the sulfur flow fields of the fossa di vulcano sulfur flow deposits at the fossa di vulcano fumarole field italy are dominated by thermal erosion features these are characteristic of sulfur flows at this location where most flows are emplaced in a combusting mode such that all flow sulfur is melted and consumed during the emplacement event further thermal erosion during emplacement results in pits and channels that mark the passage of the combusting flow these thermal erosion pits and channels are typically littered with non combusted silicate blocks show overhanging rims and an absence of sulfur if activity remains confined to a source fumarole basin then sulfur lake activity will result combustion of such a feature leaves thermally eroded pits typically a few tens of centimeters to a few meters wide and long and a few tens of centimeters deep however the increase in sulfur volume during melting and erosion of pit walls mean that overflow and breaching is common this leads to capture of new sulfur encrusted fumarole basins and flow extension flow extension away from the lake results in thermal erosion channels as much as 1 7 m wide 0 6 m deep and 23 5 m long flow direction is dictated by slope cinder ejection and sources of new sulfur thus flows are capable of moving down across and or up slope if that is the dominant source of new sulfur we estimate that sulfur flow activity has combusted 2 000 5 000 m3 or 4 000 10 000 tons of sulfur at vulcano only one noncombusted unit could be found during seven fumarole fieldwide surveys during 1998 2003 this was 7 3 m long and 0 3 m wide and had a viscosity of 0 1 40 pa s this viscosity is consistent with emplacement temperatures of 165 180 c which are lower than sulfur s combustion temperature at vulcano the commonality of thermal erosion features over noncombusted sulfur flow units indicates that combusting emplacement has been the main mode of flow emplacement at this volcano the common occurrence of combustion is also evident from reference to the same phenomenon by deodat de dolomieu in 1783

volcanic aerosol perturbations and strong el nino events no general correlation we test the hypothesis that el nino southern oscillation enso events are caused or enhanced by volcanic aerosol perturbations using two methods 1 a case by case comparison of the 16 strongest el nino events of the last 150 years with the characteristics of the largest concurrent volcanic events and 2 comparison of the timing of strong el nino events and the independently determined record of stratospheric optical depth perturbations many eruptions that occurred near times of strong el nino years produced small amounts of stratospheric aerosols in many cases the relative timing of the two events argues against triggering the correlation of 4 of 11 peaks in global stratospheric optical depth 0 025 within 3 years of strong el nino events over the last 150 years is what would be expected by chance moreover five strong el ninos occurred between 1915 and 1960 when the stratosphere was largely free of volcanic aerosols of the three strongest tropical volcanic aerosol perturbations that coincided with or were followed by strong el ninos in the period studied krakatau in 1883 el chichon in 1982 and pinatubo in 1991 the two modern ones occurred after the earliest sst warming of the el nino events the coincidence of these two phenomena indicates no causative relationship

suppression of baroclinic instabilities in buoyancy driven flow over sloping bathymetry abstractbaroclinic instabilities are ubiquitous in many types of geostrophic flow however they are seldom observed in river plumes despite strong lateral density gradients within the plume front supported by results from a realistic numerical simulation of the mississippi atchafalaya river plume idealized numerical simulations of buoyancy driven flow are used to investigate baroclinic instabilities in buoyancy driven flow over a sloping bottom the parameter space is defined by the slope burger number s nf 1 where n is the buoyancy frequency f is the coriolis parameter and is the bottom slope and the richardson number ri n2f2m 4 where m2 hb is the magnitude of the lateral buoyancy gradients instabilities only form in a subset of the simulations with the criterion that sh sri 1 2 uf 1w 1 m2f 2 0 2 where u is a horizontal velocity scale and sh is a new parameter named the horizontal slope burger number suppression of instability formation for certain flow conditions contrasts

enhancement of alongshore freshwater transport in surface advected river plumes by tides abstracta recent numerical study by isobe showed that imposing alongshore tidal forcing on buoyant coastal discharge enhances the net freshwater transport in the coastal currents the mechanisms for this transport enhancement are studied using a three dimensional primitive equation ocean model regional ocean modeling system roms lagrangian drifters are used to trace the freshwater transport paths it is found that the river plume bulge circulation largely follows the rigid body motion i e constant vorticity the buoyant fluid near the bulge s outer edge is thinner and faster behaving as a baroclinic jet the bulge currents then split after impinging on the coast the outer fluid feeds the downshelf flowing coastal currents while the inner fluid recirculates to form the bulge the coastal current transport estimated from the present and prior studies corresponds well to a baroclinic jet theory with the incident angle of bulge currents at the coast being a key parameter without tides the bulg

influence of the sea ice thickness distribution on polar climate in ccsm3 abstract the sea ice simulation of the community climate system model version 3 ccsm3 t42 gx1 and t85 gx1 control simulations is presented and the influence of the parameterized sea ice thickness distribution itd on polar climate conditions is examined this includes an analysis of the change in mean climate conditions and simulated sea ice feedbacks when an itd is included it is found that including a representation of the subgrid scale itd results in larger ice growth rates and thicker sea ice these larger growth rates represent a higher heat loss from the ocean ice column to the atmosphere resulting in warmer surface conditions ocean circulation most notably in the southern hemisphere is also modified by the itd because of the influence of enhanced high latitude ice formation on the ocean buoyancy flux and resulting deep water formation changes in atmospheric circulation also result again most notably in the southern hemisphere there are indications that the itd also modifies simulated sea

ballooning of river plume bulge and its stabilization by tidal currents when freshwater debouches into an adjacent ocean an anticyclonic eddy bulge is formed in front of the river mouth it is well known that a bulge growing offshore ballooning hardly reaches a steady state in the absence of either ambient currents or wind forcing this study provides a physical interpretation for the ballooning of river plume bulges by conducting numerical experiments in which a river plume is induced by a coastal freshwater source part of the freshwater released to the model ocean undergoes inertial instability near inertial oscillations are predominant when disturbances are not forced in ambient waters of the river plume these isotropic disturbances are amplified by inertial instability so that unstabilized freshwater can move in arbitrary directions thus unstabilized freshwater does not need to move toward the coastal boundary current on the right hand side of the river mouth freshwater unstabilized for a long time can stay in the bulge for a long time unstabilized freshwater accumulates gradually in the bulge and so ballooning occurs when the direction of disturbances is prescribed in ambient waters unstabilized freshwater is forced to move in the same direction thereby the motion of unstabilized freshwater is restricted in the alongshore direction when background disturbances are induced by alongshore tidal currents it is therefore concluded that tidal currents play a role in stabilizing the offshore growth of river plume bulges in coastal and shelf waters

coastal outflow currents into a buoyant layer of arbitrary depth the long wave reduced gravity shallow water equations the semi geostrophic equations are used to study the outflow of a river into the ocean while previous models have studied dynamics driven by gradients in density the focus here is on the effects of potential vorticity anomaly pva the river water is taken to have the same density as a finite depth upper layer of oceanic fluid but the two fluids have different uniform potential vorticities under these assumptions the governing equations reduce to two first order nonlinear partial differential equations which are integrated numerically for a prescribed efflux of river water and pva results are found to depend strongly on the sign of the pva with all fluid turning downstream in the direction of kelvin wave propagation when the river water has positive pva and anticyclonic flow upstream of the river mouth when the pva is negative in all cases a nonlinear kelvin wave propagates at finite speed ahead of the river water away from the river mouth the uniformity of one set of riemann invariants allows for similarity solutions that describe the shape of the outflow as well as a theory that predicts properties of the kelvin wave a range of behaviours is observed including flows that develop shocks and flows that continue to expand offshore the qualitative behaviour of the outflow is strongly correlated with the value of a single dimensionless parameter that expresses the ratio of the speed of the flow driven by the kelvin wave to that driven by image vorticity

different impacts of northern tropical and southern volcanic eruptions on the tropical pacific sst in the last millennium abstractthe impact of northern tropical and southern volcanic eruptions on the pacific sea surface temperature sst and the different response mechanisms arising due to differences in the volcan

dispersal of the pearl river plume over continental shelf in summer abstract satellite images of turbidity were used to study the climatological monthly and typical snapshot distributions of the pearl river plume over the shelf in summer from 2003 to 2016 these images show that the plume spreads offshore over the eastern shelf and is trapped near the coast over the western shelf eastward extension of the plume retreats from june to august monthly spatial variations of the plume are characterized by eastward spreading westward spreading or both time series of monthly plume area was quantified by applying the k mean clustering method to identify the turbid plume water decomposition of the 14 year monthly turbidity data by the empirical orthogonal function eof analysis isolated the 1st mode in both the eastward and westward spreading pattern as the time series closely related to the pearl river discharge and the 2nd mode with out of phase turbidity anomalies over the eastern and western shelves that is associated with the prevailing wind direction eight typical plume types were detected from the satellite snapshots they are characterized by coastal jet eastward offshore spreading westward spreading bidirectional spreading bulge isolated patch offshore branch and offshore filaments respectively their possible mechanisms are discussed

impacts of a pinatubo size volcanic eruption on enso observations and model simulations of the climate responses to strong explosive low latitude volcanic eruptions suggest a significant increase in the likelihood of el nino during the eruption and post eruption years though model results have been inconclusive and have varied in magnitude and even sign in this study we test how this spread of responses depends on the initial phase of el nino southern oscillation enso in the eruption year and on the eruption s seasonal timing we employ the gfdl cm2 1 global coupled general circulation model to investigate the impact of the pinatubo 1991 eruption assuming that in 1991 enso would otherwise be in central or eastern pacific el nino la nina or neutral phases we obtain statistically significant el nino responses in a year after the eruption for all cases except la nina which shows no response in the eastern equatorial pacific the eruption has a weaker impact on eastern pacific el ninos than on central pacific el ninos we find that the ocean dynamical thermostat and to a lesser extent wind changes due to land ocean temperature gradients are the main feedbacks affecting el nino development after the eruption the el nino responses to eruptions occurring in summer are more pronounced than for winter and spring eruptions that the climate response depends on eruption season and initial enso phase may help to reconcile apparent inconsistencies among previous studies

the effect of explosive tropical volcanism on enso thisstudyexaminestheresponseofelnino southernoscillation enso tomassivevolcaniceruptionsin a suite of coupled general circulation model cgcm simulations utilizing the community climate system model version 3 ccsm3 the authors find that the radiative forcing due to volcanic aerosols injected into the stratosphere induces a model climatic response that projects onto the enso mode and initially creates a la nina event that peaks around the time the volcanic forcing peaks the curl of the wind stress changes accompanying this volcanically forced equatorial region cooling acts to recharge the equatorial region heat for weaker volcanic eruptions this recharging results in an el nino event about two seasons after the peak of the volcanic forcing the results of the ccsm3 volcanic forcing experiments lead the authors to propose that the initial tropical pacific ocean response to volcanic forcing is determined by four different mechanisms one process is the dynamical thermostat mechanism the mean upwelling of anomalous temperature and the other processes are related to the zonal equatorial gradients of the mean cloud albedo newtonian cooling and mixed layer depth the zonal gradient in ccsm3 set by both mixed layer depth and newtonian cooling terms oppose the zonal sea surface temperature anomaly ssta gradient produced by the dy namical thermostat and initially dominate the mixed layer zonal equatorial heat budget response applying this knowledge to a simple volcanically forced mixed layer equation using observed estimates of the spa tially varying variables the authors again find that the mixed layer depth and newtonian cooling terms oppose and dominate the zonal ssta gradient produced by the dynamical thermostat this implies that the observed initial response to volcanic forcing should be la nina like not el nino as suggested by paleo climate records

potential vorticity dynamics of coastal outflows abstracta simple quasigeostrophic model is used to examine the outflow from a river estuary or strait into a coastal ocean as shown by johnson et al these quasigeostrophic outflows are accurately described by analytical long wave solutions this paper first uses these solutions and contour dynamics simulations to discuss the behavior of coastal outflows second it extends the model and the long wave theory to consider the effects of ambient currents tides winds or a variable source flux third consideration of the momentum flux at the source is used to understand the turning of the current showing that steady solutions conserve momentum hence resolving the momentum imbalance paradox of pichevin and nof finally a new numerical scheme to compute steady outflow boundaries is developed the model focuses on the key dynamics driven by the source velocity and the generation of vorticity as the buoyant fluid adjusts the simplicity of the model and insight given by the long wave solutions enables

modes of climate variability synthesis and review of proxy based reconstructions through the holocene abstract modes of climate variability affect global and regional climates on different spatio temporal scales and they have important impacts on human activities and ecosystems as these modes are a useful tool for simplifying the understanding of the climate system it is crucial that we gain improved knowledge of their long term past evolution and interactions over time to contextualise their present and future behaviour we review the literature focused on proxy based reconstructions of modes of climate variability during the holocene i e the last 11 7 thousand years with a special emphasis on i proxy based reconstruction methods ii available proxy based reconstructions of the main modes of variability i e el nino southern oscillation pacific decadal variability atlantic multidecadal variability the north atlantic oscillation the southern annular mode and the indian ocean dipole iii major interactions between these modes and iv external forcing mechanisms related to the evolution of these modes this review shows that modes of variability can be reconstructed using proxy based records from a wide range of natural archives but these reconstructions are scarce beyond the last millennium partly due to the lack of robust chronologies with reduced dating uncertainties technical issues related to proxy calibration and difficulty elucidating their stationary impact or not on regional climates over time while for each mode the available reconstructions tend to agree at mutidecadal timescales they show notable disagreement on shorter timescales beyond the instrumental period the reviewed evidence suggests that the intrinsic variability of modes can be modulated by external forcing such as orbital solar volcanic and anthropogenic forcing the review also highlights some modes experience higher variability over the instrumental period which is partly ascribed to anthropogenic forcing these features stress the paramount importance of further studying their past variations using long climate proxy records for the progress of climate science

coastal mixing in multiple mouth deltas a case study in the po delta italy abstract satellite imagery provides evidence of complex mixing dynamics in the coastal zone in front of multiple mouth deltas one peculiar feature identified in front of the po delta italy consists in warmer water bulges present in some periods in the coastal zone between the river mouths such features are evident during both high and low river discharge through an integrated approach based on the analysis of satellite imagery in situ field data and a high resolution oceanographic model representing the whole river delta sea system we investigated the relative contribution of the different forcing in controlling coastal mixing of riverine waters the results evidence that the occurrence of these warmer saltier water bulges is due to upwelling induced by the combined action of tides and wind regimes aligned along coastline winds from the land and along the coast drive the upwelling through the well known mechanism described by ekman the presence of river discharge enhance the water column stratification creating the conditions in which tidal action follows the tidal straining theory both processes are identified in modelling results the occurrence of these localized coastal waters with peculiar thermohaline characteristics detectable on satellite imagery of the area can be relevant in the definition of the freshwater areas of influence and the mechanisms of riverine water mixing in the near coastal zone this can shed some light eventually on characterizing the sediment dynamics as well as the thermohaline properties of waters in the area and also to identify eventual impacts on the local ecosystems and fishery

a simple criterion for gyre formation by the surface outflow from a strait with application to the alboran sea a survey of relevant numerical laboratory and observational studies combined with our own laboratory experiments suggests that the surface outflow from a strait generally forms a gyre in the adjacent sea if the exit corner is sharp the gyre grows from an initial separation bubble of radius u f where u is the current speed and f the coriolis frequency the criterion for the maintenance of a coastal jet along a curved coast instead of separation and gyre formation seems to be that the rossby number u frw 1 1 with rw the radius of curvature of the exit corner so that the coriolis force can hold the current to the coast this synthesis disregards factors such as the variation of u across the current but applied to the flow through the strait of gibraltar into the alboran sea suggests that a gyre should always form as the exit corner is sharp we suggest though that the relevant curvature is that where the interface between the two layers intersects the seafloor rather than where the sea surface meets the coast if this is the case supercritical flow or some subcritical flows at the eastern end of the strait should still always lead to gyre formation but the observed replacement of the gyre by a coastal jet along the moroccan coast could be related to subcritical flow that is reduced below its normal value by a barotropic fluctuation or by changes in the interface depth in the mediterranean

global surface temperature responses to major volcanic eruptions the impacts of pollution resulting from large explosive volcanic eruptions on the atmospheric heat budget and planetary albedo are not in doubt1 2 however the effects of volcanic aerosols on the surface climate are less clear and still controversial3 4 in a previous study5 it was shown that significant surface cooling occurs over the landmasses of the northern hemisphere in the first few months after a major eruption in that hemisphere here we extend that work using new surface air temperature compilations based on land and marine data6 for both the northern and southern hemispheres our results indicate that major northern hemisphere eruptions have an immediate effect on the northern hemisphere average surface temperature but little or no effect on the southern hemisphere average southern hemisphere eruptions affect both southern and northern hemisphere temperatures after a lag of between six months and a year

ocean response to volcanic eruptions in coupled model intercomparison project 5 simulations we examine the oceanic impact of large tropical volcanic eruptions as they appear in ensembles of historical simulations from eight coupled model intercomparison project phase 5 models these models show a response that includes lowering of global average sea surface temperature by 0 1 0 3 k comparable to the observations they show enhancement of arctic ice cover in the years following major volcanic eruptions with long lived temperature anomalies extending to the middepth and deep ocean on decadal to centennial timescales regional ocean responses vary although there is some consistent hemispheric asymmetry associated with the hemisphere in which the eruption occurs temperature decreases and salinity increases contribute to an increase in the density of surface water and an enhancement in the overturning circulation of the north atlantic ocean following these eruptions the strength of this overturning increase varies considerably from model to model and is correlated with the background variability of overturning in each model any cause effect relationship between eruptions and the phase of el nino is weak

the columbia river plume study subtidal variability in the velocity and salinity fields a comprehensive study of the strongly wind driven midlatitude buoyant plume from the columbia river located on the u s west coast demonstrates that the plume has two basic structures during the fall winter season namely a thin 5 15 m strongly stratified plume tending west to northwestward during periods of southward or light northward wind stress and a thicker 10 40 m weakly stratified plume tending northward and hugging the coast during periods of stronger northward stress the plume and its velocity field respond nearly instantaneously to changes in wind speed or direction and the wind fluctuations have timescales of 2 10 days frictional wind driven currents cause the primarily unidirectional flow down the plume axis to veer to the right or left of the axis for northward or southward winds respectively farther downstream currents turn to parallel rather than cross salinity contours consistent with a geostrophic balance in particular during periods when the plume is separated from the coast currents tend to flow around the mound of fresher water at distances exceeding about 20 km from the river mouth the along shelf depth averaged flow over the inner to midshelf is linear and depth averaged acceleration is governed to lowest order by the difference between surface and bottom stress alone in this region along shelf geostrophic buoyancy driven currents at 5 m calculated from surface density and along shelf geostrophic wind driven currents computed from a depth averaged linear model are comparable in magnitude 10 25 cm s 1

effects of tides on freshwater and volume transports in the changjiang river plume 1 effects of tides on the changjiang river plume are investigated using a numerical model of the east china and yellow seas in the absence of tides the buoyancy driven coastal current downstream of the river mouth is a surface trapped plume attached to the coast in the presence of tides however the plume shifts away from the coast and features a bottom boundary layer the freshwater transport by the coastal current accounts for only 35 of the changjiang river discharge without tides but increases to 80 with tides tidal currents stabilize the plume bulge near the river mouth and force the plume water to move in the direction of tidal currents thus increasing the downstream freshwater transport in contrast tidal residual currents are weak and make little contributions to the total freshwater transport tidal mixing reduces the plume s buoyancy but increases its thickness so that the freshwater transport is insensitive to the strength of turbulent mixing volume transport in the tidal affected buoyancy coastal current exceeds the river discharge by 4 to 12 times as opposed to 2 3 fold amplification in the plume without tides tidal mixing between the plume and ambient shelf waters produces higher salinity classes in the plume so that the volume flux in the downstream coastal current increases to discharge the freshwater released from the changjiang river

a simple theory for the fate of buoyant coastal discharges abstract a simple theory that predicts the vertical structure and offshore spreading of a localized buoyant inflow onto a continental shelf is formulated the theory is based on two competing mechanisms that move the buoyant fluid offshore 1 the radial spread of the lighter water over the ambient water being deflected by the coriolis force and producing an anticyclonic cyclostrophic plume and 2 offshore transport of buoyant water in the frictional bottom boundary layer that moves the entire plume offshore while maintaining contact with the bottom the surface expression of the cyclostrophic plume moves offshore a distance ys 2 3g h0 2i 2g h0 2i 1 2f where g is reduced gravity based on the inflow density anomaly h0 is the inflow depth i is the inflow velocity and f is the coriolis parameter the plume remains attached to the bottom to a depth given by hb 2l ih0f g 1 2 where l is the inflow width both scales are based solely on parameters of the buoyant inflow at its source there

tropical cyclone activity in the northwest pacific in relation to the el nino southern oscillation phenomenon abstract the interannual variations in tropical cyclone activity in the northwest pacific nwpac and their relationships with the el nino southern oscillation enso phenomenon were studied using the method of spectral analyses time series of a southern oscillation index soi defined as the sea level pressure difference between easter island and darwin and tropical cyclone activity in the entire nwpac ocean basin as well as in different regions of the nwpac were analyzed two spectral peaks are apparent in all these time series one corresponds to the generally accepted southern oscillation with a period of 3 to 3 5 years and another at the quasi biennial oscillation qbo frequency cross spectral analyses between the soi and tropical cyclone activity show significant coherence in these two spectral peaks the dominant peak is at the southern oscillation frequency with the soi leading typhoon activity by almost a year at the qbo frequency the two series are almost in phase cyclone activity in t

possible association of stratospheric aerosols and el nino type events to determine whether the 1982 83 el nino event and the eruption of el chichon in april 1982 are related eleven similar eruptions at low latitudes 20 show just the opposite behavior they show significant cooling of the sea surface temperatures in this region especially in the fourth and fifth season after the eruption the association is found to be significant at the 95 level

a simple model for the pacific cold tongue and enso abstract a conceptual model is constructed based upon the bjerknes hypothesis of tropical atmosphere ocean interaction it is shown that strong feedbacks among the trade winds equatorial zonal sea surface temperature contrast and upper ocean heat content occur in the tropical pacific basin coupled atmosphere ocean dynamics produce both the strong pacific cold tongue climate state and the el nino southern oscillation enso phenomenon the cold tongue climate state is unstable and gives rise to the self sustained enso which can be understood as an equatorial ocean recharge oscillator the small basin size and the influence of a wind system resulting from heating sources of its adjacent landmasses are responsible for a weak and stable atlantic cold tongue state that cannot support enso like interannual variability the presence of westerly wind associated with the walker circulation ascending at the western pacific warm pool disables the dynamical coupling processes in the equatorial indian ocean as a

a simple method for estimating barotropic tidal currents on continental margins with specific application to the m2 tide off the atlantic and pacific coasts of the united states abstract theory is developed to describe barotropic tidal currents on smooth continental shelves that is continental shelves with longshore scales much greater than the shelf width two models are considered one in which sea level don not vary significantly across the shelf and the other in which it does both models include longshore gradients and friction parameterized linearly in velocity the models were tested by calculating the m2 tidal currents off the atlantic and pacific coasts of the united states and then comparing the calculated currents to those measured results show that theory and observation are in very good agreement as far offshore as 300 km along the atlantic coast on account of the wide continental shelf current velocities are typically o 0 10 0 15 m s 1 north of cape hatteras and o 0 15 0 28 m s 1 off savannah georgia currents rotate anticyclonically and are highly elliptical ellipticity e 0 4 with the semi major axis oriented normal to the coast friction is sign

seasonal variations of the yellow river plume in the bohai sea a model study 1 we investigated the behavior of the yellow river plume in the bohai sea through a year and its controlling mechanisms using a numerical model driven by monthly averaged wind stress heat flux and river discharge the model produced a clear seasonal behavior of the yellow river plume in summer the yellow river plume extends northeastward into the central bohai sea in autumn it turns southward and flows into laizhou bay along the coast in winter most of the diluted water is found around southeastern corner of laizhou bay and in spring a low salinity area appears in southwest laizhou bay with the same model several well designed numerical experiments were performed to investigate the effect on the behavior of the yellow river plume of tidal current river discharge wind stress and thermal stratification the tidal currents promote the offshore spread of diluted water while the tide induced residual currents prevent the plume from extending further downstream in the direction of kelvin wave propagation wind stresses lead to pronounced changes in the path and shape of the plume in autumn and winter northwesterly or northerly winds drive the buoyant water into laizhou bay along the coast in summer the combination of southeasterly winds and thermal stratification drives the plume extend northeastward into the central bohai sea by changing only the magnitude of wind stress or river discharge in the experiments we examined the sensitivity of summertime plume to the magnitude of wind stress and river discharge

tidal effects on the bulge region of changjiang river plume abstract a three dimensional hydrodynamic model is developed to investigate how tide affects the bulge region of the changjiang river plume in the absence of tide the plume bulge exhibits multi eddies and grows with time in the presence of tide however the bulge is well organized strong variation of turbulent mixing over the spring neap tidal cycle causes periodic detachments and ejections of a plume patch from the river mouth the detachment occurs during the neap to spring transition when tidally generated turbulence is strong enough to break down stratification in the inner shelf region near the mouth of changjiang river estuary as a consequence the changjiang river plume moves downstream as a series of low salinity patches this detachment process occurs regardless of the river discharge conditions due to oscillating tidal currents in the changjiang estuary the freshwater outflow from the river mouth shows moderate about 20 fluctuations around the river discharge over the spring neap tidal cycle but large fluctuations about 5 times around the river discharge over the flood ebb tidal cycle however they only produce minor effects on the plume structure over the adjacent shelf

coastal flows driven by a local density flux a two layer model with a rigid lid and a flat bottom on an f plane is employed to study a flow field driven by a density flux through the sea surface or the coast for example freshwater discharged from a river the negative positive density flux into the upper layer is represented by the water beneath over the interface changing from the lower upper layer to the upper lower layer that is entrainment of the lower upper layer by the upper lower layer the subinertial flow pattern constrained by the coast has two components one is a baroclinic eddy nearby that matches the entrainment region and the other is a forced internal kelvin wave along the appropriate half of the coast

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