holocene thermal optimal and climate variability of east asian monsoon inferred from forest reconstruction of a subalpine pollen sequence taiwan the east asian monsoon holocene optimal period has been debated both about duration and whether conditions were a maximum in thermal conditions or in precipitation in this study we show holocene climate variability inferred by a forest reconstruction of a subalpine pollen sequence from peat bog deposits in central taiwan based on modern analogues of various altitudinal biomes in the region a warmer interval occurred between 8 and 4 ka bp calibrated 14 c years when the subtropical forests were more extensive the holocene thermal optimum is represented by an altitudinal tropical forest at 6 1 5 9 ka bp and 6 9 ka bp and only the latter was accompanied by wet conditions indicating decoupling of thermal and precipitation mechanism in the middle holocene abrupt and relative severe cold phases shown by biome changes occurred at about 11 2 11 0 ka bp 7 5 ka bp 7 2 ka bp 7 1 ka bp 5 2 ka bp 5 0 ka bp and 4 9 ka bp a spectral analysis of pollen of a relatively cold taxon salix reveals that the time series is dominated by a 1500 yr periodicity and similar to the cold cycle reported in the marine records of indian and western pacific oceans the cold warm conditions inferred by the change of forests show close relationship to solar energy in comparison with the production rate of be 10

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

estuary shelf interactions off the changjiang delta during a dry wet seasonal transition abstract estuary shelf interaction is very complex and vital for maintaining healthy ecosystem in the estuaries and adjacent seas the topic has been intensively studied through cruise observations and numerical models but less by long term observations at a fixed station we present here for the first time roughly 2 months adcp and ctd continuous data from the xiaoqushan pilot station of seafloor observatory aiming to deliberate river plume frontal processes off the changjiang estuary in response to river discharge transition from the dry to wet season in 2009 multiple lines of evidence attest that inner river plume is always in a bottom trapped form but isohalines and isothermals are very sensitive to seasonal variations in freshwater input wind climate and surface heating semidiurnal oscillations of salinity and temperature are good tracers for seasonal variations in plume frontal processes in the dry season both salinity and temperature have weak semidiurnal oscillations due to minimal cross shore straining under strong mixing conditions near the inner plume front where isohaline and isothermal are nearly vertical with small horizontal salinity and temperature gradient they are suddenly interrupted by a sharp increase of semidiurnal salinity oscillations owing to the arrival of newly established plume front with a less steep isocline slope but a maximum horizontal salinity gradient of 0 8 psu km the response time of inner plume front to the first discharge increasing pulse is roughly two weeks but should change a lot when examined at different plume locations and under varied river discharge increasing magnitudes and rates the frontal processes mirror well the river discharge fluctuations in the transitional period which lasts for a few weeks before entering a typical wet season the latter features strongest semidiurnal temperature oscillations linked with summer surface heating and highly depressed semidiurnal salinity oscillations because the main plume path shifts from southward to northeastward due to alternating southerly to northerly prevailing winds the three stages of inner plume frontal processes can be more clearly demarcated by the wavelet power spectral and the amplitudes of semidiurnal diurnal oscillations of salinity and temperature through wavelet transform and the associated band pass filtering methods the seasonal plume frontal transition has been vividly portrayed for the first time through secular observation at the fixed station in the river plume region significantly improving our understanding their controlling factors and mechanisms

the north pacific as a regulator of summertime climate over eurasia and north america abstract the role of the north pacific as a regulator of boreal summer climate over eurasia and north america is investigated using observational data two summertime interannual climate modes associated with sea surface temperature sst variability in the north pacific are identified the first mode shows an elongated zone of warm cold sst anomalies in the central north pacific along 40 n with temporal variability significantly correlated with el nino during the preceding spring but its subsequent evolution is quite different from el nino the second mode exhibits a seesaw sst variation between the northern and southern north pacific and is independent of el nino both modes are linked to coherent sst anomalies over the north atlantic suggesting the presence of an atmospheric bridge linking the two extratropical oceans using the principal component of the most dominant mode as the north pacific index npi composite analyses show that the positive negative phase of npi features a warm cold

holocene variations in asian monsoon moisture a bidecadal sediment record from the south china sea the east asian monsoon system involves extensive transport of sensible latent heat between land and sea and from low to high latitudes our high resolution bidecadal marine records present a first detailed history of monsoon climate change over the holocene the high amplitude perturbation in monsoon moisture centered at 8 150 years ago and the monsoon maximum in the early holocene show inter hemispheric teleconnections to both a cool episode in greenland and to the indian monsoon monitored in the arabian sea periodicities of 84 102 and especially near 775 years in monsoon variation suggest a climatic forcing both by long term oscillations in thermohaline circulation and possibly solar activity cycles

reconstruction of silicate weathering intensity and paleoenvironmental change during the late quaternary in the zhuoshui river catchment in taiwan taiwan island is one of the best places in the world for the study of earth surface processes during the late quaternary because of its unique geological geographic and climatic settings in this study we present sedimentary and element geochemical data of core jrd s drilled on the zhuoshui river delta aiming to examine the changes of sediment provenance and silicate weathering intensity in response to monsoon climate variability since the last glacial period similar rare earth element ree compositions between the core sediments and modern zhuoshui river samples suggest the zhuoshui watershed was the dominant sediment provenance for the late quaternary deposition in the river mouth while the mainland rivers in southeast china including the changjiang yangtze river could not be the major sediment suppliers due to the stable sediment provenance the geochemical proxy of the core sediments reveals the change of silicate weathering intensity during the late quaternary in the zhuoshui watershed was primarily driven by monsoon climate under an active tectonic setting the weaker monsoonal precipitation in the last glaciation caused weaker erosion thus less sediment supply in the mountainous watershed and thus increased the sediment residence time and silicate weathering intensity in contrast the enhanced holocene monsoonal precipitation might greatly increase the physical erosion and sediment transfer rate from land to sea which consequently produced more less weathered sediments this study provides in depth insights into sedimentary response to tectonic and monsoon climatic changes during the quaternary on a tectonically active high standing island which increases our better understanding of earth surface processes in the unique continental margin

the δ18o and δ13c records in an aragonite stalagmite from furong cave chongqing china a 2000 year record of monsoonal climate abstract a 7 cm long aragonite stalagmite fr0510 1 from furong cave chongqing was dated by 210pb and 230th methods revealing a 2000 year record of climate history under the influence of the east asian monsoon the fr0510 1 record resembles dongge cave da record on 10 100 year scales but quite different from the wanxiang cave wx42b record indicating that while stalagmite 18o record represents local regional moisture change spatial variability of the monsoonal rainfall over eastern china must take into account during the past 2000 years climate in chongqing was relatively wet in the intervals of 50 bc ad 250 ad 1150 1450 and ad 1600 1950 and relatively dry during the periods of ad 250 1150 and ad 1450 1600 dry conditions were prevailing over the medieval warm period whereas wet climates were dominant during the most time of the little ice age in chongqing area

the first high resolution stalagmite record from taiwan climate and environmental changes during the past 1300 years abstract this paper presents the first high resolution holocene stalagmite record of taiwan from jianfei cave 22 50 873 n 120 21 255 e in dagangshan mountain south taiwan the 13 6 cm long stalagmite dgs 1 has been dated by ams 14 c dating spanning from ad 700 to ad 1933 the 18 o 13 c and xrf scanned elemental profiles reveal interannual variations in climate and environmental conditions with light 18 o and 13 c excursions reflecting wet climate and better vegetation coverage under stronger east asia summer monsoon easm dark layers in dgs 1 containing high fe mn and sr contents were formed during dry episodes five periods with different climate regimes and vegetation conditions can be identified in the dgs 1 record period i ad 700 1200 and period v ad 1810 1933 had warm and wet climates with good vegetation coverage a drying trend probably corresponding to the switch from el nino like to la nina like oceanic condition occurred during period ii ad 1200 1400 cold but relatively wet climates with good vegetation coverage were prevailed during period iii ad 1400 1610 whereas cold and dry climates with poor vegetation coverage were dominated during period iv ad 1610 1810 based on the rainfall record of tainan since ad 1897 and the stalagmite record we found that stronger total solar irradiation tsi resulting in strong easm produces heavy rainfall in south taiwan on interannual to decadal scales and vice versa the 117 yr instrumental rainfall record of tainan showed that rainfall in tainan decreased during april to june and strongly increased during july to september in many la nina years positive soi and negative nino 3 4 this may be because weaker meiyu rainfall but stronger tropical equatorial pacific cyclones or typhoon under la nina condition thus it is better to use seasonal rainfall for detecting relationship between tainan rainfall and enso on decadal to centennial scales strong el nino like state and warm pacific decadal oscillation pdo phase are in favor of wet conditions in south taiwan

decadal relationship between the north atlantic oscillation and cold surge frequency in taiwan 1 the close decadal relationship between the north atlantic oscillation nao and the cold surge frequency in northern taiwan is identified the cold surge frequency was higher lower in 1957 1977 1981 2001 which corresponded to the negative positive phase of the nao the teleconnection pattern associated with the nao suggests that the siberian high the ridge upstream of lake baikal and the east asian trough which are well known circulation characteristics favorable for cold surge occurrences were enhanced in the negative nao phase a weakened upper level convergence over the mediterranean sahara occurring in the negative nao phase was associated with a wave like pattern spreading toward east asia along the subtropical jet stream barotropic modeling results suggest that the suppressed upper level convergence in the mediterranean sahara region may force a wave train emanating toward east asia along the subtropical jet stream which acts as a rossby waveguide the barotropic wave pattern may result in a stronger low level northerly over subtropical east asia and create a favorable background for the further southward penetration of cold air and therefore more frequent cold surge occurrence the same process may be applied to the period when the nao is in the positive phase

pollen records from southern taiwan implications for east asian summer monsoon variation during the holocene pollen records from two cores retrieved from a valley basin in southern taiwan show major changes in vegetation and climate occurring during the holocene between 11 400 and 8200 cal yr bp the up

holocene east asian monsoon variability links to solar and tropical pacific forcing 1 sedimentary geochemical records from subalpine retreat lake subtropical taiwan document the unstable east asian monsoon eam climate over the past 10 300 years with a weak eam between 10 3 and 8 6 ky b p eam intensity peaks between 8 6 and 7 7 ky b p and then gradually decrease in response to summer insolation heat and moisture transport our proxy record reveals several weak monsoon intervals that correlate to low sea surface temperatures in the western tropical pacific and cold events in the north atlantic linking the tropical pacific north atlantic and polar climates because weak eam events at 8 2 5 4 and 4 5 2 1 ky b p also correspond to low values of atmospheric methane and periods of reduced north atlantic deep water formation we therefore suggest that centennial to millennial scale monsoon variability during the holocene in the northern subtropics is globally mediated via a sun ocean monsoon north atlantic linkage

structure and eastward extension of the changjiang river plume in the east china sea 1 the hydrographic structure and offshore extension of freshwater plume discharged from the changjiang also known as the yangtze river in the northern east china sea were investigated by analyzing conductivity temperature depth ctd data and drifter trajectories collected during the summers of 1997 and 1998 from june to early september when southerly winds prevail the plume tends to move northeast in the chinese coastal area and then separates from the coastal zone to travel eastward over 400 km offshore across the western shelf of the northern east china sea during other seasons when northerly winds prevail the plume is confined to the chinese coast in the summer the plume in the midshelf confined to a thin surface layer 10 to 15 m thick extends eastward in the form of patches of low salinity water rather than spreading as a tongue shaped pattern from the changjiang mouth the eastward movement of patches in the western shelf is primarily due to upwelling favorable southerly winds upon reaching the vicinity of cheju do an island in the middle of northern east china sea the patches are advected to the korea tsushima strait by either the cheju warm current or a northward flowing mean current of the kuroshio branch current and then finally flow into the east japan sea

the dry holocene megathermal in inner mongolia the paleoclimate since 14 kyr bp 14c age was reconstructed based on a 16 22 m long sediment core collected from lake yanhaizi a saline lake located near the northern limit of the east asian summer monsoon in inner mongolia coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated these sediments have low organic carbon contents but high maturity indices indicating that they were deposited in an arid environment by contrast based on high organic contents and low maturity indices fine sediments were deposited during periods of high lake stand in a humid environment it was in general dry between 8 0 and 4 3 kyr bp the above dry and wet phases are consistent with those recovered from the arid semiarid transition zone elsewhere but are unlike the widely perceived humid holocene megathermal reported in east china and the newly reconstructed record in the alpine retreat lake in taiwan the discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon on the other hand much enhanced evaporation over higher monsoon precipitation at lake yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon this also accounts for the fact the high temperature holocene megathermal as revealed in the okinawa trough and the northern south china sea is correlated to the dry phases at lake yanhaizi conversely the 4 2 kyr bp coldest period in the holocene corresponds to a wet phase at lake yanhaizi

horizontal energy propagation in a barotropic atmosphere with meridional and zonal structure abstract to investigate how the propagation of energy away from steady sources may be influenced by the horizontal structure of the time averaged flow in the troposphere solutions to a barotropic model are displayed and interpreted the model is steady and linearized about a basic state which varies in latitude and longitude emphasis is placed on cases where the longitudinal variations are gradual many of the results can be analyzed by locally applying tools developed for zonally symmetric basic states e g ray tracing and refractive indices simple background flows are constructed which have longitudinally confined critical lines reflective surfaces wave guides and regions conducive to propagation an example is given in which longitudinal derivatives of the basic state are significant the theory of ray tracing in a two dimensional wind must be employed as an interpretive tool in this case it is concluded that zonal variations tend to enhance poleward equatorward propagation in large scale tr

a case of downstream baroclinic development over western north america abstract numerical simulations have been made of the initiation of a strong ridge trough system over western north america and the eastern pacific the terminus of the pacific storm track with the objective of determining the extent to which downstream development contributed to its growth and the possible influence of topography on the energetics of the storm while a control simulation demonstrated considerable skill in reproducing the storm a simplified simulation in which topography surface that fluxes and latent heating were removed not only reproduced the primary features of the ridge trough system permitting a clearer interpretation of the factors contributing to its growth but actually generated a stronger system suggesting that these effects as a whole inhibited storm development application of an energy budget that distinguishes between energy generation via baroclinic processes and generation via the convergence of geopotential fluxes revealed that early growth of studies that have sh

vegetation response to holocene climate change in east asian monsoon margin region abstract fossil pollen records from 20 sites with reliable chronologies and high resolution data in the east asian monsoon margin region were synthesized to document holocene vegetation and climate change and to understand the large scale controls the vegetation experienced different changes over the holocene in various sub regions 1 near the boundary between modern forest and temperate steppe in northeast china forest showed clear expansion in the middle holocene 2 in central china near the boundary between steppe forest and desert vegetation showed various patterns at different sites 3 further west on the tibetan plateau near the boundary between highland meadow steppe and semi desert desert forest expanded at most sites during the early and middle holocene our synthesis indicates that climate in the margin region was slightly moist in the early holocene wettest in the middle holocene and dry in the late holocene though there are regional differences as reflected by vegetation change this general pattern is very different from either monsoon or westerly dominated regions the maximum moisture occurred during the early holocene in the monsoon region while the arid central asia dominated by the westerlies was driest in the early holocene and wettest in the mid holocene the interplay of the asian summer monsoon westerlies topography and regional vegetation factors might have contributed to this spatial complexity

evidence of holocene water level changes inferred from diatoms and the evolution of the honghe peatland on the sanjiang plain of northeast china abstract diatom inferred changes in past water levels and the evolution of peatlands during the holocene period are investigated in the honghe national natural reserve hnnr which is located on the sanjiang plain of northeast china this investigation began with analyses of fossil diatoms and the corresponding water environments from the surface sediments of peatlands the detrended correspondence analysis dca and redundancy analysis rda methods show that the water level is one of the major factors that drives the distribution of diatom assemblages in the peatlands of the hnnr a diatom based inference model is developed and the holocene water levels are reconstructed based on the inference model applied to a one component weighted averaging partial least squares wapls model the jackknife statistical test yields a relatively high correlation coefficient and a low root mean squared error of prediction r2jack 0 220 rmsepjack 0 2339 compared with a series of models the peatland water level was relatively high from 6 5 to 2 8 ka 1 ka 1000 cal yr bp and species that prefer deep water such as aulacoseira crenulata ehrenberg krammer and navicula cuspidata kutzing were dominant at that time the water level also increased markedly from 2 8 to 2 5 ka and subsequently declined from 2 5 ka to the present a clear reciprocal shift is noted between an assemblage of deep water species that includes a crenulata and species that prefer sphagnum bogs including nitzschia perminuta grunow peragallo this evidence suggests that the water level of the hnnr peatland became shallower implying the presence of a paleolake in the early or middle holocene that was followed by the development of the peatland which is a result of paludification up to the present time these results strengthen the potential for paleo reconstructions of the hydrology of the peatlands of northeast china using multiple proxies

late holocene monsoon climate of northeastern taiwan inferred from elemental c n and isotopic δ13c δ15n data in lake sediments national science council of taiwan nsc 97 2629 m 001 025 nsc 99 2116 m 001 011 national science foundation of china 41176059 41121091

central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

intraseasonal teleconnection between north american and western north pacific monsoons with 20 day time scale abstract based on a recently released high resolution reanalysis dataset for the north american region the intraseasonal variability isv with a time scale of about 20 days of the north american monsoon nam is examined the rainfall signals associated with this phenomenon first emerge near the gulf of mexico and eastern pacific at about 20 n they subsequently migrate to the southwestern united states along the slope of the sierra madre occidental the rainfall quickly dissipates upon arrival at the desert region of arizona and new mexico aznm the enhanced rainfall over aznm is accompanied by strong southeasterly low level flow along the gulf of california this pattern bears strong resemblance to the circulation related to gulf surge events as documented by many studies the southeasterly flow is associated with an anomalous low vortex over the subtropical eastern pacific ocean off california and a midlatitude anticyclone over the central united states in the lower troposphere this flow pat

circumglobal teleconnections the jet stream waveguide and the north atlantic oscillation abstract monthly and seasonally averaged upper tropospheric northern hemisphere winter fields are examined to determine whether the waveguiding effect of the time averaged tropospheric jets on low frequency disturbances that is predicted by theory does affect the behavior of these disturbances it is found that indeed disturbances in the vicinity of the mean jets particularly the jet that stretches across south asia are fundamentally different from those that reside in regions where the mean winds have weaker meridional gradients like the mid pacific patterns of variability in the jets tend to be smaller scale and to consist of zonally oriented chains of anomalies while variability in the mid pacific is composed of patterns with distinct meridional orientation because they are meridionally trapped and zonally elongated patterns associated with the jet stream waveguide connect activity at points that are much farther apart than do patterns in other regions of the globe within the south asian waveg

ice volume forcing of east asian winter monsoon variations in the past 800 000 years particle size measurements of some typical loess soil samples taken in different localities of the chinese loess plateau demonstrate that the grain size ratio of 10 m can be used as an indicator of variations in intensity of the east asian winter monsoon winds grain size curves of the baoji and weinan sections show that this proxy indicator is very sensitive to loess soil alterations analytical results also suggest that during soil forming periods eolian dust accumulation was still substantial and hence loess deposition can be regarded as a nearly continuous process during the quaternary period in this study we compared the baoji grain size time series with the specmap marine isotope record with the objective of elucidating the dynamic linkage between changes in global ice volume and the winter monsoon circulation both records show good agreement at both time and frequency domains in particular the winter monsoon variations are also dominated by a 100 000 yr period over the past 800 000 yr it is thus inferred that direct local insolation forcing could be less important in driving the east asian winter monsoon variability and alternatively variations in glacial age boundary conditions may have played a key role in modulating and pacing its strength and timing

basin wide holocene environmental changes in the marginal area of the asian monsoon northwest china in arid regions because of spatial variability using single climate records is difficult to reconstruct the past climate change for the drainage basins holocene environmental records were collected from the upper middle and lower regions of the shiyang river drainage basin in the marginal area of the asian monsoon northwest china the main objective of this paper was to compare the records from the terminal lake and the middle and upper reaches of the basin to study the basin wide environmental changes during the early holocene the vegetation was sparse and the effective moisture was relatively low in the basin the holocene climatic optimum started between 7 0 and 8 0 cal ka bp during which the lake level reached the highest level in the terminal lake the vegetation density and the effective moisture reached the highest level during the holocene in the drainage basin from 4 7 cal ka bp the terminal lake began to shrink while the vegetation density decreased dramatically in the middle and upper regions of the drainage the effective moisture began to decrease since 3 5 cal ka bp and the arid tendency was earlier in the terminal lake than it was in the middle and upper regions of the drainage basin during the early holocene the relatively arid environment was affected by the gradually intensifying east asian monsoon and the dry westerly winds the mid holocene optimum benefited from the intensive east asian monsoon and the humid westerly winds then the east asian monsoon retreated since the late holocene in the basin the arid tendency may be related to the retracting of the east asian monsoon however the intensifying acidification after 1 5 cal ka bp may be correlated to the increasing dryness of the westerly winds

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

tracing the flow rate and mixing ratio of the changjiang diluted water in the northwestern pacific marginal seas using radium isotopes we measured ra isotopes 223ra and 228ra in surface seawater of the northwestern pacific marginal seas to trace the flow rate and mixing of the changjiang diluted water cdw in the summer of 2012 based on the horizontal distribution of 223ra activities the arrival time of cdw from the river mouth to 450 km offshore northeast was estimated to be 20 35 days which is similar to that determined in previous studies moreover we successfully calculated the relative contribution of cdw at each sampling station using a salinity and 228ra diagram using this unique method we found that the relative contribution of cdw was more than 30 in most surface seawaters of the northern east china sea the yellow sea and the southern sea off korea our results suggest that cdw is of high significance in the biogeochemistry of surface seawater of these northwestern pacific marginal seas during the summer monsoon period

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

spatial variations of monsoonal rain in eastern china instrumental historic and speleothem records abstract we select four caves and their nearby cities in the monsoonal region of china for studying the relationships among precipitation temperature summer monsoon intensity and stalagmite 18o the instrumental historic and stalagmite 18o records from these areas show strong spatial disparities on annual to decadal scales so that climatic conditions in a single location cannot represent these of the entire eastern china on time scales

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

deep sea pollen from the south china sea pleistocene indicators of east asian monsoon abstract a high resolution pollen record sampling interval averages 820 years has been obtained from odp site 1144 water depth 2037 m northern south china sea the 504 m sequence in composition length covers the last 1 03 million years according to micropaleontological and isotopic stratigraphy the pollen assemblages are characterized by high proportions of pinus and herb pollen and by their frequent alternations based on these alternations 29 pollen zones have been recognized that are closely correlated to the marine oxygen isotope stages mis 1 29 pinus dominant pollen zones correspond to interglacial periods with lighter 18o values while herb marked ones relate to the heavier 18o stages assigned to glacials judging from the pollen data the exposed northern continental shelf of the south china sea during the glacials was covered by grassland and the extensive northern shelf has formed only since mis 6 ca 150 ka probably as a result of tectonic subsidence tree pollen influx values are indicative of winter monsoon which began to intensify 600 ka ago the summer monsoon variations can be approximated by the fern percentage within the total pollen and spore abundance and the result shows high values in general occurring at interglacials with the maxima at mis 15 5e and 1 the relatively high fern percentage with smaller amplitude in variations before 600 ka might suggest more stable humid conditions before the intensification of winter monsoon

lipids of aquatic organisms as potential contributors to lacustrine sediments ii abstract the relationship between the lipid composition of organisms in the water column of an eutrophic lake and the lipid composition of underlying sediments previously examined for n alkanols and steroids is now reported for hydrocarbons ketones and carboxylic acids the n c7 alkane and alkenoic acids from two primary sources are rapidly metabolized in the water column and surficial sediment bacterial biomarkers including hopenes and i ai branched fatty acids were detected in the photosynthetic bacterial layer occurring just above the sediment water interface within the sediment the apparent conversion of free n alkanes alkan 2 ones and hydroxy acids to the corresponding bound form is noted microbiological oxidation of n alkanes to alkan 2 ones is supported by the detection of the intermediate alkan 2 ols with a distribution similar to that of the ketones the geochemistry of sediment deposited c 1900 prior to biological study of the site was interpreted from stable biomarkers and the diagenetic changes recognised in the study of contemporary deposition a qualitative difference in algal input to the older sediment is inferred from the low 7 sterol content and presence of 2 6 10 trimethyl 7 3 methylbutyl dodecane however there was still significant dinoflagellate input as indicated by the presence of 4 methylsterols a difference in higher plant input to the older sediment indicated from the n alkane alkene and triterpenoid ketone distributions is consistent with the recent development of tree cover

iso modulation on the submonthly wave pattern and recurving tropical cyclones in the tropical western north pacific abstract this study demonstrates the multiscale nature from synoptic to intraseasonal time scales of the atmospheric flow in the tropical western north pacific the multiscale features include intraseasonal oscillations iso northwestward propagating submonthly wave patterns and recurving tropical cyclones tcs in the iso westerly phase the wave pattern was better organized and the tcs were clustered near the cyclonic circulation of the wave pattern during the genesis development and propagation on the other hand the wave pattern and tcs were weak and poorly organized in the iso easterly phase the distinct characteristics between the westerly and easterly phases could be attributed to the iso modulation on the monsoon trough and the subtropical anticyclonic ridge the iso in the westerly phase provided a favorable background e g enhanced monsoon trough and moisture confluent zone for the wave tc pattern development while the iso in the easterly phase provided a less favorable environment

occurrence of rain origin nitrate patches at the nutrient depleted surface in the east china sea and the philippine sea during summer 1 nutrient concentrations at the nanomolar level were monitored in the east china sea and the philippine sea during summer using a continuous underway system with a highly sensitive colorimetric method concentrations of both nitrate and soluble reactive phosphorus srp varied generally at 1000 nm at a horizontal scale of 10 km to tens of kilometers compared with neighboring waters these nitrate patches were grouped into three types according to the associated environmental conditions with 1 lowered salinity and no changes in srp and in vivo chlorophyll fluorescence 2 lowered temperature and elevations of srp and in vivo chlorophyll fluorescence and 3 no consistent environmental variations the first type was ascribed to rainfall which is rich in nitrate but phosphate free the second type was formed near islands landmasses and was ascribed to upwelling or intense vertical mixing the third type was not characterized and was considered to include several sources nine out of 20 nitrate patches belonged to the first type within each of these nine patches nitrate concentration was negatively correlated with salinity by extrapolating this correlation nitrate concentrations in the rainwater were estimated to be within 0 14 6 2 m which is well within the reported concentrations of nitrate in rainwater on the basis of the estimated nitrate concentrations and amount of precipitation nitrogen supply from rainfall in the study area was evaluated to be in the same order as that of diffusive upward flux and n2 fixation in summer

behavior of one to two week summertime subtropical wind maxima over the south pacific during an enso cycle abstract the behavior of subtropical jet streaks over the australian south pacific region is investigated for four consecutive 6 month summer seasons november to april during the period 1985 89 the study is an extension of a recent one by ko and vincent hereafter referred to as kv in which jet streaks during the summer season of 1984 85 were examined ko and vincent found that the upper tropospheric zonal wind behaved in a quasi periodic manner with maxima recurring over the western south pacific at intervals between one and two weeks in the present study wind maxima are found to exhibit a 1 2 week periodic oscillation over the south pacific in all four years thus substantiating the finding by kv in addition a second set of jet streaks with a similar periodicity is found over the southern australian region it is also seen that the mean summertime position of the south pacific jet and its accompanying jet streaks are much farther cast during the el nino event of 1986 87 than they are in the

paleohydrological changes in northeastern taiwan over the past 2 ky inferred from biological proxies in the sediment record of a floodplain lake abstract taiwan is particularly sensitive to changes in monsoonal precipitation and to the frequency of typhoon induced heavy precipitation events many parts of this mountainous subtropical island have high erosion rates that produce high sedimentation rates in lakes and offshore ocean basins and evidence suggests that these rates have varied in the past a high resolution 2 ky record of changes in sediment delivery to dahu a floodplain lake in northeastern taiwan that suggests changes in precipitation has been inferred from organic matter pollen and spores in a 12 m sediment core and from the organic matter compositions of soil catchment plants and fluvial suspended sediment from 0 to 1400 ad the lake experienced repeated flood events principally resulting from overflows of the old ilan river one of tributaries of the lanyang river that were briefly interrupted 1000 ad by decreased precipitation and or only localized rainfall the record of heavy precipitation can be linked to the northward shift of the itcz during the early little ice age 1400 1600 ad local erosion fluctuated in association with deforestation and farming during which the itcz shifting varied as well a decrease in precipitation since 1600 ad is linked with the southward migration of the itcz

late holocene environment of subalpine northeastern taiwan from pollen and diatom analysis of lake sediments abstract we used multi decadal pollen and diatom records from sediment core tfl 1 from tsuifong lake to reconstruct the vegetation dynamics and hydroclimate in northeastern taiwan during the past 3500 cal bp coarse grained sediments in association with higher percentages of wetland pollen cyperaceae and upper conifer pollen tsuga and pinus in the lower part of the core indicate low lake levels and a relatively cold dry climate between 3500 and 2030 cal bp reflecting a decline of the east asian summer monsoon easm muddy sediments coupled with reduction of wetland pollen represent the rise of lake levels implying the re strengthening of the easm during the past 2000 years paleotemperature was inferred from the variation of pollen origin from the upper and lower mountain forest indicating the global temperature anomalies of the medieval warm period mwp and the little ice age lia in comparison to the main climate forces in the north pacific we suggest that the long term climatic trend in taiwan was controlled by variations in easm intensity while increased precipitation over the past 2000 years may also be linked to warmer sea surface temperature sst of the western pacific warm pool wpwp and increased el nino southern oscillation enso events which increased typhoon intensity higher diatom inferred ph during 2930 2030 cal bp and the lia suggest strong hydrological disturbances reflecting more typhoons passing over taiwan the frequent typhoon events could be linked by an abrupt shift of typhoon track due to the reduction of the wpwp and expansion of the northwestern pacific high which move typhoons in a more westerly direction

lipid geochemistry of sediments from upton broad a small productive lake major lipid classes isolated from 3 sections of the sediment profile of upton broad a shallow lake formed about 500 yr ago were correlated with input and with changes attributable to early diagenesis surficial sediment contains lipids characteristics of the known recent algal and microbial input preservation of chlorophyll pigments and absence of appropriate markers suggest that diagenesis is minimal older deposits from the eutrophic phase of the lake s history contain higher levels of bacterial lipids and diagenetic products the earliest sediment contains lipids characteristic of terrigenous input subjected to more extensive diagenesis than the younger sediment recognition of early diagenesis in anoxic sediment suggests that distributions of the shorter chain homologous free n alkanes alkanols and alkanoic acids result from microbial synthesis using material initially deposited at the sediment surface rather than partial preservation of the lipids of primary source organisms

hydrodynamic condition and suspended sediment diffusion in the yellow sea and east china sea based on monthly averaged current temperature and salinity we analyzed the changes of suspended sediment concentration ssc and the relationship with the warm current coastal current and cold water mass cwm in the east china seas ecss the result shows that the coastal current and surface diluted water are the route for transporting suspended sediment the kuroshio and its derived warm current branches play the important role of the continental shelf circulation system and control the diffusion of suspended sediment high ssc has been mainly concentrated in coastal current and cwm two sedimentary dynamic patterns have been identified the winter half year pattern lasts almost 7 months the coastal currents off the shandong peninsula northern jiangsu zhejiang fujian coast are the main routes for diffusion and deposition of the suspended sediment from the yellow river and changjiang river the summer half year pattern is characterized by the well developed cwm all cwms have a unique function to trap suspended sediment under the thermocline due to weakening tidal current and residual current there these cwms in the yellow sea ys and north ecs are connected together the layer above the thermocline is characterized by diluted water with low salinity high temperature suspended sediment can be transported into the okinawa trough and the south korea coast during this period a strong eddy always occur nearby the kuroshio bend at northeast taiwan which has promoted the exchange between the ecs shelf and okinawa trough and the development of the shelf edge current and taiwan warm current twc

variations of east asian summer monsoon since the last deglaciation based on mg ca and oxygen isotope of planktic foraminifera in the northern east china sea 1 variations in mg ca based sea surface temperature and oxygen isotope ratio 18o of the surface water in the northern east china sea ecs were reconstructed with high resolution during the last 18 kyr using planktic foraminifera millennial scale variations between warmer more saline surface water and cooler less saline surface water were recognized during the early deglacial period and the holocene suggesting changes in the mixing ratio between the kuroshio water and the changjiang diluted water stronger east asian summer monsoon easm precipitation events in south china are identified at 10 5 8 8 7 0 5 3 4 7 2 9 1 7 and 0 5 ka based on sea surface salinity sss records of the northern ecs weaker easm precipitation events are also detected at 9 3 8 3 7 3 6 0 3 3 2 3 0 7 and 0 4 ka during the holocene these events agree with the maxima in 18o records of stalagmites from various parts of the changjiang yangtze river drainage this agreement supports that our sss record properly captures the millennial scale dry less easm precipitation events over the drainage basin of the changjiang river during the holocene these dry events are also in good agreement with north atlantic ice rafted events suggesting a teleconnection between north atlantic climate and the easm during the holocene

the quantitative reconstruction of salinity changes using diatom assemblages in inland saline lakes in the central part of turkey during the late quaternary abstract climatic changes during the late quaternary have been studied using three sediment cores from closed and semi arid lacustrine basins in central anatolia turkey based on diatom assemblages of sediments the first step in using diatoms as salinity indicators is to obtain quantitative data concerning their ecological characteristics along salinity gradients using 51 samples of living diatoms from 38 lakes and rivers in turkey an abundance weighted mean salinity was calculated for each taxon on the basis of a strong relationship between diatom composition and salinity the diatom based transfer functions were defined for the salinity reconstruction and then applied to three drill cores from late quaternary lacustrine sediments from konya basin the oscillations of the diatom inferred salinity of the cores generally indicate glacial pluvial correlations high salinity levels were associated with inter glacial stages and low sanity levels indicate glacial stages the curves also included the phases of shorter oscillations ranging from 10 000 to 20 000 years presumably caused by global climate changes and local environmental changes

measurements of the turbulent energy dissipation rate e and an evaluation of the dispersion process of the changjiang diluted water in the east china sea 1 the large amount of fresh water discharged from changjiang spreads over the east china sea continental shelf as low salinity water particularly in the summer season to understand the primary production in the east china sea it is necessary to clarify the dispersion process of the changjiang diluted water cdw since the high production area appears to cover the cdw in this study the dispersion process of the cdw was evaluated through the estimation of the turbulent energy dissipation rate e in the cdw and calculation of the divergence in the cdw using satellite tracked drifters a large value of e was observed just above the bottom and in the surface layer whose magnitude was sometimes greater than 10 7 w kg 1 on the other hand a small value of e less than 10 8 w kg 1 was found just beneath the cdw the small value of e leads to a small value of the vertical eddy diffusivity of less than 10 5 m 2 s 1 the vertical advection of the bottom water is likely to be a major process for increasing the salinity since the horizontal diffusion would not play a significant role if the usual magnitude of the horizontal diffusivity is assumed calculation of divergence in the surface layer using the drifters data also suggests that upward velocity of o 10 5 m s 1 over the cdw area is expected the vertical transport from the bottom layer could increase the salinity of the cdw and also carry the nutrients into the euphotic zone resulting in biological production

circumglobal teleconnection in the northern hemisphere summer analysis of the 56 yr ncep ncar reanalysis data reveals a recurrent circumglobal teleconnection cgt pattern in the summertime midlatitude circulation of the northern hemisphere this pattern represents the second leading empirical orthogonal function of interannual variability of the uppertropospheric circulation the cgt having a zonal wavenumber 5 structure is primarily positioned within a waveguide that is associated with the westerly jet stream the spatial phases of cgt tend to lock to preferred longitudes the geographically phase locked patterns bear close similarity during june august and september but the pattern in july shows shorter wavelengths in the north pacific north america sector the cgt is accompanied by significant rainfall and surface air temperature anomalies in the continental regions of western europe european russia india east asia and north america this implies that the cgt may be a source of climate variability and predictability in the above mentioned midlatitude regions the cgt has significant correlations with the indian summer monsoon ism and el nino southern oscillation enso however in normal ism years the cgt enso correlation disappears on the other hand in the absence of el nino or la nina the cgt ism correlation remains significant it is suggested that the ism acts as a conductor connecting the cgt and enso when the interaction between the ism and enso is active enso may influence northern china via the ism and the cgt additionally the variability of the cgt has no significant association with the arctic oscillation and the variability of the western north pacific summer monsoon the circulation of the wave train shows a barotropic structure everywhere except the cell located to the northwest of india where a baroclinic circulation structure dominates two possible scenarios are proposed the abnormal ism may excite an anomalous west central asian high and downstream rossby wave train extending to the north pacific and north america on the other hand a wave train that is excited in the jet exit region of the north atlantic may affect the westcentral asian high and thus the intensity of the ism it is hypothesized that the interaction between the global wave train and the ism heat source may be instrumental in maintaining the boreal summer cgt

holocene diatom records of wetland development near weipa cape york australia abstract to better understand the response of tropical wetlands to holocene environmental changes two lacustrine diatom records from weipa cape york have been investigated the record from big willum bw01 commenced approx 7 9 calibrated thousand years before present k cal a bp and details stages of initial swamp development a phase of ephemeral conditions between approximately 5 7 and 2 2 k cal a bp and relative wetland stability after 2 2 k cal a bp lithological and to a lesser extent diatom assemblage changes in bw01 appear to be linked to broad scale changes in effective precipitation the record from little willum lw01 commenced around 0 9 k cal a bp and documents initial phases of swamp development until approximately 0 8 k cal a bp with subsequent relative wetland stability the uppermost 10 cm of this record approximately spanning the last 40 years coincide with mining activity in the region only minor changes in the diatom assemblage are recorded for this period implying that the overall character of the swamp probably remained unchanged both sites offer new insights into wetland dynamics in australia s dry tropics and demonstrate that changes in these lacustrine systems were probably driven by shifts in effective precipitation in particular during the late holocene

terrestrial n alkanes and their carbon isotope records from the hanon paleo maar sediment jeju island korea implications for paleoclimate and paleovegetation over the last 35 kyrs abstract the carbon isotope of total carbon 13 c org long chain n alkanes and their compound specific carbon isotope ratios 13 c alk were investigated in the hanon paleo maar sediment jeju island of korea to understand paleoclimate variabilities and their paleovegetation linkages based on the organic geochemical data toc tn and their 13 c org and 15 n the core column stratigraphy was divided into three units namely from the bottom to 14 5 ka unit i from 14 5 ka to 3 0 ka unit ii and from 3 0 ka to the core top unit iii respectively in particular 13 c org showed marked fluctuation from 17 31 to 28 68 suggesting different organic carbon sources a relatively narrow range of variation in 13 c org was observed in unit iii and drastic changes in 13 c org were observed from unit i to unit ii this may indicate a predominance of c 4 plants in unit i and drastic changes from terrestrial c 4 to c 3 in unit ii and predominance of c 3 plants in unit iii the distributions of n alkane were characterized by a continuous predominance of odd numbered n alkanes particularly n c 29 and n c 31 and by high fluctuation of the total n alkanes concentration the average chain length acl carbon preferences index cpi and paleo plant proxy p aq showed high fluctuation and glacial interglacial variations with distinctive a high and low ratio at about 9 2 ka corresponding to the switching points of 13 c org and a high concentration of n alkane distribution individual n alkane odd numbered isotopes of 13 c alk ranged between 11 80 in 13n c 21 and 34 93 in 13n c 31 suggesting different sources of n alkanes the distribution of n alkanes and their individual 13 c alk in particular 13n c 21 support paleovegetation changes and their time dependent variations matched well with glacial interglacial paleoclimate variations therefore organic geochemical proxies recorded in hanon paleo maar sediment reflects paleoclimate variabilities as well as paleovegetation changes for the last 35 kyr in jeju island korea

the history and variability of the east asian paleomonsoon climate abstract changes in the east asian paleomonsoon reflect interactions between the global atmosphere ocean land and ice systems and are also an expression of their combined effect within the boundary conditions imposed by the east asian continent and solar radiation the history of the east asian monsoon is an alternation between dominance by the dry cold winter and warm humid summer monsoons high resolution eolian sequences preserved in the chinese loess plateau reveal that the east asian monsoon may have commenced at least 7 2 ma ago they also provide evidence indicating that the pulsed uplift of the tibetan plateau at about 3 4 and 7 2 ma may have played an important role in inducing climate change the palaeoclimatic records of the last glacial cycle show high frequency variability on time scales of 1000 year or even shorter and instability of the east asian paleomonsoon system the high frequency variability could be due to a non linear response to orbital forcing or a result of the coupling processes between different components of the global system cold air activity in northern high latitudes the trans equatorial air streams from the southern hemisphere and possibly enso may have played an important role in east asian monsoon variability the synchroneity of all the palaeoclimatic events along the polar equator polar pep transect is still an open question correlation of limited palaeoclimatic records for the last 30 kyr obtained from east asia and australia suggests that the trans equatorial air streams driven by the monsoon and trade winds may have had an influence on opposite hemispheres

episodes of nonlinear internal waves in the northern east china sea 1 episodes of high frequency internal waves which lasted approximately 3 hours were detected in the northern east china sea during a specific phase of the barotropic tide i e low tide at 32 n 125 e the observed internal waves influenced the whole water column the wave packets were presumably generated near the ocean shelf break approximately 200 km to the southeast of the test site during several internal wave episodes which coincided with the neap tide large amplitude solitary wave like features emerged preceding higher frequency internal waves shear instability of tidal currents is explored as a possible mechanism for sustaining or regenerating internal waves in the packets during the course of their propagation it is suggested that rotating velocity field of tidal current supports sufficient vertical shear within wave packets to cause outbreaks of k h instability these instabilities may gradually transition to more symmetric holmboe waves following the increase of the bulk richardson number

rossby wave propagation and the rapid development of upper level anomalous anticyclones during the 1988 u s drought abstract the upper tropospheric circulation is investigated for the three months of april may and june 1988 during which the great plains region of the united states experienced one of its most severe droughts in history it is found that during this period the april june amj seasonal mean anomaly was not representative of the variability of 10 day low pass anomalies rather over north america large fluctuations on monthly and shorter timescales occurred with the dominant streamfunction anomalies not strongly anticyclonic until june in fact the amj anomaly was dominated by two episodes of rapidly developing intense anomalous anticyclones in early and late june examination of the daily 10 day low pass streamfunction anomalies at 300 mb suggests that propagating rossby waves originating in the west pacific played a dominant role in the initiation of these intense anomalous anticyclones numerical experiments with a linear time dependent barotropic model also support this hypothesis these result

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

late holocene mobilisation of loess like sediments in hohuan shan high mountains of taiwan abstract silty cover soils are found in lower slope positions in the highest massifs of the high mountains of taiwan they are not formed under present day conditions and remain well preserved in locations not affected by fluvial morphodynamics this study focuses on an outcrop in the hohuan mountain summit area the sediment infill of a gully is described and sediment properties are analysed size frequency distributions of the sediment grains suggest that they are partly aeolian deposits the loess like sediments yielded osl ages between 3 65 0 62 ka and 1 72 0 48 ka results from radiocarbon dating of organic rich bulk sediments support the age estimates from osl the timing of gully infilling coincides with a cool and dry phase reported by palynological studies from toushe basin and chitsai lake the sediment record reflects a large scale climatic change to cooler and less humid conditions in the hohuan mountain area

the paleolimnology of haynes lake oak ridges moraine ontario canada documenting anthropogenic and climatic disturbances haynes lake is a small kettle lake located on the oak ridges moraine and is within the greater metropolitan area of toronto ontario canada s most populous region lake sedimentation flux rates diatoms and thecamoebians extracted from a benthic core were used as biological proxies to evaluate changes in water quality through time as a function of anthropogenic activity and changing climate there were two periods of disturbance to the haynes lake ecosystem from ca 8 500 years before present ybp through to ca a d 2003 which were significant enough to cause changes in lake sedimentation the diatom flora and thecamoebian fauna the first disturbance was concomitant with the decline in global temperatures following the hypsithermal climate optimum ca 4 700 ybp the most significant disruption to haynes lake over the last 8 500 years however was the settlement of europeans and subsequent urban development ca a d 1875 including the construction of a road immediately adjacent to the lake anthropogenic disturbance of inorganic clays in the recent paleosediment record 5 cm is indicative of more recent eutrophication events

increasing terrigenous sediment supply from taiwan to the southern okinawa trough over the last 3000 years evidenced by srnd isotopes and geochemistry abstract high resolution sedimentary records reveal the patterns of weathering and erosion in response to climate change environmental variability and human activity here we present major and trace element data sr nd isotopic compositions and mass accumulation rates mars for the siliciclastic sediment fraction of a relatively high resolution sedimentary archive from the southern okinawa trough east china sea we reveal the sedimentary source to sink processes and the physical erosion and chemical weathering history of taiwan the sr nd isotopic data indicate that sediments were mainly sourced from northeastern and western taiwan rivers and thus the sedimentary records reflect the weathering and erosion conditions in this source region volcanic rocks aeolian dust and terrigenous sediment from rivers in mainland china and eastern taiwan have not significantly contributed to the deposits in the southern okinawa trough since ca 3000 cal yr bp multiple indices including the chemical index of alteration cia k al alk ti na and k na are used to identify variations in the intensity of regional scale chemical weathering the strength of the sediment input is estimated using the mar of the siliciclastic marsiliciclastic and the mar of ti marti the results suggest that the bedrock of small mountainous river systems in taiwan has experienced relatively stable and moderate chemical alteration and that the terrigenous sediment supply from taiwan to the southern okinawa trough has progressively increased since ca 3000 cal yr bp a comparison of these data with climate and human activity indicates that the increased input of terrigenous sediment was closely related to an intensification of rainfall in taiwan over the last 3000 years after ca 1500 cal yr bp a sustained increase in the terrigenous sediment input likely to be attributed to the combined effects of intensified heavy rainfall and human activity occurred intense physical erosion in taiwan s river basins has exerted a long term constraint on chemical weathering intensity the lack of evident link between silicate weathering and climate forcing in these catchments suggests that paleoclimate reconstruction based on sedimentary geochemical records offshore of taiwan rivers requires careful consideration

rossby wave propagation and teleconnection patterns in the austral winter abstract observational evidence of and theoretical support for the northern and southern hemisphere teleconnection patterns in the austral southern hemisphere winter are examined through an upper troposphere streamfunction teleconnectivity map and time lag cross correlation analysis using ecmwf initialized analysis 2oo hpa winds for the 11 june august periods from 1979 to 1989 as was previously found for the northern hemisphere winter the regions of strong teleconnectivity particularly in the winter hemisphere tend to he oriented in the zonal direction and coincide with the location of the major jet streams although equatorward propagation from the northern and southern hemispheres is observed little evidence of cross equatorial propagation has been found for comparison the response of a barotropic model linearized about a climatological 300 hpa june august time mean flow to localized forcing is determined it is found that the activity tends to be trapped inside each of the southern hemisphere

tongue shaped frontal structure and warm water intrusion in the southern yellow sea in winter 1 in winter a thermohaline front forms at the yellow sea ys entrance where the warm and saline cheju warm current cwc water meets cold coastal water the frontal structure as well as the northwestward intrusion of the warm water was investigated by analyzing conductivity temperature depth ctd data tracks of drifting floats moored current data and satellite images the cwc water advances westward as a tongue with its tip heading westward across the ys entrance not intruding northward along the deepest part of the ys trough whereas a secondary warm water band is developed northwestward along the western flank of the trough floats in the warm tongue moved northwestward across the western frontal zone where the frontal structure was weak reflecting the northwestward intrusion along the 50 70 m isobaths through the frontal zone currents in the trough do not always meet the upwind flow theory that in an elongated basin the wind driven flow is upwind in the deep channel but rather show the predominance of the southward downwind flow model experiments show that on the western flank of the trough both the southeastward tide induced residual flow and the southeastward flow due to the nonlinear effect between tide and wind are generated at the same time thus the intermittent intrusion of the cwc across the western frontal zone may be closely associated with the predominance of the upwind flow over the southeastward nonlinear interacted flow

climate changes inferred from integrated multi site pollen data in northern taiwan abstract in this study we synthesized the fossil pollen data from 10 lake sediments and 2 land cores to integrate the alteration of forest covered areas in northern taiwan with changes in humidity and temperature over the last 2000 years the abundance of arboreal pollen fern spores and tsuga pollen in the pollen and spore assemblages were used as indicators our results suggested that the climate in northern taiwan was stably cool and dry during 2000 1000 cal yr bp but changed to wet and warm during 1000 500 cal yr bp which corresponded to the medieval warm period mwp in addition an increased density and dispersal of tsuga pollen corresponding to 500 200 cal yr bp was observed which corresponded to the little ice age lia in recent years a decline in tsuga pollen density and increased fern spore density has been observed which indicates an increase in temperature associated with elevated rainfall based on the synthesized data set we conducted gis mapping of such changes in the north of taiwan over time the results revealed that the temporal and spatial climate changes could be inferred from the palynological gis mapping method and that the fluctuations in temperature over time matched well with the global climate events including mwp lia and recent warming

variations in monsoonal rainfall over the last 21 kyr inferred from sedimentary organic matter in tung yuan pond southern taiwan abstract changes in paleorainfall intensity linked to the strength of the east asian ea summer monsoon since 21 cal kyr bp are inferred from the organic matter contents of a 15 m sediment core from tung yuan pond in southern taiwan high total organic carbon total nitrogen toc tn values in association with increased toc content suggest that more soil derived material containing terrestrial organic matter om was delivered to the lake during periods of increased runoff associated with extensive precipitation that resulted from intensified summer monsoons whereas low values indicate om possessing a dominant algal origin during weakened summer monsoons rainfall intensity in terms of the proportion of terrestrial om was high in four periods the last deglaciation 17 2 to 12 2 ka the early holocene 10 6 to 8 6 ka the middle holocene thermal optimum 7 7 to 5 ka and the late holocene 4 2 to 2 ka whereas it was low in the intervening time periods high toc tn values coincide with peak values of summer insolation and thus the strongest ea summer monsoon during the early and middle holocene small drops in these ratios correspond to increasing and decreasing solar radiation in the deglacial period and the late holocene respectively the four intervals with low toc tn ratios as well as episodic drops of the ratios during the deglaciation and the early and late holocene are concordant with the late last glacial 21 to 17 2 ka the oldest 14 8 ka the older 13 3 ka and the younger dryas 13 to 11 5 ka the 8 2 cold event 8 6 7 7 ka and a late holocene cold event 5 4 2 ka and suggest a weakened ea summer monsoon during these times moreover high frequency hydrological variability occurred during the early holocene heavy rainfall persisted during the middle holocene and precipitation intensity generally diminished after 5 ka the tung yuan pond sediment record indicates that the toc tn ratio can be used as a paleorainfall intensity proxy to trace variations in the ea summer monsoon strength in other small lakes

reconstructing biomes from palaeoecological data a general method and its application to european pollen data at 0 and 6 ka biome models allow the results of experiments with atmospheric general circulation models to be translated into global maps of potential natural vegetation the use of biome models as a diagnostic tool for palaeoclimate simulations can yield maps that are directly comparable with palaeoecological pollen and plant macrofossil records provided these records are biomized i e assigned to biomes in a consistent way this article describes a method for the objective biomization of pollen samples based on fuzzy logic pollen types taxa are assigned to one or more plant functional types pfts then affinity scores are calculated for each biome in turn based on its list of characteristic pfts the pollen sample is assigned to the biome to which it has the highest affinity subject to a tie breaking rule modern pollen data from surface samples reflecting present vegetation across europe are used to validate the method pollen data from dated sediment cores are then used to reconstruct european vegetation patterns for 6 ka the reconstruction shows systematic differences from present that are consistent with previous interpretations the method has proved robust with respect to human impacts on vegetation and provides a rational way to interpret combinations of pollen types that do not have present day analogs the method demands minimal prior information and is therefore equally suitable for use in other regions with richer floras and or lower densities of available modern and fossil pollen samples than europe

submarine groundwater discharge sgd into the yellow sea revealed by 228ra and 226ra isotopes implications for global silicate fluxes abstract we estimated the magnitude of submarine groundwater discharge sgd into the yellow sea which is one of the largest continental shelves in the world using 226 ra and 228 ra isotopes on the basis of 228 ra and 226 ra mass balance models we estimated the advective flux of 226 ra through sgd to be 270 10 12 dpm yr 1 in the yellow sea using this 226 ra flux and the measured 226 ra activity in coastal groundwater the submarine discharge of groundwater mostly brackish groundwater was calculated to be at least 40 of the river water input 2 3 10 11 m 3 yr 1 then on the basis of the sgd and the concentration of si in coastal groundwater we estimated the flux of si through sgd to be 20 100 of that associated with river discharge 23 10 9 mol yr 1 this large sgd is likely to be due to the high tidal range up to 10 m and the wide distribution of sandy sediments in the yellow sea favorable for the recirculation of seawater through bottom sediments and rocks this result from such a large area implies that the si flux through sgd may be significant on a global scale

reconstruction of late glacial and holocene climate evolution in southern china from geolipids and pollen in the dingnan peat sequence we have carried out a multi proxy analysis of a radiocarbon dated peat core that records the history of paleoclimate change dating from 18 ka in the dingnan region of southern china fatty acid and hydrocarbon distributions total organic carbon toc concentrations pollen assemblages and sediment lithology reveal a succession of three major paleoclimate intervals plant waxes are the predominant origin of the n alkanoic acid and n alkane compositions of this sedimentary sequence contributions of these geolipid components vary relative to toc and with changes in lithology and help to refine a pollen based reconstruction of local paleoclimate evolution a period of cool and fairly wet climate 15 630 10 450 cal abp follows accumulation of coarse fluvial sediments under relatively dry deglacial conditions the second period 10 450 6040 cal abp experienced the warmest climate and the highest precipitation indicated by a minimum c18 1 c18 0 ratio together with the low cpi values of n alkanes and high acl values the third time interval 6040 3800 cal abp was a moderately dry and cool period the climate record of the most recent period 3800 cal abp is obscured by agricultural disturbance the younger dryas 12 900 11 600 cal abp appears in this record as a period of variable and very wet climate during the interval 10 450 6040 cal abp both temperature and the precipitation evaporation ratio maximized therefore we consider this period to represent the holocene optimum which coincides with that of the northern hemisphere moreover our results do not fit the spatially asynchronous pattern of the east asian monsoon holocene optimum in china suggested by previous studies they instead parallel the pattern of global paleoclimate change and consequently show that the evolution of holocene paleoclimate in southern china is consistent with changes in northern hemisphere solar radiation

a preliminary study of the basic hydrographic features and the current structures off the changjiang river mouth in the dry season abstract the structure of the changjiang river plume in the dry season is discussed by using data from ctd and anchor stations obtained since 1980 as well as historical hydrographic data the main results are as follows 1 in the dry season the changjiang diluted water is confined into a narrow band west of 122 30 e extends to the south or southeast off the south passage and at the surface layer behaves like a quasi geostrophic current instead of a jet like current which is different from what it does in the flood season 2 the southward huanghai coastal current in winter does not seem to keep its path through the changjiang estuary and does not become the southward donghai coastal current as conventionally believed in fact the huanghai coastal current water could mix up with the changjiang diluted water and the offshore water going northward there 3 a small warmer tongue in the south of the study area was found in dec 1985 and jan 1986 which is generated by a northward upwind current east of the southward donghai coastal current 4 the surface current in the study area is much affected by winds varying with short time scales but not so much by the monthly mean wind field 5 a pair of small surface eddies was found in jan 1986 which were caused by the taiwan warm current and northerly wind

high resolution evidence from southern china of an early holocene optimum and a mid holocene dry event during the past 18 000 years abstract computer models suggest that the holocene optimum for east asian summer monsoon precipitation occurred at different times in different regions of china previous studies indicate that this time transgressive holocene optimum should have been experienced about 3000 yr ago in southern china in this study we describe a section which allows us to test this timing directly we have closely examined high resolution eutrophic peat mud sequences covering the past 18 000 cal yr at dahu jiangxi on the southern boundary of the mid subtropical zone in china late pleistocene successions in the dahu record indicate cooler and much wetter conditions relative to synchronous events in north central china our results indicate that the holocene optimum occurred between ca 10 000 and 6000 cal yr ago in southern china consistent with the global pattern conditions were relatively dry and cold from 6000 to 4000 cal yr ago our data also support the conclusion that the last deglaciation to early holocene in the south was much wetter resulting in the formation of dense broad leaved forests which could have acted to moderate land temperature 10 000 to 6000 cal yr ago yielding a stable early holocene climate after 6000 cal yr forest reduction led to unstable land temperatures and possibly to a northerly shift of the subtropical high pressure system whatever the mechanism these changes resulted in decreased precipitation between 6000 and 4000 cal yr b p in southern china

coastal circulations driven by river outflow in a variable density 1 layer model a variable density 1 layer model is used to investigate the dynamics of the fresher water plumes generated by river outflow solutions are found in a north south channel and the transport mr and salinity sr of the outflow are specified as boundary conditions along a 25 km wide segment of the western boundary in most cases the river water discharges into a preexisting oceanic mixed layer with thickness h1 when mr is sufficiently low plumes remain coastally trapped immediately after the outflow is switched on a coastal kelvin wave is excited at the river mouth that establishes a southward current of oceanic water along the right hand coast in contrast all the river water first bends to the left as it exits the river mouth and the resulting plume advances northward along the left hand coast at the plume nose some of the fresher water reverses direction and this water together with some oceanic water flows southward on either side of the offshore density front between the fresher and salty waters two processes cause this upstream movement geostrophic adjustment generates the southward frontal current and kelvin wave propagation from the nose thins the layer within the plume thereby establishing the northward geostrophic coastal jet when mr is sufficiently high coastally trapped plumes no longer exist if the rossby number of the outflow is also large enough the river water flows directly offshore and only a portion of it recirculates to form a northward propagating coastal plume the angle at which the outflow leaves the river mouth becomes more southward as mr and sr increase and as h1 decreases the strength of the northward propagating plume is weakened as h1 decreases and sr increases when h1 0 so that there is no ambient oceanic layer there is no northward plume at all likewise the plume is weakened when the model includes entrainment a process that acts to prevent the layer thickness from thinning appreciably

northwestward propagation of the intraseasonal oscillation in the western north pacific during the boreal summer structure and mechanism abstract the convection of the intraseasonal timescale in the western north pacific during the boreal summer tends to propagate northwestward in the philippine sea to near 20 n and then continues propagating westward the formation of enhanced convection in the western north pacific is a result of the merging of a convective system moving eastward along the equator and a westward propagating low level convergence anomaly which is located to the east of a vortex in the subtropics a positive feedback between the anomalous circulation and convection leads to a rapid enhancement of the system the strengthened southwesterly associated with the vortex enhances evaporation over the oceans e g the eastern indian ocean the bay of bengal and the south china sea and transports moisture northeastward the moisture converges at the northwestern corner of the convection and results in a potentially unstable atmosphere the result is the northwestward propagation of the coupled circulation convection system in

late holocene 2 ka sea level river discharge and climate interrelationship in the taiwan region abstract based on the palynological study of two alpine lakes of the central mountains and a lake at 460 m elevation in northeastern taiwan a warm event which lasted several hundred years from about cal 2 ka followed a cool dry interval from about cal 3 7 2 0 ka evidence indicates a warmer annual temperature of 1 2 c and relatively higher precipitation during the warm interval compared with the cool dry interval sea level at cal 2 1 5 ka is estimated to have been 130 150 cm higher than at present based on data from the penghu islands off western taiwan chen and liu quaternary research 45 254 262 1996 in northern taiwan the corresponding sea level rise is recognized by a widening of the estuary in the taipei basin lin development of taipei city pp 159 246 1981 which is consistent with the distribution of archaeological sites around cal 2 ka the age of lower river terraces in northern lanyang and southern erhjen taiwan are consistently in the range cal 2 5 1 5 ka this suggests an island wide morphological process probably relating to climate change this study discusses the inferred climate change and possible morphological responses

lacustrine record of centennial and millennial scale rainfall variability of the east asian summer monsoon during the last deglaciation multi proxy evidence from taiwan abstract situated at the border between the southeast asian continent and the northwestern pacific taiwan s climate is primarily influenced by the east asian summer monsoon easm and episodic tropical cyclones formed in the western pacific the lake sediments in taiwan thus potentially archive the information of typhoon events and past monsoon variability a high resolution multi proxy total carbon mass accumulation rate of total carbon weight percent of wood fragments 13 c of the organic carbon magnetic susceptibility chemical weathering index and well dated lacustrine record from dongyuan lake 22 10 n 120 50 e 360 m above sea level in southern taiwan was used to reconstruct centennial to millennial timescale easm oscillations specifically for the transition from the last deglaciation to the early holocene 17 9 ka bp the temporal patterns of proxies on both timescales in our records broadly agree with those in the greenland ice core which shows enhanced easm during the warm period and weakened monsoon during the cold period different from northern high latitude climates we found two phases in the mystery interval opposite bolling allerod ba trend with maximum monsoonal rainfall in the allerod period and more gradual transition to younger dryas event in our record likely other climate forcings beyond the north atlantic climate jointly modulated the easm changes of sea surface temperature in the western tropical pacific also might have exerted synergistic control on easm precipitation in taiwan on the centennial timescale during the last deglaciation in addition several high sedimentation events accompanied by significant amounts of wood fragments were observed and coincide with the paleo record of mass wasting events identified on various downstream floodplains in taiwan since mass wasting processes were rainfall driven and threshold triggered such coherence possibly indicated an intensification of typhoon activity during the early holocene more high resolution lacustrine records are required to decipher the hydrological variation and climate dynamics that were co influenced by the intertropical convergence zone itcz and typhoon activity in southeast asia

downstream development of the summertime tropical cyclone submonthly wave pattern in the extratropical north pacific abstract the impact of tropical perturbation on the extratropical wave activity in the north pacific in the submonthly time scale is demonstrated here previous studies identified a tropical cyclone tc submonthly wave pattern which propagated north northwestward in the philippine sea and recurved in the oceanic region between japan and taiwan this study found that after the arrival of the tc submonthly wave pattern at the recurving region the eastward propagating wave activity in the extratropical north pacific was significantly enhanced it is suggested that the tc submonthly wave pattern which is originated in the tropical western north pacific enhances the eastward energy propagation of rossby wave like perturbation in the extratropical north pacific and may have an impact on the long range weather predictability in the eastern north pacific and western north america

climate and hydrology of the last interglaciation mis 5 in owens basin california isotopic and geochemical evidence from core ol 92 abstract 18 o 13 c total organic carbon total inorganic carbon and acid leachable li mg and sr concentrations on 443 samples from 32 to 83 m depth in owens lake core ol 92 were analyzed to study the climatic and hydrological conditions between 60 and 155 ka with a resolution of 200 a the multi proxy data show that owens lake overflowed during wet cold conditions of marine isotope stages mis 4 5b and 6 and was closed during the dry warm conditions of mis 5a c and e the lake partially overflowed during mis 5d our age model places the mis 4 5 boundary at ca 72 5 ka and the mis 5 6 boundary termination ii at ca 140 ka agreeing with the devils hole chronology the diametrical precipitation intensities between the great basin cold wet and eastern china cold dry on milankovitch time scales imply a climatic teleconnection across the pacific it also probably reflects the effect of high latitude ice sheets on the southward shifts of both the summer monsoon frontal zone in eastern asia and the polar jet stream in western north america during glacial periods

global teleconnections in the 250 mb streamfunction field during the northern hemisphere winter abstract teleconnections of the streamfunction in the global domain based on ecmwf 250 mb winds for the 11 northern winters from 1978 79 through 1988 89 are documented in this study a zonal structure with a node near the equator indicating an out of phase relationship between the streamfunctions in the northern and southern hemisphere appears to mask the fluctuations of the asymmetric components of streamfunction after removing zonal means a global pattern emerges as the dominant structure in the low frequency band this pattern consists of several dipoles straddling either the exit region of midlatitude jets or the equator indicating the existence of teleconnections not only between the midlatitudes and the tropics but also between the northern and southern hemispheres teleconnection patterns in the intermediate frequency band are predominantly wavelike seven waveguides are identified based on the one point lag correlation maps for base points near the maximum teleconnectivity among them are thr

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

tropical cyclone effects on arctic sea ice variability 1 in recent years increasing interest has been put on the role that intense tropical cyclones can play in the climate system the following study is aimed at highlighting the effects of strong tropical cyclones over the tropical atlantic on the mean climate their composite effect on the surface winds is made apparent by a wide cyclonic perturbation that affects a large portion of the atlantic tropical ocean teleconnection patterns which are visible in the sea level pressure anomalies associated with this tropical composite cyclone appear to link the activity of the hurricanes to the arctic ocean a significant negative correlation between the energy dissipated by hurricanes in the tropical atmosphere and the sea ice cover along the transpolar drift stream path has also been found

bathymetric effects on estuarine plume dynamics 1 the influence of bathymetry on an estuary plume at an estuary shelf transition is studied with a three dimensional ocean circulation model to understand the response of the plume to bathymetry several types of estuarine shapes and shelf geometries were adopted in this numerical study the channel s shape and its width to depth aspect ratio affected the fate of the plume by determining flow characteristics inside the estuary moreover the bathymetry of the shelf such as the shelf slope and the direction of a submarine channel defined the plume characteristics on the shelf an estuarine channel with a triangular cross section generated relatively stronger exchange flows at midestuary than a rectangular cross section which resulted in a larger surface plume over the shelf the extension of the submarine channel onto the shelf favored increased plume water transport out to the shelf a result of reduced frictional effects on the shelf the orientation of the submarine channel changed the direction of the plume over the shelf with no additional external forces two fronts developed at the edges of the submarine channel because of enhanced lateral shears in the flow when the estuary was relatively wide compared to the internal rossby radius kelvin number ke 5 or when the relative strength of the freshwater discharge compared to the estuary width was weak rossby number ro 0 05 the coastal plume did not expand up shelf in fact results indicated that freshwater up shelf transport in a coastal current moving against coriolis accelerations was proportional to ro

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

strengthening of paleo typhoon and autumn rainfall in taiwan corresponding to the southern oscillation at late holocene the purpose of this study is to improve prehistoric knowledge of paleo typhoon and winter monsoon activity in the western north pacific after 8 cal ka bp we examine two sediment cores derived from lakes located to the south and north of the ilan plain in northeastern taiwan seasonal and typhoon rainfall data over the past several decades are collected for this study region we also use mineral indicators k rb ratios and grain size to estimate sediment sources intensity of chemical weathering and rainfall intensity the results show that the chemical weathering index k rb ratio of meihua lake indicates the continuing effects of autumn rainfall while coarse grain sizes of dahu lake sediments suggest increased intensity in typhoon rainfall grain size results reveal that increasing el nino southern oscillation intensity in the tropical pacific has intensified the activity of super typhoons in the western north pacific finally we find that frequent activity of super paleo typhoons occurred in taiwan during the la nina like state and the strengthening winter monsoon activity and higher sea surface temperature enhanced plentiful autumn rainfall in el nino like state after comparing our results with the paleo typhoon data in japan and south china we suggest that the tracks of super typhoon are mainly affected by variations in the warm pool and subtropical northwestern pacific high in the western pacific copyright 2012 john wiley sons ltd

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

climate variability in east central california during the past 1000 years reflected by high resolution geochemical and isotopic records from owens lake sediments abstract core ol 97a retrieved from the depocenter of owens lake represents a depositional history spanning the past 1000 yr among the 17 elements analyzed in the acid leachable fractions of 315 salt free samples at 3 yr sample mg and li which come chiefly from authigenic mg hydroxy silicates were found to have concentration variations reflecting lake salinity and climatic changes during the past a total of 231 isotopic measurements on carbonates from the same samples in the upper 181 cm show that 18 o and 13 c values range from 5 66 to 0 12 pdb and 1 38 to 4 28 pdb respectively the rate of change with time in 18 o records the rate of change in lake s volume due to climate fluctuations whereas variations in 13 c reflect mainly variations in biological productivity nutrient supply and dissolved carbonate in the lake results indicate an effectively dry climate between a d 950 and 1220 corresponding to the medieval climatic anomaly a warm period in northern europe during which owens lake approached playa conditions wet climates prevailed during a d 1220 1480 producing relatively large and deep lakes beginning about a d 1550 the regional climate turned colder but had frequently oscillating precipitation six wet dry cycles with 50 yr duration occurred between a d 1480 and 1760 during the later half of which owens lake became a playa since a d 1880 the lake level has steadily dropped from its historic high stand under strong impact of human activity

mid late holocene changes in sedimentary organic matter on the inner shelf of the east china sea abstract marginal seas are important transitional zones for the delivery of terrestrial organic matter tom from land to the open sea and they play an important role in the carbon cycle tracing the source of sedimentary organic matter som deposited in marginal seas is fundamental to our understanding of the dispersal degradation migration and conversion of organic matter this paper presents high resolution records of bulk organic matter and biomarker proxies from core t08 that was recovered from the inner shelf of the east china sea ecs and aims to identify the contributions of marine and terrestrial organic matter over the past 3725 yrs total organic carbon toc values were low 0 50 and showed no significant change between 3725 and 1800 yr bp period i and increased continuously from 0 40 to 0 86 after 1800 yr bp period ii 1800 750 yr bp period iii 750 yr bp present the tmbr ratio of terrestrial to marine biomarkers and 13ctoc 13c of toc values showed steady tom contribution during period i and higher tom contribution driven by the increased changjiang river cr derived tom under strong east asian summer monsoon easm and el nino during period ii during period iii the increase in marine organic matter mom contribution was indicated by the tmbr and this was caused by enhanced marine productivity related to intensified vertical mixture that was driven by the strengthened east asian winter monsoon eawm 13ctoc shows a contrary trend to the tmbr during period iii probably influenced by variations in the c3 vegetation type during this period spectral analysis of the tmbr series for the last 1200 yrs shows cycles with periods of 119 75 85 and 54 yrs confirming that climate related events influenced the variation in som under the modulation of solar activity and solar irradiance at the centennial scale

summertime hydrographic features in the southeastern hwanghae abstract ctd casts in the southeastern hwanghae yellow sea were made in august 1983 and 1984 to describe the spatial structure of the summertime hydrographic features cold coastal water appeared around the southwestern coast of korea which was formed by strong tidal stirring tidal mixing in the study area seems to have been enhanced by the presence of many small islands in the deeper region beyond the tidal front stratification became much stronger and the bottom layer below seasonal thermocline was occupied mostly by the hwanghae cold water characterized by a temperature lower than 10 c and salinity of 32 5 33 0 the northeastward extension of the changjiang diluted water was shown by a tongue like plume of relatively warm fresh water confined to the thin surface layer 10 m thick there was no evidence for the hwanghae warm current carrying high salinity water into the eastern hwanghae along the korean coast the warm current was found to flow in a narrow band close to the west and north coast of chejudo cheju island and then to pass eastward through the cheju strait thus the eastern part of the cyclonic circulation in the surface layer cannot be considered to be a northward continuation of the hwanghae warm current the local salinity maximum in the lower layer off kunsan and the higher salinity on the west side of the central trough than on the east side would imply a northward flow on the west flank of the trough to compensate for the southward intrusion of the hwanghae cold water from which an anticyclonic circulation could be expected in the lower layer

offshore detachment process of the low salinity water around changjiang bank in the east china sea abstract a patchlike structure of low salinity water detached from the chanjiang diluted water cdw is frequently observed in the east china sea ecs in this study the offshore detachment process of cdw into the ecs is examined using a three dimensional numerical model the model results show that low salinity water is detached from the cdw plume by the intense tide induced vertical mixing during the spring tide period when the tidal current becomes stronger during the spring tide thickness of the bottom mixed layer in the sloping bottom around changjiang bank reaches the mean water depth implying that the stratification is completely destroyed in the entire water column as a result the offshore detachment of cdw occurs in the sloping side of the bank where the tidal energy dissipation is strong enough to overcome the buoyancy effect during this period on the other hand the surface stratification is retrieved during the neap tide period because the tidal current becomes substantially weaker

holocene monsoonal climate changes tracked by multiproxy approach from a lacustrine sediment core of the subalpine retreat lake in taiwan abstract the aim of this study is to improve the understanding of environmental changes and the linkages with the dynamics of the east asian monsoon eam during the holocene in the western north pacific we analyzed the pollen diatom and weak acid leachable fractions associated with extracted organic compounds of lacustrine sediments retrieved from the subalpine retreat lake in northwestern taiwan during the early holocene 10 100 8600 cal bp cool climate was inferred by the dominance of grass pollen with poor preservation of diatom valves in the record at that time derived biomarkers were also dominated by long chain alkanes originating from herbs the following holocene optimum 8600 6400 cal bp was characterized by a remarkable increase of tree pollen indicating the warmer and humid climate and a stronger summer eam the possible enhanced monsoon driven precipitation resulted in higher contents of total organic carbon buried in sediments however the climate and precipitation of the alpine area in taiwan might have been unstable the high variability of wetland pollen and diatom abundance reveals weak periods of eam during the late holocene optimum 6400 4500 cal bp the hiatus in the deposit during 4500 2100 cal bp suggests the continuously decline of the eam during the last 2100 years dominated wetland plant pollen accompanying stable diatom abundance indicated humid climatic conditions and a stable increase of the eam the climatic condition of study area was similar with modern situation during this late holocene