 1984 flament et al 1985 these anomalous features are believed to play a crucial role in the exchange of properties across the coastal transition zone the region between the nearshore upwelling area and the offshore ocean mooers and robinson 1984 these features were the focus of the coastal transition zone ctz experiment the fronts observed were located west of point arena california seaward of the continental shelf during upwelling conditions isopycnals dome over the shelf and the southward flowing california current develops along the continental shelf break huyer 1983 brink 1983 the strong current found along the sloping isopycnals is not confined to the shelf slope region and often features resembling meanders squirts jets and eddies form on the western edge of the upwelled front bernstein et al 1977 the cause of these features and the resulting influences that they impose on the local ocean are not understood it is believed these features modify the exchange of water between the nearshore upwelling region and the offshore ocean direct transport increased mesoscale eddy formation turbulent diffusion and intrusions near the frontal region are some of the possible mechanisms by which these variable structures enhance diffusion across the transition zone observations of micro scale processes indicate that the rate of surface induced mixing may vary with proximity to the front and that the horizontal density gradients thus established may act to accelerate the mixed layer at the front a series of detailed transects across a meander indi

observations of a mode 2 nonlinear internal wave on the northern heng chun ridge south of taiwan 1 a research cruise was carried out over the heng chun ridge during june 27 july 1 2010 near 21 34 n 120 54 e about 35 km south of taiwan the goal of the cruise was to determine if the location is an active generation site for internal tides and high frequency nonlinear internal waves nliws in the northeastern south china sea scs the method was to sample a series of across ridge sections using an underway conductivity temperature depth uctd profiler and to conduct a time series at a fixed point atop the ridge using a ctd with lowered acoustic doppler current profiler ladcp instrumentation a hull mounted adcp and acoustic backscatter device were also operated throughout the cruise the site was a very high energy region with the northward kuroshio current exceeding 100 cm s 1 and the primarily zonal barotropic tidal currents exceeding 140 cm s 1 the most remarkable feature observed was a convex type mode 2 nliw with a westward propagating core centered near 100 m depth the wave was clearly visible in the velocity and backscatter data and had surface expressions visible both on radar and with the naked eye the horizontal and vertical velocity structure was a good match for theoretical mode 2 waves in the scs the wave generation was consistent with local lee wave dynamics which favored mode 2 generation over mode 1 at peak ebb tide given the currents stratification and bottom slope at the site the wave could not be tracked farther west and apparently did not escape the opposing kuroshio

p t conditions of mineralization in the jonnagiri granitoid hosted gold deposit eastern dharwar craton southern india constraints from fluid inclusions and chlorite thermometry abstract gold mineralization at jonnagiri dharwar craton southern india is hosted in laminated quartz veins within sheared granodiorite that occur with other rock units typical of archean greenstone granite ensembles the proximal alteration assemblage comprises of muscovite plagioclase and chlorite with minor biotite and carbonate which is distinctive of low to mid greenschist facies the laminated quartz veins that constitute the inner alteration zone contain muscovite chlorite albite and calcite using various calibrations chlorite compositions in the inner and proximal zones yielded comparable temperature ranges of 263 to 323 c and 268 to 324 c respectively gold occurs in the laminated quartz veins both as free milling native metal and enclosed within sulfides fluid inclusion microthermometry and raman spectroscopy in quartz veins within the sheared granodiorite in the proximal zone and laminated auriferous quartz veins in inner zone reveal the existence of a metamorphogenic aqueous gaseous h2o co2 ch4 salt fluid that underwent phase separation and gave rise to gaseous co2 ch4 low saline 5 wt nacl equiv aqueous fluids quartz veins within the mylonitized granodiorites and the laminated veins show broad similarity in fluid compositions and p t regime although the estimated p t range 1 39 to 2 57 kbar at 263 to 323 c compare well with the published p t values of other orogenic gold deposits in general considerable pressure fluctuation characterize gold mineralization at jonnagiri factors such as fluid phase separation and fluid rock interaction along with a decrease in f o2 were collectively responsible for gold precipitation from an initial low saline metamorphogenic fluid comparison of the jonnagiri ore fluid with other lode gold deposits in the dharwar craton and major granitoid hosted gold deposits in australia and canada confirms that fluids of low saline aqueous carbonic composition with metamorphic parentage played the most dominant role in the formation of the archean lode gold systems

geochemistry of fluid inclusions from the mcintyre hollinger gold deposit timmins ontario canada type 1 h 2 o co 2 type 2 h 2 o co 2 type 3 ch 4 co 2 h 2 o and type 4 ch 4 fluid inclusions type 1 type 3 and some type 2 inclusions are primary or pseudosecondary in origin whereas type 4 and most type 2 inclusions are secondary the primary or pseudosecondary type 1 and 2 inclusions homogenized at temperatures of 220 degrees to 385 degrees c secondary type 2 inclusions homogenized at 160 degrees to 215 degrees c crushing tests confirm the presence of co 2 in samples with type 1 and 2 inclusions visually estimated x co2 values in type 1 inclusions range from 3 to 24 mole percent with bulk molar volumes of 19 to 28 cm 3 mole mineralizing fluids were at equilibrium with graphite at temperatures of 380 degrees to 480 degrees c and pressures of 1 to 3 kb calculated oxygen fugacities lie near the quartz fayalite magnetite buffer the mineralizing fluids differ compositionally from fluids in other types of ore deposits but resemble fluids derived from metamorphic rocks and deep level felsic intrusions modified journal abstract

gold mineralisation at the lady bountiful mine western australia an example of a granitoid hosted archaean lode gold deposit the lady bountiful granitoid hosted lode gold deposit located in the mid greenschist facies metamorphosed ora banda greenstone sequence is hosted predominantly by the late tectonic liberty granodiorite gold mineralisation is localised along quartz veined sinistral brittle fault zone s that transect the boundary between the liberty granodiorite and mt pleasant sill quartz vein textures indicate two stages of a single gold related vein development event with high grade gold mineralisation restricted to the second stage ore minerals include pyrite chalcopyrite pyrrhotite galena sphalerite au ag bi pb tellurides and native gold fluid infitration has resulted in narrow 1 m bleached wallrock alteration envelopes to the fault zones comprising albite k mica chlorite calcite rutile assemblages temperature pressure conditions varied from stage i 300 50 c 2 kbar to stage ii 250 50 c 0 5 to 2 kbar with the hydrothermal fluid in both stages characterised by x co2 0 15 and moderate salinity 1 28 m nacl intermittent phase separation of stage ii mineralising fluids initiated by pressure fluctuations in dilational sites and or fluid dominated fluid wallrock interaction are invoked as the dominant depositional mechanisms the granitoid hosted lady bountiful lode gold deposit shares many features with other granitoid hosted lode gold deposits in the yilgarn craton and the superior province granitoid hosted lode gold deposits such as the lady bountiful deposit provide additional evidence that the dominant control on the localisation of gold mineralisation within a granitoid host is structure with competency contrasts playing a significant role furthermore the hydrothermal wallrock alteraction and orefluid chemistry characteristics of the granitoid hosted lode gold deposits are comparable to those established for greenstone hosted lode gold mineralisation

prototypical solitons in the south china sea 1 surface signatures associated with non linear internal waves are often seen in satellite images of the western south china sea scs slope and shelf observation in the deep sea to the east are rare here we report on the evolution of an energetic packet as it propagated through the deep central basin of the scs toward the western slope and shelf the waves have amplitudes estimated at 170 m half widths of 3 km and phase speeds of 2 9 0 1 m s faster than the mode 1 linear phase speed of 2 6 m s the shape and observed phase speed were consistent with the korteweg devries kdv model over the 65 km path that they were tracked the intrinsic velocity shear of the waves is small compared to pre existing shears and the waves exhibit weak turbulence the kdv fit and a satellite derived estimate of horizontal wave extent imply a westward energy flux of 4 5 gw for each crest

speed and evolution of nonlinear internal waves transiting the south china sea abstract in the south china sea scs 14 nonlinear internal waves are detected as they transit a synchronous array of 10 moorings spanning the waves generation site at luzon strait through the deep basin and onto the upper continental slope 560 km to the west their arrival time speed width energy amplitude and number of trailing waves are monitored waves occur twice daily in a particular pattern where larger narrower a waves alternate with wider smaller b waves waves begin as broad internal tides close to luzon strait s two ridges steepening to o 3 10 km wide in the deep basin and o 200 300 m on the upper slope nearly all waves eventually develop wave trains with larger steeper waves developing them earlier and in greater numbers the b waves in the deep basin begin at a mean speed of 5 greater than the linear mode 1 phase speed for semidiurnal internal waves computed using climatological and in situ stratification the a waves travel 5 10 faster than b waves until they reach

statistical and dynamical analyses of generation mechanisms of solitary internal waves in the northern south china sea 1 this study analyzes the effects of thermocline shoaling on the ocean internal wave iw generation in the north south china sea nscs seven years of satellite synthetic aperture radar sar images from 1995 to 2001 are used for the statistical analysis of iw occurrence and field measurements of sea surface wind sea state and vertical temperature profiles are used for analyzing iw generation and sar imaging conditions latitudinal distribution of iw packets shows that 22 of iw packets distributed in the east of 118e obviously originate from the luzon strait and 78 of iw packets west of 118e may propagate from the east or evolve into the solitons originating from the east boundary owing to the fission effect of shoaling thermocline the yearly distribution of iw occurrence frequencies reveals an interannual variability implying that there are long term and large scale processes modifying the sar observed iw occurrence the monthly sar observed iwoccurrence frequencies show that the high frequencies are distributed from april to july and reach a peak in june with a maximum frequency of 20 the low occurrence frequencies are distributed in winter from december to february of next year with a minimum frequency of 1 5 in february this study proposes that the iw generation needs the necessary and sufficient conditions initial disturbance formation and wave amplitude growth owing to the dissipation effect on the initial disturbance only fully grown waves have a chance to radiate out of the source region a physical model and pkdvequation are adopted for analyzing the sufficient conditions for solitary iw amplitude growth the results indicate that the thermocline shoaling provides the forcing to soliton amplitude growth so that the soliton amplitude growth ratio sagr serves as a decisive factor for the iw occurrence frequency theoretical analysis predicts a linear relation between the two application of theoretical models to field measurements in the luzon strait gives a correlation coefficient as high as 0 845 with a confidence level of 99 for months from march to november the linear regression gives a correlation coefficient r 2 of 0 6519 and a sagr threshold minimum value of

the greenschist facies of an archean assemblage near wawa ontario a stock of trondhjemite intrudes an archean succession metamorphosed to the greenschist facies at gutcher lake 30 km north of wawa in ontario the stock is 4 km2 in plan and is partly enveloped by

the generation and evolution of nonlinear internal waves in the deep basin of the south china sea abstracttime series observations of nonlinear internal waves in the deep basin of the south china sea are used to evaluate mechanisms for their generation and evolution internal tides are generated by tidal currents over ridges in luzon strait and steepen as they travel west subsequently generating high frequency nonlinear waves although nonlinear internal waves appear repeatedly on the western slopes of the south china sea their appearance in the deep basin is intermittent and more closely related to the amplitude of the semidiurnal than the predominant diurnal tidal current in luzon strait as the internal tide propagates westward it evolves under the influence of nonlinearity rotation and nonhydrostatic dispersion the interaction between nonlinearity and rotation transforms the internal tide into a parabolic or corner shape a fully nonlinear two layer internal wave model explains the observed characteristics of internal tide evolution in the deep basin for different representative forcing cond

mechanism of internal waves in the luzon strait 1 this study suggests a western boundary current instability generation mechanism for the ocean internal waves a linear model describing this instability is developed and an analytical solution is derived from a zero order complex frequency wavenumber relation the real part of the relation represents a dispersion relation of the generated internal waves and the imaginary part is an exponential growth rate the dispersion relation describes the wave propagation characteristics while the growth rate represents the instability properties the theoretical results are used for the case of the kuroshio east of the luzon strait based on the analysis it is found that for the westward propagating disturbance the kuroshio west wing is unstable and the east wing is stable while the reverse is true for the eastern propagating disturbance the results are used to interpret satellite sar images of the ocean internal waves which were generated in the luzon strait and propagated westward reasonable estimates for the growth rate and propagation velocity are derived from a scale analysis of the kuroshio east of the luzon strait

source and propagation of internal solitary waves in the northeastern south china sea 1 large amplitude internal solitary waves isws observed near dongsha island in the south china sea originate in tide topography interactions at luzon strait their arrival times at two moorings s7 at 117 17 e 21 37 n and y at 117 13 2 e 21 2 8 n are investigated with respect to model predicted barotropic tidal currents over lan yu ridge at luzon strait each isw packet can be associated with a westward tidal current peak the time lags between the isws and the barotropic tidal currents are 57 6 0 9 hours at s7 and 55 1 1 0 hours at y consistent with the mode one internal waves propagating nondispersively through the region s bathymetry and climatological stratification larger isws usually arrive earlier than smaller ones consistent with the theoretical relation between nonlinear wave speed and wave amplitude the observation that the isws are associated with westward tidal currents with without the presence of earlier eastward tidal currents suggests that they are generated by nonlinear steepening of internal tides rather than by the lee wave mechanism an idealized nonlinearization distance over which the isws are generated in internal tide troughs is estimated to be 260 40 km from luzon strait

internal solitary waves induced by flow over a ridge with applications to the northern south china sea 1 the generation of internal solitary waves by barotropic tides over a ridge is studied in a nonhydrostatic numerical model under idealized oceanographic settings the experiments examine the effects of ridge width barotropic tidal strength and stratification on wave generation the barotropic tidal flow produces internal wave beams emitting from the ridge top if the slope of the ridge exceeds a critical value equal to the slope of the wave beam reflection and refraction of a wave beam in an upper ocean waveguide associated with a strong shallow thermocline produce horizontally propagating internal tides when the local froude number over a ridge is not small lee waves generated on the ridge convert enough energy from the barotropic tides to the internal tides to form tidal bores and solitary waves increasing stratification at ridge depths enhances the generation of internal waves particularly at the diurnal periods in the luzon strait the slope of the wave beam decreases in spring and summer as stratification at the ridge depths increases favoring the generation of internal tides without the presence of a strong shallow thermocline internal solitary waves are not observed east of the luzon strait in the northern south china sea internal solitary waves are likely observed from april to july when a strong shallow thermocline is present a deep mixed layer in winter suppresses the production of internal solitary waves