the impact of rapid coastline changes and sea level rise on the tides in the bohai sea china 1 the tidal regime in the bohai sea china is investigated using observations and an established numerical tidal model the area has recently experienced rapid coastline changes due to natural developments of the yellow river delta and large scale anthropogenic land reclamation these morphological changes are not reflected in most global bathymetric databases and are thus rarely incorporated into investigations of the bohai sea it is shown that there have indeed been significant changes in the tidal regime in the bohai sea over the last 35 years with m2 amplitudes changing up to 20 cm in some parts the model captures some of these changes when the appropriate bathymetries are used furthermore the simulations show that the tides in the bohai sea have become more sensitive to future sea level rise and the way in which it is implemented in the model i e whether or not flood defenses are included these sensitivity changes are due to the recent coastal developments

secular changes in the solar semidiurnal tide of the western north atlantic ocean 1 an analysis of twentieth century tide gauge records reveals that the solar semidiurnal tide s2 has been decreasing in amplitude along the eastern coast of north america and at the mid ocean site bermuda in relative terms the observed rates are unusually large of order 10 per century periods of greatest change however are inconsistent among the stations and roughly half the stations show increasing amplitude since the late 1990s excepting the gulf of maine lunar tides are either static or slightly increasing in amplitude a few stations show decreases large changes in solar but not lunar tides suggest causes related to variable radiational forcing but the hypothesis is at present unproven

on analysis and prediction of tides on the west coast of great britain summary long period tidal records from eight ports on the west coast of great britain are analysed using both the harmonic method and the response function time series up to 9 5 yr were used so that fine structure of certain regions of high energy in the tidal residual spectrum may be examined this also assisted in accurate separation of tides from surges according to the currently accepted formulation of m1 its composition is not compatible with its actual composition in the real tide and as such has no useful purpose to serve in computation of predictions constituents sa ssa ma and mb are adversly affected by weather and long records are essential for their accurate separation it has been observed that annual perturbations of s2 similar to those confirmed in recent years for m2 also exist but these are not readily recognisable because their speeds are the same as those of constituents t2 and r2 these perturbations being highly sensitive to meteorological forces are mainly responsible for cusps or humps in the vicinity of major tidal constituents in tidal residual spectra the relationship of radiational and gravitational tides is found to be in very good agreement with theoretical results in summer months non predictable variance reduces to about half of the annual variance reflecting the regional weather conditions of summer and winter

impact of rainfall and topography on the distribution of clays and major cations in granitic catenas of southern africa abstract soil catenas integrate and amplify gravity transfer and differentiation processes of eluviation and illuviation in soil profiles we quantified differences in these redistribution processes along granitic catenas across an arid to sub humid climate gradient in kruger national park south africa we measured soil properties in nine catenas sampled from three areas receiving annual rainfall of 470 mm arid zone 550 mm semi arid zone and 730 mm sub humid zone as rainfall increased kaolinite replaced smectite as the dominant clay mineral in all landscape positions across the catenas toeslopes showed the strongest evidence of this transition with an excess of smectite in the arid catenas but complete prevalence of kaolinite in toeslopes of sub humid catenas the concentration and distribution of clay along the catenas were dependent on landscape position as well soil profiles at and near the crests were clay depleted as low as 1 while those at the toeslopes had much more clay up to 60 clay redistribution along catenas was sensitive to climate with the least amount of redistribution occurring in the dry sites and the most occurring in the wet sites as a consequence the sub humid catenas had clay accumulation only in a small part of the toeslopes while the bulk of their length was represented by highly leached soils in contrast arid zone catenas showed little clay redistribution and semi arid sites displayed the greatest within catena clay redistribution and preservation clay movement and storage conditioned other soil properties such as cec base cation distribution base saturation and ph

sediment transport over an accretional intertidal flat with influences of reclamation jiangsu coast china this paper focuses on the hydrodynamic and suspended sediment transport processes in response to sequential reclamations over the intertidal flat jiangsu coast which used to be one of the widest intertidal flats in china investigations into the sediment transport patterns reveal that net suspended sediment fluxes increased from 102 kg m 1 on the upper intertidal flat to 103 4 kg m 1 on the lower intertidal flat per tidal cycle this variation was caused mainly by the phases of the current velocity suspended sediment concentration ssc local bed geomorphology inundation patterns and extreme weather conditions the longshore component of tidal currents intensifies seaward over the intertidal flat extreme weather conditions e g storms and strong winds were important factors affecting the current velocity structures the intensity of residual currents and the sscs the sscs were characterized by several peaks throughout the tidal cycle these peaks were associated with strong currents combined wave current interactions and intense turbulences due to the initial flood surge furthermore the suspended sediment was finer and contained more clay materials during the flood phase of the tidal cycle than during the ebb fine particles were transported within the upper water column by landward residual currents but coarse particles were transported within the lower water column by seaward residual currents overall residual currents were apt to transport fine grained sediment landward and coarse grained sediment seaward this pattern indicates that the suspended sediment fluxes are highly variable in the water column even for very shallow tidal environments the cross shore component accounted only for a small percentage of the total sediment flux however this part of sediment supply dominated accretion over the intertidal flat the intertidal flat has become narrower and steeper following sequential reclamations a negative feedback process existed to maintain the convex profile shape although the human activities i e reclamation could have modified the natural process the surficial sediment tended to become finer on the mid upper intertidal flat but coarser on the lower intertidal flat following reclamations in response to a reduction in the tidal currents over the intertidal zone and enhancement of wave action over the lower intertidal flat accretion with high rates was maintained by landward transport of sediment in such an accretional system with influences of reclamation the width or slope of the intertidal flat is adjusted continuously before the cease of reclamation the intertidal flat is unable to achieve an equilibrium shape

empirical cotidal charts of the bohai yellow and east china seas from 10 years of topex poseidon altimetry 1 harmonic analysis of 10 years of topex poseidon tp along track altimetry is performed to derive the semidiurnal diurnal long period and quarter diurnal tides in the bohai yellow and east china seas the tp solutions are evaluated through intercomparison for crossover points and comparison with the ground truth showing that the accuracy of tp solutions in the study area has achieved levels of 2 4 cm in amplitudes and 5degrees in phase lags for principal constituents m 2 s 2 k 1 o 1 and s a the tp derived s a amplitudes have a systematic bias of about 10 as compared with the ground truth indicating the possible importance of loading effect of this constituent in the study area which is generally not considered in geodetic surveys the tidal harmonics from tp altimetry and at coastal and island stations are used to give a new set of empirical cotidal charts for principal constituents m 2 s 2 k 1 o 1 and s a the accuracy of these new charts is believed to be significantly higher than the previous charts for the offshore area

nodal variations and long term changes in the main tides on the coasts of china the long term changes in the main tidal constituents o1 k1 m2 n2 and s2 along the coasts of china and in adjacent seas are investigated based on 17 tide gauge records covering the period 1954 2012 the observed 18 61 year nodal modulations of the diurnal constituents o1 and k1 are in agreement with the equilibrium tidal theory except in the south china sea the observed modulations of the m2 and n2 amplitudes are smaller than theoretically predicted at the northern stations and larger at the southern stations the discrepancies between the theoretically predicted nodal variations and the observations are discussed the 8 85 year perigean cycle is identifiable in the n2 parameters at most stations except those in the south china sea the radiational component of s2 contributes on average 16 of the observed s2 except in the gulf of tonkin on the south coast where it accounts for up to 65 we confirmed the existence of nodal modulation in s2 which is stronger on the north coast the semidiurnal tidal parameters show significant secular trends in the bohai and yellow seas on the north coast and in the taiwan strait the largest increase is found for m2 for which the amplitude increases by 4 7 mm yr in the yellow sea the potential causes for the linear trends in tidal constants are discussed

unravelling the causes of tidal asymmetry in deltas abstract tidal asymmetry in deltas is caused by both the intrinsic asymmetry resulting from the combination of astronomical tides and by nonlinear tidal interactions that occur in shallow water the relative importance of these sources of tidal asymmetry in delta channel networks have remained poorly studied partly due to the limitations of classical harmonic analysis ha in hindcasting nonstationary tides the pearl river delta prd is a multichannel system with rapidly changing bathymetry subject to severe human interventions this work applies a nonstationary harmonic model ns tide to hydrological data from 15 stations in the prd spanning the period 1961 2012 the spatiotemporal variation of multiple sources of tidal asymmetry is quantified by a skewness metric revealing how similar or dissimilar the development of alternative sources of tidal asymmetry develop in the delta subject to study a relative sensitivity coefficient rsc is introduced to decompose the contribution of tidal amplitude variations to multiple tidal asymmetries analytical results show the development of tides becoming gradually more asymmetric as they propagate into delta channel networks and how this depends on the river flow variation in the orientation of tidal asymmetries induced by different combinations of tidal constituents leads to a complex pattern of the overall tidal asymmetry in the prd our results show that tidal asymmetry in deltas can be significantly dependent on the river flow

tides and long term modulations in the caribbean sea the tidal signal and its long term variation in the caribbean sea is analyzed on the basis of hourly records from thirteen tide gauges five of which span more than 20 years the seven larger tidal constituents are studied namely the fortnightly term mf diurnal k1 o1 and p1 and semidiurnal m2 s2 and n2 the 18 61 year nodal modulation is clearly identifiable in almost all the examined constituents of lunar origin however its signal in m2 is less clear while it is almost imperceptible in n2 where the 8 85 year cycle caused by the eccentricity of the moon s orbit and the orientation of its major axis variation dominates the long term variability the effect of the nodal variation in the amplitude and phase lag of the various tidal constituents is in agreement within the 95 error limits with the theoretical gravitational estimate with the exception of the 8 85 year cycle in n2 where larger values are found overall in the caribbean the net effect of the low frequency cycles can change the maximum tidal range from 16 5 to 23 5 in a nodal cycle although the caribbean is a micro tidal environment this still results in changes of the range of up to 8 4 cm significant spatially coherent trends are found for the amplitude of s2 2 3 to 8 8 mm cy

two layer tidal modeling of the yellow and east china seas with application to seasonal variability of the m2 tide 1 the baroclinic response of tide and tidal currents in the yellow and east china seas is investigated using a two layer numerical model seasonal variability in the m2 tide especially the smaller summer amplitudes prevailing along the korea tsushima strait kang et al 1995 is investigated by a series of numerical experiments with varying degrees of stratification specific to winter and summer model results show that the summer amplitudes of the m2 tide around the southwestern tip of the korean peninsula and korea tsusima strait decrease with a peak decrease of about 14 cm off the southwestern tip of the korean peninsula while the summer amplitudes in other coastal regions tend to increase this seasonal variability generally coincides with the observations these models results indicate that seasonal stratification has several noticeable effects on the tides including varying degrees of current shear varying frictional dissipation and varying barotropic energy flux in particular it drives complicated seasonal variability in the m2 tide with a peak amplitude modulation of nearly 5 off the southwestern tip of the korean peninsula the seasonal variation of barotropic m2 energy flux through the eastern entrance of the yellow sea is thought to induce the corresponding variability in the m2 amplitude in the korea tsusima strait with smaller amplitudes found in the summer

short term changes in seafloor character due to flood derived hyperpycnal discharge typhoon mindulle taiwan july 2004 during typhoon mindulle in early july 2004 the choshui river central western taiwan discharged similar to 72 mt of sediment to the eastern taiwan strait peak concentrations were g 200 g l similar to 35 40 of which was sand box core samples and chirp compressed high intensity radar pulse sonar records taken just before and after the typhoon indicate that the hyper pycnal sediment was first deposited adjacent to the mouth of the choshui subsequently resuspended and transported northward via the taiwan warm current and redeposited as a patchy coastal band of mud dominated sediment that reached thicknesses of 1 2 m within megaripples within a month most of the mud was gone probably continuing its northward transit but more mud appeared in late august in response to typhoon aere following autumn and winter storms the entire nearshore area was again sand dominated by early spring

horizontal and residual circulations driven by wind stress curl in tokyo bay this study investigates the horizontal and residual circulations in tokyo bay using field observations numerical simulations and theoretical analysis numerical simulations show that the observed deepening of isopycnals and associated anticyclonic horizontal circulation in the bay head are mainly driven by negative wind stress curl the effects of river discharge surface heat fluxes and tides are found to be small under strong wind events the wind stress curl over the bay head can be large enough to make the surface ekman layer strongly nonlinear theoretical and numerical analyses show that under large negative wind stress curl the nonlinearity tends to induce positive pumping velocity at the base of the surface mixed layer that counteracts the ekman pumping however the typical duration of wind events in the bay head is not long enough to induce positive pumping under negative wind stress curl these results and historical wind data suggest that the average horizontal circulation and residual circulation immediately below the surface mixed layer in tokyo bay are respectively cyclonic and convergent in summer but anticyclonic and divergent in winter

diagnostic study on the vertical circulation and the maintenance mechanisms of the cyclonic gyre in lake biwa lake biwa in japan has a stable cyclonic gyre during seasons of thermal stratification a vertical circulation consisting of downwelling in the central area and upwelling near the rim of the gyre is calculated by the diagnostic model the energetics in the model indicate that this vertical circulation corresponds to the decay process of the gyre tracking of drifters in summer supports the presence of a vertical circulation though its magnitude is about 50 less than that estimated by the diagnostic model this is explained from the ratio of kinetic energy and available potential energy of the gyre the realistic value of the vertical eddy viscosity is estimated to be 0 8 2 1 cm2 s 1 in summer monthly variations of the horizontal and vertical circulations are calculated by the diagnostic model using the monthly mean density fields the gyre and the vertical circulation are maximal in september the characteristic decay time scale of the gyre is estimated to be about 10 days the effect of topographic differential heating is considered to be one of the maintenance mechanisms of the gyre in early summer and the wind stress curl to be the important maintenance force for the gyre from late summer to late fall

rapid change in semi diurnal tides in the north atlantic since 1980 1 an anomalously large trend of m2 and s2 amplitudes and phases beginning in the early 1980s is observed in the north atlantic harmonic analysis of long term sea level records from tide gauge stations along the north american atlantic coast and european atlantic coast shows a large decrease in m2 and s2 amplitudes and an increase in phase lag the characteristics of the evolution of m2 and s2 tides are similar but not fully conclusive which may suggesting different causes in general the trends may be due to global warming which significantly increased in the early 1980s in the north atlantic region several climate related driving mechanisms for the observed changes in tides are discussed

buoyancy driven current during cooling periods in ise bay japan 1 the cooling effect on buoyancy driven current is studied in the coastal embayment of ise bay japan by applying knowledge derived from studies of convection in a rotating fluid this convection process is highly sensitive to the presence of inhomogeneities in the preexisting stratification and to differential buoyancy loss on freshwater input the bay water is divided into two regions that differ in their response to the cooling from the surface one region represents a river plume which in effect shields the deeper regions from the cooler surface in the other region convective mixing is active although the mixed water forms and becomes extensive in this convection region the mixed water hardly develops in the river plume region the subsequent differential deepening of the mixed water causes gravitational circulation and yields a mixed water lens which has a reversed dome shape and rotates anticyclonically in a thermal wind balance in the mixed water lends nonvanishing stratification remains because of the rotational effect the location of the mixed water lens and associated anticyclonic circulation determines the basin wide circulation during cooling periods

nodal modulation of the lunar semidiurnal tide in the bay of fundy and gulf of maine observations numerical modeling and theoretical calculations show how the 18 6 year modulation of the main lunar semidiurnal tide in the bay of fundy and gulf of maine is reduced from its astronomical value of 3 7 percent to 2 4 percent by the effects of friction and resonance the agreement of the three approaches increases confidence in model predictions of widespread changes in the tidal regime resulting from development of tidal power

effect of stair step and piecewise linear topography on internal wave propagation in a geophysical flow model 1 the paper describes the effect of a stair step representation of bottom topography common in most numerical models on the propagation of internal waves in a geophysical flow an analytical solution was used to predict the effect of stair step and piecewise linear representations of topography on the reflection and transmission of internal waves the estuary lake and coastal model elcom was used to simulate the transmission of a train of small amplitude internal gravity waves propagated along a variable depth rectangular channel containing a linearly stratified fluid the effect of the different obstacle approximations was examined in terms of the interference of the resulting wave number content and hence the associated reflection coefficients which could be directly compared to the analytical theory it was shown that for gaussian obstacles of varying lengths and heights the full bottom cells and partial bottom cells solutions from elcom agree with the stair step and piecewise linear solutions from the theory respectively it was shown that when gaussian obstacles with weak slopes are represented by stair steps an aliasing that is similar to that in discrete fourier transform can occur resulting in reflection coefficients that are much higher than the exact solution on the other hand piecewise linear approximations produce significantly attenuated aliasing an immersed boundary technique that enforces a no flux condition at the actual sloping bottom similar to that of the analytical solution is found not to produce better numerical results

the anomalous amplification of m2 tide in the taiwan strait 1 the complex tidal wave propagation pattern in the taiwan strait invites parochialism along the eastern taiwan boundary of the strait the anomalous amplification of m2 tide in the middle often led to the parochial view that two tidal waves coming from both ends of the strait collide in the middle creating wave resonance along the western china boundary one sees a southward progressive tidal wave and hence no wave collision to reconcile we examine a few solutions of a numerical tidal model below both realistic bottom bathymetry and idealized bottom topographies are used to identify dominant mechanism leading to the complex tidal wave propagation our process of elimination identifies the wave reflection of southward propagating tidal wave by the deep trench in the southern strait as the true cause responsible for the complex wave propagation pattern

numerical experiments on stratified wind induced circulation in tokyo bay japan during summer in tokyo bay the upwelling of the anoxic water strongly affects eggs and larvae of fish and shellfish the northerly wind causes the upwelling along the eastern coast and near the bay head and downwelling along the western coast numerical experiments were carried with a three dimensional model to explain the wind induced circulation in tokyo bay when a uniform north easterly wind is imposed at the sea surface the circulation almost reaches steady state due to geostrophic adjustment after one inertial period from the beginning of the computation a forced internal kelvin wave propagating with the land on the right is found to have a great effect on the development of the steady state when the observed variable wind is given as the surface boundary condition the results of the numerical experiment agree qualitatively with data from both the sea surface temperature obtained by satellite images and field measurements at moored stations in the bay

temporal variations of tides on the west coast of great britain summary temporal variations of tides are investigated by analysing tidal observations from five ports on the west coast of great britain variations considered here are those occurring in the semi diurnal species daily in the tidal constituents resolved from analyses of 29 day sets over a period of two years 1980 81 and in the tidal constituents resolved from 1 yr sets over a period of 19 yr the time variations of tidal constituents are mainly due to inseparable terms grouping with the principal term due to the short length of data and the insufficiency of the procedures to account for them surges and surge tide interaction are affecting the resolution of tides time variations of constituents of the diurnal species induced by non tidal forces are spatially consistent the use of equilibrium relationships to account for modulations of principal constituents by waves separable in an 18 61 yr nodal cycle improves the analysis however the modulation is smaller in the real tide than in the equilibrium tide when the application of this principle is extended to a wider frequency band to cover constituents which cannot be resolved from one month of observations it may produce the opposite effect these problems start compounding with decreasing length of data i e increasing band width of resolution functional approximations of interaction coefficients bi admittance of non linear tides similar to the response admittance of linear tides are computed for semi diurnal fourth diurnal and sixth diurnal bands these functional estimates may be used to interpolate unseparable constituents to improve the quality of analyses the results are consistent with the fact that the response of the sea does not change in a narrow frequency band covering a nodal cycle of the moon the change in the equilibrium relationship between the principal term and its nodal term can be interpreted in terms of the damping effect of bottom friction

changing pattern of accretion erosion of the modern yellow river huanghe subaerial delta china based on remote sensing images abstract the yellow river shifted from the diaokou course to the qingshuigou course in 1976 and shifted again at the north bank of the qingshuigou course in 1996 as a result the entire modern yellow river delta has experienced complicated patterns of erosion and accretion multitemporal remote sensing data of landsat mss and tm from 1976 to 2000 totaling twenty scenes were used to examine the changing pattern of accretion and erosion of the modern yellow river subaerial delta with gis tools during the period 1976 to 2000 the maximum erosion occurred at the head of the last two abandoned promontories diaokou and shenxiangou promontories where the coastline retreated landward over 7 and 4 5 km respectively with mean net erosion rates of 0 29 and 0 19 km a respectively in contrast the maximum accretion occurred at the head of the qingshuigou promontory where the coastline advanced seaward over 20 km with a mean net accretion rate of 0 83 km a the coastline at the head of the q 8 promontory also advanced seaward 7 km with a mean net accretion rate of 0 29 km a during the period 1996 to 2000 total area of the diaokou and shenxiangou promontories was reduced by 141 3 km 2 with a mean net erosion rate of 6 03 km 2 a total area of the qingshuigou and q 8 promontories increased by 384 16 and 11 88 km 2 respectively with mean net accretion rates of 16 4 and 3 03 km 2 a respectively relative to the diaokou shenxiangou and qingshuigou promontories the west area of the diaokou promontory and south area of the qingshuigou promontory were relatively stable although minor erosion occurred the general pattern of accretion and erosion of the modern yellow river subaerial delta was divided into three stages rapid accretion stage 1976 1984 accretion erosion adjustment stage 1985 1995 and slow erosion stage 1996 present the factors affecting the pattern of erosion and accretion over the yellow river delta such as structural geology the yellow river sediment discharge coastal processes meteorological conditions human activity sea level rise and land subsidence were summarized the cumulative area of increase over the entire subaerial delta is closely correlated with the cumulative yellow river sediment discharge wave induced longshore current is the major driving force to transport sediment from eroded areas along the last two abandoned promontories diaokou and shenxiangou promontories mostly westerly and partially easterly together with these coastal processes is the geographical shift of the yellow river course associated with its discharge regime after 1976 leading to the accretion along the present qingshuigou promontory and then the q 8 promontory

on perturbations of harmonic constants in the thames estuary summary a long series of southend sea level observations extending over a period of 51 years 1929 79 is analysed using the harmonic method of tidal analysis the harmonic method of tidal analysis and prediction works on the assumption that the relationship of nodal terms with their respective principal terms in the physical tide is the same as in the equilibrium tide it is concluded that although this assumption is very useful in accounting for those terms which are not separable from a given length of observations it is not always fully valid as a result a systematic error is introduced in tidal analysis and prediction it is observed that small secular trends are present in amplitudes and phase lags of some principal tidal constituents in the diurnal band amplitudes of o1 and k1 are almost constant but the phase lag of k1 is increasing and the phase lag of o1 is decreasing in the semi diurnal band amplitudes of m2 s2 and k2 are increasing while the phase lag of m2 is decreasing and the phase lag of k2 is increasing the influence of these secular trends in amplitudes is to increase the tidal range and extreme levels this is confirmed by increases in the range of tide in the last one and a half centuries statistically no significance can be attached to trends in phase lags because standard errors are large a comparison of old records with tides synthesized by modern constituents for london bridge suggests that the phase of the tide was almost stable there from 1683 to 1835 then a large change occurred after 1835 similar changes are noted in the tidal range the nature of these changes indicates that they are partly due to increased input at southend resulting from secular trends in tidal harmonics and partly due to man made alterations embankment bank raising and deepening of the estuary

how can we improve a global ocean tide model at a regional scale a test on the yellow sea and the east china sea a global ocean model has been developed within the context of topex poseidon t p on the basis of a finite element hydrodynamic modeling approach combined with data assimilation based on the representer method the solution produced at global scale represents a spectacular improvement over what was available before the era of t p typically the mean discrepancy between the main tidal components and a hundred in situ tide gauges is 1 7 cm for m2 and 1 cm or less for the other components however the accuracies of this solution and of that produced by different authors within the t p tide working group are all worse near coastlines and over continental shelves this is the case for our finite element solution fes fes94 1 solution over the yellow sea and the east china sea ys ecs where the discrepancy is 33 cm for the m2 tide and 9 cm for the k1 tide when compared to a set of 192 tide gauges distributed along the coastlines this is due largely to the complex geometry of the basin and the limited knowledge of the bathymetry the aim of this paper is to investigate how our fes model can be improved with a dedicated application focused on one of the most energetic coastal basins the ys ecs 180 gigawatts for m2 i e 8 of the global energy dissipated in the whole ocean for this application a finite grid was implemented with a resolution down to 5 km along the coasts and over the continental shelf break particular attention was paid to bathymetry by complementing the etop05 database with regional maps sensitivity tests to the tuning of the bottom friction and the nonlinear interactions between the diurnal and semidiurnal components allow us to investigate the impact of dissipation parameterization and to produce an optimal solution without any data assimilation for nine main components of the tidal spectrum improvement by a factor of 2 m2 distance to the observations is now 17 5 cm global variance of 92 cm and k1 is 4 cm global variance of 21 cm as nonlinear components are significant over these basins the two main quarterdiurnal components are calculated the improvements are explained by five points 1 the choice of a mixed friction 2 a refinement of the mesh 3 a choice of reliable boundary conditions 4 a refined topography and 5 the use of a specific friction coefficient 1 5 10 3 surprisingly the energy budget for the m2 component leads to a dissipation similar to the value estimated by the global fes94 1 this is a major result of this study which leads us to the conclusion that when forcing a regional model with sea level boundary conditions along the open limits the simulated velocity field adjusts to the tuning of friction coefficients in order to dissipate the same amount of energy made available at its open boundaries

the response of three main beach types to tropical storms in south china abstract based on the observational data of 6 storms and 8 different beaches on the coasts of southern china the paper is concerned with the characteristics of storm effects on beaches with different morphodynamic types in south china a dissipative beach is very stable and has a weak response to tropical storms the storm induced morphological changes for this type of beach are characterized by erosion at the dune toe and minor changes on the beach face a low tide terrace beach has a strong response to storms with marked changes in the upper profile a barred beach usually experiences berm erosion swash bar smoothening and seaward bar migration during storms overwash may occur for the beach without backshore dune or protection in this paper backshore changes and the alteration of beach gradient in response to tropical storms are discussed with taking into account tidal influences a new morphodynamic parameter et is proposed in order to highlight the beach response intensity to storm action results show that the inherent morphodynamic properties have significant effects on the beach response to storm the more dissipative beach has a smaller response intensity and shows a moderate change in beach profile during a storm while a more reflective beach has a greater response intensity and changes markedly under storm conditions

evolution of tidal amplitudes in the eastern pacific ocean 1 global sea level gsl rise is well documented however changes in high waters including the tidal contribution are sometimes more relevant than gsl rise analysis of 34 long tidal records from the eastern pacific ocean shows that k1 and m2 amplitudes k1 and m2 are increasing except for m2 in the gulf of panama north of 18 n k1 and m2 are both growing at 2 2 century 1 the mean increase in total tidal amplitude 0 59 mmyr 1 is less than the present gsl rise 1 7 mmyr 1 however mean sea level is nearly constant in the ne pacific so tidal evolution plays a major regional role in changes in high water levels the spatial pattern of tidal evolution suggests the influence of large scale processes and the similarity in spatial patterns for k1 and m2 excludes mechanisms with strong frequency dependence increasing tidal amplitudes may impact ocean mixing nutrient supply primary production fisheries and coastal erosion

residual circulation due to internal waves shoaling on a slope we describe the residual circulation induced in a two layer system when internal waves with a wave length equal to or longer than the slope length propagate over a sloping bottom and either reflect or break for the case of no wave breaking scaling is used to derive boussinesq type equations the solution of which leads to an expression for the residual circulation adjacent to the sloping bottom this residual circulation is maintained by a weak slope on the density interface for breaking waves laboratory experiments and numerical modeling were used to ascertain the details of the residual circulation arising from the formation of gravitational intrusions results from these three investigative tools were used to determine as a function of bottom slope and incident wave amplitude the internal wave reflection coefficient and the strength of the residual circulation pattern with and without wave breaking the ocean and most lakes are thermally stratified for at least part of the year in stratified fluids the density anomaly associated with the thermal stratification supports internal waves with a range of vertical modal structures antenucci et al 2000 antenucci and imberger 2001 antenucci and imberger 2003 the gravest or first vertical mode induces a large current over the lake or ocean bottom and when the bottom slopes the waves shoal causing them to break and lose energy to dissipation the associated currents and turbulence can often lead to sediment resuspension and mixing of the water column gloor et al 1994 pierson and weyhenmeyer 1994 steinman et al 1997 the gravitational motions in turn induced by the mixing may combine with secondary internal wave motions to drive a residual circulation that may transport resuspended and dissolved material to the central area of a lake hakanson 1982 ostrovsky et al 1996 inall 2009 also demonstrated mass transport due to intrusion caused by internal wave breaking in the fjord loch etive by using a fluorescent dye tracer such intrusions have been observed but their dynamics do not seem to have received any attention in this paper the processes leading to residual circulation are described when a continuous train of internal waves with an individual wavelength equal to or longer than the slope length supported by a two layer stratification impinges perpendicularly onto a sloping bottom two cases were investigated when the waves break and when they are reflected perfectly without breaking internal waves and their associated mass transport in lakes fjords and coastal oceans are reviewed in ostrovsky and stepanyants 1989 and huthnance 1989 whereas solitary internal waves are reviewed by brown and christie 1998 lamb 2002 and grue et al 2000 regarding mass transport lamb 2002 investigated shoaling of largeamplitude internal waves and demonstrated that trapped

horizontal structure and excitation of primary motions in a strongly stratified lake a modal analysis in the horizontal plane was extended to a layer stratified basin with irregular bathymetry and the theory was applied to lake biwa to investigate the horizontal structure and excitation of the basin scale internal waves and gyres the horizontal structure of the basin scale internal waves consisted of cyclonic and anticyclonic elliptic cells each of which appeared to follow the dispersion relationship of kelvin and poincare waves in elliptic basins the internal waves were preferentially excited depending on the arrangement of the cells and the wind direction but the spatial distribution of wind stress curl over the lake primarily determined the horizontal structure of the ensuing gyres decoupled evolutionary equations for the individual modes provided a good approximation for excitation of the internal waves and early stages of excitation of the gyres before nonlinear effects and damping become significant the modal decomposition of hydrodynamic simulation results also showed that the primary action of the wind was to excite the internal waves however these internal waves were damped within a few days and the dynamics during calm periods were dominated by the gyres illustrating the importance of internal waves on mixing and gyres on long term horizontal transport

wave spectra assimilation in typhoon wave modeling for the east china sea the east china sea is a hot area for typhoon waves to occur a wave spectra assimilation model has been developed to predict the typhoon wave more accurately and operationally this is the first time where wave data from taiwan have been used to predict typhoon wave along the mainland china coast the two dimensional spectra observed in taiwan northeast coast modify the wave field output by swan model through the technology of optimal interpolation oi scheme the wind field correction is not involved as it contributes less than a quarter of the correction achieved by assimilation of waves the initialization issue for assimilation is discussed a linear evolution law for noise in the wave field is derived from the swan governing equations a two dimensional digital low pass filter is used to obtain the initialized wave fields the data assimilation model is optimized during the typhoon sinlaku during typhoons krosa and morakot data assimilation significantly improves the low frequency wave energy and wave propagation direction in taiwan coast for the far field region the assimilation model shows an expected ability of improving typhoon wave forecast as well as data assimilation enhances the low frequency wave energy the proportion of positive assimilation indexes is over 81 for all the periods of comparison the paper also finds that the impact of data assimilation on the far field region depends on the state of the typhoon developing and the swell propagation direction

relative effects of wind stress curl topography and stratification on large scale circulation in lake michigan 1 this paper uses the results from two multiseason numerical model simulations of lake michigan hydrodynamics to examine the relative effects of wind stress curl topography and stratification on large scale circulation the multiseason simulations provide a period long enough to encompass the full range of atmospheric and thermal conditions that can occur in the lake the purpose of this paper is to diagnose the relative importance of various mechanisms responsible for the large scale circulation patterns by analyzing the vorticity balance in the lake on a monthly timescale five different model scenarios are used to isolate the predominant mechanisms 1 baroclinic lake spatially variable wind stress 2 barotropic lake spatially variable wind stress 3 baroclinic lake spatially uniform wind stress 4 barotropic lake spatially uniform wind stress and 5 barotropic lake linearized equations spatially uniform wind stress by comparing the results of these five model scenarios it is shown that the cyclonic wind stress curl in the winter and the effect of baroclinicity in the summer are primarily responsible for the predominantly cyclonic flow in the lake topographic effects are also important but are not as significant as wind stress curl and baroclinic effects nonlinear effects are much smaller

summer circulation and temperature structure of lake kinneret a three dimensional lake model driven by wind stress and heat flux fields derived from an atmospheric model is applied to lake kinneret israel the summer wind field over the lake has a strong diurnal and large spatial variation due to complex terrain surrounding the lake the sharp temperature contrast between the arid land and the lake and due to the penetration of the mediterranean sea breeze msb into the lake area the daily mean wind curl field which is predominantly determined by the penetration of the msb is responsible for the generation of three lake gyres one of them dominates most of the lake and rotates counterclockwise it is flanked to the north and to the south by two smaller ones that rotate clockwise during the summer the diurnal variation of the wind over the lake is repeated daily due to consistent forcing conditions during that season numerical tests show that the rectified flow induced by the diurnal winds plays a minor role in the lake circulation the thermocline oscillation which was believed to be the free propagation of internal kelvin waves mainly responds to the surface elevation set up by the time dependent winds and it appears that no systematic counterclockwise propagating waves with large thermocline displacements exist in the lake the intense msb over the lake in the late afternoon pushes the heated surface water toward the east forcing the deep cooler water to be advected westward and creating strong mixing over the shallow western shore this results in higher temperature off the eastern shore and lower temperature off the western shore however a strong mean flow is constantly eliminating the temperature difference by counterclockwise transfer of the western cooler water eastward the results are in good agreement with available observations

secular trends in ocean tides observations and model results 1 during the last century the response of the oceans to tidal forces has changed significantly this study focuses on an analysis of long term sea level records located in the atlantic and pacific primarily in the northern hemisphere it shows that changes of tidal amplitude and or phase have taken place over large scales the principal solar semidiurnal s2 tide shows the largest trends at some locations the change in the mean tidal range due to tidal trends is significant compared with the trend in mean sea level thus it might be advisable to consider these changes in studies of the impact of rising sea level numerical simulations of the principal lunar semidiurnal tide m2 demonstrate a model sensitivity in the north atlantic to changes in glacial isostatic adjustment and sea level rise which captures 30 40 of the magnitude of the trends in observations however the spatial patterns do not agree well with those inferred from observations suggesting that forward global models are currently useful for qualitative but not quantitative understanding of the observed trends a global free oscillation synthesis indicates that sea level rise due to glacial isostatic adjustment leads to decreasing global resonant periods and increasing damping in the system and a coupled oscillator model shows that changes in sea level on the shelf are much more effective at perturbing shelf and ocean tides than sea level changes in the deep ocean