tracing tropical and intermediate waters from the south china sea to the okinawa trough and beyond 1 intermediate waters with a salinity minimum from 350 to 1350 m depths have been reported to flow out of the south china sea scs through the luzon strait this eastward flowing scs intermediate water scsiw is blocked by the northward flowing black stream kuroshio southeast of taiwan and is forced to turn to the north the scsiw subsequently enters and occupies the western half of the okinawa trough because of strong upwelling in the scs basin the scsiw contains more nutrients than does the kuroshio intermediate water in the philippine sea one of the major purposes of this note is to reconfirm that the scsiw actually does upwell onto the east china sea ecs shelf and to show that the south china sea tropical water scstw with a salinity maximum of 50 150 m in depth follows the same pathway as the scsiw and similarly occupies the western half of the okinawa trough part of these relatively nutrient rich subsurface waters upwell thereby supplying nutrients to the ecs shelves the remaining scsiw and scstw flow along with the kuroshio and can be traced as far east as 140 e south of japan this is just around the region where the oyashio joins the kuroshio to form the north pacific intermediate water

effects of biological activity on the entrainment of marine sediments nowell a r m jumars p a and eckman j e 1981 effects of biological activity on the entrainment of marine sediments mar geol 42 133 153 the effects of animal tracks and fecal pellet production on the critical entrainment velocity of marine sediments were examined experimentally laboratory measurements in a free surface seawater flume were made using three sediment sizes effects of three species of polychaetes and two species of bivalves were tested boundary shear velocity was calculated from the mean velocity profile in the logarithmic region of the boundary layer measurements were made with a hot film anemometer tracking doubled the boundary roughness and decreased the critical entrainment velocity by 20 ambient or free sediments were more easily entrained than fecal mounds which were restrained from movement by mucous adhesion between the fecal coils isolated pellets such as those egested by amphicteis scaphobranchiata transported readily as bedload over a cohesive sediment surface

numerical study of the ocean circulation on the east china sea shelf and a kuroshio bottom branch northeast of taiwan in summer using the regional ocean model system the ocean circulation on the east china sea ecs shelf was examined by a fine resolution model which was nested in a coarse resolution pacific ocean model the high resolution simulation shows an accurate volume transport of 2 70 sv sv 10 6 m 3 s 1 through the tsushima strait which is more consistent with the previous 5 5 year observation value 2 64 sv than former model results for the taiwan strait it also shows a close volume transport 1 03 sv to a recent estimate 1 20 sv at the same time the model results reproduced almost all of the known circulation structure on the ecs shelf in addition the hindcast of 2009 shows a kuroshio bottom branch current to the northeast of taiwan kbbcnt the kbbcnt is confirmed by the observational bottom high salinity water from 15 august to 2 september 2009 whose distribution is also reproduced by the model results tracer and particle experiments were carried out to elucidate the formation of the high salinity water and the pathway of the kbbcnt in light of the field observation and numerical experiments a new pathway of the kbbcnt is proposed bifurcated from the subsurface water of kuroshio northeast of taiwan it upwells northwestward gradually from 300 to 60 m then turns to northeast in the region around 27 5 degrees n 122 degrees e and finally reaches 31 degrees n off the mouth of the changjiang river along similar to 60 m isobaths forming the bottom saline water off the coast of zhejiang province china

variability of the chemical hydrography at the frontal region between the east china sea and the kuroshio north east of taiwan abstract the hydrography across the frontal region between the east china sea and the okinawa trough north east of taiwan observed during the summer of 1985 and 1988 and the early spring of 1987 was governed mainly by mixing across the front and the topographically induced upwelling of the modified kuroshio water in the okinawa trough during the periodic shelfward migration of the kuroshio the location of the front relative to the shelf break seemed to be temporally variable topographically induced upwelling was evident during the summer of 1988 and the early spring of 1987 when the front was located close to the shelf break it might not have occurred in the summer of 1985 when the front was further offshore the end member composition of the upwelling water was similar in both seasons it originated from about 300 m with a temperature and salinity of 13 c and 34 4 psu it was rich in nutrients and poor in oxygen with concentrations of nitrate phosphate silicate and oxygen of 16 1 18 and 160 m respectively this upwelling water is potentially a major source of nutrients to the east china sea the deep water in the okinawa trough at temperatures below 15 c did not participate in cross shelf mixing its chemical characteristics did not change significantly from year to year

why are there upwellings on the northern shelf of taiwan under northeasterly winds upwellings are observed on the northern shelf of taiwan during northeasterly winds analytical and realistic numerical models are used to explain how vertical motions are created by divergence and convergence produced by wind acting on the vorticity field of two strong jets the kuroshio and the taiwan warm current the seaward increase in cyclonic vorticity near the kuroshio s western edge favors a stronger ekman transport away from the jet producing upwelling at the shelfbreak under a northeasterly wind a similar mechanism for generating vertical motions is found across the taiwan warm current the numerical model results indicate that the vorticity effects can account for up to 30 50 of the total variation in the surface ekman transport except during summer s weak southwesterlies northeasterly wind is dominant over the east china sea suggesting that the vorticity effects may be prominent in the observed shelfbreak upwelling in nonsummer months

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

variation in the kuroshio intrusion modeling and interpretation of observations collected around the luzon strait from july 2009 to march 2011 this study analyzes the observed subtidal currents 1 12 global hycom model results and the observed time series to interpret seasonal and interannual patterns in the behavior of the kuroshio intrusion around the luzon strait ls the observations include current measurements conducted at mooring station n2 20 40 441 n 120 38 324 e from 7 july 2009 to 31 march 2011 surface geostrophic currents derived from the merged absolute dynamic topography and the trajectory of an argo float during the winter of 2010 2011 results from mooring station n2 confirmed the seasonal changes in the kuroshio intrusion and the variation of the kuroshio intrusion during el nino event from july 2009 to april 2010 and la nina even from june 2010 to march 2011 the strongest kuroshio intrusion occurs in the winter with successively weaker currents in spring autumn and summer comparison of relative differences max z in the maximum absolute value of monthly average zonal velocity components umax z showed that the kuroshio intrusion was stronger during the 2009 2010 winter el nino than the 2010 2011 winter la nina furthermore the relative differences max z in deeper layers exceed those of the surface layer circulation patterns in surface geostrophic currents and the argo float trajectory confirmed the results of mooring station n2 the kuroshio intrusion velocity variation modeled using the 1 12 global hycom model resembled the observation on both seasonal to interannual scales modeled variation in the zonal mean velocity anomaly was also consistent with nino3 nino4 and north equatorial current nec bifurcation latitude indices indicating concurrent impacts of the enso influence monsoon winds strongly affect the seasonal variation while the weak upstream kuroshio transport induced by el nino strongly affects the interannual variation such as 2009 2010 winter in 2010 2011 winter the impact of winter monsoon forcing still exists in the ls however the stronger upstream kuroshio transport during this period did not allow the kuroshio to penetrate into the ls deeply this explains why the 2009 2010 winter kuroshio intrusion el nino event was stronger than that of the 2010 2011 winter la nina event

seasonal and interannual changes of the kuroshio intrusion onto the east china sea shelf an advanced artificial neural network classification algorithm is applied to 20 years of multisatellite geostrophic velocity data to study the kuroshio intrusion onto the southern shelf of the east china sea the results suggest that the on shelf intrusion may occur year round but winter intrusion events are more frequent than summer events both stronger intrusion which is closely correlated to surface heat flux gradient and weaker intrusion which is correlated to wind forcing occur during wintertime but the former dominates in late winter while the latter prevails in early winter there is a significant year to year variation of the winter on shelf intrusion although on shelf intrusion is the major characteristic of the region during wintertime seldom intrusion events have been identified in the winters of 1997 1998 and 2002 2003 two conditions are responsible for the cause of the nonintrusion events during the two nonintrusion winters the upstream kuroshio transport anomaly is insignificant the kuroshio is not weakened and no significant winter cooling off northeast taiwan thus the kuroshio tends to flow along the shelf break following the 200 m isobath and on shelf intrusion ceases those two nonintrusion events take place during the winters when both the nino 3 4 index and the pdo index are large and positive

a simple model of flow sediment organism interaction abstract previous models of organism sediment interaction have been limited primarily to eddy diffusion type mixing while such models are useful in interpreting some stratigraphic records they cannot be expected to provide mechanistic insights into the diversity of interactions among sedimentary processes organism activities and boundary layer flows to provide a more general formulation capable of dealing with all three types of processes in concert a simple discrete time markov model is generated this version of the model deals explicitly only with particulate and not liquid phases the initial formulation is a two compartment ergodic model of deposit feeding particle selection by deposit feeders results in incorporation of the selected particles into fecal pellets and fecal pellet disaggregation completes the cycle particles which are more strongly selected or which are incorporated into more robust pellets thus spend more time and reach higher relative concentration in the fecal pellet compartment the next level of complexity is achieved by adding burial from the free sediment non fecal pellet compartment this model predicts that particles which are more strongly selected or incorporated into more robust fecal pellets will have greater residence times in surficial sediments both pellets and free sediments before they become part of the stratigraphic record and will therefore achieve higher concentrations in surficial sediments than will less preferred particles the full flow sediment organism system is reached by adding the potential for lateral advection of particles the probability of such advection is allowed to differ between pellets and free sediments increasing selection and robustness of fecal pellets then can either increase or decrease relative concentration and residence time of a given particle type in surficial sediments the model thus provides a means of explaining differences in stratigraphic patterns among materials deposited simultaneously it also suggests that deposit feeder selection may increase the average age i e time since initial deposition of surficial sediments by maintaining preferred particle types near the surface selection may likewise control the texture of surficial sediments in a manner which is easily confused with purely physical sorting parameters which require careful measurement in testing these simple predictions are selectivity by deposit feeders probability of selection rate of fecal pellet breakdown under realistically simulated conditions probability of pelletal disaggregation differential erodibilities of pellets versus free sediments relative probabilities of lateral advection and rates of burial of free sediments versus pelletized sediments probabilities of burial

numerical study on the pattern and origins of kuroshio branches in the bottom water of southern east china sea in summer pattern and origins of kuroshio branches in the bottom water of southern east china sea ecs were carefully examined by numerical simulations based on the regional ocean modeling system roms together with observations model results show that in the bottom water of ecs the intrusion pattern of kuroshio is mainly composed of an offshore kuroshio branch current okbc which bifurcated from the kuroshio northeast of taiwan flows nearly along the isobath of similar to 100 m and a nearshore kuroshio branch current nkbc which originated from the kuroshio northeast of taiwan upwells northwestward gradually from similar to 250 m to similar to 60 m then turns to northeast around 27 5 degrees n 122 e thereafter flows northeastward along the isobath of similar to 60 m and finally reaches at 30 5 degrees n where it turns to east furthermore we found that the nkbc mostly originated in the kuroshio subsurface water 120 250 m east of taiwan whereas the okbc mainly stemmed from the kuroshio water 60 120 m east of taiwan this pattern and origins of okbc and nkbc well addressed the observational phenomena that off the coast of zhejiang province china there were colder less saline and more phosphate rich bottom water near the isobath of similar to 60 m rather than near the isobath of similar to 100 m in august 2009 finally it is proposed that on southern ecs continental shelf kuroshio exhibits its intrusion branches by an anticyclonical stair structure bottom stair nkbc middle stair okbc and top stair kuroshio surface branch kbc

large variability of the kuroshio at 23 75 n east of taiwan synoptic features of the kuroshio at 23 75 n were quantified using nine ship based surveys between september 2012 and september 2014 the new ship based data set provides an unprecedented view of the kuroshio east of taiwan and suggest tremendous variability in its velocity hydrography volume heat and salt transports and water masses the kuroshio maximum velocity varied in 0 7 1 4 m s 1 the core current width delineated with the limit v 0 2 m s 1 ranged from 85 to 135 km and the thickness varied from 400 to 600 m a dual velocity maximum in the kuroshio core current though unexpected was observed in three of nine cruises the kuroshio core transport integrated from the directly measured velocity varied between 10 46 and 22 92 sv 1 sv 106 m3 s 1 the corresponding heat transport referenced to 0 c was 0 838 1 793 1015 w and the salt transport was 345 0 775 9 106 kg s 1 the geostrophic transport estimated using the thermal wind relation with the observed hydrographic data and reference velocity at 900 m is comparable to the directly measured kuroshio transport during most of the surveys suggesting the directly measured velocity is mostly in geostrophic balance

the crustal structure of the east anatolian plateau turkey from receiver functions an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl018192 shtml http atlas geo cornell edu turkey publications zor et al 2003 htm

summer kuroshio intrusion through the luzon strait confirmed from observations and a diagnostic model in summer 2009 abstract based on current measurements recorded at mooring station n2 20 40 441 n 120 38 324 e hydrographic data and argo observations in the period starting from july 2009 a diagnostic model with a modified inverse method is used to study the circulation in the luzon strait ls a number of new circulation features in the ls are found as follows 1 both observed and modeled currents show that the intruded kuroshio flow northwestward through the ls into the south china sea scs in the upper 400 m during july 2009 2 the diagnostic model confirms that the kuroshio is located in the area east of 121 20 e and west of 122 20 e at 20 00 n there is a meso scale cyclonic eddy at both the surface and 1000 m depth in the area west of the kuroshio near 20 00 n the meso scale cyclonic eddy forced the argo float 1 to make the cyclonic trajectory then the argo float 1 went into the area of the western kuroshio the argo float 1 was tracked as the flow moved northwestward into the scs across the ls in july and august 2009 reflecting the northwestward flow at both the surface and 1000 m depth which coincided with modeled currents these results confirm the northwestward kuroshio intrusion into the scs across the ls in summer 2009 for the first time 3 from the dimensional analysis for the equation of stream function it is seen that the joint effect of the baroclinity and relief jebar and the effect are two important mechanisms on the kuroshio intrusion into the scs in this period this summer kuroshio intrusion results from the weaker upstream kuroshio transport in summer 2009 el nino initiating period due to inertia effects and is associated with a weak volume transport across the ls 2 15 106 m3 s 1 westward 4 after comparison of the dynamics of the kuroshio intrusion during october 2008 and summer 2009 it is clear that these were influenced by the seasonal variability due to the monsoon winds and the interannual variation resulting from the weak upstream kuroshio transport affected by the enso due to inertia effects

intraseasonal to seasonal variability of the intermediate waters along the kuroshio path east of taiwan the variability of the intermediate water iw east of luzon and taiwan is investigated using data acquired from moored instrumented lines and shipboard hydrographic and current velocity surveys the iw is defined as the water mass with a local salinity minimum along the kuroshio path an empirical formula is developed to estimate the iw salinity minimum east of taiwan using temperature measurements around 580 m depth properties of the iw east of taiwan vary greatly as a result of variable contributions from three water masses including the high salinity south china sea intermediate water scsiw the low salinity north pacific intermediate water npiw and the intermediate salinity kuroshio intermediate water kiw our analysis concludes that npiw is predominantly found east of taiwan and the northward transport of kiw from northeast of luzon to east of taiwan is not a steady process concurrent mooring measurements at these two locations enable us to correlate the variations of the layer thickness of the kuroshio near its origin klto northeast of luzon to the nature of the iw east of taiwan when the kuroshio is deep i e large klto kiw is transported northward across the luzon strait where its salinity increases presumably due to turbulence mixing with scsiw this modified kiw is then transported to the east of taiwan when the kuroshio is shallow i e small klto the kiw transport east of luzon is nil or southward east of taiwan npiw feeds in below the kuroshio and is transported northward beyond the i lan ridge

interannual to decadal variability in the bifurcation of the north equatorial current off the philippines satellite altimeter sea surface height ssh data from the past 17 yr are used to investigate the interannualto decadal changes in the bifurcation of the north equatorial current nec along the philippine coast the nec bifurcation latitude migrated quasi decadally between 108 and 158n with northerly bifurcations observed in late 1992 1997 98 and 2003 04 and southerly bifurcations in 1999 2000 and 2008 09 the observed necbifurcationlatitudecanbeapproximatedwellbythesshanomaliesinthe128 148nand1278 1308ebox east of the mean nec bifurcation point using a 1 layer reduced gravity model forced by the ecmwf reanalysis wind stress data the authors find that the ssh anomalies in this box can be simulated favorably to serve as a proxy for the observed nec bifurcation with the availability of the long term reanalysis wind stress data this helps to lengthen the nec bifurcation time series back to 1962 although quasi decadal variability was prominent in the last two decades the nec bifurcation was dominated by changes with a 3 5 yr period during the 1980s and had low variance prior to the 1970s these interdecadalmodulationsin the characteristics of the nec bifurcation reflect similar interdecadal modulations in the wind forcing field over the western tropical north pacific ocean although the nec bifurcation on interannual and longer time

the tug of war between the west philippine sea and south china sea tropical waters and intermediate waters in the okinawa trough kuroshio subsurface waters are the major source of nutrients to the east china sea continental shelf a major fishing ground these subsurface waters are heavily affected by the south china sea scs tropical and intermediate waters which contain more nutrients than the tropical smax and intermediate smin waters from the west philippine sea wps a front was found to separate these waters from the scs and wps the reported front in the okinawa trough however was identified based only on one time data from a single cross section here historical hydrographic data between march 1950 and december 2011 are analyzed a vertical front tilted toward the west is found in all seasons in all years in the okinawa trough in winter the presence of the scs tropical water is the most prominent it is the weakest in autumn as for intermediate waters smin the wps and scs intermediate waters show much weaker seasonality compared with tropical waters although in summer the wps intermediate water contribution is slightly larger than during other times

interannual modulation of the pacific decadal oscillation pdo on the low latitude western north pacific to investigate the interannual variability in the northwestern pacific an empirical mode decomposition emd was applied to 17 year absolute dynamic topography adt data west of luzon island the philippines the mean sea surface height in this area is an appropriate index for the kuroshio intrusion into the south china sea scs significant interannual fluctuations were extracted by the emd the interannual variability was strongly correlated with the pacific decadal oscillation pdo index but not the el nino southern oscillation enso this indicated the potential impact of the pdo on the circulation in the area in the warm phase of the pdo positive index a southerly anomalous wind off the philippines causes a northward shift of the north equatorial current bifurcation latitude necbl this leads to a weakened kuroshio off luzon favoring kuroshio intrusion into the scs the northward migration of the necbl also results in a weakened kuroshio off southeast taiwan and a larger kuroshio transport off northeast taiwan the abundant westward propagating eddies impinging on the kuroshio in the subtropical countercurrent region increases this transport although the enso has little effect on monsoonal winds during the warm pdo phase it has a strong impact on the monsoon and meridional migration of the necbl during the cold phase of the pdo therefore necbl variations only show a close correspondence with the enso during the cold pdo phase because the influence of the enso is not stationary the impact of the pdo should be taken into account when examining interannual variability in the low latitude western north pacific

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

statistical re analysis for size dependency in deep sea mixing using the data of ruddiman et al we tested the implicit assumption that biogenic mixing intensity dbslb within a deposit is independent of particle size a conservative friedman rank sums test and the multiple comparison test for it were used to compare the downcore dispersion of several size fractions 11 500 m of volcanic ash in three of the seven cores analyzed the null hypothesis of size independent mixing was rejected fisher s method of compounding independent probabilities forced rejection of the hypothesis of size independent mixing overall p 0 001 i e when all the data for the seven cores were considered together mixing is size dependent with finer fractions being more intensely mixed the likely cause is size selective feeding by infauna the importance of the observed differences in stratigraphy among size fractions must be evaluated against the resolution required to address the problem at hand

north pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems abstract recent studies have identified the north pacific gyre oscillation npgo as a mode of climate variability that is linked to previously unexplained fluctuations of salinity nutrient and chlorophyll in the northeast pacific the npgo reflects changes in strength of the central and eastern branches of the subtropical gyre and is driven by the atmosphere through the north pacific oscillation npo the second dominant mode of sea level pressure variability in the north pacific it is shown that rossby wave dynamics excited by the npo propagate the npgo signature in the sea surface height ssh field from the central north pacific into the kuroshio oyashio extension koe and trigger changes in the strength of the koe with a lag of 2 3 yr this suggests that the npgo index can be used to track changes in the entire northern branch of the north pacific subtropical gyre these results also provide a physical mechanism to explain coherent decadal climate variations and ecosystem changes between the no