spatio temporal structure of the pentadecadal variability over the north pacific abstract using a multi taper frequency domain singular value decomposition mtm svd a pentadecadal oscillation was detected in the winter spring sea level pressure slp field over the north pacific and surface air temperature in north america which was significant at the 95 confidence level the mtm svd captured the different slp and air temperature distributions between the winter and spring seasons in a consistent manner the pentadecadal slp signature in the spring season is centered nearer the west coast of north america than in the winter season this zonal displacement is consistent with the prominent springtime pentadecadal air temperature variability in mid latitude western north america a wavelet analysis of the pacific decadal oscillation index pdoi showed that the regime shifts in the 1920s 1940s and 1970s involved simultaneous phase reversals of the bidecadal and pentadecadal variations the two interdecadal variations are synchronized with one another such that a half period of the pentadecadal oscillation one epoch of an individual regime corresponds to one and half periods of the bidecadal oscillation these results are consistent with the wavelet analysis of the north pacific index npi similar resonance between the bidecadal and pentadecadal variations is evident in air temperatures over alaska the bidecadal and pentadecadal signals have different seasonality in these time series suggesting that although the two interdecadal variations arise from two different physical mechanisms they interact with each other the most distinct seasonal difference was observed in mid latitude western north america where the bidecadal variation prevails only in the winter season and the pentadecadal variation only in the spring season alaska air temperatures in the winter and winter spring of 1999 were the coldest since 1977 as were springtime air temperatures in mid latitude western north america in contrast to the warm anomalies that prevailed in this region during 1977 98 the npi and pdoi also exhibited an opposite polarity in 1999 to the respective regime mean polarities these anomalous conditions in winter and spring seasons of 1999 may signify a major regime shift in 1998 1999 in order to verify whether or not a regime shift did occur in 1998 1999 a careful examination of additional data in coming ten or so years will be necessary

the penetration of kuroshio water into the sea of japan abstract the nonlinear leakage of kuroshio water via the tsushima strait into the sea of japan is examined using a reduced gravity analytical model the flow in our conceptual model results from the zonal sea level difference between the pacific ocean and the sea of japan the landmasses separating the pacific from the adjacent sea of japan are represented by thin walls and the tsushima strait whose width is larger than the rossby radius is represented by a gap the gap is initially closed and the problem is treated as an adjustment process resulting from an abrupt opening of the gap steady analytical solutions for the final state associated with the adjustment are constructed using the integrated momentum equation on a plane conservation of energy and potential vorticity also a perturbation expansion in l f0 the ratio of the change in the coriolis parameter as one moves from the gap to the boundary current separation latitude to the coriolis parameter at the center of the gap is used

time space modeling of the dynamics of santorini volcano greece during the 2011 2012 unrest the 2011 2012 unrest of santorini thera volcano aegean sea greece was associated with microseismicity confined to the kameni line kl a major tectonovolcanic lineament and has been regarded as a single magmatic episode produced by a spherical source derived from inversion of gps data however such a source is a few kilometers away from the kl and cannot explain observed microseismicity for this reason we divided the unrest episode into five periods based on the fluctuations of seismicity and deformation rates and investigated the connection between seismicity and two spherical magmatic point sources for each period based on a new inversion algorithm and consistent gps data we recognized during the volcano unrest episode an unstable pattern of intrusions correlating with both the kl and columbo line cl a second major tectonovolcanic lineament intrusions correlating with cl appear relatively persistent aseismic small and shallow which is consistent with marine geophysical evidence for arrested shallow dykes and geodetic evidence from a previous inflation episode during the two periods of intense seismicity sources close to the kl explaining seismicity were obtained this unstable pattern of intrusions explains both the well observed location and timing of seismicity as well as ground deformation and is consistent with results of an okada type inversion for a sill and a dyke the stress interactions between the two sources agree with coulomb failure stress models santorini appears to be affected by concurrent offset magma pulses and only recent activity from a magma pulse below the kl produced microseismic swarms

wind and buoyancy forced upper ocean circulation in two strait marginal seas with application to the japan east sea 1 the wind and buoyancy forced upper ocean circulation in a marginal sea connected to the open ocean through two straits is investigated using idealized numerical and analytical models the study is motivated by the japan east sea jes and other marginal seas found along the western north pacific it is shown that for anticyclonic wind stress curl and atmospheric cooling in the marginal sea the inflow transport branches into eastern and western boundary currents in qualitative agreement with observed branching of the tsushima current in the southern jes the eastern boundary current arises because wind forcing in the open ocean and a circulation integral around the island that separates the marginal sea from the open ocean maintains the temperature on the island to be warmer than that found in the interior of the marginal sea buoyancy forcing in the marginal sea plays a key role in maintaining the eastern boundary current the dynamics that control the water mass transformation and downwelling are described and related to the model parameters the largest heat loss to the atmosphere is found in the eastern boundary current the exchange rates with the open ocean downwelling within the marginal sea and current structure within the marginal sea predicted by a linear analytic theory compare closely with results from a shallow water numerical model

volcanology greek inflation circa 1600 bc a petrology study of the bronze age minoan eruption on the greek island of santorini finds that the sub volcanic magma reservoir was recharged in spurts during the decades to months that preceded the eruption see letter p 77 timothy druitt and co authors have studied pre eruptive magmatic processes and their timescales using chemically zoned crystals from the late 1600s bc minoan caldera forming eruption on the island of santorini greece despite the large volume of erupted magma and the 18 000 year gestation period between the minoan and the previous major eruption recharge of the magma reservoir seems to have occurred during the century before eruption and mixing between different magma batches was still taking place during the final months these observations have implications for monitoring strategies at long dormant but potentially active caldera systems such as long valley in california yellowstone in wyoming and campi flegrei in italy

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

wind driven effects on the yellow sea warm current the yellow sea is a shallow basin writh an average depth of 44 m located between china and the korean peninsula one of the dominant ocean circulation features of the yellow sea is a warm wrater intrusion known as the yellow sea warm current this feature is present throughout the year but reaches its farthest northward extension in winter the circulation of the yellow east china and bohai seas was modeled using the princeton ocean model to better understand the dynamics of the yellow sea warm current the horizontal resolution of the model varies from 8 km in the yellow sea to 25 km in the east china sea twenty four sigma levels are used to define the vertical structure the model uses daily atmospheric forcing from the navy operational global atmospheric prediction system for 1993 open boundary conditions are applied at the taiwan strait the tsushima korea strait an area south of taiwan and the tokara strait with a closed boundary south of the ryukyu islands the model results are examined to determine the effect of the wind on the northward extension of the warm water intrusion using both water mass characteristics and northward velocity components sensitivity tests and spectrum analyses performed to study the influence of the wind on the yellow sea warm current show that winds modify the pathway and extent of the yellow sea warm current the current s origin however appears to be due to external forcing from the current systems developed in the east china sea

recent upward shift of the deep convection system in the japan sea as inferred from the geochemical tracers tritium oxygen and nutrients the thermohaline circulation system in the japan sea an almost land locked marginal sea in the northwest pacific is now in a transition state comparison of vertical profiles of tritium oxygen and nutrients between 1984 and 1998 demonstrates the following two points 1 the supply of dense surface seawater to the bottom layer 2 500 m in depth has almost ceased since 1984 and 2 the intrusion of surface seawater to an intermediate depth range between 700 m and 2 000 m in depth has been reinforced during this 14 year period such transitional upward shift of the thermohaline conveyor belt in the japan sea is thought to have separeted the bottom water from the conveyor belt and brought about a stagnant mode of the bottom water

progressive multiple event location pmel abstract this paper introduces a new method of using earthquake arrival times to simultaneously determine earthquake hypocenters and station corrections progressive multiple event location pmel forms a solution in three major steps 1 hypocenters are located by conventional single event methods using current station correction estimates 2 an annulled data set pavlis and booker 1980 is formed and accumulated using householder transformations and 3 station correction perturbations are calculated from a pseudoinverse solution of the annulled data set in practice pmel converges rapidly we analyze the non uniqueness of pmel estimates in terms of resolution and covariance matrices one of the most important features of pmel is the computer algorithm that we describe which requires only a modest amount of computer memory that is independent of the number of earthquakes to be processed consequently this algorithm can process a virtually unlimited number of earthquakes we apply pmel to a set of 8049 arrival times from 652 earthquakes and 4 explosions recorded by a network in the coso range inyo county california pmel converges after four adjustments to the station corrections the final rms misfit of 0 05 sec is remarkably good and the station correction estimates correlate strongly with surface geology

a linear stratified ocean model of the coastal undercurrent the linear stratified ocean model of mccreary 1981 is used to study the wind driven response of the ocean near an eastern coast the model can be regarded as an extension of the inviscid models of lighthill 1969 and of gill clarke 1974 that allows the vertical diffusion of heat and momentum into the deep ocean solutions are still found as expansions of vertical normal modes vertical mixing affects each mode as a linear drag with a drag coefficient that increases rapidly with mode number n a zonally uniform band of steady equatorward winds forces the ocean and the resulting flow field has many features in common with observations at eastern boundaries there is a surface equatorward jet and a poleward coastal undercurrent confined within 10 20 km of the coast both currents extend well poleward of the wind band upwelling does not reach great depths but occurs only above the core of the undercurrent weak downwelling occurs at greater depths there is offshore ekman drift in the surface mixed layer and return flow at a depth slightly above the core of the undercurrent the baroclinic alongshore pressure gradient field and the vertical mixing of heat and momentum are essential elements of the model dynamics but the beta and horizontal mixing are not low order vertical modes n 6 tend toward a two dimensional balance they generate the transverse circulation pattern associated with coastal ekman pumping

effect of the change of bottom depth on the penetration of kuroshio water onto the east china sea shelf 1 a theoretical problem of the penetration of a western boundary current driven by a cross stream sea level difference onto a shallow basin to the west of the current is put forth to account for the penetration of the kuroshio onto the east china sea ecs shelf and formation of the tsushima warm current different from previous studies this study assumes that the change of bottom depth is the primary factor determining the penetration for a given depth of the shallow basin the penetration depends on two external parameters speed of the western boundary current v0 and surface elevation of the current at the edge of the shallow basin z0 two penetration modes emerge depending on the magnitude of the inertia of penetration for sufficiently large inertia which is favored by large z0 and hindered by large v0 penetration occurs in the form of a free jet mode j otherwise it is in the form of a coastal current mode c volume transport of the penetration is maximized in mode j in general volume transport width and speed of the penetrating current increase with z0 although the latter two are slightly more dependent on v0 in mode c the model considered in this study predicts that the penetration of the kuroshio onto the ecs shelf is of mode j as indicated by observations the volume transport of the penetration is somewhat overestimated possibly because bottom friction is ignored in this model although this model is highly idealized it allows one to gain insight into the behavior of the kuroshio penetrating onto the shallow ecs shelf

on the branching of the kuroshio west of kyushu trajectories of satellite tracked surface drifters released in the continental margin area west of kyushu indicate a separation of the inshore side of the kuroshio that appears to form the beginning of the tsushima current the trajectories also indicate an anticyclonic sense of circulation in the area between the separated branch and the eastward directed kuroshio main stream consistent with long term geomagnetic electrokinetograph measurements of surface currents which show a broad southward flow along the west kyushu coast a theory is put forth that ties together these observed flow features in the theory the incidence is considered of an inertial current upon a step rise in topography characterized by a step depth of h0 to simulate the west kyushu coastal bathymetry in an f plane two layered inviscid ocean with a quiescent lower layer the inertial current is of a constant potential vorticity f h where h h0 is the undisturbed upper layer depth and is bounded inshore by a free streamline along which the upper layer depth is a constant hc h the steady state downstream configuration of a separation branch and a deflected main stream along the step is connected to the upstream approach current through the consideration of the constancy of the bernoulli function and the conservation of potential vorticity and mass in the immediate neighborhood of the incidence a complicated flow region is anticipated in which recirculation is featured and an anticyclonic gyre is expected further onto the step the volume integrated balance of along step momentum of the constant potential vorticity flow allows the determination of the angle the branch current makes with the step as a function of the angle of incidence and two depth ratios hc h and h0 h the bifurcation quotient defined as the ratio of the branch current transport to that of the approach current is found to be also such a function except it is independent of the incidence angle these functions yield results that are qualitatively in agreement with the observed bifurcation of the kuroshio west of kyushu that gives rise to the tsushima current

interannual variability of the korea strait bottom cold water and its relationship with the upper water temperatures and atmospheric forcing in the sea of japan east sea 1 a 35 yearlong temperature data set is analyzed to investigate the long term temperature variability in the korea strait and its relationship with the temperature variability in the upper layer of the sea of japan east sea the second cyclostationary empirical orthogonal function mode of the vertical temperature section in the korea strait describes the interannual variability of the korea strait bottom cold water ksbcw according to the corresponding principal component time series the strength of the ksbcw fluctuates yearly with a major spectral peak around 3 years multiple regression analysis shows that the interannual ksbcw variability is closely linked with the temperature variability in the southwestern region of the sea of japan east sea at about 50 100 m depth along 40 n the source of the ksbcw is traced at about 50 m extending eastward from the east coast of korea to about 135 e at 37 n the source is traced at a deeper level about 50 100 m confined more toward the east coast of korea with a hint of double core characteristics the interannual ksbcw variability is also related to the southward wind stress along the east coast of korea it appears that strong cooling warming of upper water temperature induced by the basin scale wind stress results in the interannual ksbcw variability this connection is verified by showing a reasonable interannual covariability between the ksbcw and the basin scale wind stress

improving local earthquake locations using the l1 norm and waveform cross correlation application to the whittier narrows california aftershock sequence experiments with different earthquake location methods applied to aftershocks of the october 1 1987 whittier narrows earthquake in california ml 5 9 suggest that local event locations can be greatly improved through the use of the l1 norm station corrections and waveform cross correlation the whittier narrows sequence is a compact cluster of over 500 events at 12 to 18 km depth located within the dense station coverage of the southern california seismic network scsn a telemetered network of several hundred short period seismographs scsn travel time picks and waveforms obtained through the southern california earthquake center are examined for 589 earthquakes between 1981 and 1994 in the vicinity of the mainshock using a smoothed version of the standard southern california velocity model and the existing travel time picks improved location accuracy is obtained through use of the l1 norm rather than the conventional least squares l2 norm approach presumably due to the more robust response of the former to outliers in the data a large additional improvement results from the use of station terms to account for three dimensional velocity structure outside of the event cluster to achieve greater location accuracy waveforms for these events are resampled and low pass filtered and the p and s wave cross correlation functions are computed at each station for every event pair for those events with similar waveforms differential times may be obtained from the cross correlation functions these times are then combined with the travel time picks to invert for an adjusted set of picks that are more consistent than the original picks and include seismograms that were originally unpicked locations obtained from the adjusted picks show a further improvement in accuracy location uncertainties are estimated using a bootstrap technique in which events are relocated many times for sets of picks in which the travel time residuals at the best fitting location are used to randomly perturb each pick improvements in location accuracy are indicated by the reduced scatter in the residuals smaller estimated location errors and the increased tendency of the locations to cluster along well defined fault planes median standard errors for the final inversion are 150 m in horizontal location and 230 m in vertical location although the relative locations within localized clusters of similar events are better constrained seismicity cross sections resolve the shallow dipping fault plane associated with the mainshock and a steeply dipping fault plane associated with a ml 5 3 aftershock these fault planes appear to cross and activity began on the secondary fault plane prior to the large aftershock

long term coastal upwelling over a continental shelf slope abstract long term coastal upwelling over a continental shelf slope with emphasis on the planetary dispersion of rossby waves is studied with numerical models the ocean is forced by a wind stress with a limited longshore extent the thermocline intersects the shelf slope and the internal radius of deformation is smaller than the width of the shelf slope two case studies with and without the effect are studied lie early stage response within a week or so is similar between the two for an f plane case the whole stage response is accounted for by coastal trapped wave dynamics and only equatorward flow exists over the shelf slope at an advanced stage however inclusion of the effect leads to a significant change in the alongshore flow pattern at the advanced stage due to the westward rossby dispersion of the equatorward flow associated with the first and second coastal trapped mode responses the poleward undercurrent develops in the thermocline layer over the shelf the time for the undercurrent

linkages between surface and deep circulations in the southern japan sea during the last 27 000 years evidence from planktic foraminiferal assemblages and stable isotope records abstract we analyzed planktic foraminiferal assemblages oxygen and carbon isotope records and the presence or absence of laminations to reconstruct the paleoenvironments of the southern japan sea since the last glacial period data were collected from two well dated cores one core water depth 999 m included thinly laminated mud layers the other water depth 283 m contained nonlaminated sediments tephrochronology and accelerator mass spectrometry 14 c dating of 14 horizons revealed that the two cores contained continuous records of the last 27 cal kyr a total of 13 planktic foraminiferal species belonging to six genera were identified in down core samples the typical indicators of the tsushima current water globigerinoides ruber neogloboquadrina dutertrei pulleniatina obliquiloculata globigerinoides tenellus and globigerinita glutinata occurred since 9 3 cal kyr bp neogloboquadrina incompta which was the dominant species in the tsushima current region of the modern japan sea first occurred at 8 2 cal kyr bp and dominated the assemblage since 7 3 cal kyr bp these results clearly indicate that the warm tsushima current started to inflow into the japan sea at 9 3 cal kyr bp and the modern surface conditions in the southern japan sea were essentially established at 7 3 cal kyr bp our data and comparison of the presence or absence of laminated sediments in three locations from the southern japan sea suggest that deep circulation during the deglacial period was weaker than that at present in addition deep circulation in the modern japan sea which supplies oxygen rich water to the entire basin started probably in association with the first inflow of the tsushima current beginning at 9 3 cal kyr bp

maximal wavelet filter and its application to bidecadal oscillation over the northern hemisphere through the twentieth century based on a wavelet transform a new method referred to as maximal wavelet filter mwf is proposed to extract temporal structure changes of a climatic oscillation which varies its pattern corresponding to the changes of the oscillation period the mwf is a bandpass filter having a narrow pass band the central frequency of which temporally varies according to the periods of maximal wavelet amplitudes for a specific region mwf is applied to wintertime sea level pressures slps in the northern hemisphere from 1899 to 2000 to extract slp changes associated with the bidecadal oscillation bdo which distributes globally but has the strongest amplitudes in the north pacific in the pacific sector the bdo center of action captured by the mwf was located over alaska in the first few decades of the record and then moved southward to the central north pacific from 1920 to 1950 with maximal bdo amplitudes in the middle of the century the southward migration was accompanied by the previously reported increase of the oscillation period from 15 to 20 years on the other hand atlantic slp variations coherent with the pacific bdo had large amplitudes in midlatitudes high latitudes in the early late part of the twentieth century in association with these spatial structure changes the pattern of the recent bdo resembles the pattern of the arctic oscillation the analysis of the sea surface temperatures ssts gridded from the comprehensive ocean atmosphere data set coads and the newly digitized kobe collections suggests that bdo pattern in the ssts also shifted toward the south between the first and last few decades of the twentieth century furthermore covariability between the land air temperatures and aleutian low strength is observed through the twentieth century for alaska but only after 1940 for the midlatitudes of western north america and hawaii indicating that the bdo influence was limited to the high latitudes in the first few decades of the twentieth century in these regions consistent with the spatial structure changes in the slp field over the north pacific

comparisons between observations and numerical simulations of japan east sea flow and mass fields in 1999 through 2001 abstract the princeton ocean model pom as implemented for the japan east sea jes with mesoscale admitting resolution is driven by seasonal throughflow and synoptic atmospheric forcing for 1999 through 2001 temperature and salinity profiles from shipborne and palace float ctds and horizontal velocities at 800 m from palace float trajectories plus horizontal velocities at 15 m from woce surface drifters for 1988 through 2001 are used to assess the performance of the numerical simulations for a base case general agreement exists in the circulation at 15 and 800 m and the horizontal and vertical structure of the upper ocean temperature and salinity fields the mean observed flow at 15 m defines the two branches of the tsushima warm current and hints at the existence of a large cyclonic gyre over the japan basin which the simulations also produce the mean observed flow at 800 m defines a large cyclonic recirculation gyre over the japan basin that validates the simulated flow pattern variances of the observed and simulated flows at 15 and 800 m have similar patterns the main discrepancies are associated with the strength of the seasonal thermocline and halocline and the location of the subpolar front when smoother topography and smaller lateral friction are used in other cases the thermocline and halocline strengthen agreeing better with the observed values and when 80 of total outflow transport is forced to exit through soya strait the subpolar front extends along the coast to the north of tsugaru strait which is an observed feature absent in the base case

inter annual and decadal sea level variations in the north western pacific marginal seas abstract long term sea level changes in the okhotsk japan east east china and yellow seas have been explored based on mean monthly values of sea level from tide gauge and altimetry measurements the analysis of low frequency sea level variability reveals clearly differentiated areas the okhotsk sea and the northern sector of the japan east sea display lower sea level variances and no sea level rise the southern japan east sea presents larger sea level variability associated with the circulation regime of the warm current entering through the tsushima strait and inter annual sea level variations that are driven by steric and atmospheric changes the largest sea level variances are found in the yellow sea due to the effect of atmospheric forcing over the continental shelf inter annual variability is spatially varying within the yellow sea and the east china sea and is mainly related to the steric sea level changes regional mean sea level indices have been synthesized for each area using the longest tide gauge records and have revealed correlations between the southern japan east and yellow seas with pdo and np climatic indices linear trends at coastal sites in the japan east east china and yellow seas show a rather heterogeneous pattern with values between 1 5 and 5 5 mm yr for the period 1960 2000 during the period 1993 2008 linear trends derived from coastal tide gauges and from altimetry observations are coherent and reveal a southwards increasing pattern with maximum averaged values reached at the yellow sea 4 9 1 9 mm yr followed by the japan east sea 3 8 0 9 mm yr decadal rates of sea level change show distinct behaviour among basins as well as with the global average the southern japan east sea the east china sea and the yellow sea display decadal variability which is out of phase with respect to the global values

observations of ice ocean eddy streets in the sea of okhotsk off the hokkaido coast using radar images abstract this study examines the features of fairly regular ocean wave motion in which some eddy streets or backward breaking waves are successfully visualized using sea ice floes as a tracer these examinations are made using the time sequence of radar imagery data collected during the past 20 years 1969 88 the correspondence of the radar images with the actual pattern is partially confirmed through aircraft observations the ice ocean eddy street or backward breaking wave pattern runs parallel to the coastline at a distance of about 20 km from the hokkaido coast the eddy street also corresponds to a boundary between the soya warm current and colder less saline offshore water the wave motion is characterized by wavelengths of 40 55 km phase velocities of 14 20 km day 1 and periods of 2 3 3 5 days the regular ice ocean wave motion pattern was observed when pack ice had a small ice concentration composed of uniform sized ice floes and weak winds the sea ice floes serve as a highly effective flow i

an east west contrast of upper ocean heat content variation south of the subpolar front in the east japan sea long term variability of nonseasonal ocean heat content ohc in the upper 500 m in the east japan sea ejs exhibits a distinct east west contrast during the recent 30 years the contrasting ohc variations are revisited and investigated more in detail by analyzing two observational data sets the gridded data from 1976 to 2007 and in situ data from 1976 to 2011 in the southwestern ejs that covers the zone of western boundary current the ohc variability shows in phase and predominant decadal variation in both east and west regions before 1995 but uncorrelated and predominant interannual variations after 1995 heaving effects due to major branches of warm currents in the ejs the east korea warm current ekwc in the western part and other two branches in the eastern part mainly contribute to the ohc variations the heaving effect in the western ejs is shown to be associated with changes in winter wind stress curl field in the northern ejs weakening of the subpolar gyre due to weakening of positive wind stress curl in the japan basin related with wintertime western pacific teleconnection pattern and siberian high appears to enhance the northward penetration of the ekwc resulting in an increase of ohc in the western ejs the heaving effect in the eastern ejs is significantly correlated with the siberian high but the causative mechanism is inconclusive this study also demonstrates the importance of using highly resolved data sets for areas affected by strong and narrow boundary currents in computing and understanding the ohc variability

the north pacific a global scale estuary abstract the atmospheric net flow of water from the atlantic to the pacific ocean is supposed to maintain the salinity difference between the two oceans assuming the existence of a subsurface level of no horizontal pressure gradient in the ocean the mean sea level in the northern pacific must be higher than in the arctic ocean this mean sea level difference is supposed to drive the observed mean flow through the bering strait the estimated flow of freshwater through the bering strait is approximately equal to the estimated atmospheric net flow of water from the north atlantic to the north pacific this justifies the formulation of a simple estuary model for the north pacific in which the brackish water exits through the bering strait the salinity difference between the two oceans is shown to be controlled by the topography of the bering strait the estuary model gives residence times for water in the upper layer 1000 m thick of approximately 1000 years and in the lower layer of approximately 400

subinertial to interannual transport variations in the korea strait and their possible mechanisms 1 the voltage derived transport in the korea strait from march 1998 to april 2002 reveals various temporal variations such as subinertial monthly seasonal and interannual variations the driving mechanisms of these temporal variations in the flows through the straits and the mean sea level of the east sea sea of japan are investigated using a simple analytical barotropic model the east sea is simplified as a flat bottomed semienclosed basin and it is forced by the atmospheric pressure the along strait wind stress and the sea level differences along the straits despite its simplicity this model explains most variations and helps us understand dominant driving forces on each timescale at the subinertial periods of 2 10 days the atmospheric pressure dominantly drives the flows into or out of the east sea due to a helmholtz resonance whose period is about 3 days and the mean sea level cannot respond isostatically the effects of the atmospheric pressure on the transport variations become weak at long periods because there is enough time for the east sea to be drained or filled through the strait flows as its mean sea level responds isostatically on the other hand the changes in the adjusted sea levels outside the straits of the east sea cause the pressure gradient forces along the straits and induce most of variations in the strait flows and the mean sea level at the monthly to interannual periods

interannual to interdecadal variability in the japan sea based on a new gridded upper water temperature dataset a new gridded water temperature dataset of upper 400 m depths 0 50 100 200 300 and 400 m for the japan sea or east sea is produced by using an optimal interpolation technique from 1930 to 1996 based on oceanographic observations collected in the world ocean database 1998 the temperature data are analyzed by a complex empirical orthogonal function ceof with six levels combined using the data for a period from 1957 to 1996 during which most of gridded data are available before calculating the ceofs low pass or highpass filters cutoff period at 7 yr are applied to separate interannual and decadal temperature changes respectively one interannual and two decadal ceof modes are identified the interannual first ceof mode is characterized by the energetic variability around and south of the subpolar front in the western japan sea accompanied by northward and northeastward phase propagations emanating from the tsushima strait the decadal first ceof mode exhibits a broad structure prevailing over the whole japan sea but large amplitudes are trapped by the subpolar front with 608 908 phase lags between the northeastern and southwestern japan sea the decadal second ceof mode has a localized structure with strong correlations in the yamato basin the relation between the atmosphere and ocean is analyzed by a correlation analysis of wintertime sea level pressures slps onto the temporal coefficients of the ceof modes the interannual first ceof mode is accompanied by the slp anomalies over the western north pacific ocean with steep slp gradients over the japan sea suggesting that this mode is forced by local wind anomalies associated with the slp changes over the western north pacific the decadal first ceof mode is likely to be caused by changes of the east asian winter monsoon due to the slp variability of the northern part of the siberian high which is closely associated with the decadal fluctuations of the arctic oscillation and the north atlantic oscillation the second decadal ceof mode is accompanied by high slp correlations over the central north pacific associated with strength changes of aleutian lows suggestive of remote forcing from the central north pacific

solar forcing of centennial scale east asian winter monsoon variability in the mid to late holocene abstract centennial scale variability of the east asian winter monsoon during the holocene is poorly understood because suitable archives and proxies are lacking here we present a high resolution 30 yr spacing planktonic foraminiferal o 18 record of neogloboquadrina incompta dextral form which reflects sea surface temperature during the winter season for the last 6000 yrs from marine sediments in the western north pacific stronger winter monsoons indicated by cooler winter ssts correspond to weaker summer monsoons indicated by the cave oxygen isotopes in centennial scale variability the variability also shows good correlation with o 18 records in lake sediments and ice cores from the yukon territory canada spanning the last 4500 yrs suggesting east west climate coupling across the north pacific furthermore the climate changes across the north pacific co vary over widespread regions such as the eastern tropical pacific and the northern red sea and the reconstructed solar activity the cross spectral and wavelet analyses show that the east asian winter monsoon shares some cyclicity with the solar variability our results suggest that the solar activity is a fundamental forcing producing the centennial scale eawm variability mediated by the large scale climate linkages

teleseismic location techniques and their application to earthquake clusters in the south central pacific abstract improved methods for single and multiple event hypocenter determinations are developed and applied to the problem of locating earthquake clusters in the south central pacific ocean bayesian statistical methods are used to incorporate a priori information about arrival time variance into the derivation of hypocenter confidence ellipsoids permitting a more realistic calculation of critical parameters in the case where the number of stations is small the diagonal elements of certain projection operators called data importances by minster et al 1974 are used to evaluate network balance the hypocentroid of an event cluster is defined to be the average location of events within the cluster and the deviations of individual hypocenters from the hypocentroid are called cluster vectors the problem of estimating the cluster vectors can be decoupled from the problem of estimating the hypocentroid by a simple but fundamental mathematical result here termed the hypocentroidal decomposition theorem the algorithm based on this analysis appears to have many advantages over other published methods for multiple event location both in its efficient use of available information and its computational speed the application of this method to three clusters of shallow intraplate seismicity in the south central pacific designated regions a b and c demonstrates that the seismicity within each cluster is very localized the rms lengths of the cluster vectors for each group of epicenters are estimated to be only 9 6 and 12 km respectively estimates of the epicentroids are

interannual variability of the kuroshio onshore intrusion along the east china sea shelf break effect of the kuroshio volume transport the interannual variability of the kuroshio onshore intrusion koi across the east china sea ecs shelf break and its response to the ecs kuroshio volume transport kvt during 1993 approximate to 2010 are studied based on a high resolution real time and global ocean general circulation model since variability of kvt is mainly determined in the interior pacific it is rather a remote than a local factor for the local ecs koi on interannual time scales kvt affects koi not only in the net volume transport across the entire shelf break but also in the spatial pattern along the shelf break when kvt increases the intrusion decreases increases upstream downstream of the major intrusion region northeast of taiwan the retreating increases decreases upstream downstream of the main veering region southwest of kyushu these patterns are caused by cyclonic eddies induced by the seaward deflection of the kuroshio axis from the shelf break which ultimately results from the kvt increase a diagnostic mechanism of koi approximate to msin delta h 1 is proposed where h is the bottom depth is the angle between isobaths and the vertically averaged current and m is the absolute volume transport at the shelf break is large in the major intrusion retreating regions and stable on interannual time scales while m changes with opposite signs between upstream and downstream of the major intrusion retreating regions the mechanism explains well the relation of local kvt and the spatial pattern of koi along the shelf break in both the mean state and the interannual variations

wind driven circulation in the japan sea and its influence on the branching of the tsushima current abstract seasonal variation in the wind driven circulation in the japan sea is studied with reference to the branching of the tsushima current using a two layer model with simplified bottom and coastal topography the system is driven by wind stress an inflow corresponding to the tsushima current and by the two outflows corresponding to the tsugaru and soya currents in the first phase an annual mean wind stress is imposed and a quasi stationary state is obtained in the next phase a seasonally varying wind stress is imposed seasonal variation in the wind stress plays an important role in the branching system of the tsushima current in winter an intensified western boundary current with a prominent inner circulation is formed as a result of a strong wind stress of winter monsoon with negative wind stress curl in spring to summer the western boundary current is weak but the topographic branch along the japanese coast is intensified the weak western boundary current is caused by weak wind stress with positive wind stress curl which induces cyclonic sverdrup flow in the japan sea and causes its western boundary current to flow in the opposite direction to the prescribed northward boundary inflow current the topographic branch is strongest in late spring and moves offshore in summer in agreement with the central branch denoted by kawabe 1982b some of the observational features of the tsushima current are successfully simulated

coastal trapped wave scattering into and out of straits and bays abstract a theory for the generation of coastal trapped waves ctws by an oscillatory coastal flux through a strait is extended so as to make velocity pressure and energy flux everywhere continuous this development is achieved through the inclusion of kelvin and poineare wave modes in a match for pressure leading to a system of linear equations for the unknown amplitudes a kelvin wave incident on the eastern mouth of bass strait for example is shown to preferentially scatter energy into ctw modes 2 and 1 on the shelf as well as driving a poincare wave field that results in a velocity jet trapped to the victorian coast such coastal velocity jets are also a feature of the scattering of ctws incident on a strait for a mode n incident ctw the fraction of net energy flux that enters the strait is also shown to be well approximated by h0bn2 where h0 is the strait depth and bn coupling coefficient the scattering of the remaining energy among other ctw modes is detailed and shown to become larger as the

decadal variability of the upper ocean heat content in the east japan sea and its possible relationship to northwestern pacific variability 1 the upper ocean heat content variability in the east japan sea was investigated using a 40 year temperature and salinity data set from 1968 to 2007 decadal variability was identified as the dominant mode of variability in the upper ocean 0 300 m aside from the seasonal cycle the decadal variability is strong to the west of northern honshu west of the tsugaru strait and west of southern hokkaido temperature anomalies at 50 125 m exhibit a large contribution to the decadal variability particularly in the eastern part of the east japan sea the vertical structure of regressed temperature anomalies and the spatial patterns of regressed 10 c isotherms in the east japan sea suggest that the decadal variability is related to upper ocean circulation in the east japan sea the decadal variability also exhibits an increasing trend which indicates that the regions showing large decadal variations experienced warming on decadal time scales further analysis shows that the decadal variability in the east japan sea is not locally isolated but is related to variability in the northwestern pacific

interannual to decadal variability in the southern okhotsk sea based on a new gridded upper water temperature data set 1 a new gridded water temperature data set of upper 200 m depths 0 50 100 200 m depths for the okhotsk sea was produced using an optimal interpolation technique from 1950 to 1996 using oceanographic observations in the world ocean database 1998 temperature variability at 50 100 and 200 m depths in the southern okhotsk sea south of 52 n in the warm season may october was investigated by an empirical orthogonal function eof analysis from 1958 to 1994 for which sufficient data exist for an eof analysis the first eof mode has a monopole structure with the maximal amplitude in the kuril basin and the corresponding principal component pc exhibits prominent quasi decadal variability the first eof mode is closely related with the wintertime december february sea surface temperature anomalies over the subarctic front or oyashio front in the north pacific and with wintertime sea level pressure slp differences between northern eurasia and the northern north pacific this suggests that the temperature changes in the okhotsk sea are caused by changes in the strength of the asian winter monsoon which are associated with the slp difference a quasi decadal oscillation similar to that of the pc 1 is observed in the slp difference since the 1960s and shared by the polar eurasian pol pattern arctic oscillation ao and north atlantic oscillation nao some hints of the relating variability are observed in coastal sea level difference between wakkanai and abashiri which was used as a proxy for transport in the soya warm current also some features of sea ice extents co vary with the pc 1

low frequency current observations in the korea tsushima strait abstract high resolution continuous current measurements made in the korea tsushima strait between may 1999 and march 2000 are used to examine current variations having time periods longer than 2 days twelve bottom mounted acoustic doppler current profilers provide velocity profiles along two sections one section at the strait entrance southwest of tsushima island and the second section at the strait exit northeast of tsushima island additional measurements are provided by single moorings located between korea and tsushima island and just north of cheju island in cheju strait the two sections contain markedly different mean flow regimes a high velocity current core exists at the southwestern section along the western slope of the strait for the entire recording period the flow directly downstream of tsushima island contains large variability and the flow is disrupted to such an extent by the island that a countercurrent commonly exists in the lee of the island the northeastern section is marked b

analysis of year to year variation of water temperature along the coast of the japan sea abstract mean monthly records of coastal sea surface temperature data csst obtained from stations along the japanese coasts of the japan sea and from those in the related seas for the period 1941 1984 were analyzed by using various methods of time series analysis for the purpose of clarifying the nature of the year to year variations of the state of the japan sea the year to year variations in the japan sea were found to be closely related to those in the east china sea and in the western north pacific specific results are as follows 1 a sudden cooling in the early 1960 s occurred in the southern stations of the japan sea and continued to the end of the analyzed data 2 variations with about a 6 year periodicity were observed at most stations and were especially dominant in the southern stations of the japan sea 3 these variations could be traced back to the kuroshio region of the east china sea 4 variations with about a 10 year periodicity were also observed in the northern stations of the japan sea

the annual cycle of the japan sea throughflow abstractthe mechanism responsible for the annual cycle of the flow through the straits of the japan sea is investigated using a two layer model observations show maximum throughflow from summer to fall and minimum in winter occurring synchronously at the three major straits tsushima tsugaru and soya straits this study finds the subpolar winds located to the north of japan as the leading forcing agent which first affects the soya strait rather than the tsushima or tsugaru straits the subpolar winds generate baroclinic kelvin waves along the coastlines of the subpolar gyre affect the sea surface height at the soya strait and modify the flow through the strait this causes barotropic adjustment to occur inside the japan sea and thus affect the flow at the tsugaru and tsushima straits almost synchronously the barotropic adjustment mechanism explains well why the observations show a similar annual cycle at the three straits the annual cycle at the tsugaru strait is further shown to be weaker than t

an estimate of the cross frontal transport at the shelf break of the east china sea with the finite volume coastal ocean model 1 the finite volume coastal ocean model fvcom is used to estimate the onshore cross frontal transport at the shelf break of the east china sea boundary conditions of fvcom are provided by the princeton ocean model simulating ocean currents in the yellow sea and east china sea realistically one advantage of this study is that the unstructured triangular cell grid of fvcom resolves complex bottom topography that may trigger kuroshio frontal waves it is anticipated that these nonlinear frontal waves enhance the exchange of seawater between the kuroshio and shelf regions kuroshio frontal waves in the model are excited around the location where the bottom slope changes abruptly and have the phase speed and amplitude consistent with those observed in the east china sea in addition the model reproduces the onshore transport associated with growing frontal waves in the upper and lower layers on the basis of passive tracer experiments the annually averaged onshore transport integrated along the shelf break is estimated to be 0 85 106 m3 s

seasonal circulation patterns of the yellow and east china seas derived from satellite tracked drifter trajectories and hydrographic observations abstract we investigated seasonal circulation patterns of the yellow and east china seas yecs by reviewing previous works on the circulation and its dominant currents and taking into account newly compiled trajectories of satellite tracked drifters collected between the 1980s and 2000s the circulation patterns suggested before the 1990s can be categorized into two groups depending on the identified origin of the tsushima warm current in the korea tsushima straits i branching from the kuroshio southwest of kyushu or ii northeastward continuation of the taiwan strait throughflow the branching of the kuroshio southwest of kyushu and northeast of taiwan was clearly evidenced by current measurements and concurrent hydrographic surveys however there is still no clear evidence for the northeastward pathway of taiwan strait throughflow across the mid shelf area of the east china sea target oriented surveys in the 1990s and 2000s employing advanced instruments such as drifter tracking and acoustic doppler current profiler measurements now provide decisive proof of the clockwise rounding of the cheju warm current around jeju do throughout the year of the northeastward extension of changjiang discharge in summer and of the presence of the yellow sea warm current only in winter thus both coastal currents in shallow water and secondary branch currents of the kuroshio such as the yellow sea warm current are found to significantly change from winter to summer to better present the basic pattern of yecs circulation and its seasonality we have constructed seasonal circulations patterns based on review results on the newly compiled drifter trajectories and on hydrographic observations further investigations should be carried out in future with support of comprehensive current measurements on shelf areas and through elaborate numerical modeling

spring season flow of the tsushima current and its separation from the kuroshio satellite evidence attempts to determine where and how separation between the kuroshio and tsushima current occurs have been inconclusive spring season satellite data acquired over a number of years reveals two conditions important to this question 1 an areally extensive zone of mixing between the kuroshio and shelf waters occurring along the edge of the east china sea shelf and 2 plumes of warm water from the kuroshio extending into the mixed water west of kyushu this mixed water is observed to form the tsushima current in the outer shelf of the northern east china sea and korea strait warm plumes branching from the north wall of the kuroshio are seen with particular clarity in imagery of april 23 1981 and february 21 1982 details of the split suggest that branching was a transient event

stratigraphic relations of santorini s intracaldera fill and implications for the rate of post caldera volcanism we propose a new volcanological interpretation of santorini s intracaldera fill deposits as revealed by seismic reflection profiles this interpretation along with supplementary gravity and geophysical studies reveals three distinct volcaniclastic units 1 3 from top to bottom these units are attributed to 1 modern infilling sediment 2 shallow marine phreatomagmatic volcanism associated with the relatively recent formation of the kameni islands and 3 downfaulted minoan pyroclastic deposits which formed during caldera collapse towards the end of the bronze age eruption estimates of the volumes of the seismic units and kameni islands yield a dense rock equivalent magma volume of 4 85 0 7 km 3 the average rate of volcanism over the past c 3641 years is estimated at 1 3 10 3 km 3 a 1 and is similar to the rate since the ad 1707 eruption of 1 2 10 3 km 3 a 1 based on historical lava volume estimates

decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano caldera forming volcanic eruptions are low frequency highimpact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days with devastating effects on local and global scales1 because no such eruption has been monitored during its long build up phase the precursor phenomena are not well understood geophysical signals obtained during recent episodes of unrest at calderas such as yellowstone usa and campi flegrei italy are difficult to interpret and the conditions necessary for large eruptions are poorly constrained2 3 here we present a study of pre eruptive magmatic processes and their timescales using chemically zoned crystals from the minoan caldera formingeruption of santorini volcano greece4 which occurred in the late 1600s bc the results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption5 6 despite the large volume of erupted magma4 40 60 cubic kilometres and the 18 000 year gestation period between the minoan eruption and the previous major eruption most crystals in the minoan magma record processes that occurred less than about 100 years before the eruption recharge of the magma reservoir by large volumes of silicic magma and some mafic magma occurred during the century before eruption and mixing between different silicicmagmabatches was still taking place during the final months final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period with major growth phases immediately before eruption these observations have implications for the monitoring of long dormant but potentially active caldera systems

a numerical study of barotropic instability associated with the soya warm current in the sea of okhotsk abstract numerical model experiments have been carried out in an attempt to elucidate the generation mechanism of the eddy or wave street in the soya warm current we use a barotropic model incorporating bottom topography under realistic conditions the model produces waves whose properties are within range of the observed ones the generation mechanism of the waves proposed in this experiment is as follows when the current is driven by the mean water level difference between the japan sea and the sea of okhotsk the flow separates from the cape in the soya strait in the region of the flow separation strong positive vorticity is produced by the frictional torques occurring as the water flows through the strait and by vortex stretching as the water is pushed out to deeper depths this strong vorticity or horizontal shear induces barotropic instability in which the waves are generated in brief the system of the soya warm current accompanied by an eddy street is interpreted as a good geophysical ex

a model of buoyant throughflow with application to branching of the tsushima current abstract a reduced gravity model is used here to investigate the dynamics of a buoyant flow through a strait driven by pressure difference of the adjoining basins assuming the flow to be hydraulically controlled so that the transport is maximized flow structures in the upstream basin during its transit through the strait and along the downstream coast are determined it is found in particular that the combined effect of friction exerted by the sill and stretching of the buoyant layer as it exits the strait may cause the downstream flow to exhibit two velocity maxima along the layer outcrop and the coastal boundary when applied to the tsushima current of the japan east sea the required conditions for branching are amply satisfied the model thus provides a plausible explanation of this observed feature in addition a favorable comparison between predicted and observed transports supports the hydraulic control of the flow

a new algorithm for modelling simple and double mogi magma sources in active volcanoes accuracy sensitivity limitations and implications a new algorithm for modelling one or two mogi magma sources in actively deforming volcanoes is proposed using santorini thera greece volcano as a test site this algorithm is based on a quasi deterministic grid scan search followed by a topological inversion in rn space it avoids point solutions and local minima and is primarily designed for gps observations it can be extended to other types of magma sources defined by closed functions and to other types of data a validation of the method used an accuracy oriented approach a comparison between true or reference and inverse modelled magma sources which revealed bias free precise magma source solutions a validation of the algorithm for false alarms i e for identification of non existent sources produced by computation artefacts was also made computed solutions correspond to point sources affecting idealized media homogeneous elastic half spaces and hence ignore errors induced by magma source and lithology complexities which should be superimposed to obtain the total error budget still the solutions allow modelling of the propagation of measurement errors because of the mathematical model adopted this problem has previously been ignored a sensitivity analysis of results obtained using this method permit us to predict and quantify expected bias and uncertainties in modelled magma sources as a function of their depth and of the observation networks increased bias and noise in solutions for specific observations networks and types of data are inferred and this may explain reported discrepancies in various magma source models some implications for the santorini volcano which had an unrest episode in 2011 2012 are that the algorithm can lead to less noisy solutions of the mogi sources that the surface deformation may be recognized as resulting from inflation of two spherical sources and that differences in magma source models using different types of data may only indicate predictable uncertainties in the solutions

enso teleconnection to the isopycnal depth fluctuations of the east japan sea intermediate water in the ulleung basin during 1968 2002 abstractthis study first detects the decadal variability in the depths of the east japan sea ejs intermediate water esiw using in situ observations and relates it to strong el nino southern oscillations ensos using multitaper cross spectrum and cyclostationary empirical orthogonal function analysis this study found significant coherences at the 99 confidence level and opposite phases between nino 3 and the esiw isopycnal depths in the ulleung basin ub at a period of 14 1 yr during 1968 2002 this suggests a teleconnection between strong ensos and the esiw the cause of which is explored when a strong el nino en develops the pacific north american pattern is intensified by the en related rossby wave interfering constructively with the climatological stationary wave the amplified wave propagates upward into the stratosphere and breaks weakening the polar vortex the en related geopotential height increases over the pole with poleward converging air and decreases over the yakutsk basin yb

episodic surface intrusions in the yellow sea during relaxation of northerly winds the surface currents over the yellow and east china seas are mapped from the geostationary ocean color imager goci based on a composite of six intrusion events in january april the strong northward surface current in the yellow sea is shown to be concentrated along the deep trough accompanied by a broad northward surface current over the east china sea from the corresponding surface winds the episodic northward surface flow bursts appear to be associated with abrupt changes from the strong northerly winds to weak southerly winds during cold front passages a three dimensional model driven with observed surface winds is used to simulate the observed shelf wide response to northerly winds there is an outstanding agreement between the simulated and observed surface currents the surface intrusion in the yellow sea is shown to be driven primarily by a barotropic longitudinal surface slope while the strong northward current in the east china sea is associated with a coastal trapped wave moreover the surface intrusion is associated with a large volume transport suggesting that the transient intrusions could be important in the northward heat transport the unprecedented capability of goci satellite in providing a regional circulation pattern in conjunction with complementary model simulations could contribute greatly to understanding of the dynamics of the yellow and east china seas

formation of bottom water and its variability in the northwestern part of the sea of japan the downslope descent of dense shelf water in the northwestern part of the sea of japan is investigated from a dynamical point of view paying attention to the formation of bottom water in the winter of 2001 it is supposed that before 1980 the shelf water in peter the great bay sometimes descended far down the continental slope at least partly reaching depths in excess of 3000 m the foot of the continental slope after 1980 however the shelf water did not descend as far it either descended only moderately or not at all in winter 2001 however the dense shelf water again descended to depths greater than 3000 m resulting in the formation of bottom water descents of more than 3000 m are due to low temperatures coupled with high salinities whereas the moderate descents of the late 20th century were purely related to the low temperature of the shelf water it is estimated that over the continental slope the shelf water becomes mixed with the ambient water in a ratio of about 1 9 for deep descents whereas the ratio is about 1 5 for moderate descents the formation of bottom water is greatly influenced by interannual atmospheric variability thus in winter 2001 a combination of the strengthened siberian high especially in its northern part and the aleutian low advected very cold air into northeast asia producing dense shelf water and resulting in the formation of bottom water

quasi biennial variability in the japan sea the topex poseidon t p altimetry reveals quasi biennial qb variability in the southern japan sea sea surface height anomalies of a biennial nature are most energetic in the yamato basin the southeastern most part of the japan sea where they can be as large as 20 cm and extend for 100 200 km on the basis of the in situ measurements of maizuru marine observatory the 2 3 year variations are associated with thermohaline anomalies in the upper 300 m layer the local qb oscillation is studied with a reduced gravity model of the japan sea the model is forced by european centre for medium range weather forecasting daily wind and seasonal inflows outflows through the three major straits of the sea the model sensitivity experiments suggest that the qb variability can be associated with the sea s response to wind forcing of particular years more specifically 1992 and 1996 and to some extent 1994 an approximate kaiman filter is employed for assimilation of the t p altimeter data into the reduced gravity model it filters out observational noise and intraseasonal sea level variability and allows the model to dynamically interpolate t p observations the results of the assimilation indicate that the qb anomalies are strongest at 37 5 n 134 5 e and propagate west northwest with a speed of 0 01 m s 1 contributing to variations of the tsushima warm current

climatological coastal jet collision intermediate water formation and the general circulation of the red sea the authors present climatologies of a numerical model of the red sea focusing on the dynamics of winter intermediate water formation northward flowing boundary currents are identified as the major dynamical elements at the northern boundary the eastern current follows the geometry eventually turning back to the south at 268n and the western wall the two boundary currents collide at the collision site the denser eastern current subducts under the western boundary current the subduction forces the western boundary current eastward into the interior convection communicates the surface fluxes to the downwelled plume and intermediate water forms the estimated rate 0 11 sv sv 106 m3 s21 agrees with previous estimates the authors identify basin scale sea surface tilt to the north due to variable thermohaline forcings as the key dynamical variable the resultant geostrophic eastward cross channel flow interacts with the boundaries and creates upwelling and surface topography spatial patterns that drive the coastal jets upwelling induced vortex stretching dominates the vorticity balance and governs the separation of the western boundary current from the western wall the process ceases in the summer

separation of the kuroshio water and its penetration onto the continental shelf west of kyushu the separation of kuroshio water west of kyushu and its penetration onto the continental shelf of the east china sea were investigated by analyzing trajectories of satellite tracked surface drifters deployed during 1989 1996 conductivity temperature and depth ctd data collected in the eastern east china sea in december 1993 and late april early may 1995 were also analyzed composite trajectories of 172 drogued drifters provided direct evidence of the separation of the northeastward flowing kuroshio into two parts at the western mouth of the deep trough southwest of kyushu the kuroshio main stream turns to the east toward the tokara strait and a northward flowing branch current penetrates onto the shelf across the continental slope west of the trough analysis of the ctd data and drifter trajectories concurrently observed shows that the branch current was part of the inshore kuroshio just upstream before its separation during the periods of ctd observations the separated inshore kuroshio water intruded northward in a tongue shape along the shelf break of the trough and penetrated onto the shelf after crossing obliquely the western continental slope of the trough the water that penetrated onto the shelf continued to flow northward toward the korea strait the main path of this water was easily traced by its high salinity which is characteristic of the inshore kuroshio water application of an inverse method to the observed ctd data also supports the separation and penetration of the kuroshio and calculates the volume transport of the northward branch to be about 4 0 106 m3 s for the two different surveys the tongue shaped intrusion of the inshore kuroshio water onto the outer shelf may take place in close association with the eastward turning of the kuroshio main stream and it might be caused by the vorticity adjustment created by the eastward turning of the kuroshio

evidence for a wind driven intensification of the kuroshio current extension from the 1970s to the 1980s the spatial and temporal characteristics of oceanic thermal variations in the mixed layer and main thermocline of the midlatitude north pacific are distinctive suggesting different physical origins within the main thermocline 400 m depth the variability is dominated by a westward intensified pattern of decadal scale indicative of enhanced eastward geostrophic flow along the southern flank of the kuroshio current extension during the 1980s relative to the 1970s the authors argue that the decadal scale change in the strength of the kuroshio extension was a result of the dynamical adjustment of the oceanic circulation to a decadal variation in wind stress curl according to sverdrup theory four times daily wind stress fields from the national center for atmospheric research national centers for environmental prediction reanalysis project are used to compute the decadal change in sverdrup transport associated with the 1976 77 climate transition it is shown that the decadal changes in sverdrup transport inferred from the wind stress curl field and in observed geostrophic flow inferred from the upper ocean thermal field are consistent both in terms of spatial pattern and magnitude the decadal change in depth averaged geostrophic transport along the kuroshio extension referenced to 1 km is 11 6 sv similar to the sverdrup transport change 11 5 13 9 sv the decadal scale thermocline variation along the western boundary between 308 and 408n exhibits a lag of approximately 4 5 yr relative to the decadal variation in the basin wide wind stress curl pattern this delay may be indicative of the transient adjustment of the gyre scale circulation to a change in wind stress curl via long baroclinic rossby waves

on the origin of the tsushima warm current the origin of the tsushima warm current referred to as twc was investigated by surface drifter experiments and conductivity temperature and depth ctd surveys in the northeastern east china sea ecs at three different times july 1991 and april and november 1992 trajectories of 10 satellite tracked drifters provide direct information for the first time on the surface flow patterns in each season and ctd observations allow identification of warm and saline twc waters the results of the experiments argue against two historical concepts of twc origins i e 1 a northward flow transporting warm and saline water through the deep trough southwest of kyushu toward the korea strait after separation from the kuroshio and 2 a northeastward continuation of the taiwan current tc on the shelf of ecs after passing through the taiwan strait a persistent northward current was found to exist both on the shelf west of the trough and on the western flank of the trough the northward flow seems to bifurcate around the northwestern corner of the trough splitting into a northward continuing flow on the shelf of 100 150 m and an eastward flow along the northern wall of the trough the northward flow on the shelf which might be the shore fringe of the kuroshio corresponds to the origin of twc entering the korea strait the eastward flow on the northern slope turned back to the south along the west coast of kyushu and eventually joined the kuroshio this structure was accompanied by an anticyclonic eddy in the northern trough the second concept that of twc originating from tc contradicts the observed differences in physical properties between twc and tc waters the saline water in the taiwan strait flows out intermittently only during late winter early spring and its salinity during other seasons is lower than that of the twc water in the korea strait experiments also indicated a seasonal shift of drifter paths in the northeastern ecs and coexistence of cyclonic and anticyclonic eddies in the trough during the cold season

geostrophic control of fluctuating barotropic flow through straits abstract a simple model in which the cross strait sea surface slope is geostrophically balanced and the along strait slope is balanced by acceleration and friction is shown to be supported by the results of buchwald and miles for fluctuating flow through a gap between two semi infinite oceans for a narrow gap compared with the rossby radius and the scale of the motion in the far field the transport through it is exactly the same as that predicted by the model provided that the gap is regarded as having an elective length as determined in this paper the importance of the models is that they demonstrate that at low frequency the flow may be geostrophically controlled and the transport limited to a value much less than that which would arise in a nonrotating system the neglect of nonlinear advective terms in the models is justified by a comparison or the bernoulli set down in the strait with the driving head and the mean water depth the formula for the flux through a strait may be applied in stu

regional and teleseismic analysis of underground nuclear explosion waveforms and constraints for shear wave excitation mechanisms 1 regional and teleseismic waveforms of underground nuclear explosions unes at the balapan and the nevada test sites are analyzed to understand the nature of shear waves excited from unes the phase composition of wavefields in the source and receiver regions is examined using a source array frequency wave number analysis and polarization analyses it is observed that regional mantle lid shear waves sn often develop strongly on the other hand observed teleseismic shear waves from unes are much weaker than those from earthquakes source array analyses of the shear waves from unes display coherent energy that is polarized in a certain azimuthal direction the observation of coherent shear energy in different unes suggests that the shear energy is excited in a consistent manner at every une we constrain the dominant shear wave excitation mechanism from the observed shear wave features the observations appear to be consistent with the tectonic release model with conical rock cracking

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

branching mechanism of the tsushima current in the korea strait abstract hydrographic studies show the seasonal variation of the east korean warm current ekwc which is a branch of the tsushima current along the korean coast to understand the dynamics of the branching mechanism of the tc in the korea strait a hydraulic model with two active layers was investigated in a rectangular strait with varying depth when the lower cold water flows southward in a shallow meridional channel from the deep northern basin it separates from the eastern boundary because of the sloping bottom to conserve potential vorticity after separation the lower layer hugs the western boundary as the channel becomes shallow in a region where the lower layer is absent due to separation the northward flow in the upper layer has a positive relative vorticity to conserve potential vorticity because the bottom topography becomes deeper from south to north the northward velocity has its maximum on the eastern boundary this mechanism may explain the formation of the branch along the japanese

northward flow in the bering and chukchi seas the ocean circulation on the bering and chukchi sea shelves is investigated using a barotropic numerical model in the presence of the winter seasonal wind stress from the northeast observed northward transport through bering strait of 0 6 sv for the 8 month winter season 1981 1982 can be driven by a sea level difference of 0 4 m between the pacific and arctic oceans this sea level difference between basins is in agreement with hydrographic estimates in the absence of wind stress a 0 4 m sea level difference drives a northward transport through bering strait of 1 1 sv maximum transport through bering strait is geostrophically limited not frictionally or inertially limited major qualitative circulation features of the region are evident in the simulations westward intensification of the northward transport across the bering sea shelf is confirmed with the major transport occurring in the relatively deep gulf of anadyr in the absence of wind anadyr strait contributes 72 of the northward transport through bering strait with northeasterly winds there is a net clockwise circulation around saint lawrence island within the 20 m isobath norton and kotzebue sounds are little influenced by the general circulation northward transport in the chukchi sea bifurcates in the vicinity of point hope the predominant branch is directed toward the northwest in a broad canyon feature south of herald shoal and the balance becomes the alaskan coastal current between cape lisburne and point barrow

long shelf waves generated by a coastal flux solutions are presented for the shelf response of barotropic and stratified oceans to an oscillatory coastal flux through a strait the flux is modeled as the return interior flow due to an ekman transport that arises from a fictitious square wave longshore wind stress the width 2 d of the square wave stress is taken to be that of the strait and the response due to the coastal flux determined from longwave wind forced solutions that exist in the literature the net longshore energy flux for the nth strait forced shelf wave mode wave number kn is shown to be proportional to u2 bnsin knd knd 2 where u2 is the coastal flux spectrum and bn the modal wind coupling coefficients results compare favorably with existing barotropic theories and estimates of net longshore energy flux obtained for the australian coastal experiment region are shown to be in reasonable agreement with observations at periods of 9 days when forcing by bass strait is assumed greatest

nuclear explosion locations at the balapan kazakhstan nuclear test site the effects of high precision arrival times and three dimensional structure abstract we have investigated the potential contributions of improved arrival times using waveform cross correlation and the use of three dimensional 3 d velocity models for seismic event location capability our analyses are applied to a dataset of nuclear explosions at balapan kazakhstan for which ground truth locations and some absolute origin times are available this ground truth information allows us to determine excellent origin time estimates for the remaining explosions the combination of excellent ground truth location information and high quality origin time estimates permits us to 1 carry out a detailed examination of the quality of isc picks 2 identify probable timing errors in the digital data 3 evaluate relative and absolute location capability using data from a sparse network 4 assess the influence of event signal to noise ratio snr on relative location accuracy 5 utilize the balapan events as a source array for 3 d tomography beneath the test site and 6 test the influence of 3 d structure local and global on relative location accuracy and precision in a controlled situation our principal finding is that improved arrival times are the primary contributor to improved locations joint and individual relocations of balapan events using the full digital dataset result in average mislocations of less than 1 km and 95 confidence regions of a compatible size to mimic a ctbt scenario more realistically we also carry out relocations using very few stations 4 10 observations location accuracy degrades somewhat but the high quality picks generally result in mislocations less than 10 km even for events with very large azimuthal gaps uncertainty is generally underestimated in these cases tests with artificially degraded snr show that mislocation increases slowly as snr decreases 3 d velocity structure makes a smaller contribution to relative location accuracy than accurate time picks travel time variations due to global 3 d structure vary little across the source region so that location scatter is not reduced when travel time corrections for global 3 d structure are applied travel time variations due to the local 3 d structure estimated using source region tomography are also modest applying travel time corrections that account for the local structure does yield slight location improvement

water exchange across isobaths over the continental shelf of the east china sea abstractonshore and offshore currents and the associated volume transport across three isobaths 50 100 and 200 m over the continental shelf of the east china sea were examined using daily reanalysis data in 1993 2012 after being averaged along the isobaths the velocities across 100 and 50 m are onshore in the bottom layer but offshore in the surface layer in contrast those across the 200 m isobath are onshore in the surface and bottom layers but without a clear direction in the midlayer suggesting a three layer structure the surface offshore current across the 100 m isobath mainly arises from the taiwan strait current while the surface onshore current across the 200 m isobath mainly arises from the kuroshio both of which converge in the area between the 100 and 200 m isobaths and flow toward the tsushima strait the control of bottom ekman dynamics on the onshore bottom currents is important at the 100 m isobath partly important at the 200 m isobath and slightly important at the 50 m isobat

potential vorticity constraint on the flow between two basins abstract this paper examines the role of potential vorticity pv balance in source and sink driven flows between two basins as shown in previous studies pv advection into a basin say a positive pv advection requires a negative frictional torque to maintain a steady pv balance this sense of torque may be provided by a cyclonic boundary current within the basin the pv advection through a channel is due almost entirely to advection of planetary pv f h where f is the coriolis parameter and h is the column thickness therefore a localized change of depth and thus h in the channel directly affects the pv transport and will result in a basinwide change of the circulation pattern for example if the channel depth is made shallower while holding the transport fixed the pv advection is then increased and the result may be a strong recirculation within the basin as much as two orders of magnitude greater than the transport through the channel when the basins are connected by two channels at different

recent warming in the western north pacific in relation to rapid changes in the atmospheric circulation of the siberian high and aleutian low systems abstracton the basis of a new east asian winter monsoon eawm index and by analyzing the relationship between sea surface temperature sst anomalies and different atmospheric and oceanic factors in winter this study investigates the causes of the recent unusual warming in the western north pacific ocean analyses presented here emphasize the dual contribution from the atmosphere and ocean to the local sst variability with the relative importance of each contributor varying with the period and place during the period 1970 89 the eawm controlled mostly by the siberian high is predominantly responsible for the sst variability in most of the western north pacific whereas in the period 1990 2005 ocean dynamics become increasingly important in most places or even dominant in the kuroshio oyasio extension koe region the delayed response of the koe sst to basinwide wind stress curl forcing via rossby waves is epoch dependent and is significant at lags of 1 3 and 4 yr before 1990 but only at 1 yr aft

foreshock sequence of the 1992 landers california earthquake and its implications for earthquake nucleation the june 28 1992 landers california earthquake mw 7 3 was preceded for about 7 hours by a foreshock sequence consisting of at least 28 events in this study we examine the geometry and temporal development of the foreshocks using high precision locations based on cross correlation of waveforms recorded at nearby stations by aligning waveforms rather than trying to obtain travel time picks for each event independently we are able to improve the timing accuracy greatly and to make very accurate travel time picks even for emergent arrivals we perform a joint relocation using the improved travel times and reduce the relative location errors to less than 100 m horizontally and less than 200 m vertically with the improved locations the geometry of the foreshock sequence becomes clear the landers foreshocks occurred at a right step of about 500 m in the mainshock fault plane the nucleation zone as defined by the foreshock sequence is southeast trending to the south and nearly north trending to the north of the right step this geometry is confirmed by the focal mechanisms of the foreshock sequence which are right lateral and follow the trend as determined by the foreshock locations on the two straight segments of the fault and are rotated clockwise for foreshocks that occur within the step the extent of the foreshock sequence is approximately 1 km both vertically and horizontally modeling of the coulomb stress changes due to all previous foreshocks indicates that the foreshocks probably did not trigger each other this result is particularly clear for the mw 4 4 immediate foreshock since stress transfer in the sequence appears not to have played a significant role in its development we infer an underlying aseismic nucleation process probably aseismic creep other studies have shown that earthquake nucleation may be controlled by fault zone irregularities this appears to be true in the case of the landers earthquake although the size of the irregularity is so small that it is not detectable by standard location techniques

bang month scale eruption triggering at santorini volcano the time lag between intrusion of fresh hot magma and an ensuing eruption is of critical importance in both understanding the triggering and mitigating the consequences of volcanic eruptions this work looks at material erupted during 1925 28 at the nea kameni volcanic center in santorini greece to determine this time scale by exploiting fe mg diffusion in olivine crystals we constrained the intrusion to eruption time lag to between 3 and 10 weeks these techniques have potential application at many volcanic centers previously erupted material can be used to calibrate records of the short time scale processes common to many volcanic centers

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

fluctuations in the late quaternary east asian winter monsoon recorded in sediment records of surface water cooling in the northern japan sea the east asian monsoon climate system involves interactions between land and ocean and is composed of summer and winter monsoons cooling of surface water by the east asian winter monsoon eawm promotes the formation of sea ice and deep water in the northern japan sea modern observations suggest close relationships between intensification of the eawm and both sea ice formation and sea surface temperature sst decrease in the northeastern japan sea records of ice rafted debris ird and alkenone based sst in the northeastern japan sea are examined to clarify the temporal variability of the eawm and its controlling factors close relationships with oxygen isotope records of chinese stalagmites and northern hemisphere summer insolation are observed in the records of ird occurrence and sst during marine isotope stages mis 3 5 the co occurrence of maxima in the abundance of ird and minima in sst in the northeastern japan sea indicates that the intensity of the eawm was enhanced during periods of low summer insolation and high oxygen isotope ratios in chinese stalagmites decoupling between the ird and sst records during mis 2 and mis 6 might be the result of differences in surface water conditions caused by low sea levels and the resultant closure of the tsushima strait during mis 3 and 4 some small but clear maxima in ird and minima in sst occurred at relatively low summer insolation periods some of these peaks co occur with north atlantic heinrich events suggesting a possible climate linkage between the north atlantic and the asian monsoon the presence of finer fluctuations in the occurrence of ird than in summer insolation suggests finer millennial centurial timescale fluctuations in the intensity of the eawm furthermore some ird peaks occurred during periods of high insolation such as 39 86 103 128 145 and 153 ka some of these ird peaks correlate with minima in reconstructed sst and maxima in oxygen isotope ratios of chinese stalagmites this result suggests that extremely cold winters occur even during periods of enhanced east asian summer monsoon intensity and indicates that solar insolation is not the only factor that controls variations in the intensity of the eawm at millennial centurial timescales copyright 2012 john wiley sons ltd

a study of small magnitude seismic events during 1961 1989 on and near the semipalatinsk test site kazakhstan official russian sources in 1996 and 1997 have stated that 340 underground nuclear tests unts were conducted during 1961 1989 at the semipalatinsk test site sts in eastern kazakhstan only 271 of these nuclear tests appear to have been described with well determined origin time coordinates and magnitudes in the openly available technical literature thus good open documentation has been lacking for 69 unts at sts

a skeletal sr ca record preserved in dipsastraea favia speciosa and implications for coral sr ca thermometry in mid latitude regions 1 a core 900 mm long of the scleractinian coral dipsastraea favia speciosa was collected from iki island 33 48 n japan one of the highest latitude coral reefs known to exist at present where winter monthly mean sea surface temperature sst drops to 13 c the sr ca profile was constructed using a bulk sampling method for the uppermost 280 mm interval of the core which grew between 1966 and 2007 to test whether it could act as a suitable proxy for sst in a harsh environmental setting where reef building coral do not usually survive the sr ca sst relationship derived from the annual sr ca and sst extremes predicted the observed monthly averaged summer sst extremes within an error range of 1 1 c 1 s d n 40 the obtained sr ca sst calibration was also found to be valid for subtropical dipsastraea favia corals proving its broad applicability however low amplitude winter peaks were observed in the slow growing intervals which we confirmed using individual spot analysis along a continuous growth line result from the mixing of theca grown at different times our bulk sampling approach across multiple growth lines in the skeleton of d f speciosa led to the mixing of asynchronous skeletal part at the study site d f speciosa grows continuously even during the cold season suggesting that the skeletal sr ca obtained from specimens of d f speciosa can be used as an sst proxy in the northwest pacific marginal seas

spatiotemporal variability of interdecadal sea level oscillations in the north pacific 1 the interdecadal variations in the north pacific sea level field were investigated on the basis of two historical tide gauge data sets long term sea level records spanning 100 years but spatially limited in the midlatitudes the cl data set and records from a wider area but with a data length of about 50 years the hcl data set a seesaw like sea level oscillation between the eastern and the western pacific was extracted as the first mode of empirical orthogonal functions eof from the cl data set this mode shows a 22 5 year period of variation that has continued throughout the 20th century a similar variation was found in the hcl data set as the first mode of complex eof ceof though its dominant period was 14 5 years this interdecadal sea level oscillation is the steric sea level change associated with the pacific inter decadal oscillation pdo in the upper ocean temperature field because the temporal evolution and spatial structure in the interdecadal oscillation resemble those of the dominant modal pattern in the temperature field however this mode shows a standing wave characteristic in the midlatitudes rather than propagating though the clockwise phase propagation around the subtropical gyre has been reported in the temperature field another interdecadal oscillation is found in the ceof second mode which was dominant in the 1960s when the first mode was relatively weak the second mode shows a 15 to 16 years period of variation and phase lags of 3 4 years at the subtropical stations relative to those in the midlatitudes

evolution of interdecadal variability in sea level pressure sea surface temperature and upper ocean temperature over the pacific ocean abstract interdecadal variability in sea level pressure slp and sea surface temperature sst anomalies in the pacific ocean was quasiperiodic from 1900 91 the coherent variability of this phenomenon is investigated using gridded observational data from the turn of the century sst and slp and of upper ocean heat content hs from the recent two and a half decades the nominal cycle in atmosphere ocean variables is roughly two decades long but growth and decay can happen on a shorter timescale e g half a cycle or so the authors divide the full cycle into four phases an onset phase during which a weak slp anomaly pattern off japan takes approximately 2 4 yr to expand eastward leads to large slp anomalies in the region of the aleutian low a quasi stationary growth phase with the midlatitude slp anomaly pattern in the eastern ocean intensifies over a 2 4 yr period the persistent slp anomalies evolve in concert with large sst and hs anomalies of the same polarity located to the south sout

pycnobathic currents over the upper continental slope abstract the dynamic interaction of a sloping seafloor with along isobath density variation is calculated for cases involving a sharp pycnocline and a surface to bottom front pycnocline depth is supposed to vary in the alongshore direction only over a sloping plane seafloor the bottom trace of the surface to bottom front is supposed to cut across isobaths the calculations are diagnostic and make use of linearized equations with a linear bottom friction term the results illustrate the manner in which cross isobath baroclinic flow is converted at the slope into a barotropic flow field with velocities nearly parallel to the isobaths the forward portion of the slope that which lies in the direction of kelvin wave propagation only is affected if there is only one inflow or outflow region however for equal and opposite inflow and outflow a closed circulation pattern arises connecting these two regions accompanied by a secondary closed circulation cell forward of both the inflow and outflow legs

japan sea thermohaline structure and circulation part ii a variational p vector method abstract the second part of this work investigates the seasonal variabilities of the japan east sea jes circulation using the u s navy generalized digital environmental model gdem climatological temperature and salinity dataset public domain on a 0 5 0 5 grid a variational p vector method was developed to invert the velocity field the gdem for the jes was built up on historical 1930 97 136 509 temperature and 52 572 salinity profiles the climatological mean and seasonal variability of the current systems are well inverted especially the tsushima warm current and its bifurcation the east korean warm current ekwc the japan nearshore branch the confluence of the ekwc and the north korean cold current near the korean coast and flows northeastward along the subpolar front and a mesoscale anticyclonic eddy in the ulleng tsushima basin furthermore this method has the capability to invert flow reasonably well across the shallow straits such as the tsushima korea tsugaru and soya strait

ground truth seismic events and location capability at degelen mountain kazakhstan abstract we utilized nuclear explosions from the degelen mountain sub region of the semipalatinsk test site sts kazakhstan to assess seismic location capability directly excellent ground truth information for these events was either known or was estimated from maps of the degelen mountain adit complex origin times were refined for events for which absolute origin time information was unknown using catalog arrival times our ground truth location estimates and a time baseline provided by fixing known origin times during a joint hypocenter determination jhd precise arrival time picks were determined using a waveform cross correlation process applied to the available digital data these data were used in a jhd analysis we found that very accurate locations were possible when high precision waveform cross correlation arrival times were combined with jhd relocation with our full digital data set resulted in a mean mislocation of 2 km and a mean 95 confidence ellipse ce area of 6 6 km 2 90 ce 5 1 km 2 however only 5 of the 18 computed error ellipses actually covered the associated ground truth location estimate to test a more realistic nuclear test monitoring scenario we applied our jhd analysis to a set of seven events one fixed using data only from seismic stations within 40 epicentral distance relocation with these data resulted in a mean mislocation of 7 4 km with four of the 95 error ellipses covering less than 570 km 2 90 ce 438 km 2 and the other two covering 1730 and 8869 km 2 90 ce 1331 and 6822 km 2 location uncertainties calculated using jhd often underestimated the true error but a circular region with a radius equal to the mislocation covered less than 1000 km 2 for all events having more than three observations