an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

early middle paleozoic intraplate orogeny in the ogcheon belt south korea a new insight on the paleozoic buildup of east asia the polycyclic ogcheon belt of south korea represents the boundary between two precambrian blocks investigation on the timing and kinematics of the block agglomeration is of considerable bearing on the understanding of the constitution of the asian continent we report here structural evidence showing that the earlier tectonic event dates back to early middle paleozoic the ogcheon tectonism or orogeny the ductile piling up of nappes of the ogcheon belt corresponds to an intracontinental orogeny involving the opening and the subsequent closure of an aborted rift and not of a wide oceanic area the nappes contain unequivocal evidence for ductile shearing with a northwest over southeast sense of movement field evidence includes the presence of s1 and s1 2 foliations bearing an extensive stretching lineation perpendicular to the belt associated with a strongly noncoaxial deformation regime the f1 isoclinal folds are commonly a type and sheath folds whose axes are parallel to the stretching lineation whereas the southeast facing f2 recumbent folds have subhorizontal axes parallel to the belt all lines of evidence unconformity superposed deformations age of the metamorphism etc imply that the d1 2 ogcheon tectonism is pre middle carboniferous late silurian early devonian the subsequent indosinian middle triassic f3 upright synfolial folds that trend nne ssw and later structures clearly overprint the middle paleozoic ductile thrusts and isoclinal folds the early paleozoic ogcheon supergroup is formed of a thick volcanosedimentary pile deposited above an early platform sequence in a rift basin on the basis of the geochemical characteristics of the metavolcanics it appears that oceanization did not occur and ogcheon rift aborted soon after it was formed we suggest that middle paleozoic ductile nappe structures have been formed by the structural inversion of the rift extensional features during the ductile stacking episode the early formed foliation and isoclinal folds have been folded in a continuum during the same tectonic event middle carboniferous terrigenous formations have been deposited unconformably upon folded and thrust older rocks a tentative correlation with early paleozoic imjingang qinling and cathaysian belts within the asian continent reveals that ogcheon rift was emplaced within the south china plate and that imjingang belt should represent the limit between north and south china blocks in the korean peninsula

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

the mediaeval warm period drought recorded in lake huguangyan tropical south china the geochemistry of dated sediment cores from lake huguangyan 21o9 n 110o17 e tropical south china reveals distinct stratigraphical patterns in total organic and inorganic carbon toc tic biogenic silica bs and total nitrogen tn over the past 1400 years in this hydrologically closed lake tic variations may reeect changes in the precipitation evaporation ratio which controls the evaporative enrichment of carbonate toc bs and tn in the sediment are proxy indicators of lake productivity and nutrient input which we believe are linked to local precipitation high tic content correlates with low concentrations of toc bs and tn and indicates two drought episodes dated to ad 670 760 and ad 880 1260 in the sediments of lake huguan gyan local historical chronicles support these data suggesting that the climate of tropical south china was dry during the mediaeval warm period mwp and wet during the little ice age lia the detected mwp drought is temporally correlated with evidence for lower precipitation on the guliya china and quelccaya peru ice caps and with increased salinity in moon lake us great plains

asian summer monsoonal variations during the holocene revealed by huguangyan maar lake sediment record abstract high resolution records of summer monsoonal evolution in the holocene are essential to paleoclimate reconstruction but are hard to obtain here we provide a continuous well dated high resolution record from huguangyan maar lake located in the west pacific climate regime multi proxies including chlorophyll a toc sr rb ratio and magnetic susceptibility have been used to reconstruct the monsoon variations in the holocene higher chlorophyll a values are related with stronger summer monsoon and vice versa high temporal resolution radiocarbon dating enables us to divide summer monsoon evolution stages summer monsoon in zhanjiang area was strongest in the early holocene but began to decline at 6080 yr bp and weakened substantially since about 3600 yr bp the transition around 6080 yr bp supported by our high resolution dating lags the previous estimates by 1700 years the decreasing summer solar radiation at 30 n through the holocene is probably responsible for gradually weakened summer monsoon the anti phased co variation of summer monsoon intensity and enso activity throughout the holocene suggests that they could be interlinked driven together by solar radiation at orbital scale

rare earth patterns with positive cerium anomaly in alkaline waters from lake van turkey abstract the distribution of rare earth elements has been studied for aerobic alkaline ph 9 6 carbonate rich waters from lake van turkey shale normalized ree ree sn patterns display an almost linear increase from the light to the heavy rees and strong positive ce sn anomalies there exist neither positive nor negative gd sn anomalies the ree sn patterns are consistent with domination of ree speciation in solution by poly carbonato complexes generating enrichment of the heavy rees that is even more pronounced than that seen in seawater this is the first report of positive ce sn anomalies observed in ree sn patterns of aerobic natural waters these anomalies apparently result from stabilization of penta carbonato ce iv complexes in solution leading to enhanced abundances of ce in comparison with its trivalent ree neighbours thus in remarkable contrast to seawater positive ce sn anomalies may be general features of alkaline carbonate rich and aerobic lake waters

lacustrine lignin biomarker record reveals a severe drought during the late younger dryas in southern taiwan abstract the younger dryas yd event which punctuated the last glacial holocene transition period and had a profound impact on global climate is the most well studied millennial scale climate event although the triggering mechanism remains debate weakened asian summer monsoon during the yd is recorded in oxygen isotopes of stalagmite from mainland china however lacustrine climate record of the yd event has not been reported from the subtropical land ocean boundary of the asian continent near the pacific warm pool we provide a lignin biomarker record covering the last deglaciation and early holocene 17 9 ka bp from the dongyuan lake southern taiwan located at the frontal zone of typhoon invasion the lignin phenol ratio s v shows that the vegetation in the catchments had shifted from gymnosperm dominant to angiosperm dominant plants since 12 2 ka bp significantly decreased lignin concentrations tlp and 8 and elevated lignin degradation parameters ad al v p v s dhba v in combination with other organic proxies toc 13corg during the late yd suggest a severe drought had occurred in southern taiwan during this specific period changes in the lignin proxies from the dongyuan lake lagged the climate changes registered in stalagmite records by around 500 800 years suggesting a slow response of vegetation and soil processes to rapid climate changes

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

quantifying regional vegetation changes in china during three contrasting temperature intervals since the last glacial maximum abstract the need to reduce the uncertainty of predictions of vegetation change under global warming highlights the importance of understanding the vegetation patterns and possible mechanisms of vegetation response during past warming intervals here we present quantitative regional vegetation reconstructions for china during the last glacial maximum lgm 18 2 14c kyr b p early holocene eh 8 5 0 5 14c kyr b p and mid holocene mh 6 0 5 14c kyr b p using the biomization method and based on 249 pollen records in addition we used an inverse vegetation modeling approach to investigate the effect of climate change and co2 concentration on the observed vegetation changes the results demonstrate that during the lgm steppe expanded southeastwards reaching the present day temperate deciduous forest tede zone in contrast the forest in eastern china underwent a substantial southward retreat and its percentage reached a minimum the warm mixed forest wamf and tede shifted southwards of 10 n relative to today and tropical seasonal rain forest tsfo was almost absent in addition the forest steppe boundary shifted southwards to near the middle and lower reaches of the yangtze river during the eh and mh the tsfo wamf and tede exhibited respective northward shifts of 2 4 and 5 relative to today in mh the percentage of forest sites increased and reached a maximum and the forest steppe boundary had shifted northwestwards to near the present day 300 mm isohyet our palaeovegetation reconstructions and model sensitivity experiments suggest that temperature was the dominant factor controlling the vegetation distribution during the lgm while precipitation became increasingly more important during the holocene throughout china we further show that precipitation was the primary factor controlling palaeovegetation distribution in northern china while temperature became increasingly more important in southern china our findings are potentially important for understanding the evolution of vegetation in china in response to ongoing global warming

sedimentary evolution of the yangtze river mouth east china sea over the past 19 000 years with emphasis on the holocene variations in coastal currents abstract water mass variations in the early yangtze estuary during the postglacial transgression have not been thoroughly studied this research gap has hampered the understanding of riverine sediment source to sink processes in this region this study presents the results of integrated analyses of grain size pollen spore dinocyst assemblages benthic foraminifera and ostracods from a borehole h5 located at the northern yangtze mouth to investigate the complete sedimentary history and associated variations in coastal currents since 19 ka at the core site a fluvial floodplain developed from ca 19 11 3 ka whereas an estuary to shelf to subaqueous delta prevailed during most of the holocene based on changes in the dominant microfauna species which mainly consist of chinese coastal water species two main current patterns were distinguished one dominated by the yellow sea coastal current yscc before ca 7 9 ka and one dominated by the yangtze dilute water ydw marked increases in open sea saline species including bolivina robusta and stratified water dinocyst species spiniferites ramous and spiniferites spp were interpreted as the encroachment of the taiwan warm current twwc and the intensification of the ydw respectively the ydw and twwc penetrated the area dominated by the yscc before 7 9 ka which was likely related to intensity variations in the kuroshio current kc and asian summer monsoon asm under maximal asm and kc conditions upwelling resulted from the intensified intrusion of the twwc as indicated by the blooming of bolivina robusta from 7 9 6 3 ka after ca 6 ka the ydw clearly weakened due to the decline of the asm yet the yangtze plume prevailed due to the rapid seaward migration of the yangtze mouth considering the dominance of the yscc in the early holocene yellow river derived sediment likely represented a large proportion of the material delivered to the early yangtze estuary

late quaternary climate in southern china deduced from sr nd isotopes of huguangyan maar sediments abstract the hydro climatic conditions that prevailed during the last glacial and early to mid holocene periods in south china are inferred from chemical compositions and sr nd isotope ratios of sediments from lake huguangyan maar and its vicinity the lake sediments are comprised of organic matter volcanic materials and aeolian input from nearby granitoid derived soils variations in 87sr 86sr ratios in the lake sediments indicate two modes of climate conditions wet intervals during which the lake sediments are mainly derived from the volcanic lake rim materials expressed in low 87sr 86sr ratios and dry intervals during which fine particles from the nearby granitic soils are windblown to the lake and supply local dust expressed in high 87sr 86sr ratios in the sediments these wet and dry intervals generally correspond to regional climate records e g speleothem 18 o profiles in southeast china and correlate with global climate events e g heinrich events while 18 o records of speleothems from southeast china caves are dominated by the precession signal the huguangyan maar sr record mainly correlates with obliquity this most likely reflects masking of the precession signal due to regional climate variability accentuating the obliquity signal these local effects may also account for some of the differences that have been observed between the various east asian monsoon records more importantly the masking of the precession signal reveals the direct influence of obliquity on the hydro climate regime in south china

evidence for a widespread climatic anomaly at around 9 2 ka before present 1 the 8 2 ka event was triggered by a meltwater pulse mwp into the north atlantic and resultant reduction of the thermohaline circulation thc this event was preceded by a series of at least 14 mwps their impact on early holocene climate has remained almost unknown a set of high quality paleoclimate records from across the northern hemisphere shows evidence for a widespread and significant climatic anomaly at 9 2 ka b p this event has climatic anomaly patterns very similar to the 8 2 ka b p event cooling occurred at high latitudes and midlatitudes and drying took place in the northern tropics and is concurrent with an mwp of considerable volume 8100 km3 as the 9 2 ka mwp occurs at a time of enhanced baseline freshwater flow into the north atlantic this mwp may have been despite its relatively small volume sufficient to weaken thc and to induce the observed climate anomaly pattern

the huguang maar lake a high resolution record of palaeoenvironmental and palaeoclimatic changes over the last 78 000 years from south china abstract a series of seven piston cores from the huguang maar lake situated near the south china sea coastline provides insight into regional palaeoenvironmental and palaeoclimatic changes in southern china over the last 78 000 years the data set comprises a high resolution record of magnetic susceptibility dry density and water content total organic carbon and inorganic carbon total nitrogen biogenic silica bsio2 and palynological results the time scale was developed by ams 14c dating of 17 terrestrial plant macro fossils during the last glacial the huguang record is characterised by an alternation of more temperate and humid periods from 78 to 58 and 48 to 40 5 ka bp and periods with predominance of grassland vegetation and possibly lowered lake level from 58 to 48 and ca 40 5 to 15 ka bp the huguang data have been compared to regional marine and terrestrial records in order to discuss variability of the south east asian monsoon system for most of the last glacial period the huguang proxies do not exhibit marked millennial scale variability as known from some long se asian and many north atlantic records this picture changes at about 15 cal ka bp when the huguang and greenland records appear to correlate well a short climatic reversal which is assumed to reflect a younger dryas type event is well recorded in the huguang record during the holocene the huguang multi proxy data show a much higher variability than during the last glacial stage probably reflecting at least for the early mid holocene fluctuations in monsoon activity however the last 4000 years of the sediment record are clearly influenced by enhanced human activity and thus difficult to interpret in terms of palaeoclimate change

developing a holocene tephrostratigraphy for northern japan using the sedimentary record from lake kushu rebun island abstract palaeoclimate records in east asia offer significant potential to further our understanding of monsoon dynamics and can serve as a link between north atlantic and tropical climate systems the sedimentary core from lake kushu rebun island provides the first high resolution palaeoclimate record from northern japan in order for this regionally significant archive to be synchronised to other records and to generate a more detailed holocene tephra lattice for east asia we present the first cryptotephra stratigraphy for northern japan using the kushu rk12 core the detailed rk12 tephrostratigraphy integrates local and far travelled tephras originating from japan russia china north korea and most likely indonesia five key cryptotephra layers have been identified precisely dated and correlated to the specific eruptions or the source region b tm tephra changbaishan volcano sh 12 tephra shiveluch volcano ko g tephra komagatake volcano ma f j tephra mashu volcano and rk12 0819 tephra with possible indonesian origin these tephra horizons are very widely dispersed providing opportunities to synchronise distant palaeoclimate records from the polar region through high northern latitudes to the tropics which facilitate interregional comparison of palaeoclimate and environmental data in addition a number of the geochemically analysed horizons contain other minor numbers of compositionally distinct glass which can also be grouped and correlated to their source volcanoes these minor analyses are of interest since they provide new insight into regional tephra dispersal e g ash dispersal potential of aira and towada and could suggest that there are other potential eruptions that have yet to be identified in the geological record e g potential changbaishan eruptions the integrated lake kushu cryptotephra record extends the ash dispersal of several key tephra horizons in the region the presence of the shiveluch sh 12 tephra in lake kushu ca 1900 km away documents the first example of a russian tephra reaching the japanese archipelago furthermore glass compositions suggest that the core could preserve an eruption event derived from indonesia highlighting the future possibility to significantly extend and interlink the tephra lattice across the entirety of asia this is an essential step for the understanding of how climate changes propagate over large geographical areas indeed several of these tephra markers coincide with significant ecological changes reflected in the pollen proxy record at lake kushu using this high resolution palaeoenvironmental record we however find no significant ecological impact following the large late holocene millennium eruption from changbaishan china north korea

a magnetostratigraphic reassessment of correlation between chinese loess and marine oxygen isotope records over the last 1 1 ma abstract we present a magnetic polarity based paleoclimatic correlation between chinese loess and marine oxygen isotope stage mis records over the last 1 1 ma this revised land ocean comparison indicates that inconsistent occurrence of the matuyama brunhes boundary which lies in mis 19 in marine sediments and occurs either at the base lower part of loess l8 or the uppermost part of soil s8 in chinese loess is due to regional and or local climate variability across the chinese loess plateau and does not need to be attributed to lock in effects of loess remanence acquisition associated with pedogenesis this result implies that the geomagnetic polarity boundaries in chinese loess in general are reliable chronostratigraphic time markers therefore astronomically tuned timescales for chinese loess that presume a downward shift of polarity boundaries due to a time lag in remanence acquisition may have overestimated ages of certain loess paleosol units

rare earth element fractionations of the northwestern south china sea sediments and their implications for east asian monsoon reconstruction during the last 36 kyr abstract rare earth elements rees fractionations in siliciclastic marine sediments are related to the parent rock properties weathering degree grain size and heavy minerals the relations between marine sediment ree compositions and regional paleoclimate are not fully understood here the rees for detrital components of a core retrieved from the northwestern south china sea scs were measured results show the ree lree hree la yb n and light ree la sm n fractionation degrees have good responses to the regional paleoclimate over the past 36 kyr sea level played a key role in ree fractionations during 36 24 kyr bp manifesting as lower ree and lree fractionation degrees correspond to the decreased sea level the entire trends for lree hree la yb n and la sm n over the past 20 5 kyr are almost in phase with the regional east asian summer monsoon easm records because rees are mainly concentrated in heavy minerals the density difference of heavy minerals is probably the main controlling factor on ree fractionations clay minerals and feldspars released during the weathering process have a high content of light rees lrees in the warm wet periods holocene optimum and bolling allerod more precipitation promoted weathering and strengthened the estuarine hydrodynamic force which respectively resulted in high content of clay minerals and feldspars and high density heavy minerals e g monazite the process led to lree enrichment because the enriched minerals contain higher contents of the lrees in contrast the dry cold climate conditions during the periods heinrich 1 younger dryas and last glacial maximum resulted in the reversed ree fractionations as the weak hydrodynamic force can only carry the low density heavy minerals e g zircon that are enriched in hrees this model does not seem to apply to 36 24 kyr bp probably because of the re transport of ancient shelf sediments the study facilitates the understanding of ree application in paleoclimate reconstruction within slope sediments

sedimentary responses to the east asian monsoon and sea level variations recorded in the northern south china sea over the past 36 kyr abstract sediment grain size is an important proxy to detect sedimentary process and record paleoenvironmental variations in continental slopes grain size measurements were performed for 298 samples of the 5 96 m long core pc338 spanning the past 36 kyr recovered from the northern south china sea scs results show that sea level and climatic influences on grain size distributions are crucial a turbidite formed during the last glacial maximum lgm is ascribed to the favorable topography close to the red river estuary induced by the low sea level four end member em components for the normal sediment layers were unmixed using a lognormal parametric end member modeling emm with the sea level decreasing more em4 15 100 m and less em1 0 2 m supplied the scs slope because em2 2 10 m consisted of fluvial suspension is dominated by the east asian summer monsoon easm precipitation it has the potential to substitute for the easm intensity em2 varied in phase with many south china paleoclimate records and the 30 n july insolation over the past 36 kyr and cooling climate events including the lgm heinrich events h1 and h3 younger dryas 8 2 ka and 10 3 ka lowered the em2 content our results further confirm the synchronous easm evolution in the south china continent mainly forced by the northern hemisphere summer insolation

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

influence of atlantic meridional overturning circulation on the east asian winter monsoon east asian summer monsoon precipitation varied on millennial timescales during the last glacial period sediment records and climate modelling suggest that the winter monsoon was also affected by millenial scale variability and that the abrupt changes were driven by changes in the strength of the atlantic meridional overturning circulation

geochronology and geochemistry of late cenozoic basalts from the leiqiong area southern china abstract the leiqiong area which includes the leizhou peninsula and the northern part of the hainan island is the largest province of exposed basalts in southern china ar ar and k ar dating indicates that incipient volcanism in the leiqiong area may have taken place in late oligocene time and gradually increased in tempo toward the miocene and pliocene epoch volcanic activities were most extensive during pleistocene and declined and ended in holocene based on radiometric age dating and geographic distribution pliocene and quaternary volcanism in hainan island can be grouped into two stages and six eruptive regions the early volcanism is dominated by flood type fissure eruption of quartz tholeiites and olivine tholeiites whereas the later phase is dominated by central type eruption of alkali olivine basalts and olivine tholeiites the systematic decrease of mgo feo and tio 2 with increasing sio 2 content for basalts from hainan island indicates that fractional crystallization of olivine clinopyroxene and ti bearing opaques may have occurred during magmatic evolution from coexisting fe ti oxide minerals it is estimated that the equilibrium temperatures range from 895 986 c and oxygen fugacities range from 10 13 4 to 10 10 7 atmospheres in the basaltic magmas the incompatible element ratios and the chondrite normalized ree patterns of basalts from the leiqiong area are generally similar to oib the nb u ratios less than 37 in most of the tholeiitic rocks and the negative nb anomaly observed in the spidergram of some basalts indicated that the influence of a paleo subduction zone derived component can not be excluded in considering the genesis of the basalts from the leiqiong area the tholeiites in the leiqiong area may have mixed with a more enriched lithospheric mantle component as well as undergone relatively larger percentages of partial melting than the alkali basalts

foraminiferal end in the deep north western subtropical pacific ocean tracing changes in weathering input over the last 30 000 years abstract this study focuses on the neodymium isotopic composition end of mixed planktonic foraminifera species in sediment cores collected on the north western margin of the south china sea scs and in the western equatorial pacific the aim was to identify temporal changes in the end of the upper circumpolar deep water ucdw during its northward penetration in the western subtropical pacific and to re evaluate the significance of deep water end changes at the northern margin of the scs over the past 25 kyr the past seawater end record derived from sediments of the subtropical western pacific displays a narrow range from 2 9 0 3 to 1 6 0 4 this suggests that the end of the ucdw is greatly modified during its northward penetration through the process of boundary exchange along the western volcanic margin of the south pacific and that the unradiogenic end signature of the ucdw observed in the south pacific about 6 has not been propagated beyond the equatorial pacific at least not over the last 25 kyr seawater end values obtained from the northern scs display large variations with values that are lower 6 8 0 3 to 5 6 0 2 for the last glacial period than for the late holocene 5 7 0 3 to 4 1 0 2 such glacial end cannot be attributed to a higher proportion of southern sourced water ssw as end values of the ucdw in the equatorial western pacific are more radiogenic than those observed in the scs the evolution of the seawater end values of the northern scs during the last glacial period and the last climatic transition is coeval with variations in the contribution of sediments from the pearl river the low sea level stand of the last glacial period resulted in a more proximal position of the pearl river mouth relative to core md05 2904 which a higher input of freshwater and in particular detrital sedimentary particles originating from the pearl river that partially dissolved during sinking led to a decrease in the seawater end along the north western margin of the scs enhanced rainfalls associated with intensified monsoon and more frequent typhoon activities during the early holocene climatic optimum from 9 to 7 cal kyr bp are linked to a decrease in sea surface salinity lower 18o values of planktonic foraminifera and a decrease in end values 6 2 0 3 induced by lithogenic nd input from pronounced freshwater and sediment discharge from distal rivers

a 20 000 year high resolution pollen record from huguangyan maar lake in tropical subtropical south china abstract a high resolution pollen record from huguangyan maar lake near the south china sea spanning the past 20 400 yr bp has been presented aimed to provide an improved understanding of the response of the regional vegetation in tropical subtropical south china to climatic variations since the late last glacial maximum the results reveal the strong control of the asian summer monsoon asm strength on vegetation via orbitally induced variations in northern hemisphere summer solar insolation the trend of climatic evolution of the region consists of change from a warm temperate northern subtropical climate 20 400 18 700 cal yr bp to a southern subtropical climate 16 500 11 500 cal yr bp during the last deglaciation followed by a stepwise environmental shift from a tropical climate 11 500 8200 cal yr bp to a southern subtropical climate 8200 6600 cal yr bp and finally to a middle northern subtropical climate the bolling allerod warming is characterized by the highest percentages of evergreen quercus but the lowest percentages of xerophytic gramineae throughout the record suggesting intensified warm wet conditions during 15 000 13 000 cal yr bp by contrast the younger dryas is characterized by a marked decrease in subtropical evergreen broad leaved plants but a significant increase in herbaceous taxa representing a brief cold reversal during 13 000 12 000 cal yr bp the occurrence of two major cooling events at 8 2 and 6 6 kyr bp both of which are characterized by dramatic decreases in tropical evergreen broad leaved plants is supposed to be linked to a distinct weakening of the asm and southward migration of the intertropical convergence zone associated with marked declines in atlantic meridional overturning circulation the subsequent brief intervals of high herbaceous pollen percentages but low percentages of tropical taxa correspond to high el nino southern oscillation enso activity supporting a link between the weakening of solar isolation driven asm strength and a gradual intensification of enso

multi proxy records of holocene hydroclimatic and environmental changes on the southern coast of south korea abstract a well dated sediment core from the goheung area of the southern coast of the korean peninsula was used to reconstruct the history of environmental and vegetation changes in response to variability in the east asian summer monsoon easm and the sea level change during the holocene a multi proxy analysis palynomorphs mean grain size toc ts c n ratio and 13ctoc data indicated that the study area underwent a change in environment from a fluvio coastal a fluvial to intertidal zone to a subtidal zone due to a sea level rise at ca 7500 cal yr bp since ca 6000 cal yr bp it has gradually returned to a brackish dominant environment intertidal zone due to coastal regression with a decrease in relative sea level palynological data show that the climate of the southern coast of the korean peninsula underwent a gradual cooling trend after ca 5900 cal yr bp due to weakening easm intensity in response to decreasing insolation in the northern hemisphere therefore the long term vegetation dynamics in this study area were controlled primarily by solar insolation driven temperature changes during the holocene they were also associated with sea surface temperature sst changes in the western tropical pacific wtp the vegetation dynamics sharp reduction of broad leaved trees and freshwater discharge indicators in our study area indicate cold and dry climatic conditions since ca 4500 cal bp which may have been caused by the decreasing sst in the wtp in addition the strong link between the holocene vegetation dynamics in the east asian coastal area especially quercus lepidobalanus and pinus diploxylon and sst variation in the wtp may suggest that the centennial timescale recurring variations in easm activity have been controlled by low latitude ocean forcing induced by el nino southern oscillation activity

palaeovegetation and palaeoclimate in low latitude southern china during the last glacial maximum abstract the evolution of vegetation and climate changes in tropical regions during the last glacial maximum remains controversial a continuous high resolution terrestrial palynological data from 40 to 13 cal ka bp is recorded in sediments of huguangyan maar lake in southern china the biomization technique and pollen data are used to reconstruct the history of vegetation and climate changes during the last glacial maximum lgm the results suggest that the huguangyan area in the last glacial maximum was dominated by subtropical evergreen forest with some deciduous trees implying that the climate was drier and colder in southern china than at present grassland vegetation did not appear in this area a significant drop in temperature occurred at 18 5 cal ka bp and terminated at 15 5 cal ka bp and the annual mean temperature during the lgm was 2 3 c lower or even more than present this is in agreement with previous results from tropical low latitude regions

constraints from strontium and neodymium isotopic ratios and trace elements on the sources of the sediments in lake huguang maar abstract the sediments in lake huguang maar in coastal south china were previously thought to originate mainly from wind blown dust transported from north china such that the lake sediments recorded the varying strength of the asian winter monsoon an alternative explanation was that the local pyroclastic rocks supplied the lake sediments but the actual contributions from the different sources remained unclear geochemical analyses including 87sr 86sr and 143nd 144nd and trace elements support the local pyroclastic rock as the dominant source

magnetic mineral diagenesis abstract reduction oxidation redox reactions occur during burial because sediments contain reactive mixtures of oxidised and reduced components diagenetic chemical reactions represent the approach of all sedimentary components toward equilibrium and control the long term stability of sedimentary iron bearing minerals magnetic minerals are sensitive indicators of sedimentary redox conditions and of changes in these conditions through time with diagenetic effects ranging from subtle to pervasive despite the importance of magnetic mineral diagenesis in paleomagnetism rock magnetism and environmental magnetism and the usefulness of these subjects in the earth and environmental sciences there is no systematic single published treatment of magnetic mineral diagenesis this paper is an attempt to provide such a treatment for the full range of diagenetic environments magnetic mineral diagenesis during early burial is driven largely by chemical changes associated with organic matter degradation in a succession of environments that range from oxic to nitrogenous to manganiferous to ferruginous to sulphidic to methanic where the free energy yielded by different oxidants decreases progressively in each environment in oxic environments the most important diagenetic processes involve surface oxidation of detrital minerals and precipitation of fe3 bearing minerals from solution in ferruginous environments the most reactive detrital and authigenic iron oxides undergo dissolution often mediated by dissimilatory iron reducing bacteria which releases fe2 that becomes available for other reactions the fe2 in solution can diffuse upward where it is oxidised to form new authigenic iron oxyhydr oxide minerals or it can become bioavailable to enable magnetotactic bacteria to biomineralise magnetite generally at the base of the overlying nitrogenous zone alternatively dissimilatory iron reducing bacteria can produce extracellular magnetite within ferruginous environments in sulphidic environments iron bearing detrital mineral assemblages undergo more radical alteration hydrogen sulphide which is a byproduct of bacterial sulphate reduction or of anaerobic oxidation of methane reacts with the fe2 released from iron mineral dissolution or directly with solid iron oxyhydr oxide minerals to form iron sulphide minerals mackinawite greigite and pyrite authigenic growth of ferrimagnetic greigite has important implications for paleomagnetic recording secondary iron sulphide formation can also occur as a result of anaerobic oxidation of methane methane migration through sediments in association with biogenic or thermogenic methane production or in association with gas hydrate dissociation can disrupt the diagenetic steady state and give rise to greigite and monoclinic pyrrhotite formation that remagnetises sediments most of the above described diagenetic processes occur below 50 c with continuing burial above 50 c but at sub metamorphic temperatures magnetic minerals can undergo further thermally induced chemical changes that give rise to a wide range of mineralogical transformations that affect the magnetic record of the host sediment these changes include remagnetisations magnetic analysis can provide much valuable information concerning diagenesis in environmental processes the range of processes discussed in this paper should assist researchers in analysing sediment magnetic properties for which the assessment of diagenetic effects has become a necessary component

ti content in huguangyan maar lake sediment as a proxy for monsoon induced vegetation density in the holocene the provenance of element ti in huguangyan maar lake hgy sediment has been under debate since yancheva et al 2007a proposed its eolian source from the chinese loessplateau clp and applied it as a proxy for asian wintermonsoon we performed a comprehensive study on ti carryingminerals and ti uxes in lake sediments wall rocks andloess from the clp here we show that the chemicalcompositions and morphological features of magnetite the most important ti carrier in hgy surface sediments are identical to those in wall rocks around the lake butsubstantially different from those in clp loess samples ourcalculated modern eolian ti ux from the clp is negligiblecompared to the average total ti ux to hgy and ti uxfrom catchment erosion can provide enough ti indicating tiin hgy sediment are predominantly from wall rock erosion inverse correlation between total organic carbon toc vegetation density and ti ca ratio terrestrial input in theholocene suggests monsoon induced vegetation densitypredominates over runoff in controlling ti input to hgy s ratio represents toc directly mediated reductive diagenesisof iron oxides magnetite preservation rather than anoxic oxic condition at the bottom water induced by wintermonsoon our record shows a decreased vegetation density increased ti input and weakened reductive diagenesisthrough the holocene driven by a weakened summermonsoon

dust records from varved lacustrine sediments of two neighboring lakes in northeastern china over the last 1400 years dust storms are natural phenomena described in chinese historical documents as early as 1150 bc these documents provide a way to evaluate proxy data from different natural records the minerogenic clastic content and grain size from two closed maar lakes located a short distance apart in northeastern china were analyzed the area is located in the path of dust storms the minerogenic clastics in the studied maar lakes originate mainly from dust deposition general variations of the minerogenic clastic content in these two neighboring lakes show a good coincidence with dust concentration in a tibet ice core and dust events as recorded in historical documents the minerogenic clastic content in the lake sediments is linked with the climate conditions in the dust source regions and wind strength three periods of intensive dust events ad 1050 1330 ad 1590 1690 and the last 200 years have been identified during the past 1500 years the recent increasing pattern of clastic content could be linked to human activity in the dust source regions significantly most of the medieval warm period mwp was marked by a high frequency of dust storms

magnetism of the huguangyan maar lake sediments southeast china and its paleoenvironmental implications abstract the huguangyan hgy lake a typical maar lake in the southeast of china is sensitive to the evolution of the asian monsoon system including the east asian summer monsoon easm and the indian summer monsoon ism so far the mechanism of how magnetic properties of the hgy lake sediments respond to climate changes has not been well determined in this study we performed a detailed mineral magnetic analysis on the high resolution hgy sediments results revealed that finer grained magnetite superparamagnetic and single domain magnetite mixed with a small amount of goethite and hematite is the dominant magnetic mineral which is consistent with the magnetic properties of the red weathered soils collected from the catchments but differs greatly from that of the aeolian inputs therefore magnetic minerals of the hgy sediments were originated mainly from the lake catchment rather than the wind blown dust inputs considering the high tephra wall relative elevation of 10 20 m and great precipitation surface runoff by rainfall is interpreted as the main process to transport red soils into the lake the magnetic records of hgy sediments revealed that the summer monsoon was enhanced at the early holocene and then declined abruptly at the mid late holocene 5 5 kyr cal bp this pattern strongly mimics the evolution pattern of ism but is inconsistent with the easm thus we suggest that the magnetic records from hgy have the great potential to investigate the evolution of ism

solar forcing induced spatial synchronisation of the east asian summer monsoon on centennial timescales abstract spatial patterns in centennial scale variations of the east asian summer monsoon easm during the holocene are poorly constrained due to the lack of high resolution records with detailed chronologies especially in southern china here we present high resolution 35 yr proxy records spanning the last 7500 years from a well dated sediment core yj core from the northern inner shelf of the south china sea al ti and fe variations were employed as indicators of terrigenous influx and k al ratios were used as a tracer of chemical weathering to document variations in the intensity of the easm the results show a series of centennial scale weak easm events which are generally synchronous with those inferred from other geologic archives from monsoonal regions in the eastern and southern china moreover these events are synchronous with periods of weak solar activity and the spectral analysis demonstrates that the easm and solar activity share some general cyclicity patterns we therefore suggest that solar activity is a fundamental driving force for the spatial synchronisation of the easm on centennial timescales across the monsoon region

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

freshwater outbursts to the oceans from glacial lake agassiz and their role in climate change during the last deglaciation abstract lake agassiz was the largest lake in north america during the last deglaciation as the laurentide ice sheet lis retreated large volumes of water stored in this proglacial lake were episodically released into the oceans these waters were variably routed to the gulf of mexico arctic ocean north atlantic ocean and hudson bay during this period the three largest cooling events in the northern hemisphere closely followed 4 of the 5 largest outbursts from lake agassiz 1 the younger dryas which was preceded by a release of 9500 km 3 2 the preboreal oscillation preceded by releases of 9300 km 3 and 5900 km 3 and 3 the 8 2 ka cold event preceded by a 163 000 km 3 outburst these are respectively fluxes of 0 30 sv 0 29 sv 0 19 sv and 5 2 sv if released in 1 year because the influx of freshwater reaching the north atlantic ocean can inhibit thermohaline circulation partly depending on whether the ocean was in a glacial interglacial or transitional mode of circulation we believe that at least these large outbursts from lake agassiz may have provided the triggers for changes in ocean circulation and in turn for widespread climate change

a 16 ka oxygen isotope record from genggahai lake on the northeastern qinghai tibetan plateau hydroclimatic evolution and changes in atmospheric circulation moisture source history and changes in atmospheric circulation are the most important attributes for portraying past climate changes and for estimating possible future trends however few climate records reflecting these attributes are available from the marginal zones of the asian summer monsoon here we present a record of the oxygen isotopic composition of authigenic carbonates delta 18 ocarb of sequential sediments from genggahai lake in the northeastern qinghai tibetan plateau qtp isotopic analyses were performed on the fine grained carbonate fraction 38 mu m mollusc shells and stem encrustations from submerged plants the stratigraphic variations of the delta o 18 record from the different carbonate components exhibit a remarkably similar pattern probably reflecting the fact that delta 18 ocarb variability was controlled primarily by changes in the oxygen isotopic composition of the lake water delta 18 olw disequilibrium effects and water temperature are precluded as major factors affecting the delta 18 ocarb variations genggahai lake is hydrologically open and characterized by a rapid discharge rate as indicated by analysis of the hydrological setting of the lake system and by the observed significant positive correlation between delta o 18 lw and the oxygen isotopic composition of the inflowing water delta o 18 1 under such hydrological conditions we argue that the isotopic signals of different moisture sources should be reflected in the carbonate isotopic composition furthermore placing the delta 18 ocarb record in the context of regional palaeoclimate archives we found that the isotopic signals particularly the negative shifts from the average values cannot be interpreted consistently despite a process of evaporative enrichment at the lake surface during the early to mid holocene low delta 18 ocarb values during 10 6 9 4 and 7 4 63 ka were associated with higher lake levels and thus the record may have been significantly affected by a strengthened asian summer monsoon at those times and hence by a positive moisture balance isotopic depletions with similar magnitudes occurred at 15 14 5 13 8 13 3 12 5 11 4 5 3 4 8 3 7 3 4 2 8 2 3 1 7 1 3 and 0 6 1 a i e within the lateglacial and the late holocene these negative shifts in delta 18 ocarb corresponded to lower lake level phases and most likely were a response to intensification of the mid latitude westerly circulation that may have transported significantly more o 18 depleted moisture to the region compared to that from the asian summer monsoon overall our results suggest that the alternating influence of the asian summer monsoon and the westerlies played a significant role in determining the pattern of atmospheric circulation on the northeastern qtp c 2017 elsevier ltd all rights reserved

wally was right predictive ability of the north atlantic conveyor belt hypothesis for abrupt climate change linked abrupt changes of north atlantic deep water formation north atlantic sea ice extent and widespread climate occurred repeatedly during the last ice age cycle and beyond in response to changing freshwater fluxes and perhaps other causes this paradigm developed and championed especially by w s broecker has repeatedly proven to be successfully predictive as well as explanatory with high confidence much work remains to fully understand what happened and to assess possible implications for the future but the foundations for this work are remarkably solid

multidecadal to centennial scale 10 be variations in holocene sediments of huguangyan maar lake south china we report a new high resolution holocene be 10 record from huguangyan maar lake in subtropical tropical south china aimed to detect the atmospheric be 10 production signal in low latitude regions after minimizing climatic effects by regression analyses between be 10 concentration and climatic proxies from the same archive we successfully distinguished variations in geomagnetic field intensity and solar activity using 2 000 year low and high pass filtering respectively of the residual be 10 record a proxy of the atmospheric be 10 production rate the resulting be 10 derived record of geomagnetic field intensity is generally comparable with geomagnetic models and the solar modulated be 10 signal shows significant correlations with solar activity proxies the preservation of be 10 production signal in the sediments of this low latitude maar lake highlights the largely unexplored potential as well as limitations of be 10 as a tool to reconstruct variations in solar activity and geomagnetic field intensity plain language summary the atmospheric production rate of cosmogenic be 10 depends on the cosmic ray flux penetrating the atmosphere a process that is mainly controlled by the geomagnetic field strength and solar activity the geomagnetic imprint on be 10 has been well established in previous studies of ice cores and marine sediments the relationship between solar activity and be 10 has also been studied in ice cores and high latitude lakes here we for the first time present a high resolution be 10 record from huguangyan maar lake in subtropical tropical south china over the holocene we successfully separated the atmospheric be 10 production signal from climatic effects that contribute to up to similar to 52 of the variance in be 10 concentration after eliminating the climatic effects variations in both geomagnetic field intensity and solar activity signals were reconstructed from the residual be 10 record using 2 000 year low pass and high pass filtering respectively the geomagnetic and solar modulated be 10 production signals are evaluated by comparisons with independent records this result unambiguously indicates that the be 10 derived solar activity signal at a low latitude subtropical site can be obtained even when the be 10 signal is dominated by regional climate in our case accounting for up to similar to 65 of the variance in the record during the early middle holocene

direct and indirect effects of holocene climate variations on catchment and lake processes of a treeline lake sw china sedimentary records of inorganic elements and pigments over the last 12 000 years are used to assess major changes in limnological conditions of tiancai lake a small treeline lake sw china in response to holocene climate variations algal communities shifted from the dominance of cyanobacteria and cryptophytes in the early holocene towards siliceous algae in the mid holocene and chlorophytes in the late holocene algae responded to a combination of climate mediated vegetation and soil development associated with allochthonous inputs of dissolved nutrients and organic matter and sediment infilling decreases in al pb cu and zn from the early holocene probably resulted from soil podsolization and the sequestration of these elements within soils changes in mn and fe were likely linked to redox condition in catchment soils and water column synchronous peaks in ti ba ca sr na k and mg median grain size and magnetic susceptibility coincided with the troughs in the chemical index of alteration indicating that episodic cold events enhanced upland bedrock erosion and transported unleached and coarse detritus into the lake these cold events broadly correlate with holocene ice rafting events in the north atlantic although the cold events altered the influx of minerogenic elements by regulating upland bedrock erosion climate mediated vegetation and soil development led to a muted impact on primary producers holocene algal community shifts were subtle reflecting the relative abundance of p derived from weathering and n derived from soils throughout the record with the most pronounced effects on the lake biota being benthic expansion which occurred in response to sediment infilling

a high resolution holocene record of the east asian summer monsoon variability in sediments from mountain ganhai lake north china abstract a high resolution environmental magnetic records from a sediment profile in mountain ganhai lake has provided new insights into modulation of the east asian summer monsoon easm on climatic changes in north china from the final period of last deglacial stage to holocene large pseudo single domain psd to multidomain md detrital magnetite grains are identified in the lake samples the upwards decreasing magnetic susceptibility and anhysteretic remanent magnetic susceptibility arm are consistent with the dominant vegetation changes grassland 13 0 10 5 ka under dry and cold conditions shrub forest grassland 10 5 5 8 ka in a warm and humid climate and forest where the pinus trees increase rapidly to be the dominant taxa indicating the climate changes from warm and humid to cooler but drier between 5 8 ka and 4 0 ka the lower s 100mt and s 300mt ratios coincide with the higher degree of soil stability and a stable lake stage at 11 8 6 5 ka changes in magnetic anisotropy are also linked to environmental and climatic changes with t parameters showing higher values during warm interglacial periods the anisotropy patterns indicate three different stages of the lake evolution 1 an early stage of the lake accompanied by a disturbed high energy flow a coarse average mineral particle diameter mpd distribution 16 28 m and scattered subvertical minimum direction k3 at 13 0 11 8 ka 2 a fairly stable lake environment between 11 8 ka and 6 5 ka indicated by a low energy flow finer mpd 9 69 m and subvertical k3 axes 3 an unstable high energy flow and coarse mpd 20 03 m with tilted k3 axes thus indicating a transition from lake center to lakeside 6 5 4 0 ka these multi proxy records reveal a weak easm activity in the final period of the last deglaciation 13 0 11 8 ka a high easm intensity in the early mid holocene 11 8 4 8 ka an easm maxima in the mid holocene 8 0 5 8 ka which then generally weakens at 4 3 4 2 ka overall this study suggests the anisotropy and climatic changes in the alpine lake are significantly affected by the insolation driven easm

variation of east asian monsoon precipitation during the past 21 k y and potential co2 forcing paleoclimatic research can provide critical insight on causes of change in the east asian monsoon which influences the lives of 1 6 billion people today in this study we use paleoclimatic indexes from chinese loess deposits which have clear climatic implications and are independently dated to reconstruct the monsoon precipitation since 21 ka our results show that monsoon precipitation persistently decreased from 21 ka to ca 8 ka and increased after ca 8 ka with a precipitation peak at 8 3 ka these changes in east asian summer monsoon precipitation are synchronous with changes in high northern latitude ice volume ice cover and atmospheric co2 these new data suggest that variation of the monsoon precipitation was probably driven by co2 forced high northern latitude temperature changes shifting the location of the intertropical convergence zone that dominates monsoon precipitation our trace 21000 modeling experiment supports this interpretation

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

rapid early holocene deglaciation of the laurentide ice sheet the demise of the laurentide ice sheet during the early holocene epoch is the most recent and best constrained disappearance of a large ice sheet in the northern hemisphere and thus allows an assessment of rates of ice sheet decay as well as attendant contributions to sea level rise here we use terrestrial and marine records of the deglaciation to identify two periods of rapid melting during the final demise of the laurentide ice sheet when melting ice contributed about 1 3 and 0 7cm of sea level rise per year respectively our simulations with a fully coupled ocean atmosphere model suggest that increased ablation due to enhanced early holocene boreal summer insolation was the predominant cause of laurentide ice sheet retreat although the surface radiative forcing in boreal summer during the early holocene is twice as large as the greenhouse gas forcing expected by the year 2100 the associated increase in summer surface air temperatures is very similar we conclude that our geologic evidence for a rapid retreat of the laurentide ice sheet may therefore describe a prehistoric precedent for mass balance changes of the greenland ice sheet over the coming century

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

holocene tephrostratigraphic framework and monsoon evolution of east asia key tephra beds for synchronising palaeoclimate records abstract in east asia our understanding of holocene climate change forcing mechanisms and propagation require the precise chronological control of palaeoclimate records to allow robust integration of data sets the existing chronologies predominantly based on 14c method however are not sufficient to constrain key questions about abrupt climate shifts that occur within a century in the transitions between states widely dispersed tephra layers allow precise dating and synchronisation of sedimentary archives providing a chronological framework for integrating records especially where the visible tephra record is complemented by the addition of cryptotephra non visible ash despite significant tephra studies in this region however a comprehensive holocene tephra framework is not available to address this issue we carry out a thorough review on holocene tephra investigations undertaken in japan using widespread tephra beds we present an integrated tephra framework and suggest the way forward for establishing this as a wider approach for east asia the framework is based on twenty two ash layers that are mainly from japan and to a lesser extent china n korea s korea and russia each tephra is assessed in terms of chronology geochemistry and distribution the framework is compared with high resolution palaeoclimate records from east asia using this we demonstrate regional variations in monsoon evolution and more importantly the potential of tephra isochrons in constraining such variations given the scarce identification of tephra layers in those well resolved palaeoclimate records we advocate a more systematic employment of the cryptotephra method which would potentially lead to a significant advance in east asian tephrochronology and the correlation of palaeoclimate archives in the region

millennial and centennial scale droughts at the northern margin of the east asian summer monsoon during the last deglaciation sedimentological evidence from dali lake abstract the semi arid areas at the northern margin of the east asian summer monsoon easm have experienced an increased frequency of drought in recent decades however it is unclear whether past monsoonal precipitation in the region were determined mainly by el nino southern oscillation enso variability or high latitude cooling in this study we use a high resolution grain size dataset combined with a new bayesian age depth model of a sediment core from dali lake to analyze the occurrence of millennial and centennial scale droughts at the easm margin during the interval of climatic warming during the last deglaciation the polymodal grain size distributions are partitioned using a log normal distribution function fitting method high percentages of the coarse components c4 c5 c6 are recognized as proxy indicators of strong aeolian activities and low lake levels and thus droughts in the region the drought events indicated thereby are generally accompanied by decreases in regional temperature catchment surface runoff and bio productivity on both millennial and centennial timescales these results imply that the droughts at the easm margin were caused by a significantly weakened easm intensity in addition the droughts may be linked within the age uncertainties to the heinrich 1 h1 and younger dryas yd events on millennial timescales and to the older dryas od cold event on centennial timescales implying strong high latitude forcing given that these cold reversals over northern high latitudes were induced by the rapid input of glacial melt water to the north atlantic during the last deglaciation it is possible that ongoing climatic warming and the resulting high northern latitude ice sheet melting may cause an increased incidence of drought in northern china

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

holocene monsoon climate documented by oxygen and carbon isotopes from lake sediments and peat bogs in china a review and synthesis there has been much recent debate about holocene climate variation in the monsoon region of china especially the temporal pattern of variations in precipitation the time transgressive nature of the holocene precipitation maximum and the extent to which variations in regions influenced by the indian summer monsoon ism and the east asian summer monsoon easm have been synchronous we summarize and compare carbonate oxygen isotope records delta o 18 carb from ten lakes within the present day ism region we discuss their paleoclimate significance considering the present day moisture source isotopic composition of precipitation and the hydrological setting the delta o 18 carb records are controlled mainly by the isotopic composition of lake water which in turn is a function of regional precipitation evaporation p e balance and the proportion of precipitation that is monsoon derived we normalized the delta o 18 carb data and used these records to generate an integrated moisture index this index along with oxygen isotope records from speleothems and carbon isotope records delta c 13 org from peats within the monsoon region suggests that holocene climate was broadly synchronous across the monsoon region and within the limits of accuracy of the existing age models provides no strong evidence for previously proposed anti phasing of the ism and the easm stable isotope records from lake sediments and peat bogs have excellent potential for providing high quality paleoclimate data for monsoon asia and complement high resolution speleothem sequences which are only found in certain localities c 2011 elsevier ltd all rights reserved

the significance of maar volcanoes for palaeoclimatic studies in china abstract the sediments of maar lakes often provide paleoenvironmental records which are highly suitable for palaeoclimatic studies the main advantages of the records from maar lakes compared with other lacustrine records are as follows first the presence of varves annually laminated layers and tephra layers as well as other materials like terrestrial plant macrofossils charcoals organic carbon organic shells suitable for isotopic dating like ams 14c 210pb 137cs 238u 230th 40ar 39ar provides the possibility of developing several independent chronologies enabling the development of robust high resolution chronologies second maars and maar lakes can provide continuous sedimentary records spanning tens of thousands of years tianyang maar in china is hosted the longest known record spanning at least 400 kyr bp that are ideal for the investigation of climate change on different timescales including orbital millennial centennial and annual decadal third recent studies of biomarkers based on long chain alkenones lcas and glycerol dialkyl glycerol tetraethers gdgts have demonstrated the potential of maar lakes for quantitative paleotemperature reconstruction in this study we review some of the more significant achievements of palaeoclimatic research based on maar lake sediment sequences from china with the focus on chronology multiple timescales and quantitative paleoclimatic reconstruction

a high resolution sediment record of east asian summer monsoon from the northern south china sea spanning the past 7500 years high resolution holocene marine sediment records are limited which hampers our understanding of paleomonsoon evolution continental shelf sediment records are derived mainly from terrestrial weath

impact of the atlantic multidecadal oscillation on the asian summer monsoon 1 the impact of the atlantic multidecadal oscillation amo on the asian summer monsoon is investigated using a coupled atmosphere ocean global general circulation model by imposing the amo associated sea surface temperature anomalies in the atlantic as boundary forcing and allowing atmosphere ocean interactions outside the atlantic the positive amo phase characterized by anomalous warm north atlantic and cold south atlantic leads to strong southeast and east asian summer monsoons and late withdrawal of the indian summer monsoon these changes of monsoons are mainly through coupled atmosphere ocean feedbacks in the western pacific and indian oceans and tropospheric temperature changes over eurasia in response to the imposed forcing in the atlantic the results are in agreement with the observed climate changes in china corresponded to the amo phases they suggest a non local mechanism for the asian summer monsoon variability and provide an alternative view to understanding its interdecadal variation during the twentieth century citation lu r b dong and h ding 2006 impact of the atlantic multidecadal oscillation on the asian summer monsoon geophys res lett 33 l24701 doi 10 1029 2006gl027655

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

a holocene palaeomagnetic secular variation record from huguangyan maar lake southern china summary a composite holocene sediment profile 5 m in length constrained by both radiocarbon dating and magnetic susceptibility based correlation was obtained from three livingstone piston cores collected in 10 m water depth in the huguangyan hgy maar lake southern china the homogeneous silty clay indicates stable and continuous deposition the dominant magnetic carrier is magnetite in the pseudo single domain grain size range and thus is suitable for recording palaeomagnetic secular variations psv results show that the hgy psv curves can be correlated faithfully to the counterparts at a regional scale therefore the psv data is a potential tool for stratigraphic correlation and for further refining the chronological framework of lake sediment sequences from southern china further comparison of the hgy psv records with the coeval european and north american counterparts confirms the existence of strong permanent magnetic flux lobes at the core mantle boundary the discrepancy in amplitude and out phase pattern among the different regional records may be ascribed to the evolution of the magnetic flux lobes

paleomagnetic secular variation and relative paleointensity during the holocene in south china huguangyan maar lake revisited the scarcity of reliable paleomagnetic secular variation psv records from east asia especially from low latitude regions impedes better understanding of global psv mechanisms here we report on a radiocarbon dated holocene psv record from a composite 6 7 m long core collected from the high sedimentation rate huguangyan maar lake hml in subtropical tropical south china rock magnetic results demonstrate that the natural remanent magnetization resides in single domain magnetite alternating field demagnetization experiments at 1 cm spacing on u channel samples reveal six distinct inclination highs at 7 500 bce 5 100 bce 4 600 bce 3 600 3 400 bce 1 600 1 200 bce and 600 800 ce three inclination lows at 4 800 bce 600 300 bce and 1 000 1 300 ce and three eastward declination trends at 3 600 3 200 bce 2 600 2 400 bce and 400 bce to 200 ce the similarity between the hml psv record and other independently dated records from east asia and geomagnetic field models corroborates the robustness of our age model and holocene psv record strikingly centennial to millennial scale psv features of the hml are comparable within age uncertainties with other holocene records from europe north america and canada suggesting that such directional patterns are likely to be hemispheric in scale although relative paleointensity data of hml are affected by environmental factors e g organic matter diagenesis the record still provides a regionally important new psv reference curve whose conspicuous features may serve as stratigraphic markers for east asian paleorecords

time transgressive onset of the holocene optimum in the east asian monsoon region abstract the east asian summer monsoon affects precipitation and hence vegetation in the densely populated northwest pacific region yet a long standing controversy exists concerning the spatial and temporal dynamics of the holocene optimum ho in the east asian monsoon region here we use a detailed 14 000 year record reconstructing vegetation variations from a strategically selected crater lake from northeast china as well as a compilation of previous paleoclimatic studies to show that the ho began around 6 000 cal a bp in northeast china significantly later than generally recognized by comparing our paleoenvironmental data with holocene vegetation records from other regions of east asia we identified a marked northward shift for the onset of the ho from 10 260 cal a bp in south china to 6 000 cal a bp in northeast china the gradual northward transgression of the vegetation change could be caused by both the temperature and precipitation changes in different regions finally we fitted a regression model of the start of the ho period versus latitude which allowed us to make predictions for the beginning of the ho at different geographical locations this study reveals a strong relationship between latitude and the initiation of the ho and provides a window towards better understanding the forcing of vegetation changes in the east asian monsoon region

the role of the asian winter monsoon in the rapid propagation of abrupt climate changes during the last deglaciation abstract high resolution temperature records spanning the last deglaciation from low latitudes are scarce however they are important for understanding the rapid propagation of abrupt climate events throughout the northern hemisphere and the tropics here we present a branched gdgts based temperature reconstruction from the sediments of maar lake huguangyan in tropical china the record reveals that the mean temperature during the oldest dryas was 17 8 c which was followed by a two step increase of 2 3 c to the bolling allerod a decrease to 19 8 c during the younger dryas and a rapid warming at the onset of the holocene the oldest dryas was about 2 c warmer than the younger dryas the reconstructed temperature was weighted towards the wintertime since the lake is monomictic and the mixing process in winter supplies nutrients from the lake bottom to the entire water column greatly promoting biological productivity in addition the winter biased temperature changes observed in the study are more distinctive than the summer biased temperature records from extra tropical regions of east asia this implies that the temperature decreases during abrupt climatic events were mainly a winter phenomenon within the limits of the dating uncertainties the broadly similar pattern of winter weighted temperature change observed in both tropical lake huguangyan and in greenland ice cores indicates the occurrence of tightly coupled interactions between high latitude ice sheets and land areas in the tropics we suggest that the winter monsoon especially cold surges could play an important role in the rapid transmission of the temperature signal from the arctic to the tropics

geochemical characteristics of the miocene eolian deposits in china their provenance and climate implications 1 in the loess plateau in northern china the quaternary loess soil sequences the hipparion red earth of eolian origin red clay and the miocene loess soil sequences constitute a near continuous terrestrial record of paleoclimates for the past 22 ma in this study miocene loess and paleosol samples from qinan qa i were analyzed for their major trace and rare earth element chemistry and compared with the pliopleistocene samples from xifeng with emphasis on their provenance and paleoclimatic implications the results show similar geochemical signatures for the eolian deposits of different ages and they are also comparable to the average composition of the upper continental crust these suggest that the dust materials were all derived from well mixed sedimentary protoliths which had undergone numerous upper crustal recycling processes they also support the notion of broadly similar source areas and dust transporting trajectories for different periods since the early neogene the slightly higher k2o fe2o3 and mgo concentrations and loss on ignition values and the lower na2o content in the miocene loess samples compared to their quaternary counterparts are attributable to the finer grain size of the miocene loess associated with weaker dust carrying winds in comparison with some loess in europe and america with less extensive sources eolian deposits from northern china show higher cs and lower zr and hf content this is attributable to the sorting processes from remoter sources during transportation and could be regarded as an indication of the desert origin of the loess deposits miocene paleosol samples show higher chemical index of alteration values and lower cao mgo and na2o concentrations than does the intervening loess indicating stronger weathering of the paleosols however the moderate chemical weathering of the paleosol samples indicates a constant semiarid and subhumid climatic range in northern china since the early miocene components 9791 words 8 figures 3 tables

millennial scale asian summer monsoon variations in south china since the last deglaciation abstract characterizing spatiotemporal variability of the asian summer monsoon asm is critical for full understanding of its behavior dynamics and future impacts the present knowledge about asm variations since the last glaciation in south china largely relies on several precisely dated speleothem stable oxygen isotope 18 o records although these speleothem 18 o signals provide useful evidence for regional past environmental changes their validity for denoting asm intensity remains a great controversy the huguangyan maar lake hml provides one of the most complete archives of environmental and climatic changes in the tropical subtropical south and east asia since the last glaciation here we document a continuous centennial to millennial scale asm record over the past 16 ky bp from the high sedimentation rate hml sediments in contrast with the low amplitude variations of chinese speleothem derived 18 o signals and the chinese loess based monsoon precipitation proxy indexes our multi proxy records reveal a pattern of high amplitude regional climatic fluctuations including fine scale oscillations during the bolling allerod warming the 8 2 ka cooling event and an abrupt climate shift from 6 5 5 9 ka the existence of bond like cold dry events indicates a distinct influence of the north atlantic circulation on low latitude monsoon changes the broad comparability between the hml paleo proxies chinese speleothem 18 o records and the northern hemisphere summer insolation throughout the holocene suggests that solar insolation exerts a profound influence on asm changes these findings reinforce a model of combined insolation and glacial forcing of the asm

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

sources and exposure of the new hampshire population to arsenic in public and private drinking water supplies abstract arsenic concentrations in drinking water from 2273 households and in rock samples from 307 sites throughout the state of new hampshire were studied to understand potential links between bedrock geology and arsenic concentration in drinking water and to calculate arsenic exposure estimates for the new hampshire population though it remains clear that most of the arsenic in new hampshire drinking water is likely from bedrock sources a simple correlation between arsenic concentration in rock samples and arsenic concentration in drinking water was not observed a combination of the eh ph status of the groundwater in the aquifer and proximity to high concentrations of arsenic in bedrock are suggested to be the most likely controlling mechanisms statewide utilizing the high sampling density of drinking water along with water source and population data from the 1990 and 2000 census maps of average arsenic exposure were plotted at the census tract level integrating exposure from all types of water sources drilled bedrock wells wells in surficial deposits and municipal water systems a comprehensive estimate of exposure to various arsenic concentrations was constructed domestic bedrock wells supply water to 120 000 households with a median arsenic concentration of 1 9 g l domestic surficial wells provide water to approximately 40 000 households with a median arsenic concentration of 0 15 g l and municipal water systems provide water to 265 000 households with a median arsenic concentration of 0 41 g l above 0 61 g l domestic bedrock wells supply the largest number of households with elevated concentrations of arsenic while below this value more arsenic is delivered via municipal water systems while many studies focus on more readily available public water supply data this study points out the importance of quantifying arsenic exposure from private water supplies and provides a technique for correcting spatially variable water source parameters

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

holocene summer temperature in arid central asia linked to millennial scale north atlantic climate events and driven by centennial scale solar activity abstract the millennial and centennial scale variability of holocene climate in arid central asia aca is poorly understood due to the lack of high resolution records especially of temperature we present a high resolution 45 yr peat cellulose 13c record spanning the last 11 030 years from a well dated peat core atm10 c7 from the altai mountains in aca it is interpreted as a summer temperature record and exhibits millennial and centennial scale variability the millennial scale variability corresponds well to north atlantic ice rafting events implying a climatic link between the north atlantic and the aca via the westerlies the centennial scale cold events were synchronous with stages of low solar activity spectral and cross spectral analyses demonstrate that summer temperature and solar activity have a common cyclicity and we therefore suggest that solar activity was the fundamental driver of the centennial scale variability of summer temperature in aca during the holocene

holocene climate dynamics derived from pollen record of jiulongchi wetland in fanjing mountain southwest china abstract an alpine wetland core was obtained to a depth of 4 0 m from the fanjing mountain in southwest china sections of the core were dated with 14c data obtained with high resolution mass spectrometry ams and holocene climate changes were inferred by categorizing predominant tree and fern vegetation identified from pollen and spore counts at various core depths the temperature increased during 11 9 8 0 cal ka bp and the warmest period was during 8 0 4 6 cal ka bp then it gradually became cooler during the late holocene our temperature estimates were in good agreement with the previous studies of the holocene temperature in the asian monsoon areas there were two relatively wet periods of 10 7 8 0 cal ka bp and 4 6 2 6 cal ka bp there was an asynchronous precipitation trend in the south north and southwest china which was probably due to the different monsoon impacts in east asian summer monsoon easm area the monsoon precipitation gradually transgressed northward during the early to middle holocene and regressed southward during the late holocene our results will be useful to improve the understanding of the coherent spatio temporal patterns of climate evolution in easm region in china

biogeochemical evidence of holocene east asian summer and winter monsoon variability from a tropical maar lake in southern china abstract lake huguangyan 21 9 n 110 17 e a maar lake located near the south china sea can provide valuable sedimentary data regarding past changes of the east asian monsoonal system here we used the proxies of toc 13corg 15n and leaf wax n alkane 13c values 13cwax to reconstruct the lake conditions which in turn revealed patterns in monsoonal changes during the holocene two distinct patterns of proxy changes were identified in the sedimentary profile a marked shift in the 13cwax value at 9 2 ka thousand years ago suggests the abrupt disappearance of c4 plants signaling the enhancement of east asian summer monsoon easm between 9 2 and 1 8 ka a nearly pure c3 terrestrial ecosystem was present with the climax at ca 7 6 ka after ca 3 ka fewer tropical species and a reappearance of c4 plants at 1 8 ka indicate a weakened easm in the late holocene the toc concentration and 15n value proxies appear to be associated with lake aquatic production and upwelled nutrient supply and utilization which are modulated by and thus indicative of the strength of the east asian winter monsoon eawm the two eawm records suggest a weakening trend from the early to late holocene with the most significant transition at 6 ka thus the eawm trend was broadly in phase with that of the easm however the marked easm intensification at 9 2 ka occurred within the period of a strong eawm between 10 5 and 6 ka and lagged the monsoonal enhancement as inferred from the dongge cave 18o values our easm records displays an overall arid wet arid pattern which is in phase with the hydrological variability in tropical australia and anti phase with that in the outer tropical andes these phase relationships might be linked to changes in the thermal state of the tropical pacific during the holocene