dynamical mechanisms for the south china sea seasonal circulation and thermohaline variabilities abstract the seasonal ocean circulation and the seasonal thermal structure in the south china sea scs were studied numerically using the princeton ocean model pom with 20 km horizontal resolution and 23 sigma levels conforming to a realistic bottom topography a 16 month control run was performed using climatological monthly mean wind stresses restoring type surface salt and heat and observational oceanic inflow outflow at the open boundaries the seasonally averaged effects of isolated forcing terms are presented and analyzed from the following experiments 1 nonlinear dynamic effects removed 2 wind effects removed and 3 open boundary inflow outflow set to zero this procedure allowed analysis of the contribution of individual parameters to the general hydrology and specific features of the scs for example coastal jets mesoscale topographic gyres and countercurrents the results show that the pom model has the capability of simulating seasonal variations of the scs circulation and thermoha

observed evidence of the anomalous south china sea western boundary current during the summers of 2010 and 2011 seven years of directly measured current data from a mooring in the xisha area of the south china sea scs together with shipboard adcp and satellite data have shown the western boundary current wbc anomaly and its vertical structure during the summers of 2010 and 2011 the observed wbc presented obvious year to year variability especially in the summer overall the summer mean velocity at the mooring site over 7 year 2007 2013 was northeastward the moored adcp showed that the northeastward velocity was particularly strong in the summer of 2010 but the increase was confined in the upper 120 m in contrast the northeastward current disappeared throughout the observed depth range from 50 to 450 m in the summer of 2011 even at the deepest observed position the monthly velocity anomalies reached 14 cm s 1 westward and 12 cm s 1 southward in the zonal and meridional directions respectively both the vietnam offshore current voc and double gyres in the western scs disappeared and the southern anticyclonic gyre expanded to strengthened the northward wbc in the summer of 2010 however in summer of 2011 the voc intensified and the northern cyclonic gyre enlarged with its northern edge reaching 18 degrees n slightly north of mooring site which weakened the northeastward wbc the observed scs circulation anomalies during 2010 and 2011 were mainly induced by the basin scale wind field anomalies associated with the 2009 2010 el nino and 2010 2011 la nina

south china sea isopycnal surface circulation this paper investigates the seasonal variabilities of the south china sea isopycnal surface circulations and of the kuroshio intrusion through the luzon strait using the u s navy s climatological temperature and salinity dataset public domain with 83 8 resolution by the p vector method the representative pattern is a persistent basin scale cyclonic circulation away from the surface and a seasonally varying circulation with a weak anticylonic gyre in the summer and a strong cyclonic gyre in the winter near the surface this pattern is consistent with a classical view of mean cyclonic circulation in large stratified lakes and semienclosed marginal seas by emery and csanady and with a recent numerical simulation using the navy s layered ocean model by metzger and hurlburt the computed monthly volume transport through the luzon strait is negative inflow all year round with a minimum value of 213 7 sv in february strongest intrusion and a maximum value of 21 4 sv in september weakest intrusion the annual mean transport is 26 5 sv intrusion

a parametrization based on sea ice morphology of the neutral atmospheric drag coefficients for weather prediction and climate models 1 a hierarchy of parametrizations of the neutral 10 m drag coefficients over polar sea ice with different morphology regimes is derived on the basis of a partitioning concept that splits the total surface drag into contributions of skin drag and form drag the new derivation which provides drag coefficients as a function of sea ice concentration and characteristic length scales of roughness elements needs fewer assumptions than previous similar approaches it is shown that form drag variability can explain the variability of surface drag in the marginal sea ice zone miz and in the summertime inner arctic regions in the miz form drag is generated by floe edges in the inner arctic it is generated by edges at melt ponds and leads due to the elevation of the ice surface relative to the open water surface it is shown that an earlier fit of observed neutral drag coefficients is obtained as a special case within the new concept when specific simplifications are made which concern the floe and melt pond geometry due to the different surface morphologies in the miz and summertime arctic different functional dependencies of the drag coefficients on the sea ice concentration result these differences cause only minor differences between the miz and summertime drag coefficients in average conditions but they might be locally important for atmospheric momentum transport to sea ice the new parametrization formulae can be used for present conditions but also for future climate scenarios with changing sea ice conditions

study of the impact of ice formation in leads upon the sea ice pack mass balance using a new frazil and grease ice parameterization abstractleads are cracks in sea ice that often form because of deformation during winter months leads expose the ocean to the cold atmosphere resulting in supercooling and the formation of frazil ice crystals within the mixed layer here the authors investigate the role of frazil ice formation in leads on the mass balance of the sea ice pack through the incorporation of a new module into the los alamos sea ice model cice the frazil ice module considers an initial cooling of leads followed by a steady state formation of uniformly distributed single size frazil ice crystals that precipitate to the ocean surface as grease ice the grease ice is pushed against one of the lead edges by wind and water drag that the authors represent through a variable collection thickness for new sea ice simulations of the sea ice cover in the arctic and antarctic are performed and compared to a model that treats leads the same as the open ocean the processes of ice formation in the new module slow down the refreezing o

weakening of the kuroshio intrusion into the south china sea over the past two decades inferred from the satellite and in situ hydrographic data from the 1990s and 2000s the kuroshio intrusion into the south china sea scs had a weakening trend over the past two decades associated with the weakened kuroshio intrusion the kuroshio loop and eddy activity southwest of taiwan became weaker whereas the water above the salinity minimum became less saline in the northern scs the sea surface height southwest of taiwan increased at a slower rate compared to other regions of the scs because of the weakened kuroshio intrusion simulations using the regional ocean modeling system roms pacific model show that the strength of the kuroshio intrusion into the scs decreased from 1993 to 2010 with a negative trend 0 24 sverdrups sv yr 1 1 sv 10 6 m 3 s 1 in the total luzon strait transport lst although wind induced ekman transport through the luzon strait became weaker the magnitude at 0 001 sv yr 1 was too small to compensate for the negative trend of the lst on the other hand the piling up of the water induced by monsoon winds was an important mechanism for changing the pressure gradient across the luzon strait and eventually affecting the lst the sea level gradient between the western pacific and the scs had a negative trend 0 10 cm yr 1 corresponding to a negative trend in the geostrophic transport at 0 20 sv yr 1 the kuroshio transport east of luzon island also had a negative trend which might also be linked to the weakening kuroshio intrusion

a revisit of the interannual variation of the south china sea upper layer circulation in summer correlation between the eastward jet and northward branch the interannual variation of the south china sea upper layer circulation in summer is revisited based on analysis of current derived from altimetry data acoustic doppler current profilers moorings and numerical simulations results show not only the interannual variation of the eastward jet eastward branch but also its anti correlation with the northward branch on interannual time scale when the eastward branch is enhanced the northward branch is weakened and vice versa their variations are largely related to the change of the south china sea summer monsoon scssm and are strongly influenced by the luzon strait transport lst composite analysis reveals a stronger scssm and lst into the scs in the developing phase of el nino would lead to an eastward branch dominant circulation pattern whereas a weaker scssm and reduced lst into the scs in the decaying phase of el nino favors a northward branch dominant circulation pattern the distinct composite patterns appear in el nino and southern oscillation cycles rather than episodic event or multiyear el nino or la nina contribution of the transport of major straits in the scs to the interannual variation of the scs summer circulation is quantitatively evaluated for the first time and the results show that the change of the planetary vorticity flux through three major straits luzon strait contributes most is as equally important as the vorticity input change from local wind stress curl

abrupt change of sediment records in the southern south china sea during the last glacial period and its environment significance abstract chemical compositions of sediments at core ns07 25 6 39 945 n 113 32 936 e water depth 2006 m are analyzed to discuss abrupt change of sediment records in the southern south china sea scs during the last glacial period and its environmental implications major and trace elements experienced three significant changes which occurred at 31 9 26 1 and 18 5 ka bp respectively at 31 9 ka bp when sea surface temperature remained relatively low terrigenous sediment flux increased but biogenic activities weakened greatly at 26 1 ka bp both terrigenous sediment flux and biogenic fractions number were steady however some elemental ratios changed noticeably at that time before 26 1 ka bp core sediments with low nb ta but high zr hf ratios were mainly derived from the paleo mekong and or molengraaff rivers exposed on the sunda shelf at that time after 26 1 ka bp sediments with high nb ta but low zr hf ratios probably relate to strengthened impact of deep water current since 18 5 ka bp sea level ascended rapidly from 110 m below the present terrigenous sediment flux decreased and biogenic activities strengthened continuously probably related with the east asian monsoon evolution

a parameterization of the ice ocean drag coefficient 1 a parameterization of the ice ocean drag coefficient cw was developed through partitioning the oceanic drag force into three components 1 form drag on the floe edge 2 form drag on the ridge keel and 3 skin friction on the ice bottom through these quantities cw was expressed as a function of observable sea ice geometric parameters sensitivity studies were carried out to investigate the influence of varying sea ice conditions on cw the results revealed that cw increases first and then decreases with increasing ice concentration a similar to the observations of the air ice drag coefficient and which is mainly attributed to the nonmonotonic variation of the form drag on the floe edge with ice concentration moreover the form drag on the floe edge is always the dominant component having a proportion of more than 60 in sea ice with a large aspect ratio draft length 1 100 indicating the necessity of including this term in sea ice dynamic models particularly for the marginal ice zone miz the form drag on the ridge keel becomes dominant only when the ridging intensity is extremely high depth spacing 1 20 additionally a large value of cw cannot be caused only by the inclusion of form drag terms but also by large skin friction over rough ice bottoms finally for typical situations in the miz with moderate ridging intensity the parameterization will underestimate cw by approximately 30 for a rough ice bottom and by over 80 for a smooth ice bottom if no form drags are considered

wind stress measurements over rough ice during the 1984 marginal ice zone experiment the indirect dissipation method has been used to estimate momentum fluxes from a ship working in the outer marginal ice zone of the east greenland sea during the 1984 marginal ice zone experiment these indirect measurements have been compared with direct eddy correlation measurements whenever the ship was moored to an ice floe and a sonic anemometer could be deployed neutral drag coefficients referenced to 10 m have been grouped in categories for various ice types and concentrations during 4 to 11 m s winds there is a gradual increase in the neutral drag coefficient with ice concentration and a doubling of the value in 70 90 concentration from 2 7 0 3 10 3 mean plus or minus standard deviation for a mixture of brash small and medium floes with rafted edges to 5 3 0 5 10 3 over very rough cakes and brash with many sharp vertical edges drag coefficients in this region of multiyear floes with larger roughness features are typically higher than most values obtained over ice and reported in the literature and up to 5 times larger than open ocean values for similar wind speeds the drag coefficient is determined primarily by floe size roughness and concentration

regulation of south china sea throughflow by pressure difference sea surface height ssh data from the european centre for medium range weather forecasts ocean reanalysis system 4 ecmwf oras4 are used to determine the pressure difference in connection with variability of the south china sea throughflow scstf from 1958 to 2007 two branches of scstf the karimata sunda strait throughflow ksstf and the mindoro strait throughflow mstf are examined using the ensemble empirical mode decomposition method eemd time series of pressure difference and volume transport are decomposed into intrinsic mode functions and trend functions with the corresponding variability on different time scales pressure difference agrees with the ksstf volume transport on decadal time scale while for the mstf pressure difference varies similarly with volume transport on interannual time scale separating the dynamic height difference into the thermal and haline terms for the ksstf more than half of the dynamic height difference 32 cm is due to the thermal contributions while the remaining dynamic height difference 23 cm is due to the haline contributions for the mstf the dynamic height difference 29 cm is primarily due to the thermal contribution 26 cm

observed wintertime tidal and subtidal currents over the continental shelf in the northern south china sea synthesis analyses were performed to examine characteristics of tidal and subtidal currents at eight mooring sites deployed over the northern south china sea nscs continental shelf in the 2006 2007 and 2009 2010 winters rotary spectra and harmonic analysis results showed that observed tidal currents in the nscs were dominated by baroclinic diurnal tides with phases varying both vertically and horizontally this feature was supported by the cc fvcom results which demonstrated that the diurnal tidal flow over this shelf was characterized by baroclinic kelvin waves with vertical phase differences varying in different flow zones the northeasterly wind induced southwestward flow prevailed over the nscs shelf during winter with episodic appearances of mesoscale eddies and a bottom intensified buoyancy driven slope water intrusion the moored current records captured a warm core anticyclonic eddy which originated from the southwestern coast of taiwan and propagated southwestward along the slope consistent with a combination of plane and topographic rossby waves the eddy was surface intensified with a swirl speed of 50 cm s and a vertical scale of 400 m in absence of eddies and onshore deep slope water intrusion the observed southwestward flow was highly coherent with the northeasterly wind stress observations did not support the existence of the permanent wintertime south china sea warm current scswc the definition of scswc which was based mainly on thermal wind calculations with assumed level of no motion at the bottom needs to be interpreted with caution since the observed circulation over the nscs shelf in winter included both barotropic and baroclinic components

formation and dynamics of a long lived eddy train in the south china sea a modeling study abstracta process oriented numerical modeling study was conducted to investigate the formation and underlying forcing of an anticyclonic eddy train observed in the northern south china sea observations showed that long lived anticyclonic eddies formed an eddy train along an eastward separated jet across the northern south china sea in summer the eddy train plays a critical role in regulating ocean circulation in the region forced by the southwesterly monsoon and prevailing dipole wind stress curl in the summer the northward coastal jet separates from the west boundary of the south china sea basin and overshoots northeastward into the basin the anticyclonic recirculation of the separated jet forms the first anticyclonic eddy in the eddy train the jet meanders downstream with a strong negative shear vorticity that forms a second and a third anticyclonic eddy along the jet s path these three eddies form the eddy train these eddies weaken gradually with depth from surface but they can extend to appro

drag coefficients for winter antarctic pack ice air ice and ice water drag coefficients referenced to 10 m height winds for winter antarctic pack ice based on measurements made from r v polarstern during the winter weddell sea project 1986 wwsp 86 and from r v akademik fedorov during the winter weddell gyre study 1989 wwgs 89 are presented the optimal values of the air ice drag coefficients made from turbulent flux measurements are 1 79 0 06 x 10 exp 3 for wwsp 86 and 1 45 0 09 x 10 exp 3 for wwgs 89 a single ice water drag coefficient for both wwsp 86 and wwgs 89 estimated from periods of ice drift throught to represent free drift conditions is 1 13 0 26 x 10 exp 3 and the ice water turning angle is 18 18 deg it is suggested that for a typical antarctic winter pack ice cover the ice cover reduces the momentum flux from the atmosphere to the ocean by about 33 percent

the effect of observed ice conditions on the drag coefficient in the summer east greenland sea marginal ice zone the summer east greenland sea marginal ice zone is a region characterized by extreme horizontal variations of surface roughness characteristics the surface drag coefficient is found to be correlated with these roughness characteristics in particular ice concentration and ice floe roughness and size the estimates of wind stress and wind speed yield neutral drag coefficients cdn with standard deviations of 2 3 0 8 10 3 for areas with less than 40 ice concentration and 4 0 1 1 10 3 for ice concentrations greater than 70 much of the variation in cdn for a given ice concentration is explained by differences in ice floe size and roughness very small concentrated rough floes that have been affected by wave action produce twice as much wind stress cdn 4 2 0 7 10 3 as relatively large flat floes cdn 2 1 0 6 10 3 and 4 times as much as typical open ocean for a given wind speed and stability the drag coefficients in this region are higher than other marginal ice zones probably a result of the presence of large amounts of multiyear ice floes that extend higher above the ocean surface and create more drag than first year floes

observed near inertial kinetic energy in the northwestern south china sea based on more than 3 years of moored current meter records this study examined seasonal variability of near inertial kinetic energy nike as well as all large greater than one standard deviation from the mean nike events related to storms and eddies in the northwestern south china sea the nike in the subsurface layer 30 450 m exhibited obvious seasonal variability with larger values in autumn herein defined as august september and october all large nike events during the observation period were generated by passing storms most of the nike events had an e folding timescale longer than 7 d the phase velocity vertical wavelength and frequency shift of these events were examined the maximum nike induced by typhoon neoguri was observed in april 2008 normal mode analysis suggested that the combined effects of the first four modes determined the vertical distribution of nike with higher nike below 70 m but lower nike from 30 to 70 m another near inertial oscillation event observed in august 2007 had the longest e folding timescale of 13 5 d moreover the nike propagated both upward and downward during this event a ray tracing model indicated that the smaller brunt vaisala frequency and the stronger vertical shear of horizontal currents in an anticyclonic eddy and the near inertial wave with larger horizontal scale facilitated the unusual propagation of the nike and the long decay timescale although the nike originated from wind the water column structure affected by diverse oceanographic processes contributed substantially to its complex propagation and distribution

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

detection of monsoonal phytoplankton blooms in luzon strait with modis data abstract the luzon strait experiences a seasonal surge of phytoplankton based on ocean color data to examine the timing and position of the bloom daily modis chlorophyll data 2002 2005 were acquired and analyzed supporting data such as modis sst and nlw bands quikscat wind data river discharge and bathymetry were also used and processed in order to investigate the possible driving forces behind the bloom occurrence results show that chlorophyll concentration in the luzon strait dramatically increases during ne monsoon reaching to approximately 2 0 mg m 3 highest chlorophyll concentration is observed near the western slope of the luzon strait the monsoonal bloom in the luzon strait is likely due to upwelling and can be possibly associated with the interaction of the northward flowing luzon coastal current with the westward intrusion of kuroshio during ne monsoon the positive wind stress curl also contributes to this occurrence the influence of cagayan river is only limited within few kilometers from the river mouth

oceanic eddy formation and propagation southwest of taiwan 1 oceanic eddies are active and energetic southwest of taiwan the formation and propagation of eddies in this area were investigated using 17 year satellite altimeter data cyclonic eddies ces and anticyclonic eddies aces often coexisted but there were more ces than aces generated during the period from october 1992 to october 2009 aces were stronger and in general lived longer than ces aces occurred more often in winter than in other seasons while ces were more frequent in summer compared with the direct local wind forcing the kuroshio path variability appears to be a dominant factor for eddy formation in this area a conceptual model of an eddy kuroshio interaction is proposed in summer there exists an outflow northwest of luzon island and the kuroshio likely leaps across the luzon strait to the north of the outflow and left of the kuroshio axis ces are often formed which in turn induce aces to the west of ces in winter under the influence of northeasterly monsoon the kuroshio current loop kcl appears southwest of taiwan more frequently than in other seasons and aces are frequently shed from the kcl most of the aces propagate westward and as a result ces are often spun up to the east of the aces the surface south china sea outflow in summer and the kcl in winter are however likely related to the monsoons therefore the indirect effects of monsoon winds are also evident in the seasonal variations of eddy occurrence

impact of tidal mixing on water mass transformation and circulation in the south china sea abstractusing a high resolution regional ocean model the impact of tidal mixing on water mass transformation and circulation in the south china sea scs is investigated through a set of numerical experiments with different configurations of tide induced diapycnal diffusivity the results show that including tidal mixing in both the luzon strait ls and scs has significant impact on the ls transport and the intermediate deep layer circulation in the scs basin analysis of the density field indicates that tidal mixing in both the ls and scs are essential for sustaining a consistent density gradient and thus a persistent outward directed baroclinic pressure gradient both between the western pacific and ls and between the ls and scs basin so as to maintain the strong deep water transport through the ls further analysis of water mass properties suggests that tidal mixing in the deep scs would strengthen the horizontal density gradient intensify the basin scale cyclonic circulation induce more vigorous o

assimilating altimetric data into a south china sea model sea surface heights from the topex poseidon altimeter are assimilated into a three dimensional primitive equation model to derive the circulation in the south china sea with data assimilation the model resolves not only the basin wide circulation but also a dipole off vietnam and a low high feature near the luzon strait mesoscale features are missing in the simulation without data assimilation because of poor resolution in the wind field and inadequate knowledge of the transport through the luzon strait compared to the case without data assimilation data assimilation reduces the root mean square error between the simulated and observed sea surface heights by a factor of 2 3 circulation derived from data assimilation under climatological conditions is contrasted with that during el nino in the normal winter of 1993 1994 flow at 50 m depth is strong and cyclonic flow at 900 m depth is cyclonic as well the deep cyclone persists into the following summer during the 1994 1995 el nino winter features in the flow field at 50 m depth either weaken or disappear and circulation at 900 m depth is anticyclonic in the summer of 1995 the dipole and the eastward jet off vietnam at 50 m depth are missing and the anticyclonic circulation at 900 m depth persists temperature at 65 m shows significant warming from fall 1994 to summer 1995 a weakened flow field and warming in the upper ocean are consistent with findings from earlier el nino events

upper layer circulation in the south china sea abstract upper layer circulation is investigated by using all available historical temperature profiles combined with climatological temperature salinity relationships in the south china sea two cyclonic eddies are revealed one is located east of vietnam called the east vietnam eddy and the other is off northwest luzon called the west luzon eddy both local ekman pumping and remotely forced basin scale circulation are important mechanisms controlling these two eddies the luzon strait transport relative to 400 db is estimated to be of the order 3 0 sv 1 sv 1 106 m3 s 1 in the mean and has a seasonal cycle dominated by the annual signal with a maximum 5 3 sv in january february and a minimum 0 2 sv in june july pressure gradients are also examined to explore the dynamics of the intrusion of waters from the pacific into the south china sea through the luzon strait

heartbeat of a mountain diagnosing the age of depositional events in the karoo gondwana basin from the pulse of the cape orogen careful consideration of the effects of the cape orogeny on sedimentation in the carboniferous jurassic karoo basin provides an indirect tool for accurately dating these rocks fossil and radiometric data especially when combined with sedimentological and structural information yield partly overlapping age brackets which can be used to correlate the successive tectonic pulses with specific depositional events application of these principles to associated basins in gondwanaland can provide a firm foundation for more dependable stratigraphic correlation on a global scale the exercise also suggests that a number of widely held opinions on the age of certain stratigraphic units in the karoo supergroup may be incorrect

depositional characteristics and processes of alongslope currents related to a seamount on the northwestern margin of the northwest sub basin south china sea this study infers from 2d seismic data the presence of a seamount related deep water contourite depositional system located on the northwestern margin of the northwest sub basin of the south china sea alongslope aligned erosive features and contourite drifts developed in water depths between 1000 and 1500 m on the present seafloor a moat formed north of the seamount as a result of bottom current intensification after being deflected by an obstacle morphology indicating a major eastward flowing current due to the coriolis deflection an elongated mounded drift developed to the north of the moat and a modest plastered drift to the south onlapping the north side of the seamount bottom currents away from the seamount are less or minimally intensified generating contourite channels and furrows over the drift to the north of the moat combined with the known oceanographic setting the bottom currents could belong to the anticyclonic south china sea intermediate water circulation from the seismic data the architecture of contourite deposits during progressive burial of the seamount is documented the first appearance of contourite channels in seismic unit 1 is inferred to be the onset of the contourite depositional system which could be traced back to the early late miocene the following aggradational pattern of this system from the base of seismic unit 2 onwards indicates relatively enhanced and stable south china sea intermediate water circulation occurring on the northwestern margin of the northern south china sea subsequently the behaviour and depositional processes of bottom currents upstream and downstream the seamount are discussed the depositional model suggests that a complex contourite channel system will replace the former moat drift system once the seamount is buried finally our findings may provide new challenges for investigating the south china sea cenozoic palaeoceanography which are helpful to understand the sedimentary dynamic processes related to the south china sea deepwater circulation c 2014 elsevier b v all rights reserved

eddy heat and salt transports in the south china sea and their seasonal modulations this study describes characteristics of eddy turbulent heat and salt transports in the basin scale circulation as well as in the embedded mesoscale eddy found in the south china sea scs we first showed the features of turbulent heat and salt transports in mesoscale eddies using sea level anomaly sla data in situ hydrographic data and 375 argo profiles we found that the transports were horizontally variable due to asymmetric distributions of temperature and salinity anomalies and that they were vertically correlated with the thermocline and halocline depths in the eddies an existing barrier layer caused the halocline and eddy salt transport to be relatively shallow we then analyzed the transports in the basin scale circulation using an eddy diffusivity method and the sea surface height data the argo profiles and the climatological hydrographic data we found that relatively large poleward eddy heat transports occurred to the east of vietnam eov in summer and to the west of the luzon islands wol in winter while a large equatorward heat transport was located to the west of the luzon strait wls in winter the eddy salt transports were mostly similar to the heat transports but in the equatorward direction due to the fact that the mean salinity in the upper layer in the scs tended to decrease toward the equator using a 21 2 layer reduced gravity model we conducted a baroclinic instability study and showed that the baroclinic instability was critical to the seasonal variation of eddy kinetic energy eke and thus the eddy transports eov wls and wol were regions with strong baroclinic instability and thus with intensified eddy transports in the scs the combined effects of vertical velocity shear latitude and stratification determined the intensity of the baroclinic instability which intensified the eddy transports eov during summer and wls and wol during winter

kuroshio intrusion and the circulation in the south china sea 1 the princeton ocean model is used to study the circulation in the south china sea scs and its seasonal transition kuroshio enters leaves the scs through the southern northern portion of the luzon strait the annually averaged net volume flux through the luzon strait is 2 sv into the scs with seasonal reversals the inflow season is from may to january with the maximum intrusion of kuroshio water reaching the western scs during fall in compensation of summertime surface offshore transport associated with coastal upwelling from february to april the net transport reverses from the scs to the pacific the intruded kuroshio often forms an anticyclonic current loop west of the luzon strait the current loop separates near the dongsha islands with the northward branch continuously feeding the south china sea warm current scswc near the shelf break and the westward branch becoming the south china sea branch of kuroshio on the slope which is most apparent in the fall the scswc appears from december to february on the seaward side of the shelf break flowing eastward against the prevailing wind diagnosis shows that the onshore ekman transport due to northeasterly monsoon generates upwelling when moving upslope and the particular distributions of the density and sea level associated with the cross shelf motion supports the scswc

the aerodynamic roughness of different types of sea ice the aerodynamic roughness for all major types of sea ice is specified on the basis of surface layer measurements from ship and ice floe platforms median neutral surface drag coefficients cdn 1000 for grease and nilas ice are 0 7 and 1 6 small medium large and fused pancake ice have cdn equal to 0 9 1 6 2 4 and 1 9 young ice cdn ranges from 2 3 to 3 1 very smooth first year or multiyear ice with no pressure ridges has cdn equal to 1 5 pack ice has median values of 2 0 and 2 2 for first year and multiyear ice marginal ice zone ice averages 3 1 and 3 4 first year multiyear if unaffected by wave action wave affected ice has cdn values of 4 2 and 4 6 first year multiyear extremely rough multiyear ice in intense shear or compaction regions has cdn equal to 8 0 open ocean areas within 100 km of an ice edge averaged 1 8 while ice free water downwind of ice with small or no waves is 1 4 these values can be adjusted if heat fluxes are present the accuracy of the cdn averages is estimated to be 20 or better

sediment dynamics driven by contour currents and mesoscale eddies along continental slope a case study of the northern south china sea abstract based upon 3 d seismic reflection data published drill core studies oceanographic observations and numerical modelling this study identifies a small scale contourite depositional system that is locally confined by canyons slope failures erosional terraces and erosional slopes on the jianfeng slope northern south china sea 1500 to 2300 m water depth possible oceanic driving mechanisms for the spatial heterogeneity in sedimentation and erosion within the quaternary deposits in this complex slope system are investigated numerical simulations show that the quasi steady south china sea deep water circulation which affects the study area is characterised by low velocities maximum 4 cm s with a slight modulation by tides 1 cm s this quasi steady deep water thermohaline circulation is able to keep sediment particles in suspension rather than to erode seafloor sediment the bottom hydrodynamic regime becomes energetic when mesoscale eddies horizontal scale of 10 to 100 km approach our modelling study indicates that both surface and bottom mesoscale eddies are essential to account for the spatial heterogeneity in sedimentation pattern along the northern south china sea continental slope according to simulation the eddy front contains the highest flow velocity over a mesoscale eddy cycle 45 days exceeding the threshold for resuspension of unconsolidated sediment 15 cm s as a consequence massive resuspension is produced at various sites and redistributed by sub mesoscale horizontal scale of 1 to 10 km circulations originated from an eddy topography interaction in contrast to the surrounding areas which are subject to erosional forcing for a relatively long part 7 of an eddy cycle both the locally confined drift and a further upstream large elongated mounded drift experience little erosion

the partition of air ice ocean momentum exchange as a function of ice concentration floe size and draft a coupled sea ice ocean model is used to examine the relative magnitudes of terms in the sea ice momentum equation for ice concentrations less than 100 this numerical model for steady state horizontally homogeneous flow includes two terms that have previously been neglected in such quantitative models these are oceanic form drag and wave radiation pressure both of which are lateral forces that act on the sides of floes the former is generally decelerative while the latter is accelerative the model accepts as input variables average ice draft areal concentration and floe diameter it is found that form drag can be greater than or of the same order as skin friction drag for small thick floes at low concentrations an exception to this rule occurs when the effect of wakes between floes reduces the local form drag the higher net drag that generally exists at low concentrations implies lower ice floe speeds wave radiation pressure is negligible in all cases although this is sensitive to our choice of fetch parameterization ocean drag is often parameterized in numerical models of sea ice as a skin friction term alone with a constant drag coefficient between ice and prescribed geostrophic current velocities results from the present model are plotted in terms of such a drag coefficient which is a function of concentration floe size and draft this could be useful in future work where floe size data become regularly available for instance from radar satellite imagery

spring of no kuroshio intrusion in the southern taiwan strait 1 the taiwan strait connects the east china sea ecs to the south china sea scs typically in spring the water in the scs and a branch of the kuroshio occupy the eastern part of the strait while the china coastal waters including a large contribution from the changjiang yangtze river occupy the western part during spring 2008 when the taiwan strait was under the influence of la nina and according to field observations the kuroshio branch did not contribute much to the waters in the southern taiwan strait a numerical model verifies this observation the china coastal waters also seem to have had less effect than in typical years since the scs waters contain more nutrients than the kuroshio branch more nutrients may be transported from the scs to the ecs in a la nina spring than at other times

seasonal variability of the meridional overturning circulation in the south china sea and its connection with inter ocean transport based on soda2 2 4

overview of the multi layer circulation in the south china sea abstract the south china sea scs is a semi enclosed ocean basin with its sole deepwater renewal channel in the northeast the luzon strait connected to the northwestern pacific the circulation in the scs is endowed with a distinctive multi layer structure which is influenced by the seasonally reversing southeast asian monsoon at the surface modulated kuroshio intrusion in the upper layer and enhanced diapycnal mixing and persistent luzon strait deepwater overflow in the deep layer after being diapycnally mixed by energetic internal tides internal waves and mesoscale eddies waters entering the scs in the upper and deep layers through the luzon strait are returned to the northwestern pacific in the intermediate layer this inflow outflow inflow structure in vertical induces net inflows of potential vorticity in the upper and deep layers and a net outflow of potential vorticity in the intermediate layer of the luzon strait which are believed to be closely related with the circulation structure in the scs a sandwiched circulation in the scs namely anticyclonic in the intermediate layer and cyclonic in the upper and deeper layers was recently reported but controversial issues still remain on its spatial pattern and temporal variability to ascertain this sandwiched circulation and reveal its driving mechanism is of much scientific interest to the on going discussion on the scs circulation and its role in regional climate different from previous review articles focusing on eddies or circulation in a specific layer or area we overview the full depth circulation of the scs layer by layer and outline its possible forcing mechanisms and furthermore provide perspectives for further investigation

observed enhanced internal tides in winter near the luzon strait seasonal characteristics and nonlinear interaction of internal tides its near the luzon strait in the northeastern south china sea are investigated using 285 day in situ observation data it is found that its which are dominated by the first mode wave throughout the year are the strongest in subsurface layer baroclinic incoherent diurnal semidiurnal variance accounts for about 85 7 78 3 of diurnal semidiurnal its the amplitude and seasonal variation of the diurnal its are more prominent than those that are semidiurnal e g the largest kinetic energy densities of diurnal and semidiurnal baroclinic tidal currents are 2 81 and 0 83 kj m2 in winter respectively it is considered that there are two reasons for the significantly enhanced its in winter 1 it may be due to the kuroshio intrusion and 2 the enhanced diurnal its may be due to the enhanced diurnal barotropic tidal currents while the enhanced semidiurnal its may be caused by the strong nonlinear interaction between diurnal it constituents o1 and k1 due to their high vertical shears in subsurface layer thus harmonic semidiurnal constituent d2 with a similar frequency of constituent m2 is induced it subsequently enhances the semidiurnal its in this subsurface layer and the associated energy is carried downward to enhance the semidiurnal its in the upper and lower layers

influence of the kuroshio current intrusion on depositional environment in the northern south china sea evidence from surface sediment records the influence of the kuroshio current kc intrusion on the depositional environment of the northern south china sea scs is discussed based on multi proxies of surface sediments including planktonic foraminifera clay minerals and geochemical elements the results reveal that four typical planktonic foraminifera globigerinoides ruber g sacculifer neogloboquadrina dutertrei and pulleniatina obliquiloculata can be used to trace the kc flow route in the northern scs globigerinoides ruber is mainly distributed in shallower water than the south china sea branch of the kuroshio scsbk flow route while p obliquiloculata is mostly distributed in deeper water than the scsbk flow route there are high percentages of g sacculifer and n dutertrei at the scsbk flow route along the 1000 m isobath where bottom sediments consist of clayey silt and silty clay the scsbk also affects sediment distribution of various sources taiwan sourced sediments characterized by high illite and chlorite contents are transported southwestward into the deep sea environment by the scsbk and or deep water current the pearl river sediments characterized by high kaolinite and titanium ti contents are mostly transported southwestward to be distributed in the sea environment between the pearl river mouth and southeast of hainan island but hardly entered the abyssal basin the luzon island sediments characterized by high smectite content are generally deposited at the northwest of luzon island under the effect of an eddy west of luzon island these sediments were hardly transported northwestward onto the northern shelf of the scs throughout the scsbk flow route the sedimentary environment at the northwest of luzon island is relatively oxidized and higher in salinity than the northern scs which is probably connected with the kc intrusion through the luzon strait

seasonal variation of volume transport in the major inflow region of the taiwan strait the penghu channel abstract eight cruises of current measurements along a zonal transect 31 84 km across the major inflow region of the taiwan strait the penghu channel were carried out using the shipboard acoustic doppler current profiler during 1999 2001 on each cruise the measurement was repeated twice along the transect with a time lag of 6 h and 12 min and the repeated data were averaged to eliminate the dominant semidiurnal tidal currents velocities after removing semidiurnal tides suggest a strong northward flow in the channel with a speed of about 100 cm s in the upper 50 m in summer the northward flow becomes much weaker in winter the calculated throughflow transports vary seasonally and are correlated with the change of the east asia monsoon the estimated transport is around 0 during the peak northeast monsoon in winter increases from 0 5 to 1 sv 1 sv 106 m3 s as the northeast monsoon weakens in spring peaks to 1 5 sv at the end of southwest monsoon in summer and decreases rapidly from 1 5 to 0 sv when the northeast monsoon intensifies in fall the error mostly induced by unfiltered diurnal tidal currents is estimated to be 0 20 sv in the transport calculation

high resolution palynological record of holocene climatic and oceanographic changes in the northern south china sea abstract for the first time palynological records of terrestrial palynomorphs and dinoflagellate cysts are investigated in a sediment core from the northern south china sea scs covering the last 12 500 years both terrestrial and marine palynomorph records show strong signals of the sea level change during the studied interval the highest herb pollen content was associated with extensive grasslands on the exposed shelf at the low sea level stand during the younger dryas and early holocene the increase in fern spores and decrease in concentrations of dinoflagellate cysts and terrestrial palynomorphs was observed during the sea level rise interval from 12 500 to 6800 or 6000 cal yr bp then the sea level became stabilized and consistently low dinoflagellate cyst abundances and high abundances of fern spores were recorded a high abundance of impagidinium in the period 12 000 10 400 cal yr bp possibly resulted from increased input of western philippine sea waters into the scs and the branching of the kuroshio current a short term decrease of impagidinium at 11 700 11 000 cal yr bp corresponding to the mwp 1b event might be associated with input of the east china sea waters through the taiwan strait the relationship between the sedimentation rates and the concentrations of terrestrial palynomorphs indicates a water dominant transport for pollen and spore dispersal prior to 6300 cal yr bp whereas wind transport became more prominent thereafter the timing of this change corresponds to the highest sea level stand at 6800 6000 cal yr bp when the present oceanographic setting was formed the mid holocene optimum can be seen by the highest abundance of subtropical tropical broad leaved arboreal pollen and by the highest abundances of dapsilidinium pastielsii three strengthened winter monsoon intervals at 5500 cal yr bp 4000 cal yr bp and 2500 cal yr bp are reflected by increases in pinus pollen content after the present oceanographic condition formed

role of the south china sea in regulating the north pacific double gyre system abstractthe role of the south china sea scs in regulating the north pacific circulation is investigated using a two layer quasigeostrophic qg model the double gyre circulations in the north pacific with and without the scs are compared and analyzed it is found that the scs acts as a sink of both potential vorticity pv and energy in the pacific scs system for the mean state consequently the kuroshio and the upstream kuroshio extension ke are weaker in the presence of the scs moreover the eddy activity is also lower in the north pacific ocean because the barotropic instability is suppressed for a weaker circulation in terms of low frequency variations at interannual to decadal time scale the presence of the scs is found to enhance the variability of the latitudinal position and intensity of the ke jet this is explained by a positive feedback process that is associated with the negative correlation between the inertia of the kuroshio and its intrusion into the scs

the seasonal variation of the intrusion of the philippine sea water into the south china sea the seasonal variation of the intrusion of the philippine sea water into the south china sea was studied by analyzing the historical hydrographic station data in the northern south china sea and the philippine sea water masses at 150 200 and 250 m were classified by discriminant analysis according to their temperature salinity characteristics at each depth most water in the study region was classified into two groups representing the philippine sea water and the south china sea water respectively the geographic distribution of water masses in the south china sea shows that the philippine sea water was present along the continental margin south of china between october and january a westward current in the northern south china sea in winter was inferred from the distribution of the intrusion water

sea ice deformation state from synthetic aperture radar imagery part i comparison of c and l band and different polarization in this paper we present a quantitative comparison of l and c band airborne synthetic aperture radar imagery acquired at like and cross polarizations over deformed sea ice under winter conditions the parameters characterizing the deformation state of the ice are determined at both radar bands and at different polarizations the separation of deformed and level ice is based on a target detection technique the threshold is set such that image pixels with intensities equal to or larger than the highest 2 of the level ice intensity distribution are classified as deformed ice independent of the radar configuration and ice conditions optical imagery of sufficient quality for comparison is available only in a very few cases to characterize the deformation state the areal fraction of deformation features and the average distance between these features are evaluated the values obtained for both parameters are very sensitive to the radar frequency aeral fractions are larger and average distances are smaller at l band than at c band because of the much higher intensity contrast between the deformed and level ice at l band the differences between polarizations at one radar band are smaller but not always negligible in comparison to optical images it was observed that deformed ice areas can be distinguished from level ice over their whole length and extension at l band whereas at c band often only prominent parts are visible

observed sub inertial current variability and volume transport over the continental shelf in the northern south china sea abstract sub inertial currents sics over the continental shelf of the northern south china sea nscs are investigated using the in situ current observations of acoustic doppler current profiler adcp mooring arrays off the pearl river estuary in 2006 and 2007 the survey was carried out in four separate time periods summer winter spring before the onset of the southwesterly monsoon and fall after the establishment of the northeasterly monsoon the observations showed that the current directions were generally along the shelf consistent with the directions of monsoonal winds the currents were also affected by a few of mesoscale eddy events in summer 2006 the volume transport was northeastward with a mean magnitude of 1 4 sv through a cross shelf section from the site of the depth of 135 m to the coast in winter 2006 2007 spring 2007 and fall 2007 the volume transports were all southwestward with magnitudes of 2 0 2 1 and 0 9 sv respectively through a cross shelf section from the site of the depth of 290 m to the coast the standard deviations of the sics were generally smaller than the velocities of the mean currents and the variability of sics showed significant correlation with the local sea surface winds no persistent counter wind currents were observed in the study area during the fall and winter observational periods

development of the east asian monsoon mineralogical and sedimentologic records in the northern south china sea since 20 ma we here reconstruct the past change of the east asian monsoon since 20 ma using samples from ocean drilling program odp site 1146 in the northern south china sea based on a multi proxy approach including a monomineralic quartz isolation procedure identification of clay minerals by x ray diffraction xrd and grain size analysis of isolated terrigenous materials terrigenous supply to odp site 1146 was dominated by changes in the strength of multiple sources and transport processes grain size data modeled by an end member modeling algorithm indicate that eolian dust from the and asian inland and fluvial input have contributed on average 20 and 80 of total terrigenous material to odp site 1146 respectively specifically about 40 53 of the total quartz feldspar and only 6 11 of the total clay is related to eolian supply at the study site detailed analysis of the sedimentary environment and clay minerals combined with previous studies shows that smectite originates mainly from luzon kaolinite from the pearl river and illite and chlorite from the pearl river taiwan and or the yangtze river the proportion and mass accumulation rate mar of the coarsest end member em1 interpreted as eolian dust ratios of illite chlorite smectite quartz feldspar and mean grain size of terrigenous materials at odp site 1146 were adopted as proxies for east asian monsoon evolution the consistent variation of these independent proxies since 20 ma shows three profound shifts in the intensity of east asian winter monsoon relative to summer monsoon as well as aridity of the asian continent occurred at similar to 15 ma similar to 8 ma and the youngest at about 3 ma in comparison the summer monsoon intensified contemporaneously with the winter monsoon at 3 ma the phased uplift of the himalaya tibetan plateau may have played a significant role in strengthening the asian monsoon at similar to 15 ma 8 ma and 3 ma c 2007 elsevier b v all rights reserved

the morphologies and genesis of mega pockmarks near the xisha uplift south china sea pockmarks are normally regarded to be manifestations of fluids escape through the seabed kilometer wide depressions here called mega pockmarks occur as widespread features near the xisha uplift northern south china sea most of the pockmarks observed in this area are multi kilometers and much larger than normal pockmarks reported worldwide the maximum diameter observed is 3210 m and the maximum depth observed is 165 2 m based on multibeam data and 2d seismic data the pockmarks are circular elliptical and crescentic in plan view seismic profiles show that the genesis of pockmarks is related to fluid gas and or pore water escape according to the fluids pathways the pockmarks fall into four types 1 gas chimney related 2 depositional boundary related 3 gas chimney and inclined structure fault related 4 inclined structure related bottom currents are strong and complex in the study area the multibeam data and seismic profiles indicate that they may play an important role on extension maintenance and shaping of pockmarks the research of the study area is in its initial stage and the identification of these features as indicators of fluid flow is probably useful for hydrocarbon exploration c 2011 elsevier ltd all rights reserved

penetration of nonlinear rossby eddies into south china sea evidenced by cruise data national basic research program of china 2009cb421208 2007cb411803 natural science foundation of china 40976013 41121091 united states of america national oceanic atmospheric administration national environmental satellite data and information service ocean remote sensing 3000 11 03241

influence of the kuroshio current intrusion on holocene environmental transformation in the south china sea numerous studies have been conducted on the evolutionary history of the kuroshio current kc and other extensions however the history of the kc intrusion into the south china sea scs through the luzon strait has been little studied here we trace the holocene developmental history of the kc intrusion and its impact on environmental transformation in the northern scs this study involved a comprehensive analysis of planktonic foraminifera clay minerals and geochemical elements of core 05e306 sediments from the northeastern scs ams c 14 dates indicated that the sedimentation rate at the core site was most rapid 1000 cm ka before similar to 6 0 ka relatively rapid similar to 65 cm ka between 6 0 and 4 6 ka and slow similar to 24 cm ka since 4 6 ka the pulleniatina minimum event pme occurred between 4 6 and 2 7 ka together with high percentages of neogloboquadrina dutertrei and globorotalia menardii planktonic foraminifera indicated that the kc intrusion experienced three significant changes at 6 0 4 6 and 2 7 ka in turn depositional environments including input of terrigenous materials and development of biogenic materials similarly underwent three important transformations at 6 0 4 1 and 3 0 ka respectively abrupt changes in sedimentary records at the study core are contemporary with records from the tropical pacific during the holocene this indicates that development of the kc intrusion and its impact on depositional environments in the scs can be correlated with tropical factors from the low latitude oceans

on the modification of tides in a seasonally ice covered sea 1 new observations from eight moorings located in foxe basin hudson strait and hudson bay are used to study the seasonal variability of the m 2 tide significant seasonal variations of the m 2 surface elevation are found in all these regions and at all seasons the largest variations occur during winter while both elevation increase hudson strait and decrease hudson bay foxe basin are observed these variations are found recurrent at the stations where multiyear observations are available observations from a velocity profiler are consistent with a seasonal damping of the tides because of friction under ice numerical simulations with a sea ice ocean coupled model and realistic forcing qualitatively reproduce most of the features of the observed variability the simulations show that the winter m 2 variations are essentially caused by the under ice friction albeit with strong regional differences under ice friction mostly occurs in a limited region foxe basin and can account for both increased and decreased m 2 elevations during winter

atmospheric boundary layer structure and drag coefficients over sea ice this paper estimates the air sea drag coefficient for first year ice from recent aircraft measurements and reconciles the range of observed drag coefficients 103cd 1 2 3 7 referenced to 10 m for all sea ice types based on ice roughness and seasonal meteorology for the purpose of sea ice modeling it is necessary to define an effective drag coefficient which relates regional stress to regional wind because sea ice is heterogeneous on scales less than 20 km regional stress is influenced by the distribution of surface roughness the buoyancy flux from quasi periodic leads and external atmospheric conditions principally the inversion height 103cd is 1 3 1 5 for smooth ice but is much greater for nonflat surfaces for wind speeds greater than 5 m s and air temperatures below freezing the effective 103cd is 2 5 3 0 for nearly continuous pack ice such as first year ice in seasonal ice zones and central arctic basin the range of values of 103cd is 3 0 3 7 for unstable boundary layers typical of off ice winds in the marginal ice zone miz or even greater if the ice has been broken by a recent storm cd values at the lower end of these ranges are associated with low inversion heights these coefficients are confirmed by 103cd of 2 9 2 5 and 3 1 for first year sea ice calculated from gust probe data collected by the noaa p 3 aircraft interior to the inner miz in the bering sea during the marginal ice zone experiment mizex west in february 1983 and 103cd of 2 6 for the arctic calculated from arctic ice dynamics joint experiment aidjex aircraft data for february 1976 the effective drag coefficient with the presence of even a small concentration of sea ice is greater than the oceanic value as shown by a 103cd of 2 2 calculated from noaa p 3 gust probe data over a 40 km track of 0 4 ice concentration in the outer miz of the greenland sea in june 1984 during mizex 84 the relation of surface wind and stress to the geostrophic wind for shallow inversion heights typical of high latitudes is reviewed with a turbulent closure atmospheric boundary layer model the winter arctic is typified by low inversions 100 m low geostrophic drag coefficients and large geostrophic surface wind turning angles with low functional dependence on surface roughness seasonal ice zones are typified by a more modest influence of the inversion on boundary layer characteristics

nonlinear multiscale interactions and internal dynamics underlying a typical eddy shedding event at luzon strait eddy shedding is a highly nonlinear process that presents a major challenge in geophysical fluid dynamics using the newly developed localized multiscale energy and vorticity analysis ms eva this study investigates an observed typical warm eddy shedding event as the kuroshio passes the luzon strait in order to gain insight into the underlying internal dynamics through multiscale window transform mwt it is found that the loop form kuroshio intrusion into the south china sea scs is not a transient feature but a quasi equilibrium state of the system a mesoscale reconstruction reveals that the eddy does not have its origin at the intrusion path but comes from the northwest pacific it propagates westward preceded by a cyclonic cold eddy through the kuroshio into the scs as the eddy pair runs across the main current the cold one weakens and the warm one intensifies through a mixed instability in its development another cold eddy is generated to its southeast which also experiences a mixed instability it develops rapidly and cuts the warm eddy off the stream both the warm and cold eddies then propagate westward in the form of a rossby wave first baroclinic mode as the eddies approach the dongsha islands they experience another baroclinic instability accompanied by a sudden accumulation of eddy available potential energy this part of potential energy is converted to eddy kinetic energy through buoyancy conversion and is afterwards transferred back to the large scale field through inverse cascading greatly reducing the intensity of the eddy and eventually leading to its demise this article is protected by copyright all rights reserved

progress on the formation dynamics of the layered circulation in the south china sea abstract in the south china sea scs an alternating cyclonic anticyclonic cyclonic cac circulation is recognized in the upper middle deep layers based on the principle of stokes theorem the cac circulation is driven extrinsically by the east asia monsoonal winds a vertical sandwich like inflow outflow inflow through luzon strait ls and intrinsically by the slope current topography interaction the understandings on the formation mechanisms of cac circulation have been achieved based on different principles and the physically solid interpretation on the cac circulation need to be further clarified in this paper we review different dynamic perspectives from recent researches that describe the combined effects of surface wind forcing lateral external forcing and the intrinsic coupling among different layers our aim is to obtain a consistent understanding of the dynamics of the circulation in the scs the cac circulation forms largely from the planetary vorticity flux that is extrinsically induced by the inflow outflow inflow through ls which is predominantly balanced by the interaction between the cac flow and bottom topography inside basin the vertical motion dynamically links the circulation in three layers and its spatial pattern has a strong impact on the basin circulation particularly in the middle and deep layers vertical coupling of the layers occurs mainly over the slope because of the cross slope motion due to interaction between strong slope current and topography the internal layered circulation and intensified mixing in turn affect and maintain the layered current structure in ls based on the review of the forcing mechanisms we offer perspectives for further investigations

a three layer alternating spinning circulation in the south china sea abstractunderstanding of the three dimensional circulation in the south china sea scs is crucial for determining the transports of water masses energy and biogeochemical substances in the regional and adjacent larger oceans the circulation s kinematic and dynamic natures however are largely unclear results from a three dimensional numerical ocean circulation model and geostrophic currents derived from hydrographic data reveal the existence of a unique three layer cyclonic anticyclonic cyclonic cac circulation in the upper 1500 m layers in the scs with differing seasonality an inflow outflow inflow structure in luzon strait largely induces the cac circulation which leads to vortex stretching in the scs basin because of a lateral planetary vorticity flux in each of the respective layers the formation of joint effects of baroclinicity and relief jebar is an intrinsic dynamic response to the cac circulation the jebar arises from the cac flow topog

northern south china sea sst changes over the last two millennia and possible linkage with solar irradiance abstract high resolution surface temperature records over the last two millennia are crucial to understanding the forcing and response mechanism of earth s climate here we report a bidecadal resolution sea surface temperature sst record based on long chain alkenones in a gravity sediment core retrieved from the northern south china sea sst values varied between 26 7 and 27 5 c with a total variability 1 c over the last 2000 years the general sst variation pattern matches well with total solar irradiance tsi changes relatively warm period between 800 and 1400 ad and cool period 1400 1850 ad could be identified in agreement with the commonly defined periods of medieval warm period and little ice age within chronological uncertainty notable short cooling events at 640 670 ad 1030 1080 ad 1260 1280 ad and 1420 1450 ad coincide with large volcanic eruption events the general coincidence of sst changes with tsi and volcanic eruption events suggests strong impact of external forcing on sea surface conditions in the studied area in addition to the direct tsi changes volcanic eruptions might have induced oceanic and atmospheric circulation adjustments which might be responsible for the short cooling events as revealed in the alkenone sst record

atmospheric boundary layer modification drag coefficient and surface heat flux in the antarctic marginal ice zone during a traverse of the antarctic marginal ice zone miz near the greenwich meridian in october 1981 we launched a series of radiosondes along a 150 km track starting at the ice edge since the wind was from the north off the ocean these radiosonde profiles showed profound modification of the atmospheric boundary layer abl as the increasing surface roughness decelerated the flow the primary manifestation of this modification was a lifting of the inversion layer with increasing distance from the ice edge by the induced vertical velocity but there was also a cooling of the stably stratified mixed layer below the inversion and a consequent flux of sensible heat to the surface that averaged over 200 w m2 the magnitude of this flux suggests that atmospheric heat transport plays a significant role in the destruction of ice in the antarctic miz using the rising of the inversion and abl similarity theory we estimated the change in the neutral stability drag coefficient cd across the miz cd increased from its open ocean value 1 2 10 3 at the ice edge to 4 0 10 3 at 80 90 ice concentration we present an equation for this dependence of drag on ice concentration that should be useful for modeling the surface stress in marginal ice zones

the south china sea throughflow retrieved from climatological data abstract the salinity distribution in the south china sea scs has a pronounced subsurface maximum from 150 220 m throughout the year this feature can only be maintained by the existence of a mean flow through the scs consisting of a net inflow of salty north pacific tropical water through the luzon strait and outflow through the mindoro karimata and taiwan straits using an inverse modeling approach the authors show that the magnitude and space time variations of the scs thermohaline structure particularly for the salinity maximum allow a quantitative estimate of the scs throughflow and its distribution among the three outflow straits results from the inversion are compared with available observations and output from a 50 yr simulation of a highly resolved ocean general circulation model the annual mean luzon strait transport is found to be 2 4 0 6 sv sv 106 m3 s 1 this inflow is balanced by the outflows from the karimata 0 3 0 5 sv mindoro 1 5 0 4 and taiwan 0 6 0 5 sv str