an efficient wave extrapolation method for anisotropic media with tilt wavefield extrapolation operators for elliptically anisotropic media offer significant cost reduction compared with that for the transversely isotropic case particularly when the axis of symmetry exhibits tilt from the vertical however elliptical anisotropy does not provide accurate wavefield representation or imaging for transversely isotropic media therefore we propose effective elliptically anisotropic models that correctly capture the kinematic behaviour of wavefields for transversely isotropic media specifically we compute source dependent effective velocities for the elliptic medium using kinematic high frequency representation of the transversely isotropic wavefield the effective model allows us to use cheaper elliptic wave extrapolation operators despite the fact that the effective models are obtained by matching kinematics using high frequency asymptotic the resulting wavefield contains most of the critical wavefield components including frequency dependency and caustics if present with reasonable accuracy the methodology developed here offers a much better cost versus accuracy trade off for wavefield computations in transversely isotropic media particularly for media of low to moderate complexity in addition the wavefield solution is free from shear wave artefacts as opposed to the conventional finite difference based transversely isotropic wave extrapolation scheme we demonstrate these assertions through numerical tests on synthetic tilted transversely isotropic models

macroscale wide nutrient inversions in the subsurface layer of the japan sea during summer the nutrient concentrations at depths of 0 200 m in the southern area of the japan sea were investigated at 97 stations during six cruises between june and october in 2013 and 2014 the nutrient concentrations at the surface were depleted to less than 0 1 m except for silicates which remained at 0 8 5 m and increased below the nutricline at depths of 20 125 m the vertical profiles of nitrate silicate and or phosphate concentrations between 131 30 e 139 40 e and 35 50 n 40 40 n showed a peak in the subsurface layer at 40 71 and 6 stations respectively and nutrient inversions occurred at macroscale widths the subsurface nutrient maximum occurred at depths of 20 150 m in waters at temperatures of 15 16 c and potential densities of 25 3 25 5 on average the depths of the subsurface nutrient maximum were generally associated with a salinity maximum originating in the bottom water of the shallow tsushima strait the nutrient inversions were disturbed by phytoplankton consumption as indicated by the presence of the subsurface chlorophyll maximum at the same depth or below the salinity maximum at stations without nutrient inversions therefore it was inferred that remineralization of nutrients near the bottom from the east china sea to the tsushima strait and horizontal advection by the tsushima warm current below the euphotic layer induced macroscale subsurface nutrient inversions in the southern japan sea

geochemistry of surface sediments in the southwestern east japan sea abstract we analyzed 77 surface sediment samples collected in the southwestern east japan sea from the korea strait through the ulleung basin and the korea plateau for grain size calcium carbonate organic carbon and major na mg al fe k ca and ti and trace elements p mn sr li sc v cr co ni zn cu and pb the chemical composition of the surface sediments was found to be highly variable spatially cluster analysis of surface sediment chemical compositions indicated five major geochemical sedimentary environments basin lower slope coast and upper slope inner shelf and outer shelf continental shelf sediments were rich in shell fragments and had relict and coarse grained characteristics recent fine grained sediments were only distributed in coastal slope and basin areas concentrations of al k ca ti cr and sc were highest in the coastal and upper slope areas and decreased with water depth elemental ratios using major and trace elements indicated that coastal and upper slope detrital sediments were mixtures of sediments derived from the changjiang yangtze and nakdong rivers although the concentrations of organic carbon p mn v co ni cu and pb increased with water depth their distribution patterns indicated authigenic v cu and pb and diagenetic fe p mn co and ni origins the distribution pattern with water depth suggested that the chemical composition of surface sediment was determined by sedimentologic and geochemical processes such as the supply of detrital and biogenic materials and authigenic and post depositional diagenetic processes in sediments

wavefield tomography using reverse time migration backscattering abstractreverse time migration backscattering contains kinematic information that can be used to constrain velocity models the backscattering results from the correlation between forward scattered and backscattered wavefields from sharp interfaces i e sediment salt interfaces the synchronization between these wavefields depends on the velocity of the sediment section and the correct interpretation of the sharp boundary we have developed an optimization workflow in which the sediment velocity and the sharp boundary are updated iteratively the presence of sharp boundaries in the model lead to high and low wavenumber components in the objective function gradient the high wavenumber components correspond to the correlation of wavefields traveling in opposite directions whereas the low wavenumber components correspond to the correlation of wavefields traveling in the same direction this behavior is similar to reverse time migration in which the high wavenumber components represent the reflectors th

time reverse modelling of acoustic wave propagation in attenuating media summary time reverse modelling trm of acoustic wave propagation has been widely implemented in seismic migration and time reversal source imaging the basic assumption of this modelling is that the wave equation is time invariant in non attenuating media in the earth attenuation often invalidates this assumption of time invariance to overcome this problem i propose a trm approach that compensates for attenuation and dispersion effects during the wave propagation in attenuating media this approach is based on a viscoacoustic wave equation which explicitly separates attenuation and dispersion following a constant q model compensating for attenuation and dispersion during trm is achieved by reversing the sign of the attenuation operator coefficient while leaving the counterpart dispersion parameter unchanged in this viscoacoustic wave equation a low pass filter is included to avoid amplifying high frequency noise during trm i demonstrate the effects of the filter on the attenuation and the phase velocity by comparing with theoretical solutions in a 1 d pierre shale homogeneous medium three synthetic examples are used to demonstrate the feasibility of attenuation compensation during trm the first example uses a 1 d homogeneous model to demonstrate the accuracy of the numerical implementation of the methodology the second example shows the applicability of source location using a 2 d layering model the last example uses a 2 d cross well synthetic experiment to show that the methodology can also be implemented in conjunction with reverse time migration to image subsurface reflectors when attenuation compensation is included i find improved estimation of the source location the excitation timing of the point source the magnitude of the focused source wavelet and the reflectivity image of reflectors particularly for deep structures underneath strongly attenuating zones

efficient amplitude encoding least squares reverse time migration using cosine basis least squares reverse time migration provides better imaging result than conventional reverse time migration by reducing the migration artefacts improving the resolution of the image and balancing the amplitudes of the reflectors however it is computationally intensive to reduce its computational cost we propose an efficient amplitude encoding least squares reverse time migration scheme in the time domain although the encoding scheme is effective in increasing the computational efficiency it also introduces the well known crosstalk noise in the gradient that degrades the quality of the imaging result we analyse the cause of the crosstalk noise using an encoding correlation matrix and then develop two numerical schemes to suppress the crosstalk noise during the inversion process we test the proposed method with synthetic and field data numerical examples show that the proposed scheme can provide better imaging result than reverse time migration and it also generates images comparable with those from common shot least squares reverse time migration but with less computational cost

contemporaneity of component units of the lowstand systems tract an example from the pleistocene kazusa forearc basin boso peninsula japan the lowstand systems tract of the standard sequence stratigraphic model consists of three major component units in ascending order the basin floor fan slope fan and lowstand wedge however there are no modern or ancient examples of a lowstand systems tract that contain each of the three component units from the base to top three dimensional outcrop analysis and detailed chronostratigraphic correlation of the lowstand deposits that infilled the pleistocene kazusa forearc basin exposed on the boso peninsula of japan reveal that the three component units of the lowstand systems tract are largely age equivalent their development was controlled much more by geographic setting in conjunction with spatial variation in sediment supply and basin subsidence than by the position of relative sea level it is concluded that the lowstand systems tract of the sequence stratigraphic model is a theoretical concept that is not accurately reflected in the stratigraphic relationships shown in the present field case

three dimensional seismic full waveform inversion using the finite difference contrast source inversion method we present the extension of the so called finite difference contrast source inversion method for the three dimensional interpretation of full waveform seismic data using the acoustic approximation the finite difference contrast source inversion method does not simulate a full forward problem in its inversion process hence it is computationally more efficient than the standard non linear inversion methods furthermore it allows the use of an inhomogeneous background medium hence this method has a great potential for carrying out time lapse seismic inversion however the price that we have to pay is the storing of the lu decomposition arrays of the impedance matrix of the background medium we show some numerical examples to illustrate the dis advantages of this method

a moving boundary box model mbbm for oceans in change an application to the east japan sea 1 the east japan sea has undergone dramatic changes during the last 50 60 years as the result of a shift in its ventilation system from bottom water formation to intermediate water formation a moving boundary box model mbbm was developed to quantify these changes the model consists of three boxes for deep waters representing central deep and bottom waters respectively and two boundaries in between which are moving according to the volume changes of these water masses the model calibrated with cfc 11 and tritium distribution shows the bottom water formation of 0 02 sv in magnitude in the past slowed down and came to a complete halt in mid 1980s and late 1990s furthermore this model predicts the bottom water will disappear completely in 2040 as central water penetrates deeper considering the recent observations that many oceans are in change a mbbm could be a valuable tool to investigate the nature of such changes

on a plane wave based crosscorrelation type seismic interferometry we explored a new approach to retrieve virtual seismic responses from crosscorrelating acquired seismic data in the plane wave domain using this method slant stacking is first performed over shot or receiver locations of observed seismic data to produce plane wave transformed gathers crosscorrelation is then performed by selecting traces with the same ray parameters from different shot or receiver locations of the plane wave gathers unlike traditional crosscorrelation type time space domain interferometry where full range of ray parameters is used for each survey location this method directly selects common ray parameters to cancel overlapping raypaths this approach can be used to retrieve reflections in the presence of dispersive waves and to select certain ranges of ray parameters with directional wave paths for retrieval it can avoid spurious arrivals in supervirtual interferometry when unwanted arrivals such as reflections break the requirement of conventional interferometry in addition computation time can be saved with this approach because plane wave transform usually results in a reduction of the original data volume we demonstrate this method with synthetic and ocean bottom seismometer data examples

seismic imaging of complex onshore structures by 2d elastic frequency domain full waveform inversion quantitative imaging of the elastic properties of the subsurface at depth is essential for civil engineering applications and oil and gas reservoir characterization a realistic synthetic example provides for an assessment of the potential and limits of 2d elastic full waveform inversionfwiof wide aperture seismic data for recovering high resolution p and s wave velocity models of complex onshore structures fwi of land data is challengingbecauseoftheincreasednonlinearityintroducedbyfreesurface effects such as the propagation of surface waves in the heterogeneous near surface moreover the short wavelengths of the shear wavefield require an accurate s wave velocity starting modeliflowfrequenciesareunavailableinthedata weevaluated different multiscale strategies with the aim of mitigating the nonlinearities massively parallel full waveform inversion was implemented in the frequency domain the numerical optimization relies on a limited memory quasi newton algorithm that outperforms the more classic preconditioned conjugate gradient algorithm the forward problem is based upon a discontinuous galerkin dg method on triangular mesh which allows accuratemodelingoffree surfaceeffects sequentialinversionsofincreasingfrequenciesdefinethemostnaturallevelofhierarchyin multiscale imaging in the case of land data involving surface waves the regularization introduced by hierarchical frequency inversions is not enough for adequate convergence of the inversion a second level of hierarchy implemented with complexvalued frequencies is necessary and provides convergence of the inversion toward acceptable p and s wave velocity models amongthepossiblestrategiesforsamplingfrequenciesintheinversion successive inversions of slightly overlapping frequency groups is the most reliable when compared to the more standard sequential inversion of single frequencies this suggests that simultaneous inversion of multiple frequencies is critical when consideringcomplexwavephenomena

deposition of sheet like turbidite packets and migration of channel overbank systems on a sandy submarine fan an example from the late miocene early pliocene forearc basin boso peninsula japan abstract sheet like turbidite packets and channel overbank systems are interpreted to be major components of submarine fans spatial and temporal relationships between the two major components however are not yet clearly understood in particular for sand dominated submarine fans in active margin basins three dimensional outcrop analysis of an ancient sandy submarine fan succession in a late miocene early pliocene forearc basin on the boso peninsula japan together with mapping of chronostratigraphic markers defined by volcanic ash beds indicates that deposition of sheet like turbidite packets was intimately associated with the lateral migration of depocenters of channel overbank systems and distinct entrenchment of fan channels in response to upfan avulsion deposition of a sheet like turbidite packet is not restricted in a single interchannel low but rather is spread out over most of the channel overbank area possibly reflecting the high width to depth ratio of channel overbank systems on sandy submarine fans largely contemporaneous deposition of sheet like turbidite packets and channel overbank systems further indicates that the basin floor fan and slope fan of the sequence stratigraphic model do not necessarily characterize different parts of a relative sea level lowstand or temporally different types of depositional systems

the use of microstructures for discriminating turbiditic and hemipelagic muds and mudstones the microstructures of turbiditic and hemipelagic muds and mudstones were investigated using a scanning electron microscope to determine whether there are microstructural features that can differentiate turbiditic from hemipelagic sedimentary processes both types of muddy deposits are in general characterized by randomly oriented clay particles however turbiditic muds and mudstones also characteristically contain aggregates of edge to face contacts between clay particles with long axis lengths of up to 30 m based on observations of the clay fabric of the experimentally formed muds settled from previously agitated muddy fluids these types of aggregates hereafter referred to as aggregates of clay particles are interpreted as having been formed by the collision of component flocs in turbulent fluids furthermore some aggregates of clay particles have face to face contacts between clay particles this is similar to face to face aggregates characteristically developed in fluid mud deposits that are commonly recognized only in turbiditic mudstones indicating the possibility of a final stage of deposition under highly dense conditions such as temporary fluid muds in conjunction with earlier proposed lithofacies based and ichnofacies based criteria aggregates of clay particles should be useful for the differentiation of turbiditic and hemipelagic muddy deposits particularly with limited volumes of non oriented samples from deep water successions

south pacific dissolved nd isotope compositions and rare earth element distributions water mass mixing versus biogeochemical cycling despite its enormous extent and importance for global climate the south pacific has been poorly investigated in comparison to other regions with respect to chemical oceanography here we present the first detailed analysis of dissolved radiogenic nd isotopes end and rare earth elements rees in intermediate and deep waters of the mid latitude 40 s south pacific along a meridional transect between south america and new zealand the goal of our study is to gain better insight into the distribution and mixing of water masses in the south pacific and to evaluate the validity of nd isotopes as a water mass tracer in this remote region of the ocean the results demonstrate that biogeochemical cycling scavenging processes in the eastern equatorial pacific and release of lrees from the sediment clearly influence the distribution of the dissolved ree concentrations at certain locations nevertheless the nd isotope signatures clearly trace water masses including aaiw antarctic intermediate water average end 8 2 0 3 lcdw lower circumpolar deep water average end 8 3 0 3 npdw north pacific deep water average end 5 9 0 3 and the remnants of nadw north atlantic deep water average end 9 7 0 3 filtered water samples taken from the sediment water interface under the deep western boundary current off new zealand suggest that boundary exchange processes are limited at this location and highlight the spatial and temporal variability of this process these data will serve as a basis for the paleoceanographic application of nd isotopes in the south pacific

toward a unified analysis for source plane wave migration in complex areas with large lateral velocity variations wave equation based source plane wave migration can produce images comparable to those from shot profile migration with less computational cost image quality can be better than in ray theory based kirchhoff type methods this method requires the composition of plane wave sections from all shot gathers we provide a general framework to evaluate plane wave composition in prestack source plane wave migration our analysis shows that a plane wave section can be treated as encoded shot gathers this study provides the theoretical justification for applying plane wave migration algorithms to sparsely sampled shot gathers with irregularly distributed receivers and limited offset in addition we discuss cylindrical wave migration which is 3d migration of 2d constructed plane waves along the inline direction we mathematically prove the equivalence of shot and plane wave migration and their equivalence to cylindrical wave migration in 3d cases when the sail lines are straight examples including the sigsbee 2a model demonstrate the theory

efficient 3 d frequency domain mono parameter full waveform inversion of ocean bottom cable data application to valhall in the visco acoustic vertical transverse isotropic approximation computationally efficient 3 d frequency domain full waveform inversion fwi is applied to ocean bottom cable data from the valhall oil field in the visco acoustic vertical transverse isotropic vti approximation frequency domain seismic modelling is performed with a parallel sparse direct solver on a limited number of computer nodes a multiscale imaging is performed by successive inversions of single frequencies in the 3 5 10 hz frequency band the vertical wave speed is updated during fwi while density quality factor qp and anisotropic thomsen s parameters and are kept fixed to their initial values the final fwi model shows the resolution improvement that was achieved compared to the initial model that was built by reflection traveltime tomography this fwi model shows a glacial channel system at 175 m depth the footprint of drifting icebergs on the palaeo seafloor at 500 m depth a detailed view of a gas cloud at 1 km depth and the base cretaceous reflector at 3 5 km depth the relevance of the fwi model is assessed by frequency domain and time domain seismic modelling and source wavelet estimation the agreement between the modelled and recorded data in the frequency domain is excellent up to 10 hz although amplitudes of modelled wavefields propagating across the gas cloud are overestimated this might highlight the footprint of attenuation whose absorption effects are underestimated by the homogeneous background qp model qp 200 the match between recorded and modelled time domain seismograms suggests that the inversion was not significantly hampered by cycle skipping however late arrivals in the synthetic seismograms computed without attenuation and with a source wavelet estimated from short offset early arrivals arrive 40 ms earlier than the recorded seismograms this might result from dispersion effects related to attenuation the repeatability of the source wavelets inferred from data that are weighted by a linear gain with offset is dramatically improved when they are estimated in the fwi model rather than in the smooth initial model the two source wavelets estimated in the fwi model from data with and without offset gain show a 40 ms time shift which is consistent with the previous analysis of the time domain seismograms the computational efficiency of our frequency domain approach is assessed against a recent time domain fwi case study performed in a similar geological environment this analysis highlights the efficiency of the frequency domain approach to process a large number of sources and receivers with limited computational resources thanks to the efficiency of the substitution step performed by the direct solver this efficiency can be further improved by using a block low rank version of the multifrontal solver and by exploiting the sparsity of the source vectors during the substitution step future work will aim to update attenuation and density at the same time of the vertical wave speed

deep convection and brine rejection in the japan sea received 15 october 2002 accepted 13 january 2003 published 19 february 2003 1 direct water mass renewal through convection deeper than 1000 m and the independent process of dense water production through brine rejection during sea ice formation occur at only a limited number of sites globally our late winter observations in 2000 and 2001 show that the japan east sea is a part of both exclusive groups japan sea deep convection apparently occurs every winter but massive renewal of bottom waters through brine rejection had not occurred for many decades prior to the extremely cold winter of 2001 the sites for both renewal mechanisms are south of vladivostok in the path of cold continental air outbreaks index terms 4283 oceanography general water masses 4243 marginal and semienclosed seas 4223 4215 climate and interannual variability 3309 citation talley l d v lobanov v ponomarev a salyuk p tishchenko i zhabin and s riser deep convection and brine rejection in the japan sea geophys res lett 30 4 1159 doi 10 1029 2002gl016451 2003

reservoir characterization through target oriented ava petrophysical inversions with spatial constraints we apply three methods that use different regularization strategies to insert spatial constraints into the seismic petrophysical inversion the first method is what we call the structurally constrained inversion sci which directly uses the structural information brought by the seismic stack image to insert geological structural constraints into the inversion the second method is based on anisotropic markov random field amrf and uses the huber energy function to reasonably model the spatial heterogeneity of petrophysical reservoir properties finally the last method includes both geostatistical information describing the lateral variability of reservoir properties and hard data i e well log data constraints into the inversion kernel ghdc inversion for computationally feasibility we apply a target oriented inversion that uses the amplitude versus angle ava responses extracted along the top reservoir reflections to infer the petrophysical properties of interest i e porosity water saturation and shaliness for the target layer in particular an empirical linear rock physics model properly calibrated for the investigated area is used to rewrite the p wave reflectivity equation as a function of the petrophysical contrasts instead of the elastic constants this reformulation allows for a direct and a simultaneous estimation of petrophysical properties from ava data the implemented approaches are tested both on synthetic and field seismic data and compared against the standard method in which each ava response is inverted independently laterally unconstrained bayesian inversion lubi in the case of poor signal to noise ratio it turns out that the three considered spatially constrained methods achieve better delineations of reservoir bodies and provide more reliable results than the standard lubi approach more in detail the amrf recovers sharper geological boundaries than the sci and ghdc algorithms the sci algorithms is more sensitive to data noise whereas the key advantage of the ghdc consists in analytically providing posterior uncertainties for the model parameters finally for what concerns the computational cost the ghdc and the sci methods result the most and the least computationally demanding respectively

exploitation of data information content in elastic waveform inversions elastic waveform inversions have the potential to provide detailed subsurface images of the elastic parameters p and s wave velocities and density but acquisition of suitable data sets and their inversion are nontrivial tasks we explore the information content offered by elastic waveform data by means of a 2d synthetic study comprehensive noise free data sets that include recordings based on multicomponent directed sources and multicomponent vector receivers that fully surround the area of interest allow all elastic parameters to be reliably recovered results that are almost as good can be achieved with the more commonly used crosshole configuration if only single source components e g those oriented perpendicular to the borehole walls are used then there is no significant quality degradation of the tomographic images crosshole experiments that include pressure sources and multicomponent receivers still allow p and s wave velocities to be recovered but such data sets contain virtually

balancing the global oceanic neodymium budget evaluating the role of groundwater the distinctly different end 0 values of the atlantic indian and pacific oceans requires that the residence time of nd in the ocean i e nd be on the order of or less than the ocean mixing time of 500 1500 yr however estimates of nd based on river influxes range from 4000 to 15 000 yr thus exceeding the ocean mixing time in order to reconcile the oceanic nd budget and lower the residence time by roughly a factor of 10 an additional as yet unidentified and hence missing nd flux to the ocean is necessary dissolution of materials deposited on continental margins has previously been proposed as a source of the missing flux in this contribution submarine groundwater discharge sgd is examined as a possible source of the missing nd flux neodymium concentrations n 730 and end 0 values n 58 for groundwaters were obtained from the literature in order to establish representative groundwater values mean groundwater nd concentrations and end 0 values were used along with recent estimates of the terrestrial freshwater component of sgd 6 of river discharge on a global basis to test whether groundwater discharge to the coastal oceans could account for the missing flux employing mean nd concentrations of the compiled data base i e 31 8 nmol kg for all 730 analyses and 11 3 nmol kg for 141 groundwater samples from a coastal aquifer the global terrestrialderived sgd flux of nd is estimated to range between 2 9 10 7 and 8 1 10 7 mol yr these estimates are of the same order of magnitude and within a factor of 2 of the missing nd flux i e 5 4 10 7 mol yr applying the sgd nd flux estimates the global average end 0 of sgd is predicted to be 9 1 which is similar to our estimate for the missing nd flux 9 2 and in agreement with the mean s d end 0 measured in groundwaters i e end 0 8 9 4 2 the similarities in the estimated sgd nd flux and corresponding end 0 values to the magnitude and isotope composition of the missing nd flux are compelling and suggest that discharge of groundwater to the oceans could account for the missing nd flux future investigations should focus on quantifying the nd concentrations and isotope compositions of groundwater from coastal aquifers from a variety of coastal settings as well as the important geochemical reactions that effect nd concentrations in subterranean estuaries in order to better constrain contributions of sgd to the oceanic nd budget

rare earth element distributions in the west pacific trace element sources and conservative vs non conservative behavior abstract recent studies suggest that transport and water mass mixing may play a dominant role in controlling the distribution of dissolved rare earth element concentrations ree at least in parts of the north and south atlantic and the pacific southern ocean here we report vertically and spatially high resolution profiles of dissolved ree concentrations ree along a nw se transect in the west pacific and examine the processes affecting the ree distributions in this area surface water ree patterns reveal sources of trace element te input near south korea and in the tropical equatorial west pacific positive europium anomalies and middle ree enrichments in surface and subsurface waters are indicative of te input from volcanic islands and fingerprint in detail small scale equatorial zonal eastward transport of tes to the iron limited tropical east pacific the low ree of north and south pacific tropical waters and antarctic intermediate water are a long range i e preformed laterally advected signal whereas increasing ree with depth within north pacific intermediate water result from release from particles optimum multiparameter analysis of deep to bottom waters indicates a dominant control of lateral transport and mixing on ree at the depth of lower circumpolar deep water 3000 m water depth 75 100 explained by water mass mixing allowing the northward tracing of lcdw to 28 n in the northwest pacific in contrast scavenging in the hydrothermal plumes of the lau basin and tonga fiji area at 1500 2000 m water depth leads to ree deficits 40 60 removal and marked ree fractionation in the tropical west pacific overall our data provide evidence for active trace element input both near south korea and papua new guinea and for a strong lateral transport component in the distribution of dissolved rees in large parts of the west pacific

sand rich turbidite system of the late oligocene northern apennines foredeep physical stratigraphy and architecture of the macigno costiero coastal tuscany italy

acoustic wave propagation in tilted transversely isotropic media incorporating topography abstractsimulating two way acoustic wavefield propagation directly from a free surface boundary in the presence of topography remains a computational challenge for applications of reverse time migration rtm or full waveform inversion fwi for land seismic settings involving heavily reworked geology e g fold and thrust belts two way wavefield propagation operators should also handle commonly observed complex anisotropy including tilted transversely isotropic tti media to address these issues i have extended a system of coupled partial differential equations used to model 3d acoustic tti wave propagation in cartesian coordinates to more generalized 3d geometries including a deformed computational mesh with a domain boundary conformal to free surface topography a generalized curvilinear transformation is used to specify a system of equations governing 3d acoustic tti wave propagation in the topographic coordinate system the developed finite difference time domain numerical solution adapts e

constraining oceanic dust deposition using surface ocean dissolved al we use measurements of ocean surface dissolved al a global biogeochemical elemental cycling bec ocean model and the global dust entrainment and deposition dead model to constrain dust deposition to the oceans our al database contains all available measurements with best coverage in the atlantic vertical profiles and seasonal data exist in limited regions observations show that surface dissolved al is distributed similarly to the dust deposition predicted by dead and other models there is an equatorial atlantic al maximum that decreases toward higher latitudes there are high al concentrations in the mediterranean sea and the arabian sea and low concentrations in the pacific and the southern ocean the ocean basins maintain more distinct al profiles than fe profiles in the upper ocean consistent with a weaker biological influence on al than fe the bec predicted surface dissolved al compares relatively well with observations the al distribution reflects the combined effects of al input from dust and al removal by particle scavenging and biological uptake by diatoms model observed biases suggest a southward shift of maximum dust deposition compared to current dust model predictions dead appears to overestimate deposition north of 30 n in the pacific and to underestimate deposition south of 30 n observed al concentrations and the ocean model predicted surface al lifetime provide a semi independent method to estimate oceanic dust deposition this technique indicates that dead may overestimate dust deposition to the north equatorial atlantic but underestimate in other atlantic regions the southern ocean and the arabian sea however spatial variations in aerosol al solubility may also contribute to the model observation mismatch our results have implications for all dust borne ocean nutrients including fe and demonstrate the potential of marine geochemical data to constrain atmospheric aerosol deposition fields

breakthrough acquisition and technologies for subsalt imaging the recently introduced method of wide azimuth data acquisition offers better illumination noise attenuation and lower frequencies to more accurately determine a velocity field for imaging for the field data experiment to demonstrate the technologies we used a gulf of mexico gom wide azimuth data set that allows us to take advantage of possible low frequencies relatively large crossline offsets and increased illumination the input data was processed through true 3d azimuthal surface related multiple elimination srme with zero phasing and debubble eliminating the surface related multiples aids the velocity determination and helps uncover the subsalt sediments at the final imaging stage after the initial velocity derivation which was constrained to wells and geology full waveform inversion fwi was used to further update the velocity field to achieve an enhanced image the methodology used follows the top down approach where suprasalt sediment model is developed followed by the top of salt

seismic imaging in hardrock environments the role of heterogeneity abstract we investigate the effect of petrophysical scale parameters and structural dips on wave propagation and imaging in heterogeneous media seismic wave propagation effects within the heterogeneous media are studied for different velocity models with scale lengths determined via stochastic analysis of petrophysical logs from the matagami mine quebec canada the elastic modeling study reveals that provided certain conditions of the velocity fluctuations are met strong local distortions of amplitude and arrival times of propagating waves are observed as the degree of scale length anisotropy in the p wave velocity increases the location of these local amplitude anomalies is related to the dips characterizing the fabric of the host rocks this result is different from the elliptical shape of direct waves often defined by effective anisotropic parameters used for layered media although estimates of anisotropic parameters suggest weak anisotropy in the investigated models these effective anisotropic parameters often used in vti tti do not sufficiently describe the effects of scale length anisotropy in heterogeneous media that show such local amplitude travel time and phase distortions in the wavefields numerical investigations on the implications for reverse time migration rtm routines corroborate that mean p wave velocity of the host rocks produces reliable imaging results based on the rtm results we postulate the following weak anisotropy in hardrock environments is a sufficient assumption for processing seismic data and seismic scattering effects due to velocity heterogeneity with a dip component is not sufficient to cause mislocation errors of target structures as observed in the discrepancy between the location of the strong seismic reflections associated to the matagami sulfide orebody and its true location future work will investigate other factors that may provide plausible explanations for these mislocation problems with the objective of providing a mitigation strategy for incorporation into the seismic data processing sequence when imaging in hardrock settings

time lapse wave equation migration velocity analysis abstracttime lapse 4d analysis of seismic data acquired at different stages of hydrocarbon production or gas fluid injection has been very successful at imaging detailed reservoir changes conventional time domain analysis of 4d data sets usually assumes a linear perturbation about a reference baseline earth model however this assumption is violated when production injection significantly alters the subsurface generating large 4d velocity changes time shifts and complicated 4d wavefield coda necessitating a more robust 4d analysis involving prestack wave equation depth migration and velocity analysis we address these situations by extending conventional 3d wave equation migration velocity analysis wemva based on one way wave equations and single scattering theory to 4d velocity estimation using a parallel inversion approach involving parallel solution of two separate inversion problems recognizing that the 4d wemva strategy requires precomputed baseline monitor image difference volumes we de

three dimensional reverse time migration of ground penetrating radar signals three dimensional 3d ground penetrating radar gpr systems and 3d seismic imaging techniques have been developing fast and evolving rapidly in the last decade ray based migration methods have been successfully applied to processing 3d gpr signals based on the similarity between electromagnetic and seismic waves however reverse time migration rtm of 3d gpr signals has not been well studied in the past in this paper we present a 3d rtm based on maxwell s equations for 3d gpr surveys migration recovers the true subsurface structure from a distorted and unfocused time profile and suppresses common electromagnetic clutter and noise rtm based on maxwell s equations can consider conductivity directly and compensate for the attenuation within a high conductivity zone compared with 2d rtm 3d rtm back propagates both in line and cross line signals simultaneously and can include complex 3d permittivity and conductivity models we have integrated a parallel finite difference time domain fdtd algorithm based on a hybrid mpi and openmp scheme to reduce the computational cost of 3d problems the 3d rtm experiments on an anomaly of em shape and a realistic sand dune model demonstrate the effective recovery of 3d subsurface structures

depth migration of imaged time sections none of the leading approaches to the migration of seismic sections the kirchhoff summation method the finite difference method or the frequency domain method readily migrates seismic reflections to their proper positions when overburden velocities vary laterally for inhomogeneous media the diffraction curve for a localized buried scatterer is no longer hyperbolic and its apex is displaced laterally from the position directly above the scatterer hubral observed that the kirchhoff summation method images seismic data at emergent image ray locations rather than at the desired positions vertically above scatterers in addition distortions in diffraction shapes lead to incorrect imaging i e incomplete diffraction collapse and hence to further displacement errors for dipping reflections the finite difference method has been believed to continue waves downward correctly through inhomogeneous media in conventional implementations however both the finite difference method and frequency domain a

the sedimentary flux of dissolved rare earth elements to the ocean abstract we determined pore fluid rare earth element ree concentrations in near surface sediments retrieved from the continental margin off oregon and california usa these sites represent shelf to slope settings which lie above within and below the oxygen minimum zone of the northeast pacific the sediments are characterized by varying degrees of net iron reduction with pore fluids from the shelf sites being generally ferruginous and the slope sediments having less pronounced iron reduction zones that originate deeper in the sediment package ree concentrations show maxima in shallow upper 2 10 cm subsurface pore fluids across all sites with concentrations that rise more than two orders of magnitude higher than seawater these pore fluid enrichments highlight the importance of a sedimentary source of rees to the ocean s water column here we use our measurements to estimate the diffusive flux of nd out of ocean sediments resulting in a global flux between 18 and 110 10 6 mol nd yr 1 while we do assume that our pore fluid profiles as well as the very limited data previously published are representative of a wide array of ocean environments this calculated flux can account for the modeled missing nd source flux 76 10 6 mol nd yr 1 in global budgets arsouze et al 2009 pore fluid normalized ree patterns show distinct variation in the middle ree and heavy ree enrichments with sediment depth and amongst sites these patterns show that the heavy ree enrichment of pore fluids at our deep slope site 3000 m water depth is closest to the heavy ree enrichment of seawater this observation supports the view that ree cycling within the upper ten centimeters of deep sea marine sediments as opposed to shallower continental shelf and slope sediments plays a significant role in controlling the integrated global ree flux from the pore fluids and consequently the broad scale ree pattern in seawater

possible source of advected water mass and residence times in the multi structured sea of japan using rare earth elements 1 the sea of japan is a small fast acting model of global oceanic circulation observations from 1998 and 2001 are analyzed to clarify its circulation new bottom water formed in early 2001 off vladivostok was observed later that year near the southeastern edge of the japan basin implying a velocity of 2 3 3 9 cm s 1 tb yb patterns of rare earth elements distinguish two classes of water volume inactive old well mixed water and active relatively young water frequently affected by the subduction of the surface water originating from tsushima warm current twc the proportion of twc to old water and each residence time are 50 75 and 15 years 200 400 m and 35 80 and 38 years 600 1500 m using six strata an improved estimate of the average residence time of japan sea proper water is 86 years this includes the contributions from active and inactive strata

elastic full waveform inversion application using multicomponent measurements of seismic data collection abstractrecent computational improvements allowed us to simulate elastic wavefields in a 3d manner and undertake the challenge of executing elastic full waveform inversion efwi the 3d seg eage overthrust synthetic data were used to run the initial tests which included using all three components for the simulation the inversion targeted two regions the channel system and the overthrusted zone which proved the effectiveness of efwi to delineate geology in terms of vp and vs velocity fields for the field data experiment to demonstrate the technologies we elected to use a gulf of mexico ocean bottom cable data set which allowed us to take advantage of relatively large offsets along with the 4c acquisition the input data were minimally processed mostly through noise removal and the initial model was a gaussian smoothed version of grid tomography output which is done by a prestack migrated gather flattening process during ewfi a multiscale approach was followed to ensure convergence and the earl

importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in the northeastern indian ocean vertical profiles of dissolved rare earth elements rees were obtained in the bay of bengal and the andaman sea the ree concentrations at various depths in the bay of bengal are the highest in the indian ocean this is attributable ultimately to the large outflow of the ganges brahmaputra and irrawaddy rivers but the dissolved ree flux to surface waters alone cannot explain the large and near constant ree enrichment throughout the entire water column the underlying fan sediments serve as not a source but a sink for dissolved ree iii s absence of excess 228ra in the deep waters suggests that lateral input of dissolved rees from slope sediments is also small in these regions partial 0 3 dissolution of detrital particles which are carried by the rivers and lateral surface currents and subsequently settle through the water column appears to be a predominant source for the dissolved rees vertical profiles showing an almost linear increase with depth are common features for the light and middle rees everywhere but their concentration levels are variable from basin to basin and from element to element this suggests that their oceanic distributions respond quickly to the variation of particle flux and its ree composition through reversible exchange equilibrium with suspended and sinking particles much like the case for th the relative importance of the vertical geochemical processes of reversible scavenging over the horizontal basin scale ocean circulation with passive regeneration like nutrients decreases systematically from the light to the heavy rees using a model the mean oceanic residence times of rees in the bay of bengal are estimated to range from 37 years for ce to 140 1510 years for the strictly trivalent rees in the deep water of the andaman sea isolated from the bay of bengal by the andaman nicobar ridge maximum sill depth of 1800 m the ree concentrations are almost uniform presumably due to rapid vertical mixing the ree iii concentrations are similar to that of 1250 m depth water in the bay of bengal consistent with other oceanographic properties however the ree composition of the deep water appears to be altered slightly by preferential scavenging of the light ree iii at the bottom boundary of the basin

tomographic imaging of velocity and q with application to crosswell seismic data from the gypsy pilot site oklahoma the centroid frequency shift method is implemented tested with synthetic data and applied to field data from three contiguous crosswell seismic experiments at the gypsy pilot in northern oklahoma the similtaneous iterative reconstruction technique is used for tomographic estimations of both p wave velocity and q no amplitude corrections or spreading loss corrections are needed for the q estimation the estimated in situ velocity and q distributions correlate well with log data and local lithology the q velocity ratio appears to correlate with the sand shale ratio ranging from an average of 15 s km for the sand dominated lithologies to an average of 8 5 s km for the shale dominated ones with the result that new information is provided on interwell connectivity

changes in seawater n p ratios in the northwestern pacific ocean in response to increasing atmospheric n deposition results from the east japan sea an increase in seawater n p ratios due to enhanced atmospheric n deposition has recently been reported in the northwestern pacific ocean including the east japan sea in the pacific ocean the east sea is an ideal site to examine this effect since it is fed by the pacific surface water which has very low n concentrations relative to p concentrations n p 5 and is located in the downwind area of major n emission sources in china and korea in addition the east sea is semi enclosed without any major river inputs resulting in a long surface water residence time 2 yr for the upper 0 200 m layer vertical and horizontal distributions of nutrients determined in the east sea from 2001 to 2009 showed that the n p ratios were always lower than 10 in the mixed layer 10 30 m and constant n p 13 1 in the deep ocean 200 3500 m a simple mass balance box model shows that the combined effects of physical the rapid ventilation of the surface water with a n p ratio of 10 into the deep ocean and biological remineralization of sinking organic matter processes result in the low n p ratios 13 over the deep water column of the east sea this model predicts that n p ratios in the east sea will be lower than 14 within the predictable range of atmospheric n input in the next 100 yr indicating that the n limited condition in the northwestern pacific ocean cannot be shifted to the p limited condition in the near future

calcite dust and the atmospheric supply of nd to the japan sea abstract we report neodymium concentrations and isotope ratios e nd measured in the carbonate and silicate fractions of chinese loess the goal of the study is to investigate if the atmospheric supply of dissolved calcite dust to the oceans influences the cycling of nd in seawater we primarily focus on the japan sea because it receives large quantities of dust from eastern asia and it has a known nd isotope composition and a simple hydrologic budget a steady state atmospheric transport model is used to calculate the flux of soluble nd delivered to the japan sea surface by the wet deposition of dissolved calcite dust this information is then incorporated in a steady state two box model in order to evaluate controls on dissolved e nd values as well as to calculate the residence time of nd in seawater on average calcite in fresh chinese loess contains 150 nmol of nd g 1 with an e nd of 8 6 the atmospheric input of dissolved calcite to the japan sea surface is 7 4 10 12 g yr 1 which corresponds to a dissolved nd flux of 1 1 10 18 pmol yr 1 this flux represents the largest input of nd to the basin and it is required to produce the e nd composition of japan sea waters approximately 65 of the nd flowing from the japan sea surface into the western north pacific originates directly from the input of dissolved calcite dust downwelling surface water and the remineralization of settling particles containing nd scavenged from surface water contribute 77 of the nd in the japan sea deep which indicates that 50 of the deep nd originates from calcite dust the e nd composition of deep water is balanced by a benthic flux but the input is a factor of 10 lower than the calcite dust flux and accounts for only 23 of the deep nd surface and deep waters in the japan sea have nd residence times with respect to particle scavenging of 14 and 530 yr respectively these findings reveal that the atmospheric supply of dissolved calcite dust to the japan sea is a more important component of the marine nd cycle in this basin than previously recognized

elastic full waveform inversion of multicomponent ocean bottom cable seismic data application to alba field u k north sea elastic full waveform inversion of multichannel seismic data represents a data driven form of analysis leading to direct quantification of the subsurface elastic parameters in the depth domain previous studies have focused on marine streamer data using acoustic or elastic inversion schemes for the inversion of p wave data in this paper p and s wave velocities are inverted for using wide angle multicomponent ocean bottom cable obc seismic data inversion is undertaken using a two dimensional elastic algorithm operating in the time domain which allows accurate modeling and inversion of the full elastic wavefield including p and mode converted ps waves and their respective amplitude variation with offset avo responses results are presented from the application of this technique to an obc seismic data set from the alba field north sea after building an initial velocity model and extracting a seismic wavelet the data are inverted instages in the first stage the intermediate wavelength p wave v

receiver coupling effects in seismic waveform inversions seismic waveform inversion offers opportunities for detailed characterization of the subsurface however its full potential can only be exploited when any systematic source and receiver effects are either carefully avoided or appropriately accounted for during the inversions repeated crosshole measurements in the mont terri switzerland underground laboratory have revealed that receiver coupling may significantly affect the seismic waveforms more seriously coupling conditions may vary during the course of a monitoring experiment to address this problem we have developed a novel scheme that estimates medium properties frequency dependent source functions and frequency dependent receiver coupling factors we demonstrate the efficacy of the new scheme via a synthetic 2d crosshole experiment in which realistic receiver coupling factors are incorporated because determination of medium parameters and estimation of source functions and receiver coupling factors are largely separated the method can be

reverse time migration migration of stacked or zero offset sections is based on deriving the wave amplitude in space from wave field observations at the surface conventionally this calculation has been carried out through a depth extrapolation we examine the alternative of carrying out the migration through a reverse time extrapolation this approach may offer improvements over existing migration methods especially in cases of steeply dipping structures with strong velocity contrasts this migration method is tested using appropriate synthetic data sets

large accumulation of anthropogenic co2 in the east japan sea and its significant impact on carbonate chemistry received 19 december 2005 revised 10 july 2006 accepted 26 july 2006 published 22 november 2006 1 this paper reports on a basin wide inventory of anthropogenic co2 in the east japan sea determined from high quality alkalinity chlorofluorocarbon and nutrient data collected during a summertime survey in 1999 and total dissolved inorganic carbon data calculated from ph and alkalinity measurements the data set comprises measurements from 203 hydrographic stations and covers most of the east sea with the exception of the northwestern boundary region anthropogenic co2 concentrations are estimated by separating this value from total dissolved inorganic carbon using a tracerbased chlorofluorocarbon separation technique wintertime surface cfc 12 data collected in regions of deep water formation off vladivostok russia improve the accuracy of estimates of anthropogenic co2 concentrations by providing improved airsea co2 disequilibrium values for intermediate and deep waters our calculation yields a total anthropogenic co2 inventory in the east sea of 0 40 0 06 petagrams of carbon as of 1999 anthropogenic co2 has already reached the bottom of the east sea largely owing to the effective transport of anthropogenic co2 from the surface to the ocean interior via deep water formation in the waters off vladivostok the highest specific column inventory vertically integrated inventory per square meter of anthropogenic co2 of 80 mol c m 2 is found in the japan basin 40n 44n comparison of this inventory with those for other major basins of the same latitude band reveal that the east sea values are much higher than the inventory for the pacific ocean 20 30 mol c m 2 and are similar to the inventory for the north atlantic 66 72 mol c m 2 the substantial accumulation of anthropogenic co2 in the east sea during the industrial era has caused the aragonite and calcite saturation horizons to move upward by 80 220 m and 500 700 m respectively these upward movements are approximately 5 times greater than those found in the north pacific both the large accumulation of anthropogenic co2 and its significant impact on carbonate chemistry in the east sea suggest that this sea is an important site for monitoring the future impact of the oceanic invasion of anthropogenic co2

image domain wavefield tomography with extended common image point gathers waveform inversion is a velocity model building technique based on full waveforms as the input and seismic wavefields as the information carrier conventional waveform inversion is implemented in the data domain however similar techniques referred to as image domain wavefield tomography can be formulated in the image domain and use a seismic image as the input and seismic wavefields as the information carrier the objective function for the image domain approach is designed to optimize the coherency of reflections in extended common image gathers the function applies a penalty operator to the gathers thus highlighting image inaccuracies arising from the velocity model error minimizing the objective function optimizes the model and improves the image quality the gradient of the objective function is computed using the adjoint state method in a way similar to that in the analogous data domain implementation we propose an image domain velocity model building method using extended common image point space and time lag gathers constructed sparsely at reflections in the image the gathers are effective in reconstructing the velocity model in complex geologic environments and can be used as an economical replacement for conventional common image gathers in wave equation tomography a test on the marmousi model illustrates successful updating of the velocity model using commonimage point gathers and resulting improved image quality

coseismic slip distribution of the 1923 kanto earthquake japan 1 the slip distribution associated with the 1923 m 7 9 kanto japan earthquake is reexamined in light of new data and modeling we utilize a combination of first order triangulation second order triangulation and leveling data in order to constrain the coseismic deformation the second order triangulation data which have not been utilized in previous studies of 1923 coseismic deformation are associated with only slightly smaller errors than the first order triangulation data and expand the available triangulation data set by about a factor of 10 interpretation of these data in terms of uniform slip models in a companion study by nyst et al shows that a model involving uniform coseismic slip on two distinct rupture planes explains the data very well and matches or exceeds the fit obtained by previous studies even one which involved distributed slip using the geometry of the nyst et al two plane slip model we perform inversions of the same geodetic data set for distributed slip our preferred model of distributed slip on the philippine sea plate interface has a moment magnitude of 7 86 we find slip maxima of 8 9 m beneath odawara and 7 8 m beneath the miura peninsula with a roughly 2 1 ratio of strike slip to dip slip motion in agreement with a previous study however the miura slip maximum is imaged as a more broadly extended feature in our study with the high slip region continuing from the miura peninsula to the southern boso peninsula region the second order triangulation data provide good evidence for 3 m right lateral strike slip on a 35 km long splay structure occupying the volume between the upper surface of the descending philippine sea plate and the southern boso peninsula

dissolved aluminum indium and cerium in the sea of japan and the sea of okhotsk comparison to the marginal seas of the western north pacific 1 dissolved aluminum indium and cerium were measured in seawater from the sea of japan and the sea of okhotsk surface maxima of al in the eastern japan basin indicate a signature of atmospheric mineral dust deposition resembling that of in data from all stations in this study show that ce was markedly high in well oxygenated bottom waters the ce al ratios of settling particles and surface sediments implicate the benthic flux of ce as its cause the in al ratios found in this study are not as high as those of the south china sea and sulu sea suggesting the minor influence of atmospheric deposition on the in al ratios in seawater fractionation between in and al during scavenging processes in addition to input from the bottom sediment might contribute to the in enrichment of seawater apparent differences between in and ce distributions in the marginal seas show that the benthic supply mechanism of in is not merely a simple redox related process

improving the greater k2 area subsalt imaging with advanced seismic acquisition model building and imaging technologies a gulf of mexico case study subsalt imaging has proven challenging in part because of the complex geometries of the salt canopies which can yield highly variable illumination on subsalt reflectors the resulting complexity of the seismic wavefields has also challenged traditional velocity model building tools and migration algorithms a case study for the k2 field illustrates how improved seismic data in the form of long offset full azimuth acquisition and more advanced model building and imaging tools have substantially enhanced the imaging quality of this major subsalt field the higher fold and more complete azimuthal coverage afforded by the full azimuth coil data improved the effectiveness of the combined tomographic and full waveform inversion approach for velocity model building utilization of tti rtm migration algorithms provided further benefits not only for better delineation of the salt geometry during model building but also in delivering superior final image volumes relative to that which could be provided by less robust algorithms such as kirchhoff beam and one way wave equation

226ra in the japan sea and the residence time of the japan sea water abstract the surface water of the japan sea contained 226 ra of 70 4dpm m 3 which was nearly equal to that of the surface water in the north pacific the concentration of 226 ra in the japan sea deep water below 500 m was 151 8dpm m 3 showing a vertically and regionally small variation this concentration of 226 ra in the deep water is unexpectedly high because the japan sea deep water has a higher 14 c value by about 50 than the atlantic deep water containing the same 226 ra one of the causes to be considered is larger contribution of 226 ra from biogenic particles dissolving in the japan sea deep water but the japan sea is not so fertile in comparison to the bering sea the other more plausible cause is the internal ventilation of the japan sea water which means that the residence time of the japan sea proper water is considerably long although the water is vertically mixed fairly well especially in winter the ventilation may supply some amounts of radiocarbon and oxygen but does not change the inventory of 226 ra the residence times of the japan sea deep water and of water within the japan sea are calculated by solving simultaneous equations for 226 ra and 14 c with a three box model to be 300 400 years and 700 1000 years respectively

flux and stable c and n isotope composition of sinking particles in the ulleung basin of the east japan sea seasonal variability of sinking fluxes of total mass tmf particulate organic carbon and nitrogen poc and pon was examined using sinking particles collected from sediment traps during july 2011 to december 2011 and december 2012 to june 2013 at an offshore channel site and from november 2013 to august 2014 at a nearshore slope site of the ulleung basin in the east japan sea 13c and 15n values of sinking particles were measured to elucidate the major export processes of poc and pon annual tmf 112 638 g m 2 yr 1 and fluxes of poc and pon 9 6 32 1 g c m 2 yr 1 and 1 2 4 5 g n m 2 yr 1 respectively in the ulleung basin corresponded to the upper limit of values reported for other open seas and oceans in the world no great seasonal variability in both quantitative tmf and fluxes and contents of poc and pon and qualitative c n ratios and 13c and 15n values estimates of vertical fluxes was observed reflecting a steady standing stock of chlorophyll a in the upper part of water column furthermore high contents of poc and pon and nearly constant 13c and 15n values in sinking particles collected in the sediment traps indicate that primary production in the euphotic zone may be a good predictor of tmf and export flux of organic matter in this regard our pilot study points out the importance of high annual primary production and low water temperature 1 c beneath the 200 m water depth which would enable more sinking particles to be preserved during export process by limiting microbial decomposition activity in the water column in determining the high annual flux of sinking particles in the ulleung basin ub a simple stable isotope mixing model of sinking particles indicates that despite a slight seasonal variation the contribution of intact phytoplankton to sinking organic flux is significant to the poc and pon flux in the ub further continuous time series sediment trap experiments are proposed to estimate the contribution of allochthonus sources such as lateral advection through resuspended clay mineral and aeolian and terrestrial inputs to the sedimentary flux

neodymium isotopic composition and concentration in the western north atlantic ocean results from the geotraces ga02 section the neodymium nd isotopic composition of seawater is commonly used as a proxy to study past changes in the thermohaline circulation the modern database for such reconstructions is however poor and the understanding of the underlying processes is incomplete here we present new observational data for nd isotopes and concentrations from twelve seawater depth profiles which follow the flow path of north atlantic deep water nadw from its formation region in the north atlantic to the northern equatorial atlantic samples were collected during two cruises constituting the northern part of the dutch geotraces transect ga02 in 2010 the results show that the different water masses in the subpolar north atlantic ocean which ultimately constitute nadw have the following nd isotope characteristics upper labrador sea water ulsw end 14 2 0 3 labrador sea water lsw end 13 7 0 9 northeast atlantic deep water neadw end 12 5 0 6 northwest atlantic bottom water nwabw end 11 8 1 4 in the subtropics where these source water masses have mixed to form nadw which is exported to the global ocean upper nadw is characterised by end values of 13 2 1 0 2sd and lower nadw exhibits values of end 12 4 0 4 2sd while both signatures overlap within error the signature for lower nadw is significantly more radiogenic than the traditionally used value for nadw end 13 5 due to the dominance of source waters from the nordic seas nwabw and neadw comparison between the concentration profiles and the corresponding nd isotope profiles with other water mass properties such as salinity silicate concentrations neutral densities and chlorofluorocarbon cfc concentration provides novel insights into the geochemical cycle of nd and reveals that different processes are necessary to account for the observed nd characteristics in the subpolar and subtropical gyres and throughout the vertical water column while our data set provides additional insights into the contribution of boundary exchange in areas of sediment resuspension the results for open ocean seawater demonstrate at an unprecedented level the suitability of nd isotopes to trace modern water masses in the strongly advecting western atlantic ocean

rare earth elements and yttrium in seawater icp ms determinations in the east caroline coral sea and south fiji basins of the western south pacific ocean abstract using inductively coupled plasma mass spectrometry icp ms vertical profiles of yttrium and all the rare earth elements rees in seawater were obtained at three locations in the western south pacific the east caroline coral sea and south fiji basins based on the data we have analyzed the inter ree iii relationships and found that ree iii s heavier than dy and particularly close neighbors show strong coherencies in their oceanic behavior considering that the heavy ree iii s are less particle reactive than the light and middle ree iii s and that they have very tight correlations with regressions passing almost through the origin the neighboring element ratios of the heavy ree iii s behave virtually conservatively and are suitable as tracers of water masses the dy ho er system is practically good because its dynamic range signal to noise ratio is large in the ocean the highest ho dy ratios 0 31 are found in intermediate and deep waters throughout the western south pacific which overlie the antarctic bottom water with a low ho dy ratio 0 27 these high ho dy waters are probably formed in the polar and subantarctic frontal zone and advect northward ree iii data provide better insights into the deep water recirculation in the south pacific than those discussed based upon the regular oceanographic properties alone

the effects of tsushima warm current on the interdecadal variability of the east japan sea thermohaline circulation 1 using a four box model with a throughflow system it is shown that changes in the tsushima warm current could induce thermohaline variability comparable to the ones observed in the northern deep part of the east japan sea when the current becomes stronger salt flux to the northern surface area becomes larger the vertical stability then weakens to produce warm and salty deep water through deep convection a few years after the maximum of the inflow if the inflow salinity varies synchronously as well deep convection could occur more easily interdecal variation in the atmospheric temperature also could induce thermohaline variability when the air temperature is low cold and fresh deep water would be formed therefore neither the intensification of the current during 90s nor atmospheric cooling could explain the cold and salty deep convection observed during 2000 2001 only when both effects are combined the observed deep convection could be properly explained

rare earth elements in pore waters of marine sediments abstract the rare earth elements rees were measured in pore waters of the upper 25 cm of sediment from one site off peru and three sites on the california margin the pore water ree concentrations are higher than sea water and show systematic down core variations in both concentration and normalized pattern from these analyses and from comparison to other chemical species measured dissolved fe mn ba oxygen nitrate phosphate it is suggested that pore water rees can be grouped into three categories those that are from an fe source those that are from a poc source and cerium oxide rees from the fe source appear where anoxia is reached they have a distinctive middle ree mree enriched pattern the concentrations in this source are so elevated that they dominate ree trends in the fe oxide reduction zone the net result of flux from the poc source is relative enrichment of heavy rees hrees over light rees lrees reflecting remineralizing poc and complexation with doc a common linear ree pattern seen in both oxic and anoxic sediments is associated with this poc source as well as a hree enriched pattern that is seen in surficial sediments at the peru site overall the pore water results indicate that mn oxides are not an important carrier of rees in the oceans a ree biogeochemical model is presented which attempts to reconcile ree behavior in the water and sediment columns of the oceans the model proposes that poc fe oxide and ce oxide sources can explain the ree concentration profiles and relative abundance patterns in environments ranging from oxic sea water to anoxic pore water the model is also consistent with our observation that the ce anomaly of pore water does not exceed unity under any redox condition

depositional environments and ichnology of the deep marine succession of the amiran formation upper maastrichtian paleocene lurestan province zagros fold thrust belt iran abstract the paleoenvironmental significance of deep marine trace fossil assemblages in the upper maastrichtian paleocene amiran formation has been done for the first time in lurestan province nw zagros from the zagros fold thrust belt a semi quantitative study of trace fossil abundance bioturbation indices in the amiran formation shows that trace fossil assemblages can be very powerful discriminators of deep marine clastic fan and related environments the amiran formation is a sand rich thick bedded and coarse grained turbidite succession deep marine paleoenvironments from basin slope to basin floor settings are preserved these strata contain a diverse and abundant pre and post depositional ichnofauna proximal and axial parts of the sandy systems show low diversity and low density trace fossil assemblages dominated by post depositional trace fossils but distal environments show a general increase in trace fossil diversity abundance and number of pre depositional trace fossils the post depositional association essentially consists of dwelling feeding and grazing traces the pre depositional assemblage is rich in graphoglyptids and grazing trails and feeding structures also occur the ichnodiversity composition ethology and morphologic complexity of the pre depositional association of the heterolithic successions of thin to thick bedded turbidite sandstone and inter turbidite mudstone are characteristic of three ichnosubfacies of the nereites ichnofacies these ichnosubfacies are identified in amiran formation deposits the typical succession of ichnosubfacies can express a bathymetric trend from shallower to deeper parts and from higher to lower hydrodynamic conditions they are 1 the ophiomorpha rudis ichnosubfacies the proximal and axial parts with thick bedded channel and lobe related environments 2 the paleodictyon ichnosubfacies channel lobe transition in the distal lobe facies and 3 the nereites ichnosubfacies distal part of off axis lobe or fan fringe basin floor transition and overbank settings there is also mixed o rudis to paleodictyon ichnosubfacies channel margin lobe fringe in the proximal lobe facies the dominance of zoophycos and chondrites in poor oxygen basin floor facies may represent zoophycos ichnofacies the number of graphoglyptids increases from distal basin floor to proximal fan fringe basin floor transition fan fringe lobe complex fringe lobe complex off axis settings they are absent in the most proximal axial lobe environments due to increased volume frequency erosive power of turbidity current events and sedimentation rate grain size decreased preservation potential of shallow tier and pre turbidite trace fossils the ichnosubfacies method used here as utilized by other authors has the potential to improve paleoenvironmental analysis of other deep marine depositional settings and in outcrop investigation of turbidite systems

estimated source wavelet incorporated reverse time migration with a virtual source imaging condition manygeophysicistsperformreverse timemigrationusingavarietyofartificialsources to obtain the source wavefield upon processing the seismic data however it is difficult to recover the original phase and amplitude of the source wavelet used for seismic exploration regardless of the source we have therefore used several artificial source wavelets such as ricker or the first derivative gauss wavelets expressed by well known functions there are some differences between these artificial source wavelets and the original source wavelets resulting in imperfect migration images artificial source wavelets tend to distort the exact location of subsurface reflectors and they create noise around the boundary of the stratum to solve this problem we applied the source estimation technique to the reverse time migration algorithm the source estimation technique approximates the source wavelet to the original exploration source wavelet by a deconvolution method this technique is used in full waveform inversion and provides better inversion results as demonstrated by other studies toprovetheeffectofreverse timemigrationwithsourceestimation wetested this algorithm on the sigsbee2a model seg eage 3d salt model and 3d real field land data using the resulting images of these three models we found that the source estimation technique can yield better migration images to suppress the artefacts produced in the migration image we used a wavenumber filter and laplacian filter on 2d and 3d examples respectively furthermore we used the pseudo hessian similar to the source illumination to scale the migration image because the virtual source imaging condition was used for reverse time migration

traveltime information based wave equation inversion we propose a new wave equation inversion method that mainly depends on the traveltime information of the recorded seismic data unlike the conventional method we first apply a p transform to the seismic data to form the delayed shot seismic record back propagate the transformed data and then invert the velocity model by maximizing the wavefield energy around the shooting time at the source locations data fitting is not enforced during the inversion so the optimized velocity model is obtained by best focusing the source energy after a back propagation therefore inversion accuracy depends only on the traveltime information embedded in the seismic data this method may overcome some practical issues of waveform inversion in particular it relaxes the dependency of the seismic data amplitudes and the source wavelet

image registration guided wavefield tomography for shear wave velocity model building multicomponent acquisitions offer the opportunity to form elastic migration images and to estimate elastic parameters of the subsurface compared with better constrained p wave velocity inversions it is more difficult to estimate the s wave velocity due to strong nonlinearities introduced by converted s waves we have developed an iterative s wave velocity inversion method guided by image registration given an accurate p wave velocity and a simple initial s wave model we form p p and p s images using elastic reverse time migration we use image registration to find the shifts between the p s and p p images the s wave velocity model could be updated iteratively by minimizing the differences between the original and the fractionally warped p s images a simple layered model and a modified marmousi model are used to demonstrate the viability of the new method in both examples high quality p s images as well as smooth s wave velocity models are inverted efficiently with a homogeneous s wave initial model

3d acoustic reverse time migration1 acoustic reverse time finite difference migration for zero offset data is extended from two to three dimensional media the formulation is based on the full three dimensional acoustic wave equation and so has no dip restrictions and it involves extrapolation in a velocity distribution variable in three dimensions the algorithm is demonstrated by successful migration of synthetic data sets for three models a point diffractor an oblique pinch out and a dome overlying a planar reflector

the flow system in the japan sea caused by a sea level difference through shallow straits we investigate how the current system through the japan sea is driven and what determines the volume transport we suppose that a part of the difference in geopotential anomaly between the subtropical and subpolar gyre is converted into a barotropic sea level difference across the three shallow straits which connect the japan sea with the pacific and that this difference is the primary driving force of the current system then we examine the flow under the condition that there is a constant sea level difference between two oceans connected through a shallow strait we found that the strait acts as a source of arrested shelf waves or steady coastal flows for the timescale beyond the inertial period in the northern hemisphere steady flows are established along the shelves with the coast to the right left in the ocean of low high sea level we apply this notion to the current system through the japan sea the tsushima nearshore branch the tsugaru coastal mode and the soya current can all be interpreted as a coastally trapped flow whose source is the upstream strait further a series of northeastward flows along the south and east china seas shelves should be interpreted as coastally trapped flows whose source is the downstream tsushima strait numerical model experiments incorporating the realistic topography also simulate the observed flow fields the volume flux through each strait being limited geostrophically relations between the sea level difference and volume transport can be represented by simple formulas

migration by extrapolation of time dependent boundary values migration of an observed zero offset wavefield can be performed as the solution of a boundary value problem in which the data are extrapolated backward in time this concept is implemented through a finite difference solution of the two dimensional acoustic wave equation all depths are imaged simultaneously at time 0 the imaging condition and all dips right up to vertical are correctly migrated numerical examples illustrate this technique in both constant and variable velocity media

the geochemical balance of the rare earth elements and neodymium isotopes in the oceans profiles of ree concentrations and neodymium isotope measurements in the western indian ocean are consistent with published data from the other major oceans ree concentrations show a strong hydrographic control the influence of intermediate water masses is particularly significant surface water concentrations vary with salinity paniculate rees are less than 5 of dissolved concentration except for ce where up to 20 of total rees are present as 0 4 m particles in contrast to dissolved profiles concentration profiles of paniculate rees including ce all increase with depth ree concentrations correlate with silica over all but the deepest waters although in detail correlations are complex the neodymium isotopic composition of indian ocean seawater avg nd 0 8 3 is intermediate between that for the atlantic and pacific oceans comparison of ree data from the major oceans shows that the hrees behave more like si than do the lrees sm nd ratios are near constant for all oceans whereas ernd ratios vary between the atlantic indian and pacific oceans the fractionation of the rees in surface seawaters can be explained by fractionation factors relative to silica from 0 12 for la to 0 05 for er use of a seven box model shows that the interoceanic variations in neodymium isotopic compositions and nd concentrations cannot be reconciled unless particle water exchange is invoked the degree of exchange required is consistent with particle residence times of 1 10 yr

acoustic wave equation traveltime and waveform inversion of crosshole seismic data a hybrid wave equation traveltime and waveform inversion method is presented that reconstructs the interwell velocity distribution from crosshole seismic data this inversion method designated as wtw retains the advantages of both full wave inversion and traveltime inversion i e it is characterized by reasonably fast convergence which is somewhat independent of the initial model and it can resolve detailed features of the velocity model in principle no traveltime picking is required and the computational cost of the wtw method is about the same as that for full wave inversion we apply the wtw method to synthetic data and field crosshole data collected by exxon at their friendswood texas test site results show that the wtw tomograms are much richer in structural information relative to the traveltime tomograms subtle structural features in the wtw friendswood tomogram are resolved to a spatial resolution of about 1 5 m yet are smeared or completely absent in the traveltime tomogram this sugg

enhanced chlorophyll associated with island induced cyclonic eddies in the eastern channel of the tsushima straits the relationship between island induced cyclonic eddies and chlorophyll a chl a was investigated using field data and satellite images in the eastern channel of the tsushima straits the maximum chl a concentration around the leeward eddy of the tsushima islands was two or three times greater than that of outside the eddy two different mechanisms of chl a enhancement associated with island induced cyclonic eddies were found in the post bloom periods in summer when nutrients were depleted in the surface layer eddy pumping increased the nutrient supply in the euphotic zone resulting in enhanced chl a around the shallow thermocline near the eddy core in late autumn when the mixed layer deepened over the euphotic zone the mixed layer depth became shallow due to the doming effect of the cyclonic eddy therefore the improved irradiance condition led to an increase in the chl a concentration in the surface mixed layer nighttime satellite visible images showed a number of fishing vessels in the lee region of the tsushima islands implying that the enhanced phytoplankton biomass may have resulted in good feeding conditions for fishes and squids in the tsushima straits

rare earth elements and nd isotopes tracing water mass mixing and particle seawater interactions in the se atlantic abstract distributions of dissolved and particulate rare earth elements rees and seawater neodymium isotopic composition e nd were established in samples from the bonus goodhope bgh ipy geotraces cruise in the se atlantic sector of the southern ocean 36 s 13 e to 57 s 0 feb mar 2008 close to the south african continent in the subtropical domain particulate rees show the highest concentrations and flat paas normalized patterns clearly tracing their lithogenic origin active cerium oxidation onto suspended particles is evidenced by the mirror image relationship of the cerium anomaly between dissolved and particulate phases unradiogenic dissolved neodymium in surface waters e nd 17 1 traces the influence of old sedimentary material brought by the agulhas current and rings to the cape basin area a mass balance calculation suggests that the release of nd from dissolution of lithogenic material corresponds to a remobilization of 154 10 6 t of sediment per year i e 5 of the total sediment delivered to the southeast african coast annually at open ocean stations both dissolved and particulate rees present negative cerium anomalies indicating that particles have acquired a marine signature the increasing ree concentrations with depth and the strong linear correlations of dissolved ree with silica indicate that surface removal and deep re mineralisation of rees are partially related to the biogeochemical cycle of silicate which involves biogenic silica diatoms combined with marine carbonates these authigenic phases could explain the observed ree patterns in suspended particles except for la we suggest that the positive la anomalies in both phases are linked to the oceanic barium cycle and the partial dissolution of barite crystals especially in the polar frontal zone the e nd composition behaves conservatively in intermediate and deep waters while input processes affect the isotopic signal of subtropical surface waters and weddell gyre bottom waters an indian ocean and an atlantic variety of aaiw have been isotopically differentiated e nd 9 3 0 3 and e nd 8 0 0 5 respectively homogeneous signatures characterize circumpolar waters e nd from 8 2 to 8 4 for cdw a binary mixing model has been used to assess the contribution of undiluted nadw reaching southern latitudes

illuminating the near sonic rupture velocities of the intracontinental kokoxili mw 7 8 and denali fault mw 7 9 strike slip earthquakes with global p wave back projection imaging 1 the denali and kokoxili strike slip earthquakes are two of the longest recent intracontinental ruptures previous studies report a range of rupture velocities here we image these earthquakes by reverse time migration of the intermediate frequency p wave train recorded by global broadband seismometers this technique permits a relatively direct measure of rupture velocity speed and direction as constrained by the radiated seismic energy free from restrictive assumptions or rupture speed bounds placed on the solution we compare our results with published seismic gps displacement and surface slip inversion results both ruptures were initially subshear and transitioned over a distance no longer than 40 km to supershear speeds close to the p wave speed of 5 6 km s we investigate the accuracy of our results with synthetic data and experiment with using different imaging parameters and seismic subnetworks these tests allow us to rule out the possibility of subshear speeds along the supershear segments although we cannot exclude supershear speeds of 4 5 6 5 km s our most reliable rupture velocities of 5 6 km s are close to the local p wave speeds we hypothesize that these intracontinental faults have weak shear strengths or high breakdown slips or crustal rigidities and experience at least moderate slip or slip rate weakening our observations and previous published results lead us to speculate that very long surface extending faults with general homogeneity in prestress and fault strength together with smaller adjacent fault segments to provide triggering may be necessary ingredients for the sub rayleigh to supershear rupture speed transition in strike slip earthquakes

the 1923 kanto earthquake reevaluated using a newly augmented geodetic data set 1 this study revisits the mechanism of the 1923 ms 7 9 kanto earthquake in japan we derive a new source model and use it to assess quantitative and qualitative aspects of the accommodation of plate motion in the kanto region we use a new geodetic data set that consists of displacements from leveling and angle changes from triangulation measurements obtained in surveys between 1883 and 1927 two unique aspects of our analysis are the inclusion of a large number of second order triangulation measurements and the application of a correction to remove interseismic deformation the geometry of the fault planes is adopted from a recent seismic reflection study of the kanto region we evaluate the minimum complexity necessary in the model to fit the data optimally our final uniform slip elastic dislocation model consists of two adjacent 20 dipping low angle planes accommodating reverse dextral slip of 6 0 m on the larger eastern plane and 9 5 m on the smaller western plane with azimuths of 163 and 121 respectively the earthquake was located in the sagami trough where the philippine sea plate subducts under honshu compared to the highly oblique angle of plate convergence the coseismic slip on the large fault plane has a more orthogonal orientation to the strike of the plate boundary suggesting that slip partitioning plays a role in accommodation of plate motion what other structure is involved in the partitioning is unclear uplift records of marine coastal terraces in sagami bay document 7500 years of earthquake activity and predict average recurrence intervals of 400 years for events with vertical displacement profiles similar to those of the 1923 earthquake this means that the average slip deficit per recurrence interval is 50 of the relative plate convergence these findings of plate motion partitioning and slip deficit lead us to suggest that instead of a simple recurrence model with characteristic earthquakes additional mechanisms are necessary to describe the accommodation of deformation in the kanto region so far obvious candidates for these alternative mechanisms have not been discovered

mean residence time of the shelf water in the east china and the yellow seas determined by 228ra 226ra measurements increasing attention of oceanographers has recently been paied on east asian marginal seas regarding their role on the global environment yet geochemical investigations have been few to date we here report new data on the distribution of 228ra and 226ra in the surface water of the east china and the yellow seas in an effort to constrain the time necessary for the coastal and shelf waters to exchange with offshore waters such information is needed in evaluating the exchange of heat and water across the air sea interface that affects the local climate and the fate of pollutants nutrients and weathering products supplied from the continent based on the ra isotope signals we have estimated that the shelf water component contributes 20 of the tsushima current water passing through the tsushima strait and the mean residence time for the shelf water to mix with the kuroshio surface water is 2 3 years as many of materials derived from the continent such as heavy metals and the nutrients have their mean residence times less than a few months in the nearshore and shelf waters they must largely deposit on the shelf sediments prior to the transport from the shelf to the open sea by mixing

rare earth elements in the east sea japan sea distributions behaviors and applications abstract the distributions of rare earth elements rees were measured at 14 stations from 0 to 3365 m n 176 in the entire east sea for the first time the east sea has its own deep convection system which operates on a time scale that is approximately one tenth that of the global ocean it is also a downwind region of asian dust the vertical distributions of ree concentrations increased with depth similar to those in the north atlantic ocean however the concentrations of rees were 1 3 2 7 fold higher than those in the north atlantic ocean associated with relatively larger atmospheric depositions of dust from the asian continent in this environmental condition the removal of ce relative to the other rees was about an order of magnitude more efficient than that in the north pacific ocean as such in the deep layer below 750 m large increases of heavy rees hrees relative to light rees lrees opposite to the re mineralization trend were observed suggesting that lrees were preferentially re scavenged by sinking particles in addition the boundary scavenging of rees was also observed for all rees in the bottom layer of the east sea on the other hand the warm surface waters of rees tsushima warm water tww showed large fractionations relative to the other water masses this ree pattern traced the deep physical mixing proportions of tww up to 750 m 10 thus the unique distribution patterns of rees in this sea illustrate the geochemical scavenging characteristics of rees which are concealed in the major oceans as well as water mass mixing patterns in the upper ocean

online preconcentration icp ms analysis of rare earth elements in seawater the rare earth elements rees with their systematically varying properties are powerful tracers of continental inputs particle scavenging intensity and the oxidation state of seawater however their generally low pmol kg concentrations in seawater and fractionation potential during chemical treatment makes them difficult to measure here we report a technique using an automated preconcentration system which efficiently separates seawater matrix elements and elutes the preconcentrated sample directly into the spray chamber of an icp ms instrument the commercially available seafast system elemental scientific inc makes use of a resin with ethylenediaminetriacetic acid and iminodiacetic acid functional groups to preconcentrate rees and other metals while anions and alkali and alkaline earth cations are washed out repeated measurements of seawater from 2000 m water depth in the southern ocean allows the external precision 2 of the technique to be estimated at 23 for all rees and 15 for most comparison of nd concentrations with isotope dilution measurements for 69 samples demonstrates that the two techniques generally agree within 15 accuracy was found to be good for all rees by using a five point standard addition analysis of one sample and comparing measurements of mine water reference materials diluted with a nacl matrix with recommended values in the literature this makes the online preconcentration icp ms technique advantageous for the minimal sample preparation required and the relatively small sample volume consumed 7 ml thus enabling large data sets for the rees in seawater to be rapidly acquired

3d prestack plane wave full waveform inversion prestack depth migration has been used for decades to derive velocity distributions in depth numerous tools and methodologies have been developed to reach this goal exploration in geologically more complex areas exceeds the abilities of existing methods new data acquisition and data processing methods are required to answer these new challenges effectively the recently introduced wide azimuth data acquisition method offers better illumination and noise attenuation as well as an opportunity to more accurately determine velocities for imaging one of the most advanced tools for depth imaging is full waveform inversion prestack seismic full waveform inversion is very challenging because of the nonlinearity and nonuniqueness of the solution combined with multiple iterations of forward modeling and residual wavefield back propagation the method is computer intensive especially for 3d projects we studied a time domain plane wave implementation of 3d waveform inversion we found that plane wave gathers

separating biogeochemical cycling of neodymium from water mass mixing in the eastern north atlantic abstract the radiogenic neodymium nd isotope ratio 143nd 144nd expressed in e nd is being used as a tracer in paleo and modern ocean circulation however the mechanisms controlling input distribution and internal cycling are far from understood for example globally nd concentration nd commonly follows patterns of nutrient tracers generally increasing with depth below the thermocline while e nd tends to reflect the water masses which has often been referred to as the nd paradox here we present dissolved nd isotopes and concentrations at unprecedented vertical and spatial resolution from the eastern part of the us geotraces north atlantic zonal transect gulf of cadiz mauritanian shelf cape verde islands the nd of all samples ranges from 12 3 to 36 7 pmol kg with lowest nd usually found within the layer of highest chlorophyll a levels chl max suggesting removal through scavenging the nd isotope compositions range between e nd 13 4 and 9 9 with lower values at the surface within the extension of the saharan dust plume and a benthic nepheloid layer bnl less negative values are found in oligotrophic surface waters mediterranean outflow water mow and near the cape verde islands overall water mass mixing derived from e nd is best visible at the strait of gibraltar where mow enters the atlantic ocean most of the sub thermocline e nd varies within a small range with poor water mass distinction due to the dominance of north atlantic deep water high surface nd associated with more negative e nd is interpreted to be the result of dust deposition and dissolution local nd maxima with no apparent change in e nd compared to ambient seawater observed within a zone of minimum oxygen concentration omz at 500 m depth off mauritania suggest minor input of lithogenic nd but a rather high contribution through desorption of previously scavenged nd that is saharan dust in this area has only a minor influence on the isotope composition of water below the uppermost surface layer the low e nd values and elevated nd within the bnl on the other hand indicate release from detrital material our new high resolution dataset gives valuable insights into the nd distribution near continental margins influenced by high atmospheric inputs and changing oxygen conditions we show how vertical and lateral processes overlap to produce the observed nd distribution bringing us forward in understanding the nd paradox

a numerical study on the changjiang diluted water in the yellow and east china seas 1 a numerical simulation is performed using the princeton ocean model pom to investigate the behavior of the changjiang diluted water cdw and to evaluate the freshwater budget in the yellow and east china seas in addition the major process controlling the behavior of the cdw is discussed the simulated cdw distributions are fairly consistent with the observed distributions showing a remarkable seasonal variation the cdw extends to the northeast toward the tsushima korea straits during summer while it hugs the chinese coast to the southwest within a narrow band in winter tracer experiment is carried out to track the freshwater originating only from the changjiang and to evaluate the freshwater budget in the yellow and east china seas the result shows that about 68 percent of the changjiang discharge is transported through the tsushima korea straits and that about 27 percent is transported through the taiwan strait in autumn and winter to investigate the main process controlling the behavior of the cdw mentioned above another experiment is carried out without wind forcing it is found that the eastward extension of the cdw is strongly constrained by the taiwan tsushima warm current system over the shelf regime the wind is however responsible for the northeastward extension of the cdw in summer in addition the southwestward extension at the taiwan strait during winter is done by strong northeasterly monsoon the experiment without wind forcing shows that freshwater transport through the tsushima korea straits increases to 90 percent of the total changjiang discharge