holocene climate changes in the monsoon arid transition reflected by carbon concentration in daihai lake of inner mongolia two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for total inorganic and organic carbon tic and toc concentrations the tic concentration is inferred to reflect temperatures over the lake region and an increase in the tic concentration implies an increase in the temperature toc concentration is considered to reflect the precipitation in the lake basin and higher toc concentrations denote more precipitations thus ams 14c time series of the tic and toc records of daihai lake sediments uncovers a detailed history of changes in temperature and precipitation in north central china during the last c 12 000 yr the holocene an epoch of postglacial warmth started c 11 500 cal yr bp and can be subdivided into three stages the early c 11 500 8100 cal yr bp middle c 8100 3300 cal yr bp and the late holocene c 3300 0 cal yr bp the climate was warm and dry during the early holocene warm and wet during the middle holoce

a penultimate glacial monsoon record from hulu cave and two phase glacial terminations oxygen isotope records of three stalagmites from hulu cave china extend the previous high resolution absolute dated hulu asian monsoon record from the last to the penultimate glacial and deglacial periods the penultimate glacial monsoon broadly follows orbitally induced insolation variations and is punctuated by at least 16 millennial scale events we confirm a weak monsoon interval between 135 5 1 0 and 129 0 1 0 ka prior to the abrupt increase in monsoon intensity at asian monsoon termination ii based on correlations with both marine ice rafted debris and atmospheric ch 4 records we demonstrate that most of marine termination ii the full rise in antarctic temperature and atmospheric co 2 and much of the rise in ch 4 occurred within the weak monsoon interval when the high northern latitudes were probably cold from these relationships and similar relationships observed for termination i we identify a two phase glacial termination process that was probably driven by orbital forcing in both hemispheres affecting the atmospheric hydrological cycle and combined with ice sheet dynamics

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

episodic reductions in bottom water currents since the last ice age although north atlantic deep water formation was greatly reduced during the last glacial maximum bottom water currents were as vigorous as at present however they were weakened during periods of north atlantic surface freshening a strong correlation can be seen between bottom water current strength and greenland air temperature records thus confirming a close connection between ocean circulation and abrupt climate change past changes in the freshwater balance of the surface north atlantic ocean are thought to have influenced the rate of deep water formation and consequently climate1 2 although water mass proxies are generally consistent with an impact of freshwater input on meridional overturning circulation3 there has been little dynamic evidence to support this linkage here we present a 25 000 year record of variations in sediment grain size from south of iceland which indicates vigorous bottom water currents during both the last glacial maximum and the holocene period together with reconstructions of north atlantic water mass distribution vigorous bottom currents suggest a shorter residence time of northern source waters during the last glacial maximum relative to the holocene period the most significant reductions in flow strength occur during periods that have been associated with freshening of the surface north atlantic the short term deglacial oscillations in bottom current strength are closely coupled to changes in greenland air temperature with a minimum during the younger dryas cold reversal and a maximum at the time of rapid warming at the onset of the holocene our results support a strong connection between ocean circulation and rapid climate change

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

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

a 550 000 year record of east asian monsoon rainfall from 10be in loess cosmogenic 10 be flux from the atmosphere is a proxy for rainfall using this proxy we derived a 550 000 year long record of east asian summer monsoon easm rainfall from chinese loess this record is forced at orbital precession frequencies with higher rainfall observed during northern hemisphere summer insolation maxima although this response is damped during cold interstadials the 10 be monsoon rainfall proxy is also highly correlated with global ice volume variations which differs from chinese cave 18 o which is only weakly correlated we argue that both easm intensity and chinese cave 18 o are not governed by high northern latitude insolation as suggested by others but rather by low latitude interhemispheric insolation gradients which may also strongly influence global ice volume via monsoon dynamics

late quaternary aeolian activity in the mu us and otindag dune fields north china and lagged response to insolation forcing 1 dune fields in parts of northern china contain important stratigraphic records of late quaternary change in the east asian monsoon in this study 33 new optically stimulated luminescence osl ages and other measurements from aeolian sediment sections are used to reconstruct the timing of wet dry climate variation in the mu us and otindag dune fields of north china the results indicate dune activity and dry climate in the last few hundred years 14 ka to about 7 8 ka and 50 ka to 60 ka the dunes were mainly stable implying a wetter climate between about 7 8 ka and 2 4 ka these results imply a lag of several thousand years between peak summer insolation at 10 11 ka and high summer monsoon rainfall after 7 8 ka in the investigated regions the monsoon climate may not respond directly to orbital forcing over millennial time scales land surface feedbacks may account for lagged dune field response

holocene climate changes over the desert loess transition of north central china a 2 m trench section at the desert loess transition of north central china was analyzed at 2 cm intervals for grain size distribution md m and total organic carbon toc ams 14c time series of the md and toc records provides direct information on variations of the east asian monsoon climate during the last 10 000 yr md is considered to represent the wind strength and high md reflects strong winter monsoon winds toc denotes the degree of vegetation cover a function of the intensity of summer monsoon circulations from ca 10 000 to 7000 cal yr bp the climate was dominated by a strong winter monsoon and a very weak summer monsoon as indicated by high md and low toc values subsequently climatic conditions became warmer gradually from ca 7000 to 5500 cal yr bp the period between ca 5500 and 2700 cal yr bp displayed the highest toc and lowest md values over the last 10 000 yr marking a stable state of a warm humid climate i e the holocene climatic optimum of china during the interval of ca 2700 1500 cal yr bp the expansion and intensification of agrarian activities could have led to desertification and acceleration of deposition of coarse grained particles resulting in a decreased organic carbon accumulation rate however the toc during this interval still has values as high as during the episode of ca 7000 5500 cal yr bp reflecting a relatively stronger summer monsoon circulation since ca 1500 cal yr ago high amplitude fluctuations of toc that fluctuate in phase with the clay size fraction imply that the climate experienced three major oscillations with a prominent peak of enhanced summer monsoon circulation at ca 1300 cal yr ago and with two intervals of increased winter monsoon strength occurring around ca 1000 and 300 cal yr ago the md and toc records over the past 5000 yr demonstrate a good correlation with the archaeological phenological and historical records of china climate changes in the east asian monsoon region were not only related to the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but were also controlled by the pattern and intensity of the atmospheric circulation

east asian summer monsoon variations during the last deglaciation recorded from a stalagmite at linyi northern china abstract a230th dated stalagmite record from linyi shandong province provides a detailed history of the east asian summer monsoon easm in northern china during the last deglaciation our record reveals changes that are similar to previously published stalagmite records from the east asian monsoon region on centennial and millennial scales although some subtle and detail discrepancies are observed comparisons with other paleoclimate records show that the easm was jointly controlled by the north atlantic climate and low latitude tropical processes during the last deglaciation ocean atmospheric interactions particularly sea surface temperature changes in the tropical pacific might have contributed to the increasing trend of the easm during the bolling allerod and to the lesser weakening in the easm during the younger dryas in addition the significantly higher growth rates of the stalagmite during the heinrich event 1 might have been driven by the co2 degassing processes future studies with long term monitoring of the calcite deposition rate at this site will be needed to support our arguments on the co2 degassing processes

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

correlation between indian ocean summer monsoon and north atlantic climate during the holocene there has been a number of investigations for the correlation between the asia monsoon and the north atlantic climate for the last glacial however little research has been done for the present interglacial the holocene here we present for the first time a high resolution composite proxy record for the indian ocean summer monsoon spanning around 12 000 years based on the 13c time series of both a single plant species carex mulieensis remains cellulose and the total plant assemblage cellulose in the hongyuan peat bog from the tibet plateau the records show that the strength of the indian ocean summer monsoon had abrupt variations during the last 12 000 years the weakest monsoon occurred in the younger dryas period following rapid strengthening from around 11 200 to 10 800 a bp the monsoon kept a generally strong level for around 5300 years from around 5500 a bp onwards the monsoon strength tended to gradual decrease in addition there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales which superimpose the general tendency of the monsoon variation in every case when the ice rafted debris events in the north atlantic occurred the summer monsoon strength decreased correspondingly these evidences show that teleconnection between the indian ocean summer monsoon and the north atlantic climate is present not only in the last glacial but also in the holocene which may be linked to abrupt reorganizations of the ocean thermohaline circulation leading to redistribution of energy changing temperature and moisture gradient over the southern subtropical indian ocean and eventually controlling the variability of the indian ocean summer monsoon

holocene stalagmite δ18o records in the east asian monsoon region and their correlation with those in the indian monsoon region we compare well dated holocene stalagmite delta o 18 records from the east asian summer monsoon easm region and from the indian summer monsoon ism region we found that the pattern of latitudinal change of speleothem delta o 18 values from the indian monsoon region to the east asian monsoon region is almost identical to that of modern precipitation this suggests that the modern moisture transport route from the indian ocean to the east asian monsoon region has existed since at least the early holocene the delta o 18 records from both regions exhibit a remarkably similar trend of variation in that the values are more negative during the early holocene rapidly become heavy from the mid holocene and are heaviest during the late holocene the stalagmite delta o 18 changes in the east asian monsoon region are statistically well correlated with those in the indian monsoon region both over the entire holocene and in detail over the last 2000 years however in contrast to the obvious consistency of the delta o 18 values in all of the speleothem records both instrumental and historical climate records indicate significant spatial variations in rainfall over eastern china the early holocene strong easm pattern referred from speleothem delta o 18 in the east asian monsoon region is quite different to that of other paleoclimatic records such as holocene paleosol development in the chinese loess plateau eolian activity in the northern chinese sandlands and lake sediments in easm dominated region in china in which the strongest easm was documented during the mid holocene these findings suggest that the speleothem delta o 18 record from the east asian monsoon region may not record easm variability but rather that it is controlled by variations in the isotopic composition of precipitation which is determined mainly by rainfall variability in the ism region

coherent pan asian climatic and isotopic response to orbital forcing of tropical insolation the oxygen 18 isotope composition of calcite in stalagmites across southern and eastern asia are highly correlated to one another on orbital time scales large negative excursions are coincident with maxima in summer insolation in the subtropics of the northern hemisphere nh these isotopic excursions reflect changes in the precipitation weighted isotopic composition of precipitation 18op we present results from two core experiments using an isotope enabled climate model the high insolation and low insolation experiments in which the model is forced by extrema in nh summer insolation compared to the low insolation experiment the high insolation climate features profound large scale changes in the pattern of monsoon precipitation spanning from africa to southeast asia that are due to changes in the relative contributions of temperature and moisture to the near surface equivalent potential temperature e under high insolation a more rapid increase in land surface temperature in early summer causes the greatest e and hence precipitation to shift from the oceans in low insolation such as today to be over land in high insolation such as the early holocene the model captures the general pattern of isotopic excursions seen in caves spanning from israel to western china including large drops in 18op over eastern tibet 7 the arabian peninsula and northeast africa 4 although there are large changes in precipitation over tibet the change in 18op is due to changes in the 18o of water vapor that is delivered and subsequently precipitated it does not inform on local precipitation amount or intensity

reconciliation of hydroclimate sequences from the chinese loess plateau and low latitude east asian summer monsoon regions over the past 14 500years we discuss replicated stalagmite 18o records with interannual to multidecadal resolution from lianhua cave on the chinese loess plateau to illustrate the precipitation history of the east asian summer monsoon easm region over the last 14 5 thousand years ka bp before 1950 ce hereafter and to re evaluate the inconsistency in the proxy inferred palaeoclimate time series in northern china agreement between the stalagmite 18o from lianhua and other caves from central southern china indicates that regional climate changes after the last glacial were concurrent across mainland china indicating that insolation was the primary factor controlling the evolution of the asian summer monsoon asm the stalagmite 18o enrichment of 2 5 in the younger dryas and 1 7 during the 8 2 ka bp event in lianhua were larger than those in caves from central and southern china the evidence suggests that different meridional responses of weak precipitation conditions in the asm realm occurred during these two abrupt events driven by high latitude forcing in the northern hemisphere the heterogeneous hydroclimate sequences in northern china inferred from different natural archives are most likely attributable to the complexity of the formations and or some chronological uncertainty

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

antarctic link with east asian summer monsoon variability during the heinrich stadial bolling interstadial transition abstract previous research has shown a strong persistence for direct teleconnections between the east asian summer monsoon easm and high northern latitude climate variability during the last glacial and deglaciation in particular between monsoon weakening and a reduced atlantic meridional overturning circulation amoc however less attention has been paid to easm strengthening as the amoc was reinvigorated following peak northern hemisphere nh cooling moreover climate model simulations have suggested a strong role for antarctic meltwater discharge in modulating northward heat transport and hence nh warming yet the degree to which southern hemisphere sh climate anomalies impacted the asian monsoon region is still unclear here we present a new stalagmite oxygen isotope record from the easm affected region of central china which documents two prominent stages of increased 18 o depleted moisture delivery to the region through the transition from heinrich stadial 1 hs1 to the bolling allerod b a interstadial this is in general agreement with the other monsoonal records from both nh and sh mid to low latitudes through novel comparisons with a recent iceberg rafted debris ird record from the southern ocean we propose that the two stage easm intensification observed in our speleothem records were linked with two massive antarctic icesheet discharge aid events at 16 0 ka and 14 7 ka immediately following the peak hs1 stadial event notably the large increase in easm intensity at the beginning of the hs1 b a transition 16 ka is relatively muted in the nh higher latitudes and better aligns with the changes observed in the sh indicating the antarctic and southern ocean perturbations could have an active role in driving the initial easm strengthening at this time indeed antarctic freshwater input to the southern ocean during these aid events would have cooled the surrounding surface waters and caused an expansion of sea ice restricting the southern extent of the sh westerlies moreover increased meltwater flux during ird events would have freshened antarctic intermediate water leading to the increased formation of north atlantic deep water and enhanced north atlantic subsurface heat release and causing a strengthening of the amoc during the hs1 bolling transition the result of this sequence of events would have been warming in the north atlantic whilst at the same time cooling in the antarctic the ensuing interhemispheric temperature gradient would have acted to push the itcz northward weakening the australian indonesian summer monsoon aism whilst intensifying the easm

hydroclimatic changes in china and surroundings during the medieval climate anomaly and little ice age spatial patterns and possible mechanisms abstract investigating hydroclimatic changes during key periods such as the medieval climate anomaly mca 1000 1300 ad and the little ice age lia 1400 1900 ad is of fundamental importance for quantifying the responses of precipitation to greenhouse gas induced warming on regional and global scales this study synthesizes the most up to date and comprehensive proxy moisture precipitation records during the past 1000 years in china and surroundings the proxy data collected include 34 records from arid central asia aca and 37 records from monsoonal asia our results demonstrate a pattern of generally coherent regional moisture variations during the mca and lia in mid latitude asia north of 30 n monsoonal northern china north china and northeast china was generally wetter while aca northwest china and central asia was generally drier during the mca than in the lia a west east mode the boundary between wetter northern china and drier aca was roughly consistent with the modern summer monsoon boundary in monsoonal china to the east of 105 e the northern part was generally wetter while the southern part was generally drier during the mca than in the lia a north south mode with a boundary roughly along the huai river at about 34 n these spatial patterns of moisture precipitation variations are also identified by instrumental data during the past 50 years in order to understand the possible mechanisms related to the moisture variations during the mca and lia we investigate the major sst and atmospheric modes e g the el nino southern oscillation enso the atlantic multidecadal oscillation amo and the north atlantic oscillation nao which affect the moisture precipitation variations in the study region using both the instrumental data and the reconstructed time series it is found that the enso may play an important role in determining hydroclimatic variability over china and surroundings on a multi centennial time scale and that the foregoing spatial patterns could be attributed to the la nina like el nino like condition during the mca lia in addition amo and nao may also have their own contributions

lessons learned from oxygen isotopes in modern precipitation applied to interpretation of speleothem records of paleoclimate from eastern asia abstract variability in oxygen isotope ratios collected from speleothems in chinese caves is often interpreted as a proxy for variability of precipitation summer precipitation seasonality of precipitation and or the proportion of 18o to 16o of annual total rainfall that is related to a strengthening or weakening of the east asian monsoon and in some cases to the indian monsoon we use modern reanalysis and station data to test whether precipitation and temperature variability over china can be related to changes in climate in these distant locales we find that annual and rainy season precipitation totals in each of central china south china and east india have correlation length scales of 500 km shorter than the distance between many speleothem records that share similar long term time variations in 18o values thus the short distances of correlation do not support though by themselves cannot refute the idea that apparently synchronous variations in 18o values at widely spaced 500 km caves in china are due to variations in annual precipitation amounts we also evaluate connections between climate variables and 18o values using available instrumental measurements of 18o values in precipitation these data from stations in the global network of isotopes in precipitation gnip show that monthly 18o values generally do not correlate well with either local precipitation amount or local temperature and the degree to which monthly 18o values do correlate with them varies from station to station for the few locations that do show significant correlations between 18o values and precipitation amount we estimate the differences in precipitation amount that would be required to account for peak to peak differences in 18o values in the speleothems from hulu and dongge caves assuming that 18o scales with the monthly amount of precipitation or with seasonal differences in precipitation insofar as the present day relationship between 18o values and monthly precipitation amounts can be applied to past conditions differences of at least 50 in mean annual precipitation would be required to explain the 18o variations on orbital time scales which are implausibly large and inconsistent with published gcm results similarly plausible amplitudes of seasonal cycles in amounts or in seasonal variations in 18o values can account for less than half of the 4 5 difference between glacial and interglacial 18o values from speleothems in china if seasonal cycles in precipitation account for the amplitudes of 18o values on paleoclimate timescales they might do so by extending or contracting the durations of seasons a frequency modulation of the annual cycle but not by simply varying the amplitudes of the monthly rainfall amounts or monthly average 18o values amplitude modulation allowing that several processes can affect seasonal variability in isotopic content we explore the possibility that one or more of the following processes contribute to variations in 18o values in chinese cave speleothems different source regions of the precipitation which bring different values of 18o in vapor different pathways between the moisture source and the paleorecord site along which exchange of 18o between vapor surface water and condensate might differ a different mix of processes involving condensation and evaporation within the atmosphere or different types of precipitation each may account for part of the range of 18o values revealed by speleothems and each might contribute to seasonal differences between past and present that do not scale with monthly or even seasonal precipitation amounts

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

holocene enso related cyclic storms recorded by magnetic minerals in speleothems of central china extreme hydrologic events such as storms and floods have the potential to severely impact modern human society however the frequency of storms and their underlying mechanisms are limited by a paucity of suitable proxies especially in inland areas here we present a record of speleothem magnetic minerals to reconstruct paleoprecipitation including storms in the eastern asian monsoon area over the last 8 6 ky the geophysical parameter irmsoft flux represents the flux of soil derived magnetic minerals preserved in stalagmite hs4 which we correlate with rainfall amount and intensity irmsoft flux exhibits relatively higher values before 6 7 ky and after 3 4 ky and lower values in the intervening period consistent with regional hydrological changes observed in independent records abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial el nino southern oscillation enso patterns documenting the occurrence of enso related storms in the holocene spectral power analyses reveal that the storms occur on a significant 500 y cycle coincident with periodic solar activity and enso variance showing that reinforced subdued storms in central china correspond to reduced increased solar activity and amplified damped enso thus the magnetic minerals in speleothem hs4 preserve a record of the cyclic storms controlled by the coupled atmosphere oceanic circulation driven by solar activity

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

the variation of summer monsoon precipitation in central china since the last deglaciation abstract two stalagmites c996 1 and c996 2 collected from the jiuxian cave in the shaanxi province in central china have been studied with u series dating and stable isotope analysis thirty eight 230 th dating results showed that the stalagmite c996 1 was continuously deposited through the last 8 5 ka bp thousand years before present present 1950 ad and c996 2 was deposited through the last 19 ka bp excluding two growth hiatuses between 8 3 and 5 7 ka bp and 15 4 and 11 9 ka bp with a relatively stable boundary condition we interpret the 18 o of speleothem calcite as most indicative of the amount of summer monsoon precipitation although temperature and other factors might have some minor impact the 18 o records show notable changes within the last glacial maximum lgm resembling other east asian monsoon records such as those from the hulu and sanbao caves suggesting that significant monsoonal climate changes occurred in eastern asia as far north as the qinling mountains during the lgm interval a comparison of our records to precisely dated contemporaneous speleothem records from other caves shows that the increasing trend of 18 o during the holocene commenced as early as 7 5 ka bp in the low latitude monsoonal area i e the hoti cave while at higher latitudes this shift occurred later such as 7 0 ka bp in the dongge cave 5 3 ka bp in the heshang cave 4 7 ka bp in the sanbao cave and 4 5 ka bp in the jiuxian cave these results imply an asynchronous change of the summer monsoon precipitation occurred in east asia during the holocene the asynchrony may be related to the responses of a coupled tropical and subtropical monsoon system to changes of the insolation and the differences in thermal forcing which result from the complex geographical configuration the variation of sea surface temperature sst in the western tropical pacific may also have important impacts on the summer monsoon precipitation changes in central and northern china because it affects the northwestern pacific subtropical high a monsoon front regulator more robust tests are needed to confirm this phenomenon and to evaluate the contribution of different factors in detail

the asian monsoon over the past 640 000 years and ice age terminations oxygen isotope records from chinese caves characterize changes in both the asian monsoon and global climate here using our new speleothem data we extend the chinese record to cover the full uranium thorium dating range that is the past 640 000 years the record s length and temporal precision allow us to test the idea that insolation changes caused by the earth s precession drove the terminations of each of the last seven ice ages as well as the millennia long intervals of reduced monsoon rainfall associated with each of the terminations on the basis of our record s timing the terminations are separated by four or five precession cycles supporting the idea that the 100 000 year ice age cycle is an average of discrete numbers of precession cycles furthermore the suborbital component of monsoon rainfall variability exhibits power in both the precession and obliquity bands and is nearly in anti phase with summer boreal insolation these observations indicate that insolation in part sets the pace of the occurrence of millennial scale events including those associated with terminations and unfinished terminations records of the asian monsoon have been extended to 640 000 years ago and confirm both that the 100 000 year ice age cycle results from integral numbers of precessional cycles and that insolation influences the pacing of major millennial scale climate events prior records of the asian monsoon have revealed cyclic variations over hundreds of thousands of years probably driven by variations in insolation caused by the precession of earth s orbit hai cheng and colleagues now provide a speleothem record from chinese cave samples that extends earlier records to 640 000 years ago close to the maximum age possible with uranium thorium dating this spectacular record confirms that the characteristic 100 000 year ice age cycle corresponds to an integral number four or five of precession cycles and that insolation influences millennial scale variations in monsoon strength

transient simulation of last deglaciation with a new mechanism for bolling allerod warming we conducted the first synchronously coupled atmosphere ocean general circulation model simulation from the last glacial maximum to the bolling allerod ba warming our model reproduces several major features of the deglacial climate evolution suggesting a good agreement in climate sensitivity between the model and observations in particular our model simulates the abrupt ba warming as a transient response of the atlantic meridional overturning circulation amoc to a sudden termination of freshwater discharge to the north atlantic before the ba in contrast to previous mechanisms that invoke amoc multiple equilibrium and southern hemisphere climate forcing we propose that the ba transition is caused by the superposition of climatic responses to the transient co 2 forcing the amoc recovery from heinrich event 1 and an amoc overshoot

asynchronous evolution of the isotopic composition and amount of precipitation in north china during the holocene revealed by a record of compound specific carbon and hydrogen isotopes of long chain n alkanes from an alpine lake both the timing of the maximum east asian summer monsoon easm intensity in monsoonal china and the environmental significance of the chinese stalagmite oxygen isotopic record delta o 18 have been debated here we present a ca 120 year resolution compound specific carbon delta c 13 and hydrogen sd isotopes of terrestrial long chain n alkanes extracted from a well dated sediment core from an alpine lake in north china our delta c 13 data together with previously reported pollen data from a parallel core demonstrate a humid mid holocene from ca 8 5 ka bp assuming that the climatic humidity of north china is an indicator of the easm intensity then the maximum easm intensity occurred in the mid holocene our sd data reveal a similar long term trend to the delta o 18 record from nearby lianhua cave indicating that the synchronous sd and delta o 18 records faithfully record the sd and delta o 18 of precipitation respectively the most negative sd and delta o 18 values occur in t he early mid holocene from ca 11 5 ka bp this contrast in the timing of isotopic variations demonstrates a complex relationship between the isotopic composition of precipitation and precipitation amount or easm intensity further comparisons indicate a possible linkage between the precipitation amount in north china and the west east thermal gradient in the equatorial pacific in addition the temperature of the moisture source area may play an important role in determining the isotopic composition of precipitation in monsoonal china c 2016 elsevier b v all rights reserved

east asian monsoon variability since the mid holocene recorded in a high resolution absolute dated aragonite speleothem from eastern china abstract paleoclimatic conditions associated with the east asian monsoon are reconstructed for the mid to late holocene using 18o values 819 measurements from a precisely dated 10 230th dates aragonite stalagmite from lianhua cave hunan province china 18o values 1 6 to 7 0 are interpreted to reflect the precipitation amount effect related to the strength of summer monsoonal circulation throughout this period the intensity of east asian summer monsoonal circulation declined in response to changes in insolation and a southward shift in the intertropical convergence zone itcz punctuating this first order trend are abrupt millennial to decadal scale fluctuations the most prominent of which occurred around 3337 5 yr bp and records a dramatic weakening in summer monsoonal circulation that coincides with the beginning of neoglacial conditions comparisons between the 18o values of stalagmite a1 and previously published data from stalagmite hs 4 from heshang cave and stalagmites d4 and da from dongge cave china demonstrate a similar regional response to changes in east asian monsoonal circulation several spectral analysis techniques and wavelet analysis were applied to these stalagmite records to evaluate the nature and character of cyclicity in the east asian monsoon during the holocene multi taper method mtm lomb scargle and single spectrum analysis ssa results reveal common periodicities that are unlikely to be artifacts of any single technique the periodicities expressed in the stalagmite 18o records occur at both solar and non solar frequencies and support previous interpretations that variability in monsoonal circulation responds to both solar forcing and internal climatic mechanisms wavelet analysis demonstrates that some of these frequencies are intermittent and recur at semi regular intervals which may indicate long term cyclicity that is unconstrained by the chronology of the record

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

decreasing monsoon precipitation in southwest china during the last 240 years associated with the warming of tropical ocean based on an absolutely dated stalagmite 18o record from yunnan province china we reconstructed monsoon precipitation variations in southwest china since 1760 ad with a resolution of about 2 years combining the speleothem 18o and observed rainfall records we find an overall decreasing trend in monsoon precipitation in this region and suggest that the recent drought in 2009 2012 ad has been the driest since 1760 ad our speleothem record is consistent with the monsoon precipitation records reconstructed from tree rings in the nepal himalaya and southeastern tibetan plateau however it is anti correlated with a speleothem record from central india which confirms the observed anti phase variations of indian monsoon precipitation with moistures from the bay of bengal and arabian sea on multi decadal to centennial timescales during historical time the long term warming of tropical ocean may have caused the decrease of the land sea thermal gradient and the amount of moisture transported from the bay of bengal which may reduce precipitations in southwest china during the last 240 years on decadal scale el nino like conditions of tropical pacific sea surface temperature may cause drought in this region climate model simulations suggest el nino like conditions exist in tropical pacific under global warming scenarios as a result it is crucial to have adaptive strategies to overcome future declines in precipitation and or drought events in southwest china

a high resolution record of holocene rainfall variations from the western chinese loess plateau antiphase behaviour of the african indian and east asian summer monsoons tropical monsoons are key mechanisms for transfer of heat and moisture to higher latitudes here we present a high resolution terrestrial proxy summer monsoon record for the southeast asian monsoon from a rapidly accumulating holocene loess soil sequence in the western chinese loess plateau we use magnetic and clastic grain size proxies to make quantitative estimates of holocene rainfall and identify variations in winter monsoon intensity our record reveals cyclical millennial and multimillennial rainfall changes as with the northwest african southwest asian monsoon records a short arid interval at 12 5 to 11 5 ka bp the younger dryas and subsequent summer monsoon intensification are recorded however at 6 ka bp the southeast asian summer monsoon weakened when the northwest african southwest asian monsoons strengthened and then from 5 ka bp intensified when northwest africa southwest asia became dry these antiphase monsoonal relationships may reflect competition between sea surface temperature changes and solar forcing the intensity of the southeast asian winter monsoon intensified from 9 ka bp onwards varying in its phase relationships with summer monsoon intensity after 2 25 ka bp extreme climatic instability is indicated by both climate proxies

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

timing and duration of the east asian summer monsoon maximum during the holocene based on stalagmite data from north china we present a continuous c o isotope series that shows the detailed variability of east asian summer monsoon easm since 11 0 ka bp the series is based on two stalagmites namely dsy1 and lm2 wh

holocene itcz and indian monsoon dynamics recorded in stalagmites from oman and yemen socotra abstract high resolution oxygen isotope 18o profiles of holocene stalagmites from four caves in northern and southern oman and yemen socotra provide detailed information on fluctuations in precipitation along a latitudinal transect from 12 n to 23 n 18o values reflect the amount of precipitation which is primarily controlled by the mean latitudinal position of the itcz and dynamics of the indian summer monsoon ism during the early holocene rapidly decreasing 18o values indicate a rapid northward displacement in the mean latitudinal position of the summer itcz and the associated ism rainfall belt with decadal to centennial scale changes in monsoon precipitation correlating well with high latitude temperature variations recorded in greenland ice cores during the middle to late holocene the summer itcz continuously migrated southward and monsoon precipitation decreased gradually in response to decreasing solar insolation a trend which is also recorded in other monsoon records from the indian and east asian monsoon domains importantly there is no evidence for an abrupt middle holocene weakening in monsoon precipitation although abrupt monsoon events are apparent in all monsoon records they are short lived and clearly superimposed on the long term trend of decreasing monsoon precipitation for the late holocene there is an anti correlation between ism precipitation in oman and inter monsoon spring autumn precipitation on socotra revealing a possible long term change in the duration of the summer monsoon season since at least 4 5 ka bp together with the progressive shortening of the ism season gradual southward retreat of the mean summer itcz and weakening of the ism the total amount of precipitation decreased in those areas located at the northern fringe of the indian and asian monsoon domains but increased in areas closer to the equator

investigating the long term palaeoclimatic controls on the δd and δ18o of precipitation during the holocene in the indian and east asian monsoonal regions abstract this paper aims to achieve an improved understanding of the long term change trends of precipitation d and 18 o values d p and 18 o p in the asian monsoonal region and their relationship with the corresponding humidity trends during the holocene to do this we first review the observed modern spatial pattern of summer precipitation distribution in the east asian summer monsoon easm region under different easm intensities and the relationship between modern observed 18 o p values and corresponding precipitation amounts on monthly and inter annual timescales in the easm and indian summer monsoon ism regions second we compare holocene lacustrine and marine compound specific hydrogen isotopic records of n alkanes n alkanoic acid d n lacustrine authigenic carbonate and cave stalagmite oxygen isotopic records 18 o c and 18 o s from the asian monsoonal region all of which are closely related to d p and 18 o p variations the results demonstrate that in both the ism and easm regions all of these isotopic records exhibit roughly similar long term characteristics i e they were all more negative during the early holocene and early mid holocene ca 11 6 ka b p b p means before present present 1950 ad and then became more positive towards the late holocene third we compare representative paleo humidity records from the asian monsoonal region the results confirm that in the ism region a humid interval occurred in the early holocene and early mid holocene ca 11 6 ka b p and subsequently the climate became more arid towards the late holocene this indicates an enhanced ism during the early holocene and early mid holocene ca 11 6 ka b p and an ism of decreasing intensity towards the late holocene on a holocene orbital scale both 18 o p and d p appear to be controlled by an amount effect in the ism region consistent with the region s inter annual modern 18 o p data this evidence indicates that both 18 o p and d p paleo records are significantly related to paleo humidity in the ism region in contrast holocene humidity variations in the easm region exhibit clear spatial differences a humid mid holocene interval ca 8 3 ka b p occurred in southern and northern china but an arid interval from ca 7 3 ka b p occurred in central china in the middle reaches of the yangtze river based on precipitation distribution patterns under different easm intensities in the easm region over the past few decades we conclude that easm intensity was enhanced during the mid holocene ca 8 3 ka b p relative to the ism intensity the response of easm intensity to summer insolation was relatively slow in the easm region the relationship between climate and 18 o p and d p is more complex consistent with analyses of regional inter annual modern 18 o p data this evidence demonstrates that both 18 o p and d p paleo records cannot be used directly as paleo humidity i e precipitation amount or easm intensity indicators in the easm region further comparison and analyses demonstrate that the coupled variations in west east equatorial pacific temperature gradients and the west pacific subtropical high wpsh played an important role in determining easm intensity during the holocene

abrupt changes in indian summer monsoon strength during 33 800 to 5500 years b p speleothem proxy records from northeastern ne india reflect seasonal changes in indian summer monsoon strength as well as moisture source and transport paths we have analyzed a new speleothem record from mawmluh cave meghalaya india in order to better understand these processes the data show a strong wet phase 33 500 32 500 years b p followed by a weak dry phase from 26 000 to 23 500 years b p and a very weak phase from 17 000 to 15 000 years b p the record suggests abrupt increase in strength during the bolling allerod and early holocene periods and pronounced weakening during the heinrich and younger dryas cold events we infer that these changes in monsoon strength are driven by changes in temperature gradients which drive changes in winds and moisture transport into northeast india

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

evolving history of the east asian summer monsoon intensity during the mis5 inconsistent records from chinese stalagmites and loess deposits as an important component of the global monsoon system the intensity of east asian summer monsoon easm influences lives and economic development of more than 2 billion people the last interglacial period also known as marine isotope stage 5 mis 5 has been thoroughly investigated due to its similarity to the modern interglacial period mis 1 according to records from chinese stalagmites and loess deposits evolving history of easm intensity during mis5 can be divided into 5 sub stages i e 5a 5e however during the 3 warm sub stages 5a 5c and 5e evolving history of easm intensity recorded by chinese stalagmites and loess deposits is apparently different oxygen isotope 18o records of stalagmites demonstrate that the easm intensity during mis5e 5c and 5a is not obviously different on the other hand easm intensity apparently decreased from mis5e to 5c and 5a based on chinese loess deposits records the discrepancy between chinese stalagmite and loess deposits reveals that 18o records of stalagmites may not be a pure indicator of easm intensity the relationship between 18o and easm intensity is not linear based on 18o data of modern precipitation from 21 weather stations within major monsoon area in china mmac ca 110 e to 122 e 18 n to 41 n we speculate that chinese stalagmite 18o values recorded changes of 18o of summer precipitation as well as adjustment from 18o of winter precipitation inconsistent records from chinese stalagmites and loess deposits indicate that further investigations are needed to study the mechanism and fractionation of 18o in stalagmites collected in china

timing and structure of the younger dryas event in northern china a high resolution and absolute dated stalagmite record from kulishu cave beijing characterizes asian monsoon am history in northern china between ca 14 and 10 5 ka bp thousand yrs before present present 1950 including the entire younger dryas yd event using 230 th dates and counting of annual layers the shift into the yd began at 12 850 40 yr bp and took w340 yrs and the shift out of the yd began at 11 560 40 yr bp and took 38 yrs best estimate w20 yrs broadly similar to previously reported am records from central and southeastern china the more gradual nature of the start of the yd event as observed in the am records appears to contrast with the more abrupt beginning observed in the greenland ice records the total amplitude of the am yd event is also smaller than the amplitude of the am heinrich stadial 1 event in addition the general rising trend of the am during the bolling allerod period contrasts with the general cooling trend in greenland temperature during that time the influence of rising insolation on the am may explain this observation

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 step decrease in sediment concentration in a highly modified tidal river delta following the 1983 el nino floods abstract anthropogenic activities in watersheds can have profound effects on sediment transport through river systems to estuaries disturbance in a watershed combined with alterations to the hydro climatologic regime may result in changes to the sediment flux and exacerbate the impacts of extreme events such as large magnitude floods on sediment transport in the san francisco estuary suspended sediment has been declining over the past 30 years as a result of declining sediment supply contributing to dramatic changes in the ecology and geomorphology of the estuary however the decline has not been gradual recent observations of an abrupt decrease in suspended sediments in the san francisco bay have been explained by a model that suggests that the step change has occurred due to exceedance of a sediment regulation threshold that triggered the change from a sediment transport regime to a supply limited system we investigated structural changes in the historical record of total suspended solids tss concentration measured in the upper estuary to verify the model predictions tss in the upper estuary exhibited an abrupt step decrease in 1983 corresponding to the record high winter and summer flows from the 1982 to 1983 el nino event after this step change tss concentrations had a significant declining trend despite subsequent near record high flows the abrupt change in tss followed by the declining trend provides evidence for the hypothesis of sediment supply limitation in the san francisco estuary

holocene vegetation history precipitation changes and indian summer monsoon evolution documented from sediments of xingyun lake south west china we present a pollen based precipitation reconstruction and multi proxy records from a 485 cm long sequence from a sediment core from xingyun lake yunnan plateau south west china which depicts the evolution of the indian summer monsoon ism during the last 8500 years pollen and other palaeoenvironmental records document several stages of vegetation history and climate change the warmest and wettest climate in the xingyun lake catchment occurred before 5500 cal a bp and subsequently the climate became gradually drier after 2000 cal a bp the regional environmental conditions became unstable and a wet medieval warm period is probably recorded our reconstruction of the ism is similar to that portrayed by holocene speleothem o 18 records from southern china but is distinctly different from the east asian summer monsoon easm evolution which features a mid holocene maximum our results support the hypothesis that the ism and easm evolved asynchronously during the holocene and imply that the chinese speleothem o 18 records from southern china may principally reflect changes in moisture source from the indian monsoon domain and thus record the history of the ism rather than the easm

holocene moisture evolution in arid central asia and its out of phase relationship with asian monsoon history we synthesize palaeoclimate records from the mid latitude arid asian region dominated today by the westerlies arid central asia aca to evaluate spatial and temporal patterns of moisture changes during the holocene sediment records from i i takes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200 year time slices the proxies used in these records include pollen and diatom assemblages sediment lithology lake levels and geochemistry mainly isotope data the results of our synthesis show that aca as a whole experienced synchronous and coherent moisture changes during the holocene namely a dry early holocene a wetter less dry early to mid holocene and a moderately wet late holocene during the early holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka 1 ka 1000cal a bp hence the effective moisture history in aca is out of phase with that in monsoonal asia as documented by numerous palaeoclimate records in monsoonal asia a strong summer monsoon and humid climate characterized the early holocene and a weakened summer monsoon and drier climate prevailed during the late holocene which were mainly controlled by changes in low latitude summer insolation in contrast we propose that the pattern of holocene effective moisture evolution in the westerly dominated aca was mainly determined by north atlantic sea surface temperatures ssts and high latitude air temperatures that affect the availability amount and transport of water vapor also topography of the tibetan plateau and adjacent asian highlands could have contributed to the intensification of dry climate in aca during the early holocene as a result of strengthening the subsidence of dry air masses associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation summer insolation might have played a key role in directly controlling moisture conditions in aca but only after the northern hemisphere ice sheets had disappeared in the mid and late holocene c 2007 elsevier ltd all rights reserved

relative impacts of insolation changes meltwater fluxes and ice sheets on african and asian monsoons during the holocene in order to better understand the evolution of the afro asian monsoon in the early holocene we investigate the impact on boreal summer monsoon characteristics of 1 a freshwater flux in the north atlantic from the surrounding melting ice sheets and 2 a remnant ice sheet over north america and europe sensitivity experiments run with the ipsl cm4 model show that both the meltwater flux and the remnant ice sheets induce a cooling of similar amplitude of the north atlantic leading to a southward shift of the inter tropical convergence zone over the tropical atlantic and to a reduction of the african monsoon the two perturbations have different impacts in the asian sector the meltwater flux results in a weakening of the indian monsoon and no change in the east asian monsoon whereas the remnant ice sheets induce a strengthening of the indian monsoon and a strong weakening of the east asian monsoon despite the similar coolings in the atlantic ocean the ocean heat transport is reduced only in the meltwater flux experiment which induces slight differences between the two experiments in the role of the surface latent heat flux in the tropical energetics in the meltwater experiment the southward shift of the subtropical jet acts to cool the upper atmosphere over the tibetan plateau and hence to weaken the indian monsoon in the ice sheet experiment this effect is overwhelmed by the changes in extratropical stationary waves induced by the ice sheets which are associated with a larger cooling over the eurasian continent than in the meltwater experiment however these sensitivity experiments suggest that insolation is the dominant factor explaining the relative changes of the african indian and east asian monsoons from the early to the mid holocene

climate significance of speleothem δ18o from central china on decadal timescale abstract speleothem based oxygen isotopic sequences have been widely used to reveal regional climatic changes worldwide however the climatic significance of speleothem 18o variations in monsoonal china on decadal to annual timescales remains in debate which limits its application to paleoclimate reconstruction in the world s largest country by population in this study we analyzed a seasonally resolved 18o record of an annually layered stalagmite xl21 whose variability covers a period of 98 years 1912 2009 ad from xianglong cave central china the annual 18o trend shows an inverse relationship with local monsoon precipitation suggesting speleothem 18o variations in this area can reflect monsoon precipitation at least on decadal timescale changes in moisture sources and transport pathways have little effect on the 18o variations in speleothems monsoon precipitation on decadal timescale which may be ascribed to similar distances from this region to the two main moisture sources the bay of bengal and west pacific there is an anti phase relationship between speleothem 18o records from central china and india during the last 98 years which indicates the relationship between indian monsoon intensity and speleothem 18o from central china on short timescales requires further investigation

new insights on chinese cave δ18o records and their paleoclimatic significance abstract in the last two decades stalagmite oxygen isotope 18o records have been widely used to study the evolution of the paleomonsoon nevertheless interpreting cave 18o records in eastern monsoonal china as an indicator of east asian summer monsoon easm rainfall has been intensively debated this study provides new insights into chinese cave 18o records and their paleoclimatic significance based on recent research progress the following points are highlighted 1 chinese cave 18o records do not reflect changes in summer rainfall throughout the whole of eastern monsoonal china which is evident by comparing monitored summer rainfall amount in eastern china and an integrated chinese cave 18osyn proxy 2 chinese cave 18o records can document millennial scale easm events due to the sensitive response to large scale atmospheric circulation changes 3 during the early holocene before 7 ka a decoupled relationship between chinese cave 18o records and easm rainfall as represented by precipitation in north china is attributed to the reduction of rainfall in north china due to the influence of remnant melting ice sheets in the northern high latitude region 4 when the ice sheet boundary conditions were stable and ice sheets were small after 7 ka there is an indirect correlation between the chinese cave 18o and rainfall changes in north china 5 the first continuous speleothem 18o record spanning the entire holocene is synthesized for the core region of the indian summer monsoon ism domain comparison of this integrated ism proxy with chinese cave 18o records reveals that in china cave 18o is primarily a signal of changes in the tropical monsoon and related large scale circulation the coupled relationship between rainfall in north china and tropical monsoon ism rainfall is attributed to the response of downstream circulation to changes in circulation upstream while their decoupled relationship is due to the possible effects of northern high latitude ice sheets on reducing rainfall in north china 6 due to the imprecise definition of monsoon intensity we suggest that cave 18o can be used as an easm proxy if monsoon intensity is defined by changes in atmospheric circulation

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

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

concordant monsoon driven postglacial hydrological changes in peat and stalagmite records and their impacts on prehistoric cultures in central china asian monsoon records are widely documented but specific proxies of monsoonal rainfall are limited we present here two new independent proxy records from peatland and stalagmite archives that indicate a high degree of concordance between monsoon driven hydrological changes occurring since the last deglaciation in a broad region of central china the wet periods elevated the water table in the dajiuhu peatland as recorded by reduced mass accumulation rates of hopanoids biomarkers for aerobic microbes confirmed by molecular phylogenic analyses the hopanoid based reconstruction is supported by the first report of the environmental magnetism parameter arm sirm anhysteretic remanent magnetization saturation isothermal remanent magnetization ratio of fine magnetic particles to total ferrimagnetic particles in a stalagmite from heshang cave in central china heavy rainfall resulted in the enhanced transport of coarse particles to the cave and thus low arm sirm values in the stalagmite the hydrological conditions inferred from the two records reveal three relatively long wet periods in central china 13 11 5 k y ago 9 5 7 0 k y ago and 3 0 1 5 k y ago archaeological evidence for the hydrological impacts on regional populations comes from the observation that temporal shifts among six distinctive cultures of the neolithic period to the iron age in central china occurred during wet periods or flood episodes spatiotemporal distributions of 1600 prehistoric settlement sites correlate with the proxy inferred fluctuating hydrological conditions with enhanced flooding risk forcing major relocations of human settlements away from riparian zones

holocene variability of the east asian summer monsoon from chinese cave records a re assessment oxygen isotope records from stalagmites in caves in southern china interpreted as proxy rainfall records reflecting the intensity of the east asian summer monsoon indicate gradual monsoon weakening for the last 9000 years as also documented for the indian monsoon coupled with high precision dating the speleothem proxy records have been used to test monsoon links with orbital forcing solar changes iceberg discharges in the north atlantic ocean currents and atmospheric methane however these benchmark cave records do not match other published dated e asian proxy rainfall record specifically here independently calibrated rainfall records from loess palaeosol magnetic properties and cave oxygen isotope intercomparisons which show variable e asian monsoon intensity through the entire holocene the strong correlation of the cave records with the extraregional indian monsoon record yet their mismatch with these other dated chinese rainfall records might be reconciled if the speleothem isotope variations reflect not changes in holocene rainfall amount but in rainfall source declining holocene influence of isotopically lighter indian monsoon sourced moisture over china would have resulted in increasing proportions of isotopically heavier rainfall sourced from the more oceanic e asian monsoon individual speleothems may thus regionally record holocene changes in indian monsoon intensity and isotopic influence conversely the other chinese proxy records described here reflect changes in rainfall amount and thus in e asian summer monsoon intensity for the holocene the e asian and the indian monsoon responses to orbital forcing are likely to have differed specifically due to e asian internal feedbacks and the seasonal contrasts between the two monsoon systems

how to measure the strength of the east asian summer monsoon defining the intensity of the east asian summer monsoon easm has been extremely controversial this paper elaborates on the meanings of 25 existing easm indices in terms of two observed major modes of interannual variation in the precipitation and circulation anomalies for the 1979 2006 period the existing indices can be classified into five categories the east west thermal contrast north south thermal contrast shear vorticity of zonal winds southwesterly monsoon and south china sea monsoon the last four types of indices reflect various aspects of the leading mode of interannual variability of the easm rainfall and circulations which correspond to the decaying el nino while the first category reflects the second mode that corresponds to the developing el nino the authors recommend that the easm strength can be represented by the principal component of the leading mode of the interannual variability which provides a unified index for the majority of the existing indices this new index is extremely robust captures a large portion 50 of the total variance of the precipitation and three dimensional circulation and has unique advantages over all the existing indices the authors also recommend a simple index the reversed wang and fan index which is nearly identical to the leading principal component of the easm and greatly facilitates real time monitoring the proposed index highlights the significance of the mei yu baiu changma rainfall in gauging the strength of the easm the mei yu which is produced in the primary rain bearing system the east asian ea subtropical front better represents the variability of the easm circulation system this new index reverses the traditional chinese meaning of a strong easm which corresponds to a deficient mei yu that is associated with an abnormal northward extension of southerly over northern china the new definition is consistent with the meaning used in other monsoon regions worldwide where abundant rainfall within the major local rain bearing monsoon system is considered to be a strong monsoon

a high resolved record of the asian summer monsoon from dongge cave china for the past 1200 years abstract two annually laminated and 230th dated stalagmite oxygen isotope 18o records from dongge cave china provided a high resolution asian summer monsoon asm history for the past 1200 years a close similarity between annual band thickness and stable isotope analyses 13c and 18o suggests the calcite 18o is most likely a proxy associated with asm precipitation the two duplicated stalagmite 18o records show that the asm varies at a periodicity of 220 years concordant with a dominant cycle of solar activity a period of strong asm activity occurred during the sporer minimum 1450 1550 a d followed by a striking drop circa 1580 a d potentially consistent with the social unrest in the final decades of china s ming dynasty 1368 1644 a d centennial scale changes in asm precipitation over the last millennium match well with changes in tropical atlantic sea surface temperatures ssts and south american summer monsoon precipitation our findings suggest that variations in low latitude monsoon precipitation are probably driven by shifts in the mean position of the intertropical convergence zone itcz which is further mediated by solar activity and tropical ssts

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

a detailed east asian monsoon history surrounding the mystery interval derived from three chinese speleothem records the mystery interval mi 17 5 14 5 ka was the first stage of the last deglaciation a key interval for understanding mechanisms of glacial interglacial cycles to elucidate possible causes of the mi here we present three high resolution precisely dated oxygen isotope records of stalagmites from qingtian and hulu caves in china reflecting changes in the east asian summer monsoon easm then based on well established chronologies using precise 230th dates and annual band counting results the two cave 18o profiles of 7 yr resolution match well at decadal timescales both of the two cave records document an abrupt weakening 2 of 18o rise within 20 yr in the easm at 16 1 ka coinciding with the transition of the two phased mi reconstructed from new mexico s lake estancia our results indicate that the maximum southward displacement of the intertropical convergence zone and associated southward shift of polar jet stream may generate this two phase feature of the mi during that time we also discover a linear relationship among decreasing easm intensity rising atmospheric co2 and weakening atlantic meridional overturning circulation between the mi and younger dryas episodes suggesting a strong coupling of atmospheric oceanic circulations in response to the millennial scale forcing which in turn regulates global climate changes and carbon cycles

asian monsoon hydrometeorology from tes and sciamachy water vapor isotope measurements and lmdz simulations implications for speleothem climate record interpretation observations show that heavy oxygen isotope composition in precipitation 18 o p increases from coastal southeastern se china to interior northwestern nw china during the wet season contradicting expectations from simple rayleigh distillation theory here we employ stable isotopes of precipitation and vapor from satellite measurements and climate model simulations to characterize the moisture processes that control asian monsoon precipitation and relate these processes to speleothem paleoclimate records we find that 18 o p is low over se china as a result of local and upstream condensation and that 18 o p is high over nw china because of evaporative enrichment of 18 o as raindrops fall through dry air we show that 18 o p at cave sites over southern china is weakly correlated with upstream precipitation in the core of the indian monsoon region rather than local precipitation but it is well correlated with the 18 o p over large areas of southern and central china consistent with coherent speleothem 18 o p variations over different parts of china previous studies have documented high correlations between speleothem 18 o p and millennial timescale climate forcings and we suggest that the high correlation between insolation and speleothem 18 o p in southern china reflects the variations of hydrologic processes over the indian monsoon region on millennial and orbital timescales the 18 o p in the drier part north of 30 n of china on the other hand has consistently negative correlations with local precipitation and may capture local hydrologic processes related to changes in the extent of the hadley circulation

variations of monsoonal rain and vegetation during the past millennium in tiangui mountain north china reflected by stalagmite δ18o and δ13c records from zhenzhu cave abstract an 11 cm long stalagmite zz12 collected from zhenzhu cave tiangui mountain northwest of the north china plain ncp has been measured by 230 th u ams 14 c and 210 pb dating methods only ams 14 c dating yielded the chronology successfully while 230 th u did not due to low uranium content and the young age of the stalagmite the top layers in the stalagmite contain nuclear bomb carbon signal and the ams 14 c dates of charcoal and carbonate samples at the bottom are similar based on a series of ams 14 c dates which contain minimal dead carbon influence dci in the stalagmite the age model of the stalagmite has been constructed indicating that the stalagmite was 1970 years old a total of 470 subsamples from the upper 51 mm since 1180 ce of the stalagmite have been analyzed for 18 o and 13 c the 18 o record of stalagmite zz12 reflects changes in the summer monsoonal rainfall in the ncp being comparable with the local and north central china dry wet index the driest periods were found in 14th 15th centuries in the little ice age lia and since 1970s perhaps due to weakening of east asian summer monsoon the 13 c of zz12 mainly recorded vegetation changes in tiangui mountain and revealed deforestation in two major periods 1500 1600 ce and 1830 1940 ce caused by local human activities spectral analysis of the 18 o record suggests that the pacific decadal oscillation pdo and atlantic multidecadal oscillation amo may both play important roles in changes of multi decadal monsoonal rainfall in the ncp with more rainfall responding to the negative pdo la nino like and positive amo phases

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

coupling an agcm with an ism to investigate the ice sheets mass balance at the last glacial maximum the aim of this paper is to investigate the consistency between the ice sheets reconstruction at the lgm and the climate simulated by agcm in particular to investigate whether the laurentian and the fennoscandian ice sheets have an equilibrated mass balance we use two complementary approaches first we analyze the changes of snow and water budgets over the ice sheets only using the model results of lgm runs second we use a thermomechanical ice sheet model ritz et al 1997 forced with the agcm simulated climate to perform long term runs at finer spatial resolution analyzing the results obtained with both approaches we show that the ice sheet mass balance computed directly from agcm results may be biaised moreover we show using two versions of the lmd agcm that the ice sheet mass balance computed by the ism is drastically sensitive to the summer surface temperatures simulated by the agcm

orbital scale timing and mechanisms driving late pleistocene indo asian summer monsoons reinterpreting cave speleothem δ18o 1 southeast china cave 18o often interpreted as a pure east asian summer monsoon proxy lags maximum northern hemisphere summer insolation by 2 9 0 3 kyrs at the precession cycle the arabian sea summer monsoon stack lags by 8 1 kyr consistent with 13 other indian and east asian summer monsoon proxies from marine lake and terrestrial archives this 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology it requires reconciliation in the context of proxy interpretation both of these lags are incompatible with a direct response to northern hemisphere summer insolation implicating additional forcing mechanisms analysis of heterodynes in the cave 18o spectrum demonstrates that variance contained in the arabian sea summer monsoon proxies also resides in the cave 18o record this variance is subtracted from the cave 18o record yielding a residual that is highly coherent and in phase with precession minima reflecting the impact of winter temperature change on cave 18o meteorological precipitation under cold conditions thus we argue that the timing of light cave 18o peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone the 2 9 kyr precession band phase lag of cave 18o reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima this interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast china

a high resolution stalagmite record of the holocene east asian monsoon from mt shennongjia central china high resolution oxygen isotope 18o profiles of six stalagmites from sanbao cave in hubei province central china established with 1413 oxygen isotope data and 65 230th ages provide a continuous history of east asian summer monsoon easm intensity for the period from 13 0 2 thousand years before present ky bp relative to ad 1950 the 18o record includes four distinct stages in the evolution of the easm 1 an abrupt transition 11 5 ky bp into the holocene 2 a period of gradual increase in monsoon intensity 11 5 9 5 ky bp 3 the maximum humid period 9 5 6 5 ky bp and 4 a period of gradual decline in monsoon intensity 6 5 0 2 ky bp comparison of sanbao with regional records of comparable resolution reveals that the timing of the beginning and end of the holocene optimum as defined by the minimum in 18 o was similar in the indian and east asian monsoon systems this supports the idea that shifts in the monsoon tied to shifts in the mean position of the inter tropical convergen

palaeosol development in the chinese loess plateau as an indicator of the strength of the east asian summer monsoon evidence for a mid holocene maximum the interpretation of the stalagmite delta o 18 record from southern china as an indicator of east asian summer monsoon easm rainfall amount or intensity is strongly debated soil development in the chinese loess plateau clp situated in the modern summer monsoon domain has long been treated as a direct and reliable easm proxy in this study we compiled 81 loess and 229 palaeosol dates from 77 profiles across the clp and synthesized the data statistically in order to investigate the easm history during the holocene the resulting history of holocene loess deposition and palaeosol development demonstrates that 1 loess deposition decreased and palaeosol formation increased across the clp after 11 5 ka 1 ka 1000 cal yr bp revealing a gradually intensified easm during the early holocene 2 numerous palaeosols developed in the clp between 8 8 ka and 3 4 ka indicating a generally strong easm during the mid holocene 3 the number of palaeosol dates decreased rapidly at around 3 ka suggesting a sudden retreat of the easm in the late holocene these trends of easm evolution are broadly consistent with variations in aeolian sand activity in the four main sandlands the mu us otindag horqin and hulun buir sandlands along the modern monsoon fringe in northern china and are supported by a wide range of independent evidence in addition we also found that high loess deposition and stronger aeolian activity occurred at similar to 5 ka representing a weak easm event within the context of an overall strong mid holocene easm the strong mid holocene easm revealed by palaeosol development in the clp and aeolian sand activity in the sandlands in northern china contrasts with the early holocene easm maximum suggested by stalagmite delta o 18 data from southern china our results are compatible with the proposal that the stalagmite delta o 18 variations in china do not result from changes in easm rainfall amount or intensity but instead reflect changes in moisture source driven by variations in atmospheric oceanic circulation c 2014 elsevier ltd and inqua all rights reserved

timing duration and transitions of the last interglacial asian monsoon thorium 230 ages and oxygen isotope ratios of stalagmites from dongge cave china characterize the asian monsoon and low latitude precipitation over the past 160 000 years numerous abrupt changes in 18o 16o values result from changes in tropical and subtropical precipitation driven by insolation and millennial scale circulation shifts the last interglacial monsoon lasted 9 7 1 1 thousand years beginning with an abrupt less than 200 years drop in 18o 16o values 129 3 0 9 thousand years ago and ending with an abrupt less than 300 years rise in 18o 16o values 119 6 0 6 thousand years ago the start coincides with insolation rise and measures of full interglacial conditions indicating that insolation triggered the final rise to full interglacial conditions

chinese stalagmite δ 18 o controlled by changes in the indian monsoon during a simulated heinrich event carbonate cave deposits in india and china are assumed to record the intensity of monsoon precipitation because the 18 o of the carbonate tracks the isotopic signature of precipitation these records show spatially coherent variability throughout the last ice age and suggest that monsoon strength was altered during the millennial scale climate variations known as dansgaard oeschger events and during the heinrich cooling events here we use a numerical climate model with an embedded oxygen isotope model to assess what caused the shifts in the oxygen isotope signature of precipitation during a climate perturbation designed to mimic a heinrich event our simulations show that a sudden increase in north atlantic sea ice extent during the last glacial period leads to cooling in the northern hemisphere reduced precipitation over the indian basin and weakening of the indian monsoon the precipitation is isotopically heavier over india and the water vapour exported to china is isotopically enriched our model broadly reproduces the enrichment of 18 o over northern india and east asia evident in speleothem records during heinrich events we therefore conclude that changes in the 18 o of cave carbonates associated with heinrich events reflect changes in the intensity of indian rather than east asian monsoon precipitation