effective medium theories for fluid saturated materials with aligned cracks there is general agreement between different theories giving expressions for the overall properties of materials with dry aligned cracks if the number density of cracks is small there is also very fair agreement for fluid filled isolated cracks however there are considerable differences between two separate theories for fluid filled cracks with equant porosity comparison with recently published experimental data on synthetic sandstones gives a good fit with theory for dry samples however although the crack number density in the laboratory sample is such that first order theory is unlikely to apply expressions correct to second order in the number density provide a worse fit it also appears that the ratio of wavelength to crack size is not sufficiently great for any detailed comparison with effective medium theories which are valid only when this ratio is large the data show dispersion effects for dry cracks and scattering neither of which will occur at sufficiently long wavelengths data from the water saturated samples indicate that the effect of equant porosity is significant although the two theories differ strongly as to just how significant once again and in spite of the reservations mentioned above a reasonable fit between theory and observation can be shown

observed cross shelf flow induced by mesoscale eddies in the northern south china sea abstractcross shelf flow induced by mesoscale eddies has been investigated in the northern south china sea nscs using velocity observations from long ranger adcp moorings mesoscale eddies influe

an exceptional anticyclonic eddy in the south china sea in 2010 the highest sea level near the xisha islands in recent 20 years occurred during august 2010 satellite altimeter data indicated that the extreme event was largely due to an anticyclonic eddy whose amplitude exceeded 20 cm and size exceeded 400 km on 11 august 2010 cruise observations showed the eddy raised the center temperature by 7 7 degrees c at 75 m and vertically extended to 500 m eddy tracking showed it had a life span of more than 8 months and propagated far from the south of xisha islands such strong and long lasting eddy that moved northward for such a long distance was observed for the first time in the south china sea scs observational data from ctd xbt and the reconstructed three dimensional temperature and salinity were used to explore the eddy s features and vertical structure our analyses show the 2010 summer monsoon and current in the western boundary of the scs were largely altered after the 09 10 el nino event from may onward the wind blew northward and strengthened over the northwestern scs such wind drove a strong northward current along the western boundary which carried the eddy northward by advection from may to july energy budget showed during the eddy northward propagation the boundary current passed energy to the eddy which led to the continuing growth of the eddy in both strength and size

anti cyclonic eddies northwest of luzon in summer fall observed by satellite altimeters anti cyclonic eddies northwest of luzon of the philippines in summer fall are identified in the merged data products of satellite altimeters of topex poseidon jason 1 and european research satellites the generation and propagation of the anti cyclonic eddies which are confirmed by satellite ocean color data are found to be a seasonal phenomenon that is phase locked to the onset of the southwesterly monsoon and the relaxation of the cyclonic wind curl in the northeastern south china sea the eddies originate from northwest of luzon in summer move across the northeastern south china sea to reach the china continental slope in fall and propagate southwestward along the continental slope in fall winter inducing shelfbreak current variations in the western south china sea in fall winter the anti cyclonic eddy discovered by li et al 1998 in the northern south china sea is found to originate from northwest of luzon and carry primarily the south china sea waters it does not appear to be an eddy shed from the kuroshio in the luzon strait area as alluded by li et al 1998 and others

a new look at deformation as a diagnostic for large scale flow abstractdeformation plays a key role in atmospheric dynamics because it provides a dynamical measure of the interaction between different scales such as in frontogenesis a climatology of deformation constructed from interim ecmwf re analysis era interim data 1979 2013 reveals four main processes associated with deformation 1 frontogenesis at lower levels 2 movement and evolution of jet streams in the upper troposphere 3 orographic blocking and 4 rossby wave breaking the merits of deformation as an additional perspective are discussed for these processes on the basis of case studies and composite analyses in conjunction with analytic solutions this study shows that deformation can be used to unambiguously detect orographic blocking through the local strength of the flow diversion around orography moreover the deformation signature for orographic blocking observed in case studies and composites closely resembles the analytic solution for two dimensional flow around an obstacle the climatolo

clay minerals as indicators of sources of terrigenous sediments their transportation and deposition bering basin russian alaskan arctic abstract cluster analysis of clay mineral abundances in surficial sediments from 52 stations revealed the presence of four station cluster groups within the bering basin and contiguous eastern aleutian trench forearc these results can be explained using two end members of terrigenous clay mineral sources and their admixtures the first end member cluster group i consists of the highest average concentration of illite 48 and chlorite plus kaolinite 40 and lowest of expandable minerals 12 in contrast the second end member cluster group iv has the highest concentration of expandable minerals 43 and lowest concentrations of illite 30 and chlorite plus kaolinite 27 the group i assemblages come from two regions the eastern aleutian trench forearc and the northwestern margin of the bering basin off koryak mountains east siberia clays in the former region are derived primarily from the meta sedimentary and meta volcanic rocks of the chugach mountains with infiltrations from alaska peninsula and are transported from the southeastern kodiak shelf of the gulf of alaska to the trench forearc by the alaska current alaskan stream similar clays are derived from the koryak mountains group iv clays located within the komandorsky and bowers basins and unmak plateau originated from the mio pliocene andesites and basalts of the eastern kamchatka peninsula and aleutian islands respectively it is postulated that group ii clays in the southcentral aleutian basin and bowers ridge basin area and group iii clays in the northern aleutian basin are mixtures obtained primarily from terrigenous sources of group i and iv the distribution patterns and boundaries of the cluster groups reflect the dispersal pathways of clays from the primary sources and the extent of their mixing by regional and local surface currents and mesoscale gyres eddies presumably the minor infiltration of anadyr river clays into group iii is a result of clay transport by episodic turbidity currents most of the clays derived from the alaska mainland and russia proper do not reach the bering basin as these clays are trapped within the bering sea shelf

chronology of warm core ring 82b a chronology constructed from satellite derived thermal imagery is presented to describe the formation and life history of warm core ring 82b this overview provides insight into a classification of features and discrete events associated with gulf stream warm core rings and allows these events as well as our limited shipboard observations to be placed in a broader spatial and temporal context than would otherwise be possible without the satellite data events influencing the evolution of 82b include environmental factors such as meteorological influences and gulf stream interactions as well as those stimulated by encounters with changes in bottom topography the interactions of the ring with surrounding waters are especially noteworthy and the existence of vortex vortex interactions is shown to be a significant cause of local water advection through streamer activity ring events are documented by following changes in ring size shape translation and surface thermal structure our satellite observations are supported by extensive contemporaneous shipboard observations including xbt ctd bops biooptical profiling system temperature profiles and along track sea surface temperature measurements in addition acoustic velocity profiling and drifter trajectories have been used to corroborate hydrographic features of the ring and environs these ship and satellite data form a coherent space time overview of the ring and its environment and show them to be closely related and continually interacting

progress on upwelling studies in the china seas east asian marginal seas surrounding china exhibit rich ocean upwelling mostly in response to the southwesterly summer monsoon upwelling in the china seas namely the south china sea the taiwan strait the east china sea the yellow sea and the bohai sea has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem socioeconomic and climate impacts this paper reviews the progress of upwelling studies in the china seas since the year 2000 by presenting the principal characteristics and new understanding of 12 major upwelling regions in the china seas upwelling exhibits long term variability at intraseasonal to multi decadal scales as well as short term variability frequently caused by tropical cyclones it is also associated with the el nino southern oscillation local environmental variation and biogeochemical factors the coastal upwelling around hainan island and the upwelling or cold dome northeast of taiwan island are specifically highlighted because they have attracted great interest for decades this paper summarizes upwelling mechanisms in terms of wind topography tide stratification and background flow with applications mostly to the china seas finally we propose some topics for future upwelling research i e potential intensification of coastal upwelling under global climate change downwelling intrusion of upwelling into coastal embayments and the influence of upwelling on fishery and biogeochemical processes

friction frontogenesis and the stratification of the surface mixed layer the generation and destruction of stratification in the surface mixed layer of the ocean is understood to result from vertical turbulent transport of buoyancy and momentum driven by air sea fluxes and stresses in this paper it is shown that the magnitude and penetration of vertical fluxes are strongly modified by horizontal gradients in buoyancy and momentum a classic example is the strong restratification resulting from frontogenesis in regions of confluent flow frictional forces acting on a baroclinic current either imposed externally by a wind stress or caused by the spindown of the current itself also modify the stratification by driving ekman flows that differentially advect density ekman flow induced during spindown always tends to restratify the fluid while wind driven ekman currents will restratify or destratify the mixed layer if the wind stress has a component up or down front i e directed against or with the geostrophic shear respectively scalings are constructed for the relative importance of friction versus frontogenesis in the restratification of the mixed layer and are tested using numerical experiments of mixed layer fronts forced by both winds and a strain field the scalings suggest and the numerical experiments confirm that for wind stress magnitudes mixed layer depths and cross front density gradients typical of the ocean wind induced friction often dominates frontogenesis in the modification of the stratification of the upper ocean the experiments reveal that wind induced destratification is weaker in magnitude than restratification because the stratification generated by up front winds confines the turbulent stress to a depth shallower than the ekman layer which enhances the frictional force ekman flow and differential advection of density frictional destratification is further reduced over restratification because the stress associated with the geostrophic shear at the surface tends to compensate a down front wind stress

seismic velocity anisotropy of phyllosilicate rich rocks characteristics inferred from experimental and crack model studies of biotite rich schist summary seismic velocity anisotropy of biotite schist 30 per cent mode biotite was measured under confining pressures up to 150 mpa the rock shows weak orthotropy which was altered from transverse isotropy ti generated by biotite preferred orientation the orthotropy was caused by microfolding in the rock the velocity increase under confining pressure indicates that most crack planes are aligned parallel to the cleavage planes silicate sheet of the oriented biotite minerals the anisotropy of the rock is basically ti due to both the aligned biotite minerals and cracks which have a common symmetry axis we found that other sheet silicate rich rocks have a similar anisotropy with the biotite schist in which the ti type anisotropy is characterized by the slow p and s wave velocities along the symmetry axis this is caused by the preferred orientation of sheet silicate minerals and the extremely slow p and s wave velocities along the axis perpendicular to the silicate sheet compared to the directions along the silicate sheet when rock contains a large percentage of highly oriented sheet silicates the fast and slow shear waves exchange their polarities at some off symmetry axis directions indicating that the qswave quasi s wave velocity exceeds the sh wave velocity the phase velocity distribution of qs wave shows an asymmetry with respect to the angle from the symmetry axis which is characterized by a bulge in this distribution located near the symmetric axis this is inherent to most sheet silicate minerals when crack density of aligned cracks increases the p wave velocity along the symmetry axis decreases considerably the qs wave phase velocity in the off axis directions also decreases in accordance with the decrease of the p velocity along the symmetry axis the asymmetry of the qs wave phase velocity distribution increases as the p wave velocity decreases along the symmetry axis this relationship can be well understood by means of berryman s extended thomsen approach

satellite observation of upwelling along the western coast of the south china sea abstract we observed the evolution of upwelling along the western coast of the south china sea scs the data we used are noaa national oceanic and atmospheric administration satellite avhrr advanced very high resolution radiometer ir infrared images taken in 1996 and 1997 summer at the hrpt high resolution picture transmission receiving station built on tai ping island which is located in the central scs an upwelling intensity defined by the total heat loss in the upwelling cold water region is used to determine the relationship between coastal upwelling and the wind stress derived from the ers 2 european remote sensing satellite data the results show that the upwelling intensity has a good linear relationship with the total alongshore wind stress while it has a low correlation with the cross shore component of wind stress these results imply that the alongshore wind stress is the main factor to pump the cold water up to the sea surface layer meanwhile the satellite infrared images also indicate that the centroid of cold water moved southward from 15 n to 11 n during the observation period the size of upwelling area changed as well and finally evolved into a cold jet stretching offshore along 11 n 12 n in the mid august 1997 satellite infrared and altimeteric data show that the evolution of upwelling region is closely associated with the development of two anticyclonic circulations in the western scs

intraseasonal variability of cross slope flow in the northern south china sea abstractcross slope flow plays an important role in the exchange of material heat and momentum between the continental shelf and the open sea in the northern south china sea scs long period ob

sub mesoscale ocean vortex trains in the luzon strait 1 this study uses the argos satellite tracked surface drifter trajectory data and envisat european satellite asar advanced synthetic aperture radar images to illustrate the ocean vortex trains ovt in the luzon strait two cases that occurred in the northwest of babuyan island are observed the first train of three cyclonic vortices showed up on drifter trajectories from 20 to 20 5 n and from 120 to 121 e and the second consisting of five pairs of cyclonic anticyclonic vortices occurred on the upstream side of the first one from 19 5 to 20 0 n and from 121 0 to 122 0 e and showed up on the asar images acquired on 19 november 2006 the total length of the vortex train axis reaches about 250 km all vortices propagate northwestward 315 tn the mean angular velocity is 2 07 0 18 10 5 s 1 theoretical models of ocean vortex radar image derived from radar imaging theories are used to extract dynamical parameters from asar imagery signatures which include the distance between two consecutive vortices and that between two rows of vortices of 22 6 1 9 km and 8 2 1 2 km respectively the maximum rotational velocity radius as 4 70 km and the vortex rotational angular velocity 3 10 5s 1 dynamical analyses give the mean velocity of the current of 0 65 ms 1 and the propagation velocity of the vortex 0 58 ms 1 the vortex shedding rate is estimated as 2 57 10 5 s 1 the reynolds number is estimated as 50 to 500 for the individual vortex and the vortex train the rossby numbers are o 0 4 and o 0 5 respectively implying that both vortex and vortex train observed in the luzon strait have a sub mesoscale nature this study also reveals a strong current with an average surface current velocity of around 0 7 ms 1 and the direction of around 315 tn flowing directly from the pacific to scs passing through the southern luzon strait the mean flow velocity can be calculated using methods developed in this study and ovt dynamical models this information may provide more insight to the circulation systems in the area including the origin of kuroshio

the influence of nonlinear mesoscale eddies on near surface oceanic chlorophyll oceanic rossby waves have been widely invoked as a mechanism for large scale variability of chlorophyll chl observed from satellites high resolution satellite altimeter measurements have recently revealed that sea surface height ssh features previously interpreted as linear rossby waves are nonlinear mesoscale coherent structures referred to here as eddies we analyze 10 years of measurements of these ssh fields and concurrent satellite measurements of upper ocean chl to show that these eddies exert a strong influence on the chl field thus requiring reassessment of the mechanism for the observed covariability of ssh and chl on time scales longer than 2 to 3 weeks the dominant mechanism is shown to be eddy induced horizontal advection of chl by the rotational velocities of the eddies

three dimensional distribution of turbulent mixing in the south china sea abstracta three dimensional distribution of turbulent mixing in the south china sea scs is obtained for the first time using the gregg henyey polzin parameterization and hydrographic observations from 2005 to 2012 results indicate that turbulent mixing generally increases with depth in the scs reaching the order of 10 2 m2 s 1 at depth in the horizontal direction turbulence is more active in the northern scs than in the south and is more active in the east than the west two mixing hotspots are identified in the bottom water of the luzon strait and zhongsha island chain area where diapycnal diffusivity values are around 3 10 2 m2 s 1 potential mechanisms responsible for these spatial patterns are discussed which include internal tide bottom bathymetry and near inertial energy

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

the unique 2009 2010 el nino event a fast phase transition of warm pool el nino to la nina 1 the latest el nino event in 2009 2010 which is classified as warm pool el nino holds a unique ground in that it marks the strongest warming signal in the central pacific but rapidly decays to strong la nina the strong eastward propagating cold anomaly at the subsurface level is found to be a key factor and two possible mechanisms are suggested that resulted in the fast phase transition of the 2009 2010 event 1 the anomalously warm indian ocean induces a surface easterly over the western edge of the pacific which generates the forced kelvin waves 2 the record breaking high sea surface temperature in the central pacific excites a strong rossby response that is to be reflected as an upwelling kelvin wave at the western boundary the strong subsurface anomaly then propagates eastward and results in an unusually fast phase transition of the 2009 2010 warm pool el nino event

upwelling in the continental shelf of northern south china sea associated with 1997 1998 el nino 1 a strong upwelling off the continental shelf of the northern south china sea scs in 1998 summer is reinvestigated using a suite of new satellite measurements and numerical modeling previous studies indicate that the upwelling in the western scs especially off the vietnam coast almost disappears during 1998 summer following the el nino because of the weakened southwest monsoon this study identifies that the coastal upwelling in the adjacent northern scs nscs is significantly strengthened during 1998 summer and the alongshore wind stress is dramatically enhanced over the region as a result the offshore ekman transport in 1998 summer is the strongest almost twice the average of the other 17 years during 1997 2007 the chl a concentrations in the representative upwelling regions are much higher than any in other years further analysis suggests that two adjacent basin scale upwellings in the scs have different responses and maintaining mechanisms because of the anticyclonic atmospheric circulation anomaly over the scs and northwest pacific the northern flank of the atmospheric circulation anomaly intensifies the monsoonal winds off the nscs coast while the southern flank suppresses the southwesterly winds along the vietnam coast

mesoscale eddies cases study at xisha waters in the south china sea in 2009 2010 analyzing the observed currents at xisha 110 3899 degrees e 17 1038 degrees n during may 2009 to may 2010 it is found that the kinetic energy has significant mesoscale variability and each peak responds to large positive negative ocean surface current curl caused by mesoscale eddies compared the kinetic energy with the wind stress work and the pressure work it is also found that the barotropic pressure work which is mainly contributed by the sea surface height ssh corresponding to the mesoscale eddies behaves like the kinetic energy the contribution of the mesoscale eddies to the kinetic energy can be up to 90 sometimes and reach deep level every time using the satellite altimeter data the paths of mesoscale eddies contributing to the kinetic energy variability are traced back in the winter half of the year the mesoscale eddies propagating along the northern south china sea shelf or across the basin from the west of the philippines toward xisha arrive at xisha influencing the kinetic energy in the summer half of the year the mesoscale eddies are mainly from the south which were shed from the vietnam coast current and the cause for eddy shedding may be related to the relaxation of the ekman transport anomalies

discovery of two new large submarine canyons in the bering sea abstract the beringian continental margin is incised by some of the world s largest submarine canyons two newly discovered canyons st matthew and middle are hereby added to the roster of bering sea canyons although these canyons are smaller and not cut back into the bering shelf like the five very large canyons they are nonetheless comparable in size to most of the canyons that have been cut into the u s eastern continental margin and much larger than the well known southern california canyons both igneous and sedimentary rocks of eocene to pliocene age have been dredged from the walls of st matthew and middle canyons as well as from the walls of several of the other beringian margin canyons thus suggesting a late tertiary to quaternary genesis of the canyons we speculate that the ancestral yukon and possibly anadyr rivers were instrumental in initiating the canyon cutting processes but that due to restrictions imposed by island and subsea bedrock barriers cutting of the two newly discovered canyons may have begun later and been slower than for the other five canyons

characteristics of anisotropy and dispersion in cracked medium abstract in upper crustal conditions where effective pressure is not high enough to close them all rocks contain cracks understanding the effect of cracks on both the elastic anisotropy and the elastic waves frequency dependence dispersion is of major interest to underground storage monitoring reservoir monitoring and fault mechanics the challenge is to extract from geophysical data the maximum information with a minimal number of assumptions and model parameters this is possible if reference data exist at the laboratory scale and if extrapolation from laboratory to field scale is not biased in order to check that investigating few basic idealized cases can provide useful guidelines let us consider an isotropic rock matrix and assume that dispersion is the result of squirt flow in this paper we will not consider crack to pore but rather focus on crack to crack squirt flow three basic cracks configurations are quantitatively investigated for which the elastic symmetry is transverse isotropy ti our aim is to check if from first principles high frequency laboratory data can be used for field data interpretation in these three cases the first case is that of identical cracks aligned in the same direction a sufficiently strong deviatoric stress field in a given plane is expected to induce such a distribution at the field scale 1 2 3 we show that it results in a maximum anisotropy but with virtually no dispersion because there is no dispersion high frequency data obtained in the laboratory mhz ultrasonic range are directly applicable to field data hz to khz range interpretation thomsen parameters provide then a direct proxy for crack density a second case is that of identical cracks with random orientations isotropic distribution such a situation could exist at the field scale if cracks result from the superposition of several independent tectonic episodes associated with different directions of principal stresses in that case 1 2 3 this configuration could also result from thermal cracking in an initially isotropic metamorphic rock obviously there is no overall anisotropy then but we show that dispersion may be large due to dispersion ultrasonic laboratory data are not directly applicable to field data interpretation unless the medium is dry a third intermediate case is that of cracks randomly distributed in zone with a given axis the corresponding symmetry is that of a so called axi symmetric triaxial test which in fact is biaxial it is of interest because it represents a classical laboratory experiment situation it can also exist at the field scale if one principal stress is much larger than both others 1 2

eddy heat and salt transports in the south china sea and their seasonal modulations this study describes characteristics of eddy turbulent heat and salt transports in the basin scale circulation as well as in the embedded mesoscale eddy found in the south china sea scs we first showed the features of turbulent heat and salt transports in mesoscale eddies using sea level anomaly sla data in situ hydrographic data and 375 argo profiles we found that the transports were horizontally variable due to asymmetric distributions of temperature and salinity anomalies and that they were vertically correlated with the thermocline and halocline depths in the eddies an existing barrier layer caused the halocline and eddy salt transport to be relatively shallow we then analyzed the transports in the basin scale circulation using an eddy diffusivity method and the sea surface height data the argo profiles and the climatological hydrographic data we found that relatively large poleward eddy heat transports occurred to the east of vietnam eov in summer and to the west of the luzon islands wol in winter while a large equatorward heat transport was located to the west of the luzon strait wls in winter the eddy salt transports were mostly similar to the heat transports but in the equatorward direction due to the fact that the mean salinity in the upper layer in the scs tended to decrease toward the equator using a 21 2 layer reduced gravity model we conducted a baroclinic instability study and showed that the baroclinic instability was critical to the seasonal variation of eddy kinetic energy eke and thus the eddy transports eov wls and wol were regions with strong baroclinic instability and thus with intensified eddy transports in the scs the combined effects of vertical velocity shear latitude and stratification determined the intensity of the baroclinic instability which intensified the eddy transports eov during summer and wls and wol during winter

seismic properties of rocks with distributions of small cracks summary hudson s theory of multiple scattering for the dynamic properties of cracked rock is applied to media containing cracks of varying orientation radius and aspect ratio angular variation of velocity and attenuation due to parallel and nearly parallel cracks and cracks with normals at a fixed angle to a given axis are presented anisotropy gradually decreases as the distribution of orientations is widened from exactly parallel to random increasing the aspect ratio of thin saturated cracks generally causes the elastic properties to approach those due to dry gas filled cracks for fluid filled cracks the line singularity where the birefringent shear waves have equal velocity moves closer to the symmetry axis as either the distribution of orientations is widened or the aspect ratio is increased calculated attenuations due to rayleigh scattering and viscous dissipation in crack filling fluids are many orders of magnitude less than reported attenuations in the earth viscous dissipation varies linearly with frequency and aspect ratio of thin fluid filled cracks a power law distribution of crack radii intended to represent that found in the earth s crust has no effect on the angular variations of seismic velocities or viscous attenuation but scattering attenuation is sensitive to the power law exponent lognormal distributions of aspect ratio also corresponding to observations in real rock affect velocity as well as attenuation velocities derived from the theory are compared with those measured in laboratory specimens with known geometries of cracks

winter eddy genesis in the eastern south china sea due to orographic wind jets abstract generation of mesoscale eddies in the eastern south china sea scs in winters during august 1999 to july 2002 is studied with a reduced gravity model it is found that the orographic wind jets associated with the northeast winter monsoon and the gaps in the mountainous island chain along the eastern boundary of the scs can spin up cyclonic and anticyclonic eddies over the scs results suggest that direct wind forcing could be an important generation mechanism for the rich eddy activity in the scs and that to simulate this mechanism the resolution of the wind forcing has to be high enough to resolve the local wind jets induced by orographic effects

eddy dynamics in a primitive equation model sensitivity to horizontal resolution and friction a primitive equation model of an idealized ocean basin driven by simple study wind and buoyancy forcing at the surface is used to study the dynamics of mesoscale eddies model statistics of a six year integration using a fine grid 1 6 0 2 with reduced coefficients of horizontal friction are compared to those using a coarser grid 1 3 0 4 but otherwise identical configuration eddy generation in both model cases is primarily due to the release of mean potential energy by baroclinic instability horizontal reynolds stresses become significant near the midlatitude jet of the fine grid case with a tendency for preferred energy transfers from the eddies to the mean flow using the finer resolution eddy kinetic energy nearly doubles at the surface of the subtropical gyre and increases by factors of 3 4 over the jet region and in higher latitudes the spatial characteristics of the mesoscale fluctuations are examined by calculating zonal wavenumber spectra and velocity autocorrelation functions with the higher resolution the dominant eddy scale remains approximately the same in the subtropical gyre but decreases by a factor of 2 in the subpolar areas the wavenumber spectra indicate a strong influence of the model friction in the coarse grid case especially in higher latitudes using the coarse grid there is almost no separation between the energetic eddy scale and the scale where friction begins to dominate leading to steep spectra beyond the cutoff wavenumber using the finer resolution an inertial subrange with a k 3 power law begins to emerge in all model regions outside the equatorial belt despite the large increase of eddy intensity in the fine grid model effects on the mean northward transport of heat are negligible strong eddy fluxes of heat across the midlatitude jet are almost exactly compensated by changes of the heat transport due to the mean flow

three long lived anticyclonic eddies in the northern south china sea 1 in august 2007 three long lived anticyclonic eddies ace1 ace2 and ace3 were detected by both satellite sea level anomaly sla map and in situ measurements in the northern south china sea scs ace3 had a two core ace3 1 and ace3 2 structure in situ stations along 18 degrees n almost cut through the centers of ace2 and ace3 2 near the centers of ace2 and ace3 2 mean temperature and sound velocity are similar to 0 65 degrees c and similar to 2 m s 1 larger than those in their surrounding areas respectively while mean salinity and density are similar to 0 02 psu and similar to 0 15 m 3 s 1 smaller than those in their surrounding areas due to downwelling near the eddy cores the depths of maximum and minimum salinity near the eddy cores are similar to 65 m and similar to 35 m larger than those in their surrounding areas the vertical depth with current speed larger than 0 05 m s 1 can reach similar to 900 m their detailed evolutionary processes were depicted based on the variation of geostrophic currents and the trajectories of five drifting buoys ace1 lasted 147 days while ace2 and ace3 lasted 168 days and 210 days respectively ace1 had a smaller mean sla 18 8 cm in its lifetime than ace2 21 8 cm and ace3 25 3 cm but had a larger negative mean vorticity 7 7 x 10 6 s 1 than ace2 7 0 x 10 6 s 1 and ace3 7 0 x 10 6 s 1 one short lived anticyclonic eddy that split from ace2 and another one that merged with ace3 both had a smaller sla negative vorticity and diameter than ace2 and ace3 respectively

extreme sea level events at hawaii influence of mesoscale eddies 1 the highest daily mean sea levels recorded at the honolulu harbor tide gauge occurred during september 2003 examination of tide gauge satellite altimeter and hydrographic measurements in the region indicate that the extreme event was largely due to an anticyclonic eddy with offshore amplitude of about 15 cm and a diameter of 300 km the eddy propagated from approximately 3 000 km to the east over a one to two year period although eddies of this size are not uncommon at hawaii the september 2003 sea level was extreme because the eddy coincided with high periods in both the seasonal and decadal cycles and because sea level at honolulu has been rising at 1 5 cm decade for the past century this long term trend has increased the impact of short term events on coastal sea level prediction of such events requires real time altimeter data and improved modeling near hawaii

influence of crack distribution of rocks on p wave velocity anisotropy a laboratory and field scale study the purpose of this paper is the comparison of p wave velocity and velocity anisotropy measured at different scales under laboratory and field conditions a shallow seismic refraction survey with shot receiver spacing of up to 10 m was carried out on a flat outcrop of lhertzolite in the southern part of the balmuccia massif oriented rock samples were also obtained from the locality the particular advantage of the laboratory method used is the possibility of measuring velocity in any direction under controlled conditions laboratory tests were made on spherical peridotite samples 50 mm in diameter by ultrasonic velocity measurements in 132 directions meridian and parallel networks under confining stress ranging from atmospheric to 400 mpa the mean p wave velocity of the field and laboratory data differed by between 20 30 in addition p wave velocity anisotropy of 25 was detected in the field data whereas the anisotropy in the laboratory samples in the same orientation as the field surveys was less than 2 this observed scaling factor is related to the different sampling sizes and the difference in frequencies of applied elastic waves with an ultrasonic wavelength of 10 mm laboratory samples represent a continuum the field velocities and velocity anisotropy reflect the presence of cracks which the laboratory rock samples do not contain three sub vertical fracture sets with differing strikes were observed in the field outcrop estimates of fracture stiffness from the velocity anisotropy data are consistent with other published values these results highlight the difficulty of using laboratory velocity estimates to interpret field data

an idealized model of weddell gyre export variability recent observations suggest that the export of antarctic bottom water aabw from the weddell sea has a seasonal cycle in its temperature and salinity that is correlated with annual wind stress variations this variability has been attributed to annual vertical excursions of the isopycnals in the weddell gyre modifying the water properties at the depth of the orkney passage recent studies attribute these variations to locally wind driven barotropic dynamics in the northern weddell sea boundary current this paper explores an alternative mechanism in which the isopycnals respond directly to surface ekman pumping which is coupled to rapidly responding mesoscale eddy buoyancy fluxes near the gyre boundary a conceptual model of the interface that separates weddell sea deep water from circumpolar deep water is described in which the bounding isopycnal responds to a seasonal oscillation in the surface wind stress different parameterizations of the mesoscale eddy diffusivity are tested the model accurately predicts the observed phases of the temperature and salinity variability in relationship to the surface wind stress the model despite its heavy idealization also accounts for more than 50 of the observed oscillation amplitude which depends on the strength of the seasonal wind variability and the parameterized eddy diffusivity these results highlight theimportanceofmesoscaleeddiesinmodulatingtheexportofaabwinnarrowboundarylayersaroundthe antarctic margins

anticyclonic eddy sheddings from kuroshio loop and the accompanying cyclonic eddy in the northeastern south china sea abstractsheddings of kuroshio loop current klc eddies in the northeastern south china sea scs are investigated using mooring arrays multiple satellite data and data assimilative hycom products based on altimeter sea surface heights between 1992 and 2014 a total of 19 prominent klc eddy shedding klces events were identified among which four events were confirmed by the concurrent moored and satellite observations compared to the leaping behavior of kuroshio klces is a relatively short duration phenomenon that primarily occurs in boreal autumn and winter the klc and its shedding anticyclonic eddy ae trap a large amount of pacific water with high temperature salinity and low chlorophyll concentration in the upper layer the corresponding annual mean transport caused by klces reaches 0 24 0 38 sv 1 sv 106 m3 s 1 accounting for 6 8 10 8 of the upper layer luzon strait transport altimeter based statistics show that among 90 of the historical klces events a cyclonic eddy ce is immedi

circulations and eddies over the south china sea derived from topex poseidon altimetry topex poseidon t p altimeter data were used to derive time varying circulation and eddies over the south china sea scs for 1993 1999 large variabilities of sea surface heights and dense distribution of eddies were found to occur along a band across the scs basin a cross over method is introduced to compute pointwise velocity components the t p derived circula tions and eddies are consistent with the drifter results from the world ocean circulation experi ment data center 1 because of monsoons the scs circulation is largely cyclonic in winter is largely anticyclonic in summer and is modulated interannually by el nifio southern oscillation 2 both cold and warm core eddies were found in the waters east of vietnam west of luzon and west of the luzon strait but their times of occurrence and the way they evolved vary interannually 3 the reversal of the alongshore currents east of vietnam was in complete accordance with wind stress the locations and kinematic properties of eddies over scs were estimated by the least squares method the averaged vorticities of the cold and warm core eddies are 1 684x 10 6 and 1 738x l0 6 tad s respectively and the shearing and stretching deformations are one thousandth of the vorticities the angular velocity of eddy decreases with increasing radius coherence analy sis suggests that the interannual and seasonal variations of circulation are largely due to wind stress and the semi annual variation is largely due to wind stress curl the angular velocities of eddies over the central scs basin are coherent with the magnitudes and signs of wind stress curl the seasonal steric anomaly was also computed and its spatial pattern and scale are quite different from those of circulation and eddy

the hudson shelf valley its role in shelf sediment transport abstract freeland g l stanley d j swift d j p and lambert d n 1981 the hudson shelf valley its role in shelf sediment transport mar geol 42 399 427 the hudson shelf valley was deeply incised by pleistocene lowstands of the sea during the holocene transgression fluvial estuarine and estuary mouth depositional environments were displaced landward and sedimentation in these environments partially filled the valley holocene sediment thickness in the seaward half of the valley is about the same as on the shelf to either side but in the landward half of the valley 22 m of sediment is present versus 5 10 m on the adjacent shelf sediment volume calculations in the upper shelf valley show that there is about three times the infill volume east of the thalweg as compared to the infill to the west this configuration indicates that the valley has served as a sediment trap and records the westward migration of the thalweg during the holocene most of the infill was the result of littoral drift which transported sand westward along the south shore of long island during the holocene transgression modern sediment transport as calculated from current meter observations and inferred from bedform observations is mainly south westward along the regional trend of the isobaths and across the shelf valley therefore infill on the eastern side of the shelf valley is continuing at present observations of the regional distribution of sediment types indicate that the asymmetrical valley fill is part of a pattern of bottom response to flow the former drainage divides on both sides of the shelf valley are surfaced by coarse lag deposits on slopes facing northeast into the direction from which the major storm flows come while the down current sides are mantled with fine sand

mesoscale to submesoscale transition in the california current system part i flow structure eddy flux and observational tests in computational simulations of an idealized subtropical eastern boundary upwelling current system similar to the california current a submesoscale transition occurs in the eddy variability as the horizontal grid scale is reduced to o 1 km this first paper in a series of three describes the transition in terms of the emergent flow structure and the associated time averaged eddy fluxes in addition to the mesoscale eddies that arise from a primary instability of the alongshore wind driven currents significant energy is transferred into submesoscale fronts and vortices in the upper ocean the submesoscale arises through surface frontogenesis growing off upwelled cold filaments that are pulled offshore and strained in between the mesoscale eddy centers in turn some submesoscale fronts become unstable and develop submesoscale meanders and fragment into roll up vortices associated with this phenomenon are a large vertical vorticity and rossby number a large vertical velocity relatively flat horizontal spectra contrary to the prevailing view of mesoscale dynamics a large vertical buoyancy flux acting to restratify the upper ocean a submesoscale energy conversion from potential to kinetic a significant spatial and temporal intermittency in the upper ocean and material exchanges between the surface boundary layer and pycnocline comparison with available observations indicates that submesoscale fronts and instabilities occur widely in the upper ocean with characteristics similar to the simulations

distinguishing oil and water layers by interpreting acoustic logging data with changing well diameters during surveys water layers may interfere with the detection of oil layers in order to distinguish between oil and water layers research on the properties of well diameters and oil and water layers and their relation to acoustic logging rules is essential using hudson s crack theory we simulated oil and water layers with different well diameters or crack parameters angle and number density we found that when the well radius increases from 0 03 m to 0 05 m the variation ratio of compressional wave amplitude for the oil layer is less than that for the water layer the difference of stoneley wave amplitude between the crack parameters angle and number density is greater in the case of the water layer than in the case of the oil layer the response sensitivity of wave energy is greater for the water layer than that for the oil layer when the well radius increases from 0 05 m to 0 14 m the maximum excitation intensity for oil layer is greater than that for the water layer we conclude that the propagation of an elastic wave is affected by medium composition and well diameter and the influence has certain regularity these results can guide further reservoir logging field exploration work

mesoscale dongsha cyclonic eddy in the northern south china sea by drifter and satellite observations 1 near the center of the northern south china sea nscs the dongsha atoll is situated on the continental slope that runs from taiwan to hainan a mesoscale cyclonic eddy south or southwest of dongsha seems to appear annually and has been identified as the dongsha cyclonic eddy dce historical drifter 1988 2005 and satellite altimeter 2000 2005 data were adopted to study the variations to and characteristics of the dce some typical features were derived such as mean tangential speed of 20 cm s moving speed of 8 km d i e 9 cm s eddy size of 22 103 km2 center sea surface lowering height difference dif of 6 cm and angular velocity of 9 d mean tangential speeds of 12 16 cm s in late spring and summer are slower than those of 16 31 cm s in winter and early spring moving speeds are of the order of the rossby wave at nscs latitudes variations in the time series of eddy size and dif are generally similar and show a positive linear relation between them the dce starts near dongsha and moves southwestward along the continental slope at a depth of 1000 2000 m the eddy peaks with maximum eddy size and dif when reaching 114 e and then diminishes south of hainan because of trapping of the underwater bay formed by the continental slope the dce typically exists 1 2 times per year and lasts 1 3 months roughly 90 of observed dces formed in winter or spring a unique dce was identified in the summer of 2000 and lasted for over 4 months its birth was associated with typhoon kai tak the positive linear relationship between eddy size and dif in this case was unique before reaching 114 e and then returned to the typical relationship of other dces the dif of this unique dce attained the highest of 24 cm right at the climax longitude according to avhhr and seawifs images such a dce is associated with a core of which sea surface temperature is 2 c lower and chlorophyll a concentration is 0 1 mg m3 higher than those of surrounding seas migration of the dce may be linked to tuna fish farms in the nscs

seismic wave propagation in cracked porous media summary the movement of interstitial fluids within a cracked solid can have a significant effect on the properties of seismic waves of long wavelength propagating through the solid we consider three distinct mechanisms of wave induced fluid flow flow through connections between cracks in an otherwise non porous material fluid movement within partially saturated cracks and diffusion from the cracks into a porous matrix material in each case the cracks may be aligned or randomly oriented leading respectively to anisotropic or isotropic wave speeds and attenuation factors in general seismic velocities exhibit behaviour that is intermediate between that of empty cracks and that of isolated liquid filled cracks if fluid flow is significant in the range of frequencies for which considerable fluid flow occurs there is high attenuation and dispersion of seismic waves fluid flow may be on either a wavelength scale or a local scale depending on the model and whether the cracks are aligned or randomly oriented resulting in completely different effects on seismic wave propagation a numerical analysis shows that all models can have an effect over the exploration seismic frequency range

mesoscale eddies off peru in altimeter records identification algorithms and eddy spatio temporal patterns relatively little is known about coherent vortices in the eastern south pacific along the peruvian coast even with regard to basic facts about their frequency of occurrence longevity and structure this study addresses these issues with nearly 15 years of relatively high resolution satellite altimetry measurements we first compare two distinct automated methods for eddy identification the objective validation protocol shows that the rarely used geometrical or winding angle method based on the curvature of the streamline functions is more accurate than the commonly used okubo weiss algorithm which defines a vortex as a simple connected region with values of okubo weiss parameter weaker than a given threshold we then investigate vortices off peru using more than 20 000 mesoscale eddies identified by the winding angle method coherent eddies characterized by a high ratio of vorticity to deformation rate are typically formed along the coast and propagate westward at 3 6 cm s 1 the vortices have a mean radius of 80 km increasing northward and are most frequently observed off of chimbote 9s and south of san juan 15s the mean eddy lifetime is about 1 month but if eddies survive at least 2 months the probability for surviving an additional week or month is constant at 90 or 67 anticyclonic eddies tend to propagate northwestward whereas cyclonic vortices migrate southwestward in general cyclones and anticyclones are similar except for eddies surviving at least 6 months in this case after a similar 3 4 months of radius and amplitude growth amplitudes or sizes decay particularly rapidly for anticyclonic or cyclonic eddies in terms of intensity cyclonic eddies show a rapid decay during the first 3 months before arriving at a quasi constant value whereas anticyclones exhibit steady decline finally eddy temporal variations were examined at seasonal and interannual scales in the coastal region favorable to the formation of energetic mesoscale structures on seasonal scales eddy activity is maximal in fall and minimum in spring at interannual scales the eddy activity index was maximal during the strong el nino of 1997 1998 but another strong maximum of eddy activity also occurred late in 2004 these temporal variations are probably associated with the intensification of the upwelling thermal front and with the passage of coastal trapped waves which generate baroclinic instabilities further investigation of the mechanisms involved on the eddy genesis is needed

penetration of nonlinear rossby eddies into south china sea evidenced by cruise data national basic research program of china 2009cb421208 2007cb411803 natural science foundation of china 40976013 41121091 united states of america national oceanic atmospheric administration national environmental satellite data and information service ocean remote sensing 3000 11 03241

mesoscale eddies in the south china sea mean properties spatiotemporal variability and impact on thermohaline structure we investigated mean properties and the spatiotemporal variability of eddies in the south china sea scs by analyzing more than 7000 eddies corresponding to 827 eddy tracks identified using the winding angle method and 17 years of satellite altimetry data eddies are mainly generated in a northeast southwest direction and southwest of luzon strait there is no significant difference between the numbers of two types of eddies anticyclonic and cyclonic in most regions the mean radius and lifetime of eddies are 132 km and 8 8 weeks respectively both depending on where the eddies are formed anticyclonic and cyclonic eddies tend to deform during their lifetimes in different ways furthermore eddy propagation and evolution characteristics are examined in the northern scs eddies mainly propagate southwestward along the continental slope with velocities of 5 0 9 0 cm s 1 while in the central scs eddies tend to move with slight divergence but still in a quasi westward direction with velocities of 2 0 6 4 cm s 1 eddy propagation in the western basin to the east of vietnam is quite random with no uniform propagate direction investigation of 38 long lived eddies shows that eddies have a swift growing phase during the first 12 weeks and then a slow decaying phase that affects the eddy radii and eddy energy densities nevertheless vorticity has less variability in addition the effect of eddies on the thermocline and halocline is analyzed using 763 argo temperature profile data cyclonic eddies drive the thermocline shallower and thinner and significantly strengthen the thermocline intensity whereas anticyclonic eddies cause the thermocline to deepen and thicken and weaken the thermocline intensity to a certain degree the halocline impacted by cyclonic eddies is also shallower and thinner than that impacted by anticyclonic eddies finally eddy temporal variations are examined at seasonal and interannual scales eddy activity is sensitive to the wind stress curl and in the northern scs it is also related with the strength of the background flows

interdecadal variability of the eastward current in the south china sea associated with the summer asian monsoon abstract based on the simple ocean data assimilation soda dataset and three types of sverdrup streamfunction an interdecadal variability of the eastward current in the middle south china sea scs during summer is identified both the pattern and strength of the summer asian monsoon wind stress curl over the scs contribute to the interdecadal variability of this current from 1960 to 1979 the monsoon intensified and the zero wind stress curl line shifted southward both the core of positive wind stress curl in the northern scs and the negative curl in the southern scs moved southward and thus induced a southward shift of both the southern anticyclonic and northern cyclonic gyres resulting in a southward displacement of the eastward current associated with these two gyres in the meantime the southern northern scs anticyclonic cyclonic ocean gyre weakened strengthened and therefore also induced the southward shift of the eastward current near the intergyre boundary in contrast the eastward cu

eddy effects on sea surface temperature and sea surface wind in the continental slope region of the northern south china sea 1 warm and cold sea surface temperature sst tongues on weather timescales are detected in the continental slope region of the northern south china sea nscs and their effects on sea surface wind are studied using satellite observations crossing the basin scale sst front geostrophic currents between cyclonic and anticyclonic eddies induce the warm and cold sst tongues during the northeast monsoon corresponding to the warm and cold sst tongues the sea surface wind is highly uneven in spatial distribution its speed is faster slower over the warm cold sst tongues than the surrounding areas the sst and sea surface wind non uniformity in space shifts southwestward with eddy motion along the continental slope these new findings from satellite observations give us an opportunity to study oceanic eddy s roles in ocean atmosphere interaction on weather timescales

average circulation seasonal cycle and mesoscale dynamics of the peru current system a modeling approach h isolines the pccc appears to be directly forced by the cyclonic wind stress curl the model is able to produce the upwelling front the cold water tongue which extends toward the equator and the equatorial front as described in the literature model seasonal changes in sst and ssh are compared to measurements for the central pcs model eke is 10 to 30 lower than the observations the model eddy diameters follow a strong equatorward increase the injection length scales derived from the energy spectra strongly correlate to the rossby radius of deformation confirming the predominant role of baroclinic instability at 3 s the model solution appears to switch from a turbulent oceanic regime to an equatorial regime dominated by zonal currents

overall properties of heterogeneous material summary small scale heterogeneity in crustal structure can be very complex and difficult to describe in detail and yet at the same time can be very important for the description of for instance tectonic stress and porosity statistical properties of such heterogeneity can be derived from the properties of waves of relatively large wavelength as they propagate through the crust the differences between measured wavelengths and attenuation coefficients and those of compact rock and the variations of these quantities in space and time provide in principle a means of determining quantities like the density and orientations of microfractures and the nature of crack infill material the theoretical basis for inferences of this kind is the concept of the effective or equivalent material based on an averaging process taken over the microstructure a number of methods have been used to calculate the properties of the effective medium several of which are described here

organization of storm tracks in zonally varying flows abstract a simple two layer quasigeostrophic model is employed to investigate the sensitivity of storm tracks to changes in an externally imposed zonally varying large scale flow zonally asymmetric temperature and horizontal deformation fields are varied systematically in order to compare the effects of baroclinicity and horizontal deformation on storm track dynamics the sensitivity of the storm tracks to uniform barotropic zonal flows is also examined the results show two competing processes for storm track organization one associated with a local maximum in baroclinicity and the other with a local minimum in horizontal deformation when the equilibrium state consists of a zonally symmetric temperature field and a barotropic stationary wave the maximum in synoptic scale transient eddy energy storm track is located in the entrance region of the upper jet just downstream of the point of minimum horizontal deformation as zonal variations in baroclinicity become large keeping the upper layer horizo

an airborne expendable bathythermograph survey of the south china sea may 1995 an extensive airborne expendable bathythermograph survey of the south china sea scs conducted in may 1995 and historical data are used to analyze and infer the upper layer 300 m synoptic structure and general circulation the primary thermal feature observed was a central scs warm pool surrounded by several cool pools the size of the warm pool decreased with depth from approximately 200 000 km2 at 50 m depth to about 70 000 km2 at 300 m depth the maximum temperature of the warm pool was 30 c appearing near the surface at the depth of 50 m the temperature of the central scs warm pool was 29 c and the temperature of the five surrounding cool pools ranged from 26 c to 22 c a three dimensional estimate of the absolute velocity field was obtained from the observed temperature field and a climatological salinity field using the spiral method striking circulation features were the existence of dual anticyclonic eddies in the central scs warm pool and the existence of cyclonic eddies associated with the cool pools in the upper layer the tangential velocity of the dual central scs anticyclonic warm core eddies is around 30 40 cm s and that of the five cyclonic cool core eddies varies from 10 cm s to 40 cm s the tangential velocity of all the eddies decreased with depth at 300 m depth it became less than 5 cm s for all the eddies

three dimensional oceanic eddy analysis in the southern california bight from a numerical product with eight islands complex coastlines and bottom topography strong wind curls and frequent upwelling fronts the southern california bight scb is an area with strong eddy activity by applying an automated eddy detection scheme to a 12 year high resolution numerical product of the oceanic circulation in the scb a three dimensional eddy data set is developed it includes information for each eddy s location polarity intensity size boundary and moving path at nine vertical levels through a series of statistical analyses applied to the eddy data set three dimensional statistical characteristics of mesoscale and submeoscale eddy variations in the scb are elucidated these shed light on how eddies are generated evolve and terminate a significant percentage of eddies is found to be generated around islands and headlands along the coastline which indicates that islands in the scb play a vital role in eddy generation three types of eddies based on shape are identified from the numerical product bowl lens and cone a dynamic analysis shows that some submesoscale eddies with finite local rossby numbers tend to be ageostrophic balanced while mesoscale eddies are in geostrophic balance the present research results are useful for the interpretation of data sets obtained during the interdisciplinary santa barbara channel radiance in a dynamic ocean radyo field experiment conducted on september 3 25 2008

an annual cycle of submesoscale vertical flow and restratification in the upper ocean abstractnumerical simulations suggest that submesoscale turbulence may transform lateral buoyancy gradients into vertical stratification and thus restratify the upper ocean via vertical flow howev